Comprehensive Review in Clinical Neurology: A Multiple Choice Question Book for the Wards and Boards

Chapter 1. Cranial Nerves and Neuro-ophthalmology

Questions

Questions 1–3

  1. Which of the following represents the actions of the superior oblique muscle?

      a.  The primary action is eye elevation and secondary action is intorsion

      b.  The primary action is eye depression and secondary action is extorsion

      c.  The primary action is eye elevation and secondary action is extorsion

      d.  The primary action is eye depression and secondary action is intorsion

      e.  The primary action is eye depression and secondary action is adduction

  2. Which of the following represents the actions of the inferior rectus muscle?

      a.  The primary action is eye elevation and secondary action is extorsion

      b.  The primary action is eye depression and secondary action is extorsion

      c.  The primary action is eye elevation and secondary action is intorsion

      d.  The primary action is eye depression and secondary action is adduction

      e.  The primary action is eye depression and secondary action is intorsion

  3. Which of the following muscles is not innervated by the oculomotor nerve?

      a.  Superior rectus

      b.  Inferior oblique

      c.  Lateral rectus

      d.  Inferior rectus

      e.  Medial rectus

Questions 4–6

  4. A 58-year-old man presents with a left-sided headache and neck pain that occurred during weight lifting. He was concerned because he felt like his left eye was “droopy.” On examination, you confirm that he has slight ptosis of the left eye. What is the cause of this finding?

      a.  Overactivity of the parasympathetics

      b.  Impairment in oculomotor nerve function

      c.  Underactivity of the sympathetics

      d.  Underactivity of the parasympathetics

      e.  Overactivity of the sympathetics

  5. Which of the following is not a known association with this disorder?

      a.  Depression of the left lower eyelid

      b.  Miosis of the left pupil

      c.  Depression of the left upper eyelid

      d.  Left-sided facial anhidrosis

      e.  Enophthalmos of the left eye

  6. During your examination, you attempt to better localize the extent of the lesion. Which of the following findings would suggest that the lesion is proximal to the carotid bifurcation?

      a.  Depression of the left upper eyelid

      b.  Left-sided facial anhidrosis

      c.  Miosis of the left pupil

      d.  Elevation of the left lower eyelid

      e.  Enophthalmos of the left eye

Questions 7–10

  7. You are consulted on a 76-year-old man who is referred for right eyelid ptosis and right pupillary constriction. He also mentions that when he exerts himself, he notices that the right side of his face does not seem to sweat like the left side. Using this information, which of the following would not be a probable cause for these symptoms?

      a.  A tumor affecting C8-T2 spinal levels

      b.  A lesion between hypothalamus and ciliospinal center of Budge

      c.  Tumor in the right lung apex

      d.  Large hematoma formation under the subclavian artery following attempted central line placement

      e.  Internal carotid dissection involving the midcervical region

  8. Which of the following is false regarding the sympathetic pathway to the orbit and face?

      a.  The oculosympathetic fibers travel with the ophthalmic division of the trigeminal nerve (V1) to the orbit

      b.  The sympathetic fibers arise from the posterior thalamus

      c.  The ciliospinal center of Budge is located at spinal levels C8 to T2

      d.  The vasomotor and sweat fibers travel to the face along the ECA

      e.  The superior cervical ganglion is located near the level of the carotid bifurcation

  9. You are determined to further try to localize the lesion. After placing 4% cocaine eye drops in his eyes, you notice that the left eye dilates further, whereas the right eye remains unchanged. Which of the following can be definitively concluded on the basis of this finding?

      a.  The lesion lies between the second- and third-order sympathetic neurons of the right eye

      b.  There is sympathetic denervation to the right eye

      c.  The lesion lies between the first- and second-order sympathetic neurons of the right eye

      d.  The lesion lies between the first- and second-order sympathetic neurons, and third order sympathetic neurons of the right eye

      e.  This finding is nonconfirmatory of a Horner’s syndrome

10. You next use 1% hydroxyamphetamine eye drops to help you localize the lesion further. After instillation, both pupils dilate. Which of the following can be definitively concluded on the basis of this finding?

      a.  The lesion involves the third-order sympathetic neurons of the right eye

      b.  This finding disproves the presence of a true Horner’s syndrome

      c.  The lesion lies between the second- and third-order sympathetic neurons of the right eye

      d.  The lesion lies between the first- and third-order sympathetic neurons of the right eye

      e.  The lesion is proximal and does not involve the third-order sympathetic neurons of the right eye

Questions 11–14

11. A 61-year-old woman with a history of diabetes, hyperlipidemia, and hypertension presents to the emergency department with double vision that she woke up with this morning. On examination, you find that she has a complete left oculomotor nerve palsy with intact pupillary function. Which of the following is the most likely cause of her examination findings?

      a.  Myasthenia gravis

      b.  Brainstem infarction involving the midbrain

      c.  Diabetic oculomotor nerve palsy

      d.  Aneurysmal compression of the oculomotor nerve

      e.  Neoplastic infiltration of the oculomotor nerve

12. Which of the following is false regarding the oculomotor nuclear complex?

      a.  The inferior rectus subnucleus innervates the ipsilateral inferior rectus muscle

      b.  The superior rectus subnucleus innervates the contralateral superior rectus muscle

      c.  The inferior oblique subnucleus innervates the contralateral inferior oblique muscle

      d.  A single lesion to the levator palpebrae superioris nucleus will result in bilateral ptosis

      e.  The medial rectus subnucleus innervates the ipsilateral medial rectus muscle

13. Which of the following is true regarding the course of the oculoparasympathetic innervation of the eye?

      a.  The parasympathetic fibers travel on the peripheral aspect of the ophthalmic division of the trigeminal nerve (V1)

      b.  The parasympathetic fibers travel on the peripheral aspect of the oculomotor nerve

      c.  The parasympathetic fibers travel together with the sympathetic fibers along the oculomotor nerve

      d.  The parasympathetic fibers travel on the central aspect of the ophthalmic division of the trigeminal nerve (V1)

      e.  The parasympathetic fibers travel on the central aspect of the oculomotor nerve

14. Which of the following is false regarding the pupillary light response and oculoparasympathetic pathways?

      a.  The lateral geniculate body is not involved in the afferent pathway of the pupillary light response

      b.  The efferent pathway of the pupillary light response begins in the Edinger–Westphal nucleus

      c.  Each pretectal nucleus receives light input from the contralateral visual hemifield

      d.  The preganglionic parasympathetic fibers originate from the pretectal nuclei

      e.  The ciliary muscle is activated for accommodation, resulting from increased curvature of the lens

Questions 15–17

15. A 9-year-old girl presented to your office with complaints of diplopia. This began after she had a bad fall off her bicycle, hitting her head. On the basis of the directions of gaze noted on your examination, and shown in Figure 1.1, what nerve is involved?

FIGURE 1.1 Directions of gaze. Courtesy of Dr. Gregory Kosmorsky. Shown also in color plates

      a.  Right trochlear nerve

      b.  Left trochlear nerve

      c.  Right abducens nerve

      d.  Left abducens nerve

      e.  Left oculomotor nerve

16. In this type of nerve lesion, which of the following corrective head positions would be expected to lessen the severity of diplopia?

      a.  Head tilted left

      b.  Head tilted forward (flexion)

      c.  Head rotated left

      d.  Head tilted right

      e.  Head rotated right

17. Which of the following is true regarding the course and innervation of this nerve?

      a.  The motor neurons that this nerve originates from innervate the ipsilateral superior oblique muscle

      b.  The motor neurons that this nerve originates from innervate the contralateral inferior oblique muscle

      c.  This nerve passes between the posterior cerebral and superior cerebellar arteries

      d.  This nerve has the shortest intracranial course

      e.  The axons from this nerve decussate prior to exiting ventrally at the level of the midbrain

Questions 18–19

18. A 68-year-old woman with diabetes, hypertension, and hyperlipidemia presents to your office for diplopia. Her extraocular motor examination is seen in Figure 1.2. On pupillary examination, you note that her right pupil is dilated and nonreactive. Which of the following nerves is affected?

FIGURE 1.2 Directions of gaze. Courtesy of Dr. Gregory Kosmorsky. Shown also in color plates. A, looking forward in primary gaze; B, looking forward in primary gaze with right eyelid lifted; C, looking down; D, looking left

      a.  Right oculomotor nerve

      b.  Left oculomotor nerve

      c.  Right abducens nerve

      d.  Left abducens nerve

      e.  Right trochlear nerve

19. Which of the following would be the least likely cause of this patient’s findings?

      a.  Aneurysm of the basilar tip

      b.  Aneurysm of the PCA

      c.  Aneurysm of the SCA

      d.  Aneurysm of the PICA

      e.  Aneurysm of the Pcomm

Questions 20–22

20. A 42-year-old woman with a history of multiple sclerosis presents for a complaint of recent onset of diplopia, especially when she looks to the right. On examination, you find that on right lateral gaze she has impaired adduction of the left eye and nystagmus of the abducted right eye. Where do you suspect this lesion is localized?

      a.  Left PPRF

      b.  Left MLF

      c.  Left MLF and left PPRF

      d.  Right MLF

      e.  Right PPRF

21. Your patient returns 2 weeks later with complaints of diplopia in all directions of gaze. On examination, you find that she now has exotropia of both eyes on primary gaze and no voluntary horizontal adduction. Where do you localize her findings to?

      a.  Left MLF and right PPRF

      b.  Bilateral PPRFs

      c.  Right MLF and right PPRF

      d.  Bilateral abducens nucleus

      e.  Right and left MLF

22. Three months after treatment with pulse corticosteroid therapy and return of normal extraocular function, your patient presents to you again with new ocular complaints. On examination, you find that she has no horizontal movements of the right eye and only has abduction of the left eye associated with nystagmus. Where do you localize her current findings to?

      a.  Right abducens nucleus and left MLF

      b.  Right PPRF

      c.  Left PPRF and right MLF

      d.  Right abducens nucleus and right MLF

      e.  Bilateral MLF

23. Which of the following cranial nerves would most likely be affected in a patient presenting to your office with papilledema, headache, and significant obstructive hydrocephalus?

