Schwartz's Principles of Surgery ABSITE and Board Review, 9th Ed.

CHAPTER 42. Neurosurgery

BASIC SCIENCE QUESTIONS

1. The motor strip of the cerebral cortex is located in the

A. Frontal lobes

B. Temporal lobes

C. Parietal lobes

D. Occipital lobes

Answer: A

The frontal areas are involved in executive function, decision making, and restraint of emotions. The motor strip, or precentral gyrus, is the most posterior component of the frontal lobes, and is arranged along a homunculus with the head inferior and lateral to the lower extremities superiorly and medially. The motor speech area (Broca’s area) lies in the left posterior inferior frontal lobe in almost all right-handed people and in up to 90% of left-handed people. The parietal lobe lies between the central sulcus anteriorly and the occipital lobe posteriorly. The postcentral gyrus is the sensory strip, also arranged along a homunculus. (See Schwartz 9th ed., p 1516.)

2. The maximum level of intracranial pressure (ICP) that is considered normal is

A. 6 mmHg

B. 10 mmHg

C. 14 mmHg

D. 18 mmHg

Answer: C

ICP normally varies between 4 and 14 mmHg. Sustained ICP levels above 20 mmHg can injure the brain. The Monro-Kellie doctrine states that the cranial vault is a rigid structure, and therefore, the total volume of the contents determines ICP. The three normal contents of the cranial vault are brain tissue, blood, and CSF. The brain’s contents can expand due to swelling from traumatic brain injury (TBI), stroke, or reactive edema. Blood volume can increase by extravasation to form a hematoma, or by reactive vasodilation in a hypoventilating, hypercarbic patient. CSF volume increases in the setting of hydrocephalus. Addition of a fourth element, such as a tumor or abscess, also will increase ICP. (See Schwartz 9th ed., p 1520.)

3. The sympathetic nervous system arises from

A. Cranial nerves III, VII, IX, and X

B. Cranial nerves II, IV, V, and VII

C. The thoracolumbar spinal segments

D. Spinal segments S2, S3, and S4

Answer: C

The ANS is divided into the sympathetic, parasympathetic, and enteric systems. The sympathetic system drives the ‘fight or flight’ response, using epinephrine to increase heart rate, blood pressure, blood glucose, and temperature, as well as to dilate the pupils. It arises from the thoracolumbar spinal segments. The parasympathetic system promotes the ‘rest and digest’ state, and uses acetylcholine to maintain basal metabolic function under nonstressful circumstances. It arises from cranial nerves III, VII, IX, and X, and from the second to fourth sacral segments. The enteric nervous system controls the complex synchronization of the digestive tract, especially the pancreas, gallbladder, and small and large bowels. It can run autonomously but is regulated by the sympathetic and parasympathetic systems. (See Schwartz 9th ed., p 1518.)

4. Motor information is carried from the brain in the

A. Corticospinal tract

B. Medial lemnicus tracts

C. Spinothalamic tracts

D. Mesencephalic tracts

Answer: A

The brain stem consists of the midbrain (mesencephalon), pons (metencephalon), and medulla (myelencephalon). Longitudinal fibers run through the brain stem, carrying motor and sensory information between the cerebral hemispheres and the spinal cord. The corticospinal tract is the major motor tract, while the medial lemniscus and the spinothalamic tracts are the major sensory tracts. The nuclei of cranial nerves III through XII are also located within the brain stem. These nerves relay the motor, sensory, and special sense functions of the eye, face, mouth, and throat.

The principal motor tract is the corticospinal tract. It is a two-neuron path, with an upper motor neuron and a lower motor neuron. The upper motor neuron cell body is located within the motor strip of the cerebral cortex. The axon travels through the internal capsule to the brain stem, decussates at the brain stem–spinal cord junction, and travels down the contralateral corticospinal tract to the lower motor neuron in the anterior horn at the appropriate level. The lower motor neuron axon then travels via peripheral nerves to its target muscle. Damage to upper motor neurons results in hyperreflexia and mild atrophy. Damage to lower motor neurons results in flaccidity and significant atrophy. (See Schwartz 9th ed., p 1517.)

CLINICAL QUESTIONS

1. The standard treatment for an asymptomatic 2-cm chronic subdural hematoma is

A. Observation and serial CT scan

B. Placement of bedside ventriculostomy

C. Burr hole drainage

D. Crainiotomy

Answer: C

A chronic SDH >1 cm or any symptomatic SDH should be surgically drained. Unlike acute SDH, which consists of a thick, congealed clot, chronic SDH typically consists of a viscous fluid, with a texture and the dark brown color reminiscent of motor oil. A simple burr hole can effectively drain most chronic SDHs. However, the optimal treatment of chronic SDH remains controversial. Most authorities agree that burr hole drainage should be attempted first to obviate the risks of formal craniotomy. A single burr hole placed over the dependent edge of the collection can be made, and the space copiously irrigated until the fluid is clear. A second, more anterior burr hole can then be placed if the collection does not drain satisfactorily due to containment by membranes. The procedure is converted to open craniotomy if the SDH is too congealed for irrigation drainage, the complex of membranes prevents effective drainage, or persistent hemorrhage occurs that cannot be reached with bipolar cautery through the burr hole. (See Schwartz 9th ed., p 1526.)

2. The most common malignant tumor of the brain in children is

A. Ganglioneuroma

B. Neuroblastoma

C. Medulloblastoma

D. Glioblastoma multiforme

Answer: C

Neural and mixed tumors are a diverse group that includes tumors variously containing normal or abnormal neurons and/or normal or abnormal glial cells. Primitive neuroectodermal tumors arise from bipotential cells, capable of differentiating into neurons or glial cells.