      a.  Facial nerve

      b.  Trochlear nerve

      c.  Abducens nerve

      d.  Trigeminal nerve

      e.  Oculomotor nerve

Questions 24–25

24. A 34-year-old woman with diabetes presents to your office complaining of mild left eye ache and an increased left pupil size that she noticed in the mirror yesterday. On examination, you find that her right pupil reacts normally to light, but her left pupil is nonreactive to direct and consensual light, or to accommodation. What do you suspect as the likely cause?

      a.  Argyll–Robertson pupil from neurosyphilis

      b.  Optic neuritis

      c.  Aneurysmal compression of oculomotor nerve

      d.  Tonic (Adie’s) pupil

      e.  Diabetic cranial neuropathy

25. In the chronic stage of this disease process, which of the following pupillary findings are most often seen?

      a.  Miotic with intact pupillary light response, but minimal-to-absent accommodation

      b.  Miotic with minimal-to-absent pupillary light response and minimal-to-absent accommodation

      c.  Mydriatic with minimal-to-absent pupillary light response, but intact accommodation

      d.  Mydriatic with minimal-to-absent pupillary light response and minimal-to-absent accommodation

      e.  Miotic with minimal-to-absent pupillary light response, but intact accommodation

Questions 26–28

26. A 29-year-old woman with a history of hypertension presents with complaints of right eye pain on eye movement, impaired and blurry vision, and the feeling that some colors “don’t look right.” On examination, you notice that her right pupil is poorly responsive to direct light, but responds briskly on consensual response light stimulation of the left eye. Her visual acuity is significantly impaired in the right eye, as is red color perception. Which of the following is not a possible cause of this finding?

      a.  Bilateral asymmetric optic nerve disease

      b.  Severe macular disease

      c.  Optic chiasm involvement

      d.  Right optic nerve disease

      e.  Right lateral geniculate body lesion

27. Her fundoscopic examination of the right eye is shown in Figure 1.3. What diagnosis do you suspect?

FIGURE 1.3 Courtesy of Anne Pinter. Shown also in color plates

      a.  Papilledema

      b.  Giant cell arteritis

      c.  Posterior ischemic optic neuropathy

      d.  Acute optic neuritis

      e.  Anterior ischemic optic neuropathy

28. A brain MRI with contrast confirms your suspicion. Which of the following would be the most appropriate next course of treatment?

      a.  Oral prednisone taper

      b.  Intravenous methylprednisolone followed by an oral prednisone taper

      c.  Observation, initiate treatment at the next episode

      d.  Begin interferon therapy

      e.  Begin plasma exchange

29. A 52-year-old man with diabetes, hypertension, and hyperlipidemia presents with severe painless visual blurring and “cloudiness” in the left eye which he woke with this morning. The fundoscopic examination findings of the left eye are shown in Figure 1.4. What diagnosis do you suspect?

FIGURE 1.4 Courtesy of Anne Pinter. Shown also in color plates

      a.  Acute optic neuritis

      b.  Giant cell arteritis

      c.  Posterior ischemic optic neuropathy

      d.  Papilledema

      e.  Anterior ischemic optic neuropathy

Questions 30–31

30. A 64-year-old man presents with a right homonymous hemianopia. Which of the following is the most likely localization for this finding?

      a.  Left upper lip of the calcarine cortex

      b.  Right optic tract

      c.  Left parietal lobe

      d.  Left lateral geniculate body

      e.  A temporal lobe infarct

31. A 57-year-old woman presents with a left upper quadrantanopsia. Which of the following would be the most likely localization?

      a.  Right lower bank of the calcarine cortex

      b.  Right upper bank of the visual cortex

      c.  Right parietal lobe

      d.  Left upper bank of the calcarine cortex

      e.  Left lower bank of the visual cortex

32. A 67-year-old female with a chronic neurologic disease describes a long progressive loss of vision in the left eye greater than the right eye over the past 15 years. Her fundoscopic examination of the left eye is seen in Figure 1.5, and she has a relative afferent pupillary defect in the same eye. What do you suspect as the cause of this finding?

FIGURE 1.5 Courtesy of Anne Pinter. Shown also in color plates

      a.  Acute optic neuritis

      b.  Papilledema

      c.  Posterior ischemic optic neuropathy

      d.  Optic atrophy

      e.  Anterior ischemic optic neuropathy

33. A 56-year-old male with diabetes presents with 1 week of fever, double vision, and visual blurring. He has proptosis bilaterally, bilateral abduction weakness, visual acuity 20/50 in the right eye and 20/100 in the left, and facial numbness in V2 on the right eye. You suspect the following diagnosis:

      a.  Midbrain infarction with hypothalamic hyperthermia

      b.  Chronic meningitis with cranial nerve palsies

      c.  Cavernous sinus involvement with mucormycosis

      d.  Diabetic third nerve palsy

      e.  Idiopathic cranial polyneuropathy

Questions 34–36

34. A 58-year-old female with a history of hypertension, diabetes, and hyperlipidemia presents to the emergency department for left “facial droop.” She woke this morning and noticed unilateral facial paralysis on the left, which was not present the prior night. She also reports hyperacusis in the left ear and says food tastes different. There have been no other new symptoms over the last year of any kind. On examination, you notice left facial droop and inability to close the left eye. She is unable to wrinkle the left side of her forehead. What is the most likely diagnosis?

      a.  Acute pontine stroke

      b.  Cholesteatoma

      c.  Lyme disease

      d.  Bell’s palsy

      e.  Multiple sclerosis

35. What is the most appropriate diagnostic and/or management strategy at this time?

      a.  Brain MRI and MRA of circle of Willis

      b.  Brain CT angiogram

      c.  Lumbar puncture

      d.  MRI of the internal auditory canals

      e.  Observation

36. What initial treatment do you recommend at this time for this patient?

      a.  Prednisone

      b.  Doxycycline

      c.  Otolaryngology consult

      d.  Referral to a neurosurgeon for peripheral nerve decompression

      e.  Electric nerve stimulation

37. Which of the following cranial nerves does not have a synapse in the thalamus before terminating in the cortex?

      a.  Trigeminal nerve

      b.  Optic nerve

      c.  Olfactory nerve

      d.  Vestibulocochlear nerve

      e.  Facial nerve

38. A 43-year-old man with a history of right-sided Bell’s palsy the prior year, who made a good recovery, comes to you complaining of excessive tearing of the right eye, mainly when he is eating. What do you attribute this to?

      a.  Early recurrence of Bell’s palsy

      b.  Absence of normal facial nerve inhibition of overactivity due to prior damage from Bell’s palsy

      c.  Reinnervation of lacrimal glands by glossopharyngeal nerve axons after facial nerve injury

      d.  Reinnervation of lacrimal glands by trigeminal nerve axons after facial nerve injury

      e.  Reinnervation of lacrimal glands by misdirected facial nerve axons

Questions 39–43

39. A 56-year-old woman with hypertension, diabetes, and hyperlipidemia presents to the emergency department with complaints of severe vertigo, unsteadiness, nausea, and vomiting. These symptoms began this morning and she has had several exacerbations since then, each lasting about a minute or so, especially on neck extension. Her examination is normal with exception of nystagmus and nausea brought on by certain head movements. You are trying to decide if her vertigo is central or peripheral in origin. What would be the next step in evaluation of this patient?

      a.  Brain MRI to evaluate for stroke

      b.  Brain MRI to evaluate for acoustic schwannoma

      c.  Dix–Hallpike maneuver

      d.  Avoiding neck rotation and Dix–Hallpike maneuver until vertebral dissection is ruled out by neck MRI with fat saturation

      e.  Epley maneuver

40. Which of the following is most suggestive of central vertigo?

      a.  Suppression of nystagmus by visual fixation

      b.  Absent nystagmus latency

      c.  Preserved walking with mild unsteadiness toward one direction

      d.  Horizontal nystagmus with a torsional component

      e.  Unilateral decrease in hearing

41. Which of the following is incorrect regarding nystagmus from a peripheral etiology?

      a.  The fast phase of nystagmus is directed toward the affected side

      b.  Nystagmus is suppressed by visual fixation

      c.  Amplitude of nystagmus increases with gaze directed toward the fast phase

      d.  The slow phase of nystagmus is directed toward the affected side

      e.  Amplitude of nystagmus increases with gaze directed toward the unaffected side

42. What is the pathophysiology for the disease process you suspect in this patient?

      a.  Vertebral dissection

      b.  Acute pontine stroke

      c.  Acute infarct of vestibular nuclei

      d.  Canalithiasis

      e.  Acoustic schwannoma

43. What would be the best initial treatment at this time for this patient?

      a.  Begin anticoagulation with heparin

      b.  Referral to neurosurgery for schwannoma resection options

      c.  Nasogastric tube placement to prevent aspiration until further evaluation is complete

      d.  Decrease blood pressure to prevent dissection extension

      e.  Epley maneuver

Questions 44–46

44. Regarding the vestibular sensory organs, which of the following is correct?

      a.  The ampulla is located within the saccule

      b.  The otolithic organs are more sensitive to vertical motion of the head

      c.  The semicircular canals contain otoconia that are involved in detecting motion

      d.  The ampulla is located within the utricle

      e.  The semicircular canals are considered otolithic organs

45. Which of the following is correct regarding the vestibuloocular reflex (VOR) when the head is turned to the right side in a purely horizontal plane, while the eyes are focused directly ahead on an object?

      a.  The right medial rectus would be inhibited

      b.  The left lateral rectus would be activated

      c.  The right superior rectus would be inhibited

      d.  The left superior oblique would be activated

      e.  The right inferior oblique would be activated

46. You are consulted on a comatose 79-year-old man who was found down at home for an unknown amount of time. On the basis of cold calorics, you suspect that he is not brain dead. If the ice water is infused into the left ear canal, which of the following responses would not be expected in a patient with an intact brainstem?

      a.  The left lateral rectus is activated

      b.  There will be tonic deviation of the eyes to the left

      c.  The right lateral rectus is inhibited

      d.  The right medial rectus is activated

      e.  There will be a slow conjugate movement directed to the right

Questions 47–49

47. Which of the following muscles is not innervated by the trigeminal nerve?

      a.  Mylohyoid

      b.  Lateral pterygoid

      c.  Posterior belly of the digastric

      d.  Tensor veli palatini

      e.  Tensor tympani

48. Which of the following muscles is not innervated by the facial nerve?

      a.  Stapedius

      b.  Tensor tympani

      c.  Stylohyoid

      d.  Posterior belly of the digastric

      e.  Buccinator

49. Which of the following muscles is innervated by the glossopharyngeal nerve?

      a.  Mylohyoid

      b.  Stylopharyngeus

      c.  Stylohyoid

      d.  Posterior belly of the digastric

      e.  Tensor veli palatini

Questions 50–54

50. A 39-year-old woman presents to your office with left-sided facial weakness involving the entire left half of the face. Taste is impaired and sound is excessively loud in her left ear. She denies problems with dry or runny eyes. A lesion in which of the following facial nerve locations could explain these symptoms?

      a.  The left facial nerve nucleus

      b.  Between the geniculate ganglion and the stapedius nerve

      c.  Between the chorda tympani and the stylomastoid foramen

      d.  Between the stapedius nerve and the chorda tympani

      e.  Between the facial nerve nucleus and the geniculate ganglion

51. If this patient presented with the same symptoms, except that she only had the left facial weakness and taste impairment, without the hearing complaints mentioned above, where would you expect the lesion to be?

      a.  Between the geniculate ganglia and the stapedius nerve

      b.  The left facial nerve nucleus

      c.  Between the facial nerve nucleus and the geniculate ganglia

      d.  Between the chorda tympani and the stylomastoid foramen

      e.  Between the stapedius nerve and the chorda tympani

52. Which of the following is true regarding the facial nerve and its branches?

      a.  The chorda tympani provides parasympathetic innervation to the nasal glands

      b.  The greater petrosal nerve provides parasympathetic innervation to the lacrimal glands

      c.  Parasympathetic innervation to the lacrimal glands travels in the ophthalmic (V1) branch of the trigeminal nerve

      d.  The chorda tympani provides innervation for taste sensation to the posterior one-third of the tongue

      e.  The pterygopalatine ganglion contains the nerve cell bodies of taste axons for the tongue

53. Which of the following cranial nerve nuclei supplies the parasympathetics to the head and neck?

      a.  Superior salivatory nucleus

      b.  Nucleus ambiguus

      c.  Inferior salivatory nucleus

      d.  Nucleus solitarius

      e.  Dorsal motor nucleus of vagus

54. Which of the following glands are not innervated by the facial nerve?

      a.  Lacrimal glands

      b.  Nasal mucosal glands

      c.  Sublingual glands

      d.  Parotid glands

      e.  Submandibular glands

Questions 55–57

55. Which of the following cranial nerve nuclei is involved in the sensation of taste?

      a.  Superior salivatory nucleus

      b.  Nucleus ambiguus

      c.  Inferior salivatory nucleus

      d.  Nucleus tractus solitarius

      e.  Dorsal motor nucleus of vagus

56. Which of the following cranial nerve nuclei receives the initial afferent signals in the baroreceptor reflex?

      a.  Superior salivatory nucleus

      b.  Nucleus ambiguus

      c.  Inferior salivatory nucleus

      d.  Nucleus tractus solitarius

      e.  Dorsal motor nucleus of vagus

57. Which of the following cranial nerve nuclei innervates the muscles of the pharynx and larynx?

      a.  Superior salivatory nucleus

      b.  Nucleus ambiguus

      c.  Inferior salivatory nucleus

      d.  Nucleus tractus solitarius

      e.  Dorsal motor nucleus of vagus

Questions 58–60

58. A 67-year-old male presents with symptoms suspicious for cavernous sinus thrombosis. Which of the following nerves is not located in the cavernous sinus?

      a.  Mandibular branch of the trigeminal nerve

      b.  Trochlear nerve

      c.  Abducens nerve

      d.  Oculomotor nerve

      e.  Maxillary branch of the trigeminal nerve

59. Regarding the trigeminal nerve, which of the following is correct?

      a.  The maxillary division supplies the skin of the lower lip

      b.  The ophthalmic division innervates the entire cornea

      c.  The mandibular division provides sensory innervation to the upper teeth

      d.  The mandibular division provides tactile sensation to the anterior two-thirds of the tongue

      e.  The trigeminal nerve provides the afferent and efferent limbs of the corneal reflex

60. Regarding the course of the trigeminal nerve from the cranium, which of the following is incorrect?

      a.  The maxillary division exits through the foramen rotundum

      b.  The ophthalmic division exits through the superior orbital fissure

      c.  The ophthalmic and maxillary divisions are the only trigeminal divisions that travel through the cavernous sinus

      d.  The three divisions of the trigeminal nerve arise from the sphenopalatine ganglion

      e.  The mandibular division exits through the foramen ovale

61. Which of the following is true regarding the hypoglossal nerve (cranial nerve XII)?

      a.  A lesion to the hypoglossal nerve causes contralateral tongue deviation on tongue protrusion

      b.  Corticobulbar input to the hypoglossal nucleus is by crossed innervation only

      c.  Each genioglossus muscle pulls the tongue anterior and lateral

      d.  The genioglossus and palatoglossus are the largest hypoglossal-innervated muscles

      e.  If tongue deviation was due to an upper motor neuron lesion, the deviation would be contralateral to the lesion

62. Which of the following is incorrect regarding the accessory nerve?

      a.  A lesion in the corticobulbar fibers affects the ipsilateral sternocleidomastoid (SCM)

      b.  Activation of the accessory nerve causes ipsilateral head rotation

      c.  A lesion in the corticobulbar fibers affects the contralateral trapezius

      d.  Activation of the accessory nerve causes ipsilateral head tilt

      e.  An accessory nerve lesion will cause ipsilateral shoulder drop

63. A 68-year-old man with an extensive history of smoking is hospitalized for aspiration pneumonia. You are consulted for generalized weakness. Besides generalized weakness, you notice that he has a poor gag reflex as well as a slightly lowered left soft palate with mild deviation of the uvula to the right. Which of the following is correct?

      a.  The afferent limb of the gag reflex is mediated by the vagus nerve

      b.  This patient has clinical findings of a left glossopharyngeal nerve lesion

      c.  This patient has clinical findings of a right-sided vagus nerve lesion

      d.  The efferent limb of the gag reflex is mediated by the glossopharyngeal nerve

      e.  The gag reflex is mediated by the nucleus ambiguus

Answer Key

1. d

2. b

3. c

4. c

5. a

6. b

7. e

8. b

9. b

10. e

11. c

12. c

13. b

14. d

15. b

16. d

17. c

18. a

19. d

20. b

21. e

22. d

23. c

24. d

25. e

26. e

27. d

28. b

29. e

30. d

31. a

32. d

33. c

34. d

35. e

36. a

37. c

38. e

39. c

40. b

41. a

42. d

43. e

44. b

45. b

46. e

47. c

48. b

49. b

50. b

51. e

52. b

53. a

54. d

55. d

56. d

57. b

58. a

59. d

60. d

61. e

62. b

63. e

Answers

 1. d, 2. b, 3. c

There are six muscles for each eye: superior oblique, inferior oblique, superior rectus, inferior rectus, medial rectus, and lateral rectus. Each muscle has a primary action and a secondary action (except the medial rectus and lateral rectus, which work only in the horizontal plane). The secondary action of the “superior” muscles is intorsion, whereas that of the “inferior” muscles is extorsion. The primary and secondary actions, respectively, of each muscle are described below:

Superior oblique: Depression/intorsion
Inferior oblique: Elevation/extorsion
Superior rectus: Elevation/intorsion
Inferior rectus: Depression/extorsion
Medial rectus: Adduction
Lateral rectus: Abduction

All extraocular muscles are innervated by the oculomotor nerve except for two: the superior oblique (innervated by the trochlear nerve) and the lateral rectus (innervated by the abducens nerve).

 Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves in Health and Disease, 2nd ed. Ontario: B.C. Decker Inc., 2002.

 4. c, 5. a, 6. b

There are several muscles with varied innervation involved in the resting state of the eyelids, and lesion location will cause different severities of clinical signs. The upper and lower eyelids open and close due to facial nerve innervation of the orbicularis oculi. The levator palpebrae superioris helps with opening of the upper eyelid and is innervated by the oculomotor nerve. Müller’s muscle arises from the undersurface of the levator palpebrae superioris, and has sympathetic innervation, contributing to 1 to 2 mm of upper eyelid elevation. The sympathetics also innervate the superior and inferior tarsal muscles that contribute to slight upper eyelid elevation and lower eyelid depression, respectively. Due to the sympathetic innervation of the eyelid muscles, slight over-elevation of the eyelid may be seen in high sympathetic states (such as fear), and subtle ptosis may be seen in low sympathetic states (such as fatigue). In normal patients, the upper eyelid should cover the superior 1 to 1.5 mm of the limbus (junction of the sclera with the cornea), and the lower eyelid should lie at the inferior limbus.

This patient has a left-sided Horner’s syndrome due to reduced sympathetic innervation to the left eye. This patient likely has a left internal carotid dissection that has affected the sympathetic fibers running along it. Horner’s syndrome is characterized by ptosis of the upper eyelid (due to impaired superior tarsal and Müller’s muscles, which normally contribute to upper eyelid elevation and unopposed orbicularis oculi action), slight elevation of the lower eyelid (due to impaired inferior tarsal function, which normally contributes to lower eyelid depression), pupillary miosis (impaired pupillodilator function) and facial anhidrosis (if dissection (or other lesion) extends proximal to the region of the carotid bifurcation, because sweating fibers travel primarily with ECA), and enophthalmos (appearance of enophthalmos from decrease in palpebral fissure).

 Beard C. Müller’s superior tarsal muscle: Anatomy, physiology, and clinical significance. Ann Plast Surg. 1985; 14:324–333.

 Biousse V, Touboul PJ, D’Anglejan-Chatillon J, et al. Ophthalmologic manifestations of internal carotid artery dissection. Am J Ophthalmol. 1998; 126(4):565–577.

 7. e, 8. b, 9. b, 10. e

This patient has a classic Horner’s syndrome. The sympathetic pathway to the eye is a three-neuron pathway. Horner’s syndrome can result from a lesion anywhere along this pathway. The first-order neurons (central neurons) originate in the posterior hypothalamus (not thalamus) and descend through the brainstem to the first synapse, located in the lower cervical and upper thoracic spinal cord (levels C8 to T2). This spinal segment is called the ciliospinal center of Budge. The second-order neurons (preganglionic neurons) exit the spinal cord, travel across the apex of the lung, under the subclavian artery, and ascend the neck and synapse in the superior cervical ganglion, near the bifurcation of the carotid artery at the level of the angle of the mandible. The third-order neurons (postganglionic neurons) travel with the branches of the carotid artery. The vasomotor and sweat fibers branch off at the superior cervical ganglion near the level of the carotid bifurcation and travel to the face with the ECA. The oculosympathetic fibers continue with the ICA, through the cavernous sinus to the orbit, where they then travel with the ophthalmic (V1) division of the trigeminal nerve to their destinations. These pathways are illustrated in Figure 1.6.

FIGURE 1.6 Sympathetic innervation to the eye. ECA; ICA. Illustration by Joseph Kanasz, BFA. Reprinted with permission of the Cleveland Clinic Center for Medical Art and Photography. © 2010. All rights reserved. Shown also in color plates

Differentiation between causes of Horner’s syndrome can be difficult and depends on location along the pathway. In general, a lesion to the first-order neurons (central neurons) will be associated to brainstem or other focal neurologic findings from a central lesion. A second-order (preganglionic) lesion is often associated with lesions of the neck, mediastinum, or lung apex. A third-order (postganglionic) lesion is often associated with pain or headache, caused by conditions such as a skull base tumor, or carotid dissection. Cocaine 4% or 10% eye drops are sometimes used for confirmation of a Horner’s syndrome. Cocaine blocks the reuptake of norepinephrine released at the neuromuscular junction of the iris dilator muscle, allowing more local availability of norepinephrine. Following instillation of cocaine, the sympathetically denervated eye will not respond and the anisocoria will become more pronounced. (The Horner’s pupil will not change, but the unaffected pupil will become more dilated.) Therefore, in this patient, this test will only confirm the sympathetic denervation and the presence of a Horner’s syndrome, but will not further localize it. Hydroxyamphetamine 1% eye drops will differentiate between a lesion affecting the first- or second-order neurons from a third-order neuron. There is no pharmacologic test to distinguish between a first- and second-order lesion. Hydroxyamphetamine causes release of stored norepinephrine in the third-order neurons. Following instillation, if the Horner’s pupil dilates, the lesion is either first- orsecond order. If the Horner’s pupil does not dilate, there is a third-order lesion. This correlates with the finding of anhidrosis on the right face in this patient, consistent with a first- or second-order neuron lesion.

 Kardon R. Anatomy and physiology of the autonomic nervous system. In: Walsh and Hoyt Clinical Neuro-ophthalmology, 6th ed, Miller NR, Newman NJ, Biousse V, Kerrison JB (Eds), Baltimore, MD: Williams & Wilkins; 2005; 649–712.

 Kardon RH, Denison CE, Brown CK, Thompson HS. Critical evaluation of the cocaine test in the diagnosis of Horner’s syndrome. Arch Ophthalmol. 1990; 108:384–387.

 Maloney WF, Younge BR, Moyer NJ. Evaluation of the causes and accuracy of pharmacologic localization in Horner’s syndrome. Am J Ophthalmol. 1980; 90:394–402.

11. c, 12. c, 13. b, 14. d

Using the findings, this patient most likely has a diabetic cranial nerve palsy involving the oculomotor nerve. A complete pupil-sparing oculomotor nerve palsy without other neurologic findings is most often caused by ischemia to the oculomotor nerve. This is frequently associated with diabetes, especially in the setting of other vascular risk factors. The pupil sparing in diabetic oculomotor nerve palsies is explained on the basis of the anatomy of the nerve itself. The pupillomotor fibers travel along the peripheral aspects of the oculomotor nerve, whereas the somatic fibers to the muscles innervated by the oculomotor nerve travel centrally. The terminal branches of the arterial supply to the nerve are most affected by microvascular changes from diabetes and other risk factors as the vessels decrease in diameter from the periphery of the nerve to the central regions. Therefore, the supply to the periphery of the nerve (where the pupillomotor fibers reside) is spared, whereas the central fibers are affected. Compressive lesions (such as PCA aneurysms) typically affect the peripheral pupillomotor fibers, leading to pupil dilatation with poor response to light (although rarely there may be some pupil sparing).

At the level of the superior colliculus in the dorsal midbrain, there are paired and separate oculomotor subnuclei for the inferior rectus, medial rectus, and inferior oblique—all providing ipsilateral innervation. It is rare for these muscles to be affected in isolation from central lesions without nearby subnuclei also being affected. There is a paired superior rectus subnucleus that provides contralateral innervation. There are paired midline Edinger–Westphal subnuclei providing parasympathetic innervation to the iris sphincters and ciliary muscles. There is also a midline subnucleus providing innervation to both levator palpebrae superioris muscles. Therefore, a lesion to this single midline nucleus can cause bilateral ptosis; it would be rare to affect only this nucleus without affecting nearby structures, so other clinical findings are expected to be present.

The optic pathways are illustrated in Figure 1.7. Afferent neurons beginning in retinal ganglion cells (carrying signals from light stimulation) travel through the optic nerve to the optic chiasm where decussation occurs. Nasal retinal fibers (carrying information from temporal fields) decussate at the chiasm and travel in the contralateral optic tract. Temporal retinal fibers (carrying information from nasal fields) travel ipsilaterally in the optic tract. In the optic tracts, some neurons project to the ipsilateral lateral geniculate body (for vision) and a few leave the optic tract, ipsilaterally enter the brachium of the superior colliculus, and synapse in the ipsilateral pretectal nuclei (for pupillary response). Therefore, each pretectal nucleus receives light input from the contralateral visual hemifield. From each pretectal nucleus, the afferent fibers travel via interneurons and synapse ipsilaterally and contralaterally in the Edinger–Westphal nuclei, respectively, completing the afferent arm. From the Edinger–Westphal nucleus, efferent preganglionic parasympathetic fibers travel concurrently through the bilateral oculomotor nerves to the ciliary ganglia, which innervate the iris sphincter muscles and the ciliary muscles, resulting in pupillary constriction and ciliary muscle activation that leads to accommodation (for near vision) from increased curvature of the lens.

FIGURE 1.7 Pupillary light reflex. Periaqueductal gray (PAG). Illustration by Joseph Kanasz, BFA. Reprinted with permission of the Cleveland Clinic Center for Medical Art and Photography. © 2010. All rights reserved. Shown also in color plates

Myasthenia gravis would present more often with bilateral fatigable ptosis. Neoplastic infiltration would be a slower process. Brainstem infarct would have additional neurologic features.

 Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology, 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007.

 Leigh RJ, Zee DS. The Neurology of Eye Movements, 3rd ed. New York, NY: Oxford University Press; 2006.

 Sanders S, Kawasaki A, Purvin VA. Patterns of extra-ocular muscle weakness in vasculopathic pupil-sparing, incomplete, third nerve palsies. J Neuroophthalmol. 2001; 21:256–259.

 Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves in Health and Disease, 2nd ed. Ontario: BC Decker Inc; 2002.

15. b, 16. d, 17. c

This patient has a left trochlear nerve palsy (cranial nerve IV). This nerve is the only cranial nerve that exits dorsally from the brainstem. Of note, the trochlear nerves decussate just before they exit dorsally at the level of the inferior colliculi of the midbrain. Therefore, motor neurons from each trochlear nucleus innervate the contralateral superior oblique muscle. After exiting, the trochlear nerve curves ventrally around the cerebral peduncle and passes between the posterior cerebral and superior cerebellar arteries, lateral to the oculomotor nerve. Although it is the smallest nerve, the trochlear nerve has the longest intracranial course due to this dorsal exit, making it more prone to injury, as seen in this patient. The trochlear nerve innervates the superior oblique muscle, which allows for depression and intorsion of the eye, especially when the eye is adducted.

Patients with trochlear nerve palsies may complain of vertical diplopia and/or tilting of objects (torsional diplopia). Because of loss of intorsion and depression from the superior oblique muscle, the affected eye is usually extorted and elevated due to unopposed action of its antagonist, the inferior oblique. Objects viewed in primary position or downgaze may appear double (classically, when going down a flight of stairs). Symptoms of diplopia often improve with head tilting to the contralateral side of the lesion, and the patient adapts to this primary head position to avoid the diplopia. In this patient, vertical and torsional diplopia due to her left trochlear nerve palsy improve with the head tilted toward the right and with the head slightly flexed (chin downward). This occurs because the left eye is in a slightly extorted and elevated position in primary gaze due to the lesion. On tilting right, the right eye must intort, and when it matches the same degree that the left eye is extorted, the diplopia improves.

 Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology, 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007.

 Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves in Health and Disease, 2nd ed. Ontario: BC Decker Inc; 2002.

18. a, 19. d

This patient has a right oculomotor nerve palsy (cranial nerve III) in the classic “down and out” position. Aneurysms involving all the choices except the posteroinferior cerebellar artery (PICA) are the most likely to cause a complete oculomotor nerve palsy with pupillary involvement. The oculomotor nerve and nucleus are discussed in questions 11 to 14. Briefly to review, the oculomotor nerve supplies the levator palpebrae superioris muscles of the eyelid (single central nucleus controls both sides) and four extraocular muscles: medial rectus (ipsilateral nucleus), superior rectus (contralateral nucleus), inferior rectus (ipsilateral nucleus), and inferior oblique (ipsilateral nucleus). The actions of these muscles are discussed in questions 1 to 3, and paresis of the levator palpebrae leads to ptosis. In the setting of an oculomotor palsy, the unopposed actions of the nonparetic muscles innervated by the trochlear and abducens nerve lead to the “down and out” position in primary gaze (as shown in Figure 1.2). The oculomotor nerve also carries the parasympathetic fibers from the Edinger–Westfall nucleus that supply the ciliary muscle and the iris sphincter as detailed in questions 11 to 14. After exiting the brainstem and entering the subarachnoid space, the oculomotor nerve passes between the posterior cerebral and superior cerebellar arteries (near the basilar tip), in proximity to the posterior communicating artery, as well as the uncus of the temporal lobe. Therefore, aneurysms in any of these arteries could potentially cause a compressive lesion of the oculomotor nerve. Uncal herniation also is a classic cause of third nerve palsy, although the patient is often comatose by the time this would occur. As compression occurs, the parasympathetics are often first involved given their peripheral distribution in the nerve, as discussed in question 11.

 Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology, 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007.

 Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves in Health and Disease, 2nd ed. Ontario: BC Decker Inc; 2002.

20. b, 21. e, 22. d

In question 20, this patient has a left internuclear ophthalmoplegia (INO) resulting from a left MLF lesion. INO is characterized by impaired adduction of the affected side and nystagmus of the abducting contralateral eye (the normal side).

The pathways mediating horizontal eye movements are illustrated in Figure 1.8. The PPRF is also known as the conjugate gaze center for horizontal eye movements. The PPRF receives contralateral cortical input. Normally, on horizontal eye movement initiated by the contralateral premotor frontal cortex, the PPRF activates the ipsilateral abducens nerve and, thus, the ipsilateral lateral rectus muscle. From the activated ipsilateral abducens nerve, fibers cross the midline, enter into the contralateral MLF, and activate the contralateral medial rectus subnucleus of the oculomotor complex and, thus, the contralateral medial rectus muscle. The end result is a finely coordinated gaze deviation to one side, with abduction of one eye and adduction of the other.

FIGURE 1.8 Pathways of horizontal gaze. MLF, medial longitudinal fasciculus; PPRF, paramedian pontine reticular formation. Illustration by Joseph Kanasz, BFA. Reprinted with permission of the Cleveland Clinic Center for Medical Art and Photography. © 2010. All rights reserved. Shown also in color plates

An INO results from a lesion in the MLF, ipsilateral to the impaired adducting eye, as it runs through the pons or midbrain tegmentum. Patients may complain of horizontal diplopia on lateral gaze, which is not usually present in primary gaze. The classic findings include impaired adduction on lateral gaze (the side of the affected MLF), with nystagmus in the contralateral abducting eye. Slowing of the adducting eye may be a sign of a partial INO, as can be detected on optokinetic nystagmus testing.

There are some important variations of INO. A bilateral INO, due to bilateral MLF lesions, will cause exotropia of both eyes and is known as “wall-eyed bilateral INO” (WEBINO), as depicted in question 21. A lesion to both the ipsilateral abducens nucleus or PPRF and ipsilateral MLF results in loss of all horizontal eye movements on that side, and abduction of the contralateral eye is the only lateral eye movement retained (which is also typically associated with abduction nystagmus). This finding is known as the “one-and-a-half syndrome” and is described in question 22.

 Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology, 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007.

 Frohman EM, Frohman TC, Zee DS, et al. The neuro-ophthalmology of multiple sclerosis. Lancet Neurol. 2005; 4:111–121.

23. c

The abducens nerve (cranial nerve VI) is prone to a stretching injury, especially as it passes over the petrous ridge, and is the most likely nerve to be involved with elevated intracranial pressure. An abducens nerve palsy due to elevated intracranial pressure is often bilateral and is termed a “false localizing sign” because this long cranial nerve could be affected anywhere along its path, and does not necessarily reflect a specific central lesion. The action of the abducens nerve is purely abduction of the eye due to its innervation of the lateral rectus muscle.

 Patel SV, Mutyala S, Leske DA, et al. Incidence, associations, and evaluation of sixth nerve palsy using a population-based method. Ophthalmology. 2004; 111(2):369–375.

24. d, 25. e

This patient has an idiopathic tonic (Adie’s) pupil. It is thought to result from a lesion in the postganglionic parasympathetic pathway to either the ciliary ganglion or the short ciliary nerves and is most often attributed to viral etiology, although evidence is lacking. Acutely, there is unilateral mydriasis and the pupil does not constrict to light or accommodation because the iris sphincter and ciliary muscle are paralyzed. Sectoral palsy of part of the iris sphincter may be involved, and is considered the earliest and most specific feature. Patients often complain of photophobia, visual blurring, and ache in the orbit. Within a few days to weeks, denervation supersensitivity to cholinergic agonists develops and this is most often tested with low-concentration pilocarpine 0.125%, in which the tonic pupil will constrict but the normal pupil is unaffected by the low concentration. Eventually, slow, sustained constriction to accommodation and slow redilation after near constriction occur, and the baseline pupil decreases slightly in size (in ambient light), whereas the other features remain. In general, the chronic stage is characterized by the pupillary light reflex rarely improving, whereas the accommodation reflex does improve, although it often remains slower (tonic). This is termed “light-near dissociation.” It is sometimes associated with diminished or absent deep tendon reflexes and this is referred to as “Holmes–Adie syndrome,” or Adie’s syndrome.

Argyll–Robertson pupils are classically associated with neurosyphilis. They are characterized by bilateral irregular miosis with little to no constriction to light, but constriction to accommodation without a tonic response as opposed to Addie’s pupil. Optic neuritis would be associated with a relative afferent pupil defect. An aneurysm would likely have more oculomotor involvement (although not necessarily). Diabetic oculomotor neuropathy is classically associated with pupil sparing, although the appearance of Argyll–Robertson pupils can occur as well.

 Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology, 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007.

 Loewenfeld IE, Thompson HS. Mechanism of tonic pupil. Ann Neurol. 1981; 10(3):275–276.

 Thompson HS, Kardon RH. The Argyll Roberson pupil. J Neuroophthalmol. 2006; 26(2):134–138.

26. e, 27. d, 28. b

This finding is called a relative afferent pupillary defect (RAPD), also known as a Marcus Gunn pupil, and is most commonly caused by a lesion anywhere from the optic nerve to the optic chiasm. In general, retrochiasmal lesions do not cause a pure RAPD. However, a RAPD combined with contralateral hemianopia secondary to an optic tract lesion may occur infrequently. Retinal lesions, refractive errors, amblyopia, and disease of the lens, cornea, and retina do not cause RAPD, although rarely, severe macular disease has been associated with RAPD. The pathway of the pupillary light reflex is discussed in detail in questions 11 to 14. RAPD is frequently seen in optic neuritis. A lesion to the lateral geniculate body would cause a homonymous hemianopia. This structure is involved in vision and not in pupillary responses.

This patient’s fundoscopic examination reveals optic nerve edema consistent with optic neuritis. Optic neuritis develops over hours to days and is associated with symptoms of reduced color perception (especially red, called red desaturation), reduced visual acuity (especially central vision), visual loss, eye pain, and photopsias. Only one-third of patients have papillitis with hyperemia and swelling of the disc, blurring of disc margins, and distended veins. The rest of cases have only retrobulbar involvement, and therefore, have a normal fundoscopic examination.

The Optic Neuritis Treatment Trial (ONTT) randomized patients to one of three groups: oral prednisone for 14 days with a 4-day taper versus intravenous methylprednisolone followed by oral prednisone for 11 days with a 4-day taper versus oral placebo for 14 days. The intravenous methylprednisolone group showed faster visual recovery, but at 1 year, visual outcomes were similar. The intravenous methylprednisolone group also had a reduced risk of conversion to multiple sclerosis (MS) within the first 2 years compared with the other groups. At 5 years, there were no differences in the rates of multiple sclerosis between treatment groups though. Interestingly, only the oral prednisone group was found to have a higher 2-year risk of recurrent optic neuritis compared to both the intravenous methylprednisolone and placebo groups. At 10 years, the risk of recurrent optic neuritis was still higher in the oral prednisone group when compared with the intravenous methylprednisolone group, but not the placebo groups.

Papilledema is not present in this fundoscopic examination. An early finding in papilledema is loss of spontaneous venous pulsations, although the absence of spontaneous venous pulsations can also be a normal variant. Disc margin splinter hemorrhages may be seen early also. Eventually, the disc becomes elevated, the cup is lost, and disc margins become indistinct. Blood vessels appear buried as they course the disc. Engorgement of retinal veins lead to a hyperemic disc. As the edema progresses, the optic nerve head appears enlarged and may be associated with flame hemorrhages and cotton wool spots, as a result of nerve fiber infarction. Anterior ischemic optic neuropathy (AION) is discussed in later questions. In giant cell arteritis (GCA), the optic disc is more often pallid, rather than hyperemic.

 Beck RW, Cleary PA, Anderson MM Jr, et al. A randomized, controlled trial of corticosteroids in the treatment of acute optic neuritis. The Optic Neuritis Study Group. N Engl J Med. 1992; 326:581–588.

 The Optic Neuritis Study Group. The 5-year risk of MS after optic neuritis. Experience of the Optic Neuritis Treatment Trial. Optic Neuritis Study Group. Neurology. 1997; 49:1404–1413.

29. e

This patient has anterior ischemic optic neuropathy (AION). AION is considered to be the most common optic nerve disorder in patients older than age 50. It can also affect the retrobulbar optic nerve in isolation, in which case it is termed posterior ischemic optic neuropathy (diagnosis of exclusion). Patients often have risk factors for cardiovascular and cerebrovascular diseases, such as diabetes and hypertension. AION is a result of ischemic insult to the optic nerve head. Clinically, it presents with acute, unilateral, usually painless visual loss, although 10% of patients may have pain that can be confused with optic neuritis. Fundoscopic examination shows optic disc edema (unless retrobulbar), hyperemia with splinter hemorrhages, and crowded and cupless disc.

The painless vision loss is one key feature in differentiating AION from optic neuritis, which is often associated with painful eye movements. Optic neuritis is discussed in question 26. In addition, optic neuritis presents more often in younger (especially female) patients and may be associated with disc edema (but not always), but without splinter hemorrhages. In contrast to giant cell arteritis (GCA), the optic disc edema in AION is more often hyperemic rather than pallid, as would be more common in GCA. Papilledema is not present in this fundoscopic examination and is discussed in question 26.

 Hayreh SS, Zimmerman MB. Nonarteritic anterior ischemic optic neuropathy: Natural history of visual outcome. Ophthalmology. 2008; 115:298–305.

 Rucker JC, Biousse V, Newman NJ. Ischemic optic neuropathies. Curr Opin Neurol. 2004; 17:27–35.

30. d, 31. a

The visual pathways are illustrated in Figure 1.9. A right homonymous hemianopia could be caused by a left lateral geniculate body lesion, and a left upper quadrantanopsia could be caused by a lesion to the right lower bank of the calcarine cortex. A homonymous hemianopia is caused by lesions of the retrochiasmal visual pathways that consist of the optic tract, lateral geniculate nucleus, optic radiations, and the cerebral visual (calcarine, occipital) cortex. At the optic chiasm, the retinal ganglion afferents from the temporal retina (nasal visual field) continue in the ipsilateral lateral optic chiasm and pass into the ipsilateral optic tract, whereas the retinal ganglion afferents from the nasal retina (temporal visual field) decussate in the optic chiasm and continue into the contralateral optic tract. Therefore, beyond the optic chiasm, each optic tract contains crossed and uncrossed nerve fibers relaying visual information from the contralateral visual field. The optic tracts continue to the lateral geniculate body. Beyond the lateral geniculate body, the optic radiations continue carrying the visual information from the contralateral visual field to the primary visual cortex in the occipital lobe. The superior fibers of the optic radiations carry information from the inferior visual field as they pass through the parietal lobe. The inferior fibers of the optic radiations carry information from the superior visual field as they pass through the temporal lobe, forming Meyer’s loop. When this visual information reaches the visual cortex, the upper bank of the calcarine cortex receives projections representing the inferior visual field, whereas the lower bank of the calcarine cortex receives information representing the superior visual field.

FIGURE 1.9 Visual pathways. Illustration by Joseph Kanasz, BFA. Reprinted with permission of the Cleveland Clinic Center for Medical Art and Photography. © 2010. All rights reserved. Shown also in color plates

 Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology, 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007.

32. d

The fundoscopic examination reveals optic nerve atrophy, consistent with a long-standing history of multiple sclerosis. The other choices are described in questions 26 and 29. Signs of chronic optic neuritis include persistent visual loss, color desaturation (especially red), and possibly a persistent relative afferent pupillary defect. Optic atrophy occurs and the disc appears shrunken and pale, especially in the temporal half, and this pallor extends beyond the margins of the disc.

 Bradley WG, Daroff RB, Fenichel GM, Jankovic J. Neurology in Clinical Practice, 5th ed. Philadelphia, PA: Elsevier; 2008.

 Ropper AH, Samuels MA. Adams and Victor’s Principles of Neurology, 9th ed. New York, NY: McGraw-Hill; 2009.

33. c

This patient has mucormycosis involving the cavernous sinus and posterior orbits. This can occur in poorly controlled diabetes. It causes proptosis, visual blurring, and unilateral or bilateral cavernous sinus syndrome (combination of III, IV, VI, V2 and VI cranial nerve involvement), and visual acuity may also be impaired. The contents of the cavernous sinus are illustrated in Figure 1.10. A chronic meningitis would not cause proptosis. A midbrain infarction could cause third and fourth nerve palsies, but would not cause facial numbness or visual blurring. A third nerve palsy would not present in this fashion. Idiopathic cranial polyneuropathy is a diagnosis of exclusion and would not cause proptosis.

FIGURE 1.10 Cavernous sinus. Illustration by Ross Papalardo, BFA. Reprinted with permission of the Cleveland Clinic Center for Medical Art and Photography. © 2010. All rights reserved. Shown also in color plates

 Bradley WG, Daroff RB, Fenichel GM, Jankovic J. Neurology in Clinical Practice, 5th ed. Philadelphia, PA: Elsevier; 2008.

 Ropper AH, Samuels MA. Adams and Victor’s Principles of Neurology, 9th ed. New York, NY: McGraw-Hill; 2009.

34. d, 35. e, 36. a

This patient most likely has Bell’s palsy. No testing is necessary at this time and steroids should be initiated. “Bell’s palsy” is the term often used for an acute peripheral facial nerve palsy of unknown cause. It is frequently seen in the third trimester of pregnancy or in the first postpartum week and is also seen in patients with diabetes. A herpes simplex–mediated viral inflammatory mechanism has been proposed as a controversial etiology. Other common viruses have also been associated with Bell’s palsy, including varicella-zoster virus as in Ramsay–Hunt syndrome. Ischemia of the facial nerve has also been suggested, especially in patients with diabetes.

Patients with Bell’s palsy typically present with relatively abrupt onset of unilateral facial paralysis, which often includes difficulty closing the eye, drooping eyebrow, mouth droop with loss of nasolabial fold, loss of taste sensation on the anterior two-thirds of the tongue (in distribution of facial nerve), decreased tearing, and hyperacusis. Patients may complain of discomfort behind or around the ear prior to symptom onset. There may also be a history of recent upper respiratory infection. It is important to differentiate between a peripheral and central (upper motor neuron) lesion. Sparing of the forehead muscles suggests a central lesion because of bilateral innervation to the facial subnuclei innervating the forehead, as opposed to unilateral facial subnucleus innervation of the ipsilateral lower face (below the eye). However, a lesion to the facial nerve nucleus itself in the pons can lead to complete facial paralysis (of both the upper and lower face). Bell’s palsy should classically involve only the facial nerve, although additional cranial nerve involvement has been infrequently reported, including the trigeminal, glossopharyngeal, and hypoglossal nerves. Some studies have reported ipsilateral facial sensory impairment suggesting trigeminal neuropathy, although this sensation has often been attributed to abnormal perception on the basis of “droopy” facial muscles.

Diagnostic studies are not necessary in all patients. Those with a typical history and examination consistent with Bell’s palsy do not need further studies initially. Imaging should be considered if there is slow progression beyond 3 weeks, if the physical signs are atypical, or if there is no improvement at 6 months. If imaging is pursued, an MRI with and without gadolinium is optimal. Electrodiagnostic studies may be considered in patients with clinically complete lesions for prognostic purposes if they do not improve. If the history suggests an alternate etiology, evaluation should be targeted as such. A pontine stroke would be unlikely to affect only the facial nerve nucleus without affecting surrounding structures; hemiparesis contralateral to the facial nerve palsy would suggest involvement of corticospinal structures, as in Millard–Gubler syndrome (see Chapter 2), and ipsilateral impairment of eye abduction would suggest involvement of the ipsilateral cranial nerve VI nucleus, as in Foville’s syndrome (see Chapter 2). These additional focal symptoms should prompt investigation for pontine infarct. This patient did not have a history or symptoms consistent with Lyme disease or multiple sclerosis. Multiple sclerosis would be highly suspected in a young patient with bilateral Bell’s palsy, although Lyme disease and sarcoidosis would also be in the differential. A cholesteatoma would present with a much slower onset.

Treatment of Bell’s palsy has been controversial. In general, early treatment with oral glucocorticoids for all patients with Bell’s palsy is recommended and optimal treatment should begin within 3 days of symptom onset. There have been two large clinical trials showing no significant benefit for antiviral therapy, so its use is controversial. Some feel that the addition of antivirals to glucocorticoids is beneficial anecdotally, especially in those with severe facial palsy and suggest early combined prednisone (60 to 80 mg per day) plus valacyclovir (1000 mg three times daily) for 1 week in these patients. Artificial tears and eye patches should also be used for eye protection when needed. Nerve stimulation and surgical decompression are not routinely recommended on the basis of current evidence.

Prognosis of Bell’s palsy depends on severity of the lesion, and in general, clinically incomplete lesions tend to recover better than complete lesions. In addition, the prognosis is favorable if some recovery is seen within the first 21 days of onset.

 Bradley WG, Daroff RB, Fenichel GM, Jankovic J. Neurology in Clinical Practice, 5th ed. Philadelphia, PA: Elsevier; 2008.

 Engstrom M, Berg T, Stjernquist-Desatnik A, et al. Prednisolone and valaciclovir in Bell’s palsy: A randomised, double-blind, placebo-controlled, multicentre trial. Lancet Neurol. 2008; 7:993–1000.

 Grogan PM, Gronseth GS. Practice parameter: Steroids, acyclovir, and surgery for Bell’s palsy (an evidence-based review): Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 2001; 10;56(7):830–836.

 Sullivan FM, Swan IR, Donnan PT, et al. Early treatment with prednisolone or acyclovir in Bell’s palsy. N Engl J Med. 2007; 357:1598–1607.

37. c

The olfactory nerve is the only nerve listed that does not have a synapse in the thalamus prior to traveling to the cortex. Afferents for all sensory modalities, except for the olfactory nerve, have a synapse in the thalamus prior to terminating in the cortex. From the olfactory bulb, secondary neurons project directly to the olfactory cortex and then have direct connections to the limbic area. The limbic area plays a role in memory formation and this explains why some smells provoke specific emotions and memories. The olfactory cortex has connections with autonomic and visceral centers, including the hypothalamus, thalamus, and amygdala. This may explain why some smells can cause changes in gut motility, nausea, and vomiting. The facial nerve has autonomic fibers descending from the thalamus to the superior salivatory nucleus. It also has sensory afferents for taste that travel to the ventral postero-medial (VPM) nucleus of the thalamus and subsequently to the cortex.

 Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves in Health and Disease, 2nd ed. Ontario: BC Decker Inc; 2002.

38. e

This phenomenon is called “crocodile tears”, and results when misdirected regenerating facial nerve axons originally supplying the submandibular and sublingual salivary glands innervate the lacrimal gland through the greater petrosal nerve. This results in abnormal unilateral lacrimation when eating. In addition, some axons from the motor neurons to the labial muscles involved in smiling may regenerate and misdirect to the orbicularis oculi, which results in closure of the eye on smiling. This phenomenon is termed synkinesis. The reverse may also occur and result in twitching of the mouth on blinking.

 Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves in Health and Disease, 2nd ed. Ontario: BC Decker Inc; 2002.

39. c, 40. b, 41. a, 42. d, 43. e

A provoking maneuver should be done to evaluate for benign paroxysmal positional vertigo (BPPV) in patients such as this with a typical history. History and examination are less consistent for acute stroke, vertebral dissection or a slow-growing acoustic schwannoma. BPPV is most commonly attributed to calcium debris in a semicircular canal (canalithiasis) and most commonly occurs in the posterior canal. This debris likely represents loose otoconia made up of calcium carbonate crystals within the utricular sac that have migrated into the semicircular canal. The Dix–Hallpike maneuver is most commonly done for this reason and is performed as follows. With the patient sitting, the neck is extended and turned to one side. The patient is then rapidly brought back to a supine position, so that the head hangs over the edge of the bed. This position is kept until 30 seconds have passed if no nystagmus occurs. The patient is then returned to a sitting position and observed for another 30 seconds for nystagmus. Then the maneuver is repeated with the head turned to the other side. This maneuver is most useful for diagnosing posterior canal BPPV (the most common form), and the nystagmus is usually characterized by beating upward and torsionally. After it stops and the patient is sitting again, the nystagmus may occur in the opposite direction (reversal). Besides posterior BPPV, there are three other types of BPPV, including anterior canal, horizontal canal, and pure torsional BPPV. Anterior canal BPPV (superior canal BPPV) has similar provoking factors as posterior canal BPPV, but the nystagmus is downbeat and torsional. Horizontal canal BPPV is provoked by turning the head while lying down and sometimes by turning it in the upright position, but not by getting in or out of bed or extending the neck. Therefore, the nystagmus is elicited by a lateral head turn in the supine position, rather than with the head extended over the edge of the bed, and is characterized by horizontal nystagmus beating toward the floor after turning the affected ear down. The nystagmus lasts less than 1 minute, pauses for a few seconds, and then a reversal of the nystagmus is seen. Pure torsional nystagmus may mimic a central lesion, and results from canalithiasis, simultaneously involving both the anterior and posterior canals, though is less common. This form of BPPV tends to persist longer than other forms of BPPV.

Absence of nystagmus latency would be suggestive of a central lesion. Central nystagmus has the following characteristics: nonfatiguing, absent latency (onset of nystagmus immediately after provocative maneuver), not suppressed by visual fixation, duration of nystagmus is greater than 1 minute, and may occur in any direction. Although purely torsional or vertical nystagmus is classically central in origin, pure torsional BPPV may mimic central nystagmus. Central vertigo is usually subjectively less severe than peripheral vertigo, but gait impairment, falls, and unsteadiness are much more pronounced and other neurologic signs often coexist. Hearing changes and tinnitus are usually absent. Peripheral nystagmus is characterized by fatigability with repetition, latency typically of 2 to 20 seconds, suppression by visual fixation, duration of nystagmus less than 1 minute, unidirectional, and usually horizontal, occasionally with a torsional component. Walking is typically preserved, although unilateral instability may exist. Hearing changes and tinnitus are more common with peripheral lesions.

A unilateral peripheral vestibular lesion, such as in BPPV, leads to an asymmetry in vestibular activity. This results in a slow drift of the eyes away from the target in one direction (toward the affected side and away from the unaffected side), followed by a fast cortical corrective movement to the opposite side (toward the unaffected side, away from the affected side). The amplitude of nystagmus increases with gaze toward the side of the fast phase (toward the unaffected ear and away from the affected ear), and this is known as Alexander’s law. As above, peripheral nystagmus is suppressed by visual fixation and this helps differentiate it from central nystagmus.

Initial treatment of BPPV is symptomatic and should begin with a particle-repositioning maneuver, consisting of a sequence of head and body repositioning with the goal of moving the debris from the semicircular canal back into the utricular cavity. The most commonly used is the Epley maneuver, or modified Epley maneuver, although other variations exist. These specific sequences are beyond the scope of this discussion. The Epley maneuver is most efficacious for posterior canal repositioning, whereas anterior and horizontal canal repositioning often require different maneuvers. Self-treatment exercises should be given for the patient to use at home. Postmaneuver activity restrictions, such as use of a cervical collar and maintenance of an upright head position for 2 days after treatment, had previously been recommended to prevent return of particles into the semicircular canal. Recent studies have shown no significant benefit from postmaneuver activity restrictions, or the use of meclizine.

 Bradley WG, Daroff RB, Fenichel GM, Jankovic J. Neurology in Clinical Practice, 5th ed. Philadelphia, PA: Elsevier; 2008.

 De la Meilleure G, Dehaene I, Depondt M, et al. Benign paroxysmal positional vertigo of the horizontal canal. J Neurol Neurosurg Psychiatry. 1996; 60:68–71.

 Imai T, Takeda N, Uno A, et al. Three-dimensional eye rotation axis analysis of benign paroxysmal positioning nystagmus. ORL J Otorhinolaryngol Relat Spec. 2002; 64:417–423.

 Korres S, Riga M, Balatsouras D, Sandris V. Benign paroxysmal positional vertigo of the anterior semicircular canal: Atypical clinical findings and possible underlying mechanisms. Int J Audiol. 2008; 47:276–282.

 Oas JG. Benign paroxysmal positional vertigo: A clinician’s perspective. Ann NY Acad Sci. 2001; 942:201–209.

44. b, 45. b, 46. e

The vestibular sensory organs consist of the otolithic organs and semicircular canals. The otolithic organs are the saccule and utricle, and these two organs are expansions of the membranous labyrinth. Within each of these organs there is a macula, which is a layer of hair cells overlain by a heavy gelatinous otolithic membrane covered by calcium carbonate particles (the otoconia). During linear acceleration of the head, the head moves relative to the otoconia. This results in bending of the hair cells and a subsequent change in neuronal activation. The otolithic organs detect linear and vertical motions of the head relative to gravity.

There are three semicircular canals within each vestibular apparatus on each side, oriented at right angles to each other. These are tubes of membranous labyrinth extending from each utricle. Therefore, there are two horizontal canals, two vertically directed anterior canals, and two vertically directed posterior canals. The semicircular canals contain endolymph and an ampulla. Each ampulla contains sensory hair cells, which are embedded in a gelatinous cap termed the cupula, and does not contain otoconia. During head rotation, inertia causes the endolymph to lag behind and push on the cupula. Similar to the otolithic organs, this bends the hair cells and causes neuronal activation. The semicircular canals are more sensitive to angular motions of the head.

Information regarding head movement is transmitted to the ocular motor nuclei, resulting in eye movement in an equal and opposite amount to the head turn, allowing the eyes to remain stationary in space despite head movement. This phenomenon is termed the vestibuloocular reflex (VOR). Head movement in the direction of a semicircular canal will excite that respective semicircular canal and the correlative extraocular muscles. The VOR keeps the line of sight stable in space while the head is moving (e.g., keeping your eyes focused on one object while shaking your head back and forth). This occurs because each semicircular canal has excitatory and inhibitory projections to agonist and antagonist extraocular muscles (one per eye; the agonistic muscle is activated, whereas the antagonistic muscle is inhibited). Each semicircular canal has excitatory projections to a pair of agonistic extraocular muscles (one in each eye) and inhibitory projections to a pair of antagonistic extraocular muscles (one in each eye). The medial and lateral recti adduct and abduct the eye, respectively, in a purely horizontal plane. When the head turns right, the right horizontal canal is stimulated. This leads to excitation of the right medial rectus and left lateral rectus, along with inhibition of the right lateral rectus and left medial rectus.

Cold caloric testing is done to assess brainstem integrity (which helps define whether brain death is present or not) and this is a passive way to evaluate the VOR. It should be done using cold water at 30°C and by bringing the head of the bed to 30° from horizontal in order to bring the horizontal canals into a more vertical plane for optimal testing. The temperature difference between the body and the infused water creates a convective current in the endolymph of the nearby horizontal semicircular canal. Hot and cold water produce currents in opposite directions and therefore a horizontal nystagmus in opposite directions. With cold water infusion, the endolymph falls within the semicircular canal, decreasing the rate of vestibular afferent firing and both eyes then slowly deviate toward the ipsilateral ear. Therefore, if cold water is infused into the left ear, the following will occur; excitatory signals are sent to the left lateral rectus and right medial rectus, as well as inhibitory signals to the left medial rectus and right lateral rectus. This results in tonic deviation of the eyes to the left. In a healthy person with normal functioning cortex, following a latency of about 20 seconds, nystagmus appears and may persist up to 2 minutes. The fast phase of nystagmus reflects the cortical correcting response and is directed away from the side of the ice water stimulus. If the cortical circuits are impaired (e.g., comatose state, as in this patient), the nystagmus will be suppressed and not present, and only the tonic deviation will be evident (with intact brainstem). The opposite of these findings should occur with warm water. Nystagmus is named in the direction of the fast phase and thus the well-known mnemonic COWS (cold opposite warm same) for caloric testing.

 Purves D, Augustine GA, Fitzpatrick D, et al. Neuroscience, 4th ed. Sunderland, MA: Sinauer Associates Inc; 2008.

 Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves in Health and Disease, 2nd ed. Ontario: BC Decker Inc; 2002.

47. c, 48. b, 49. b

The trigeminal nerve innervates the anterior belly of the digastric, whereas the posterior belly is innervated by the facial nerve. The tensor tympani is innervated by the trigeminal nerve and not the facial nerve. The only muscle innervated by the glossopharyngeal nerve is the stylopharyngeus muscle.

The muscles innervated by the trigeminal nerve are medial and lateral pterygoids, masseter, deep temporal, anterior belly of the digastric, mylohyoid, tensor veli palatini, and tensor tympani.

The muscles innervated by the facial nerve are stapedius, posterior belly of the digastric, stylohyoid, frontalis, occipitalis, orbicularis oculi, corrugator supercilii, procerus, buccinator, orbicularis oris, nasalis, levator labii superioris, alaeque nasi, zygomaticus major and minor, levator anguli oris, mentalis, depressor anguli oris, depressor labii inferioris, risorius, and platysma.

 Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves in Health and Disease, 2nd ed. Ontario: BC Decker Inc; 2002.

50. b, 51. e, 52. b, 53. a, 54. d

The facial nerve (cranial nerve VII) is a mixed nerve, containing motor fibers to the facial muscles, parasympathetic fibers to the lacrimal, submandibular, and sublingual salivary glands, special sensory afferent fibers for taste from the anterior two-thirds of the tongue, and somatic sensory afferents from the external auditory canal and pinna. Lesions of the facial nerve can easily be localized by remembering the course of the facial nerve and where the branches arise, keeping in mind that everything before the lesion would be unaffected and everything after the lesion would be affected. A lesion anywhere from the facial nerve nucleus to the distal branches can cause facial weakness in a peripheral distribution. Determining which other facial nerve functions are involved is what helps localize the lesion.

Two roots arise from the pontomedullary junction and merge to form the facial nerve. One of these roots provides motor innervation to the facial muscles. The second root is a mixed visceral nerve carrying parasympathetic fibers and is called the nervus intermedius. The preganglionic cell bodies of the parasympathetics are scattered in the pontine tegmentum, which are called the superior salivatory nuclei (SSN), and their fibers travel in the nervus intermedius. The facial nerve courses laterally through the cerebellopontine angle with the vestibulocochlear nerve to the internal auditory meatus leading to the facial, or fallopian, canal. The facial canal is located in the petrous part of the temporal bone and consists of labyrinthine, tympanic, and mastoid segments. Within the labyrinthine segment, the facial nerve bends sharply backward. At this genu, there is a swelling that forms the geniculate ganglion. This ganglion contains nerve cell bodies of taste axons from the tongue and somatic sensory axons from the external ear, auditory meatus, and external surface of the tympanic membrane.

The parasympathetic greater petrosal nerve arises from the geniculate ganglion and is the first branch of the facial nerve. The greater petrosal nerve leaves the geniculate ganglion anteriorly, enters the middle cranial fossa extradurally, and enters the foramen lacerum en route to the pterygopalatine (sphenopalatine) ganglion. From the pterygopalatine ganglion, postganglionic fibers travel with branches of the maxillary portion of the trigeminal nerve (V2) to supply the lacrimal and mucosal glands of the nasal and oral cavities.

After the geniculate ganglion region and the branch of the greater petrosal nerve, the facial nerve axons then pass backward and downward toward the stylomastoid foramen. The next branch as the facial nerve passes downward is the nerve to the stapedius, prior to exit from the stylomastoid foramen. The stapedius muscle dampens the oscillations of the ossicles of the middle ear. Impairment of the stapedius nerve and muscle will cause hyperacusis, in which sounds are much louder. Question 50 refers to a lesion between the geniculate ganglion/greater petrosal nerve (normal lacrimation) and nerve to the stapedius (hyperacusis).

After the branch of the stapedius nerve and just before the exit from the stylomastoid foramen, the facial nerve gives off the third branch, the chorda tympani nerve. The chorda tympani nerve passes near the tympanic membrane, where it is separated from the middle ear cavity by a mucus membrane. It continues anteriorly and joins the lingual nerve of V3 where it carries general sensory afferents for the anterior two-thirds of the tongue. The chorda tympani contains secretomotor fibers to sublingual and submandibular glands, as well as visceral afferent fibers for taste. The cell bodies of the gustatory neurons lie in the geniculate ganglion and travel via the nervus intermedius back to the nucleus tractus solitarius (gustatory nucleus). Therefore, the nervus intermedius carries efferents from the superior salivatory nucleus and taste afferents to the nucleus tractus solitarius. It is important to remember that the parotid glands are innervated by the glossopharyngeal nerve, whereas all other glands in the head and face are innervated by the facial nerve. Question 51 refers to a lesion between the nerve to the stapedius (absent hyperacusis) and the chorda tympani (impaired taste).

The facial nerve then exits at the stylomastoid foramen, turns anterolaterally, and travels through the parotid gland. After the facial nerve exits the stylomastoid foramen, it gives off different branches to the various facial muscles.

 Monkhouse WS. The anatomy of the facial nerve. Ear Nose Throat J. 1990; 69(10):677–683.

 Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves in Health and Disease, 2nd ed. Ontario: BC Decker Inc; 2002.

55. d, 56. d, 57. b

The nucleus tractus solitarius is involved with both taste and baroreceptor reflexes. The rostral part of this nucleus is involved with taste and receives taste afferents from the facial nerve (anterior two-thirds of the tongue), glossopharyngeal nerve (posterior one-third of the tongue), and the vagus nerve (base of tongue, epiglottis, and pharynx). The caudal part of this nucleus is involved in the baroreceptor reflexes. Baroreceptors in the wall of the carotid sinus are stimulated by increased blood pressure and the glossopharyngeal afferents travel to the caudal nucleus tractus solitarius. As a result, interneurons stimulate the dorsal motor nucleus of the vagus nerve, leading to activation of parasympathetic vagal efferents projecting to the heart and causing slowing of the heart rate. The nucleus ambiguus is the central nucleus responsible for innervation of the muscles of the larynx and pharynx, innervated by the glossopharyngeal and vagus nerves (with some laryngeal muscle innervation contributed by the spinal accessory nerve).

The superior salivatory nucleus is the source of parasympathetic innervation to the head and neck. The inferior salivatory nucleus innervates the parotid gland via the glossopharyngeal nerve.

 Crossman AR, Neary D. Neuroanatomy; An Illustrated Colour Text, 2nd ed. London, UK: Churchill-Livingstone; 2000.

 Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves in Health and Disease, 2nd ed. Ontario: BC Decker Inc; 2002.

58. a, 59. d, 60. d

The trigeminal nerve carries sensory information from the face, and supplies the sensory and motor innervation to the muscles of mastication. The nerve emerges from the midlateral surface of the pons. Its sensory ganglion (trigeminal or gasserian or semilunar ganglion) sits in a depression (Meckel’s or trigeminal cave) in the floor of the middle cranial fossa. Three primary divisions emerge from the gasserian ganglion (not the sphenopalatine ganglion, which is discussed below): the ophthalmic (V1), maxillary (V2), and mandibular (V3).

The ophthalmic division (V1) leaves the gasserian ganglion and exits the cranium through the cavernous sinus and the superior orbital fissure en route to the orbit. It branches into the tentorial, frontal, lacrimal, and nasociliary nerves. It mediates the afferent limb of the corneal reflex while the efferent limb is provided by the facial nerve. The V1 division supplies sensation to the skin of the nose, upper eyelid, forehead, and scalp (as far back as lambdoidal suture); upper half of cornea, conjunctiva, and iris, mucus membranes of frontal, sphenoidal, and ethmoidal sinuses, upper nasal cavity and septum, and lacrimal canals; and dura mater of the anterior cranial fossa, falx cerebri, and tentorium cerebelli.

The maxillary division (V2) leaves the gasserian ganglion, travels through the cavernous sinus, exits the cranium through the foramen rotundum, enters the sphenopalatine fossa, and then enters the orbit through the inferior orbital fissure. Branches include the zygomatic, infraorbital, superior alveolar, and palatine nerves. The V2 division supplies sensation to the lower eyelid, lateral nose, upper lip and cheek, lower half of cornea, conjunctiva, and iris; mucus membranes of maxillary sinus, lower nasal cavity, hard and soft palates, and upper gum; teeth of the upper jaw; and dura mater of the middle cranial fossa.

The mandibular division (V3) leaves the gasserian ganglion, exits the cranium through the foramen ovale, travels in the infratemporal fossa, and branches into the buccal, lingual, inferior alveolar, and auriculotemporal nerves. The V3 division does not travel through the cavernous sinus and is therefore spared in cavernous sinus thrombosis. Besides the muscles of mastication, V3 supplies sensation to skin of the lower lip, lower jaw, chin, tympanic membrane, auditory meatus, upper ear; mucus membranes of floor of the mouth, lower gums, anterior two-thirds of the tongue (not taste, which is facial nerve), and teeth of lower jaw; and dura mater of the posterior cranial fossa (although most of posterior fossa innervation arises from upper cervical nerves).

The cavernous sinus contains the ICA (siphon), postganglionic sympathetic fibers, and cranial nerve VI on the medial wall (adjacent to the sphenoid sinus), whereas cranial nerves III, IV, V1, and V2 are found along the lateral wall. The cavernous sinus receives blood from the middle cerebral vein and drains into the jugular vein (via the inferior petrosal sinus) and into the transverse sinus (via the superior petrosal sinus). The two cavernous sinuses are connected by intercavernous sinuses that lie anterior and posterior to the hypophysis forming a venous circle around it.

The sphenopalatine ganglion (pterygopalatine ganglion) is a parasympathetic ganglion found in the pterygopalatine fossa. It is the largest of four parasympathetic ganglia of the head and neck, along with the submandibular ganglion, otic ganglion, and ciliary ganglion. The sphenopalatine ganglion is associated with the branches of the trigeminal nerve. It supplies the lacrimal glands, paranasal sinuses, glands of the mucosa of the nasal cavity and pharynx, the gingiva, and the mucus membrane and glands of the hard palate.

 Brazis PW, Masdeu JC, Biller J. Localization in Clinical Neurology, 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007.

 Crossman AR, Neary D. Neuroanatomy; An Illustrated Colour Text, 2nd ed. London, UK: Churchill-Livingstone; 2000.

 Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves in Health and Disease, 2nd ed. Ontario: BC Decker Inc; 2002.

61. e

Most of the corticobulbar projections to the hypoglossal nuclei are bilateral, although there is one exception. The cortical neurons that drive the genioglossus muscles project only to the contralateral hypoglossal nucleus. There is one genioglossus muscle on each side of the tongue and they pull the tongue anterior and medial. Therefore, if tongue deviation is due to an upper motor neuron lesion affecting the genioglossus projections, tongue deviation will be contralateral. A lower motor neuron lesion causes ipsilateral tongue deviation.

The hypoglossal nerve provides innervation to all intrinsic tongue muscles and three (genioglossus, styloglossus, and hypoglossus) of the four extrinsic tongue muscles, with the fourth (palatoglossus) being innervated by the vagus nerve.

 Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves in Health and Disease, 2nd ed. Ontario: BC Decker Inc; 2002.

62. b

Activation of the accessory nerve causes ipsilateral head tilt and contralateral head rotation. The accessory nerve innervates the sternocleidomastoid and the trapezius muscle on each side. The action of each sternocleidomastoid (SCM) is to pull the mastoid process toward the clavicle, resulting in contralateral head rotation and turning of chin to the contralateral side (ipsilateral head tilt). Each SCM is innervated by the ipsilateral motor cortex, whereas each trapezius is innervated by the contralateral motor cortex.

 Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves in Health and Disease, 2nd ed. Ontario: BC Decker Inc; 2002.

63. e

The gag reflex is mediated by the nucleus ambiguus. The afferent limb is by the glossopharyngeal nerve and the efferent limb is by the vagus nerve. The vagus nerve exits the cranium through the jugular foramen with the glossopharyngeal and spinal accessory nerves. It innervates the palatal, pharyngeal, and laryngeal muscles via the nucleus ambiguus. A vagus nerve lesion will cause impaired swallowing (likely the cause of this patient’s aspiration pneumonia), hoarse voice, and flattening and lowering of the palate, which causes the uvula to point toward the contralateral side. The dorsal motor nucleus of the vagus supplies parasympathetic innervation to the heart, lungs, gastrointestinal (GI) tract, and trachea. The vagus nerve also supplies sensation to the base of the tongue, epiglottis, and pharynx.

 Wilson-Pauwels L, Akesson EJ, Stewart PA, et al. Cranial Nerves in Health and Disease, 2nd ed. Ontario: BC Decker Inc; 2002.