Primitive neuroectodermal tumor is the most common type of medulloblastoma. Most occur in the first decade of life, but there is a second peak around age 30. Medulloblastoma is the most common malignant pediatric brain tumor. (See Schwartz 9th ed., p 1540.)

3. Which of the following spinal fractures should be suspected in a patient wearing a lap belt at the time of a head-on collision?

A. Jefferson fracture

B. Hangman’s fracture

C. Chance fracture

D. Burst fracture

Answer: C

Chance fracture is a flexion-distraction injury causing failure of the middle and posterior columns, sometimes with anterior wedging. Typical injury is from a lap seat-belt hyperflexion with associated abdominal injury. It often is unstable and associated with neurologic deficit.

Jefferson fracture is a bursting fracture of the ring of C1 (the atlas) due to compression forces.

Traditionally considered a hyperextension/distraction injury from placement of the noose under the angle of the jaw, hangman’s fractures also may occur with hyperextension/compression, as with diving accidents, or hyperflexion.

Burst fracture is a pure axial compression injury causing failure of the anterior and middle columns. (See Schwartz 9th ed., p 1528.)

4. Invasive monitors of intracerebral pressure are usually placed in the

A. Right frontal lobe

B. Left frontal lobe

C. Right parietal lobe

D. Left parietal lobe

Answer: A

There are several methods of monitoring intracranial physiology. The three described here are bedside intensive care unit (ICU) procedures and allow continuous monitoring. All three involve making a small hole in the skull with a hand-held drill. They generally are placed in the right frontal region to minimize the neurologic impact of possible complications such as hemorrhage. The most reliable monitor, always, is an alert patient with a reliable neurologic examination. If a reliable neurologic examination is not possible due to the presence of brain injury, sedatives, or paralytics, and if there is active and unstable intracranial pathology, then invasive monitoring is required. (See Schwartz 9th ed., p 1519.)

5. Following a closed head injury, clear fluid is seen draining from a patient’s nose. Which of the following tests is most sensitive in determining if the fluid is cerebrospinal fluid (CSF)?

A. Glucose level

B. Halo test

C. Fluid:serum LDH ratio

D. Beta-transferrin

Answer: D

Copious clear drainage from the nose or ear makes the diagnosis of CSF leakage obvious. Often, however, the drainage may be discolored with blood or small in volume if some drains into the throat. The halo test can help differentiate. Allow a drop of the fluid to fall on an absorbent surface such as a facial tissue. If blood is mixed with CSF, the drop will form a double ring, with a darker center spot containing blood components surrounded by a light halo of CSF. If this test is indeterminate, the fluid can be sent for beta-transferrin testing, which will only be positive if CSF is present. (See Schwartz 9th ed., p 1523.)

6. Which of the following is NOT part of Cushing’s triad?

A. Hypertension

B. Pinpoint pupils

C. Irregular respirations

D. Bradycardia

Answer: B

Patients with increased ICP, also called intracranial hypertension (ICH), often will present with headache, nausea, vomiting, and progressive mental status decline. Cushing’s triad is the classic presentation of ICH: hypertension, bradycardia, and irregular respirations. This triad is usually a late manifestation. (See Schwartz 9th ed., p 1521.)

7. The most common tumor of peripheral nerves is

A. Nerve sheath sarcoma

B. Schwannoma

C. Neurofibroma

D. Neuroepithelioma

Answer: B

Schwannomas are the most common peripheral nerve tumors, also referred to as neurilemomas or neurinomas. Most occur in the third decade of life. These benign tumors arise from Schwann cells, which form myelin in peripheral nerves. The most characteristic presentation is a mass lesion with point tenderness and shooting pains on direct palpation.

Neurofibromas arise within the nerve and tend to be fusiform masses, unlike schwannomas, which tend to grow out of the nerve. Neurofibromas often present as a mass that is tender to palpation. They usually lack the shooting pains characteristic of schwannomas.

Malignant nerve sheath tumors include solitary sarcomas, degenerated neurofibromas, and neuroepitheliomas. Patients with malignant peripheral nerve tumors typically complain of constant pain, rather than pain only on palpation, and are more likely to have motor and sensory deficits in the distribution of the parent nerve. (See Schwartz 9th ed., p 1549.)

8. Clinical findings which can be seen in a patient who is brain dead include

A. Minimally reactive pupil unilaterally

B. No spontaneous breathing with a PaCO2 of 50 mmHg

C. Minimal, unilateral decorticate posturing to painful stimulus

D. Positive triple flexion reflex of the leg

Answer: D

A neurologist, neurosurgeon, or intensivist generally performs the clinical brain death examination. Two examinations consistent with brain death 12 hours apart, or one examination consistent with brain death followed by a consistent confirmatory study generally is sufficient to declare brain death (see below). Hospital regulations and local laws regarding documentation should be followed closely.

Establish the absence of complicating conditions before beginning the examination. The patient must be normotensive, euthermic, and oxygenating well. The patient may not be under the effects of any sedating or paralytic drugs.

Documentation of no brain stem function requires the following: nonreactive pupils; lack of corneal blink, oculocephalic (doll’s eyes), oculovestibular (cold calorics) reflexes; and loss of drive to breathe (apnea test). The apnea test demonstrates no spontaneous breathing even when PaCO2 is allowed to rise above 60 mmHg.

Deep central painful stimuli are provided by bilateral forceful twisting pinch of the supraclavicular skin and pressure to the medial canthal notch. Pathologic responses such as flexor or extensor posturing are not compatible with brain death. Spinal reflexes to peripheral pain, such as triple flexion of the lower extremities, are compatible with brain death. (See Schwartz 9th ed., p 1527.)

9. Following a gunshot wound to the spine, a patient has loss of motor control on one side of his body. The most likely diagnosis is

A. Crush injury to the spinal cord

B. Brown-Sequard syndrome

C. Central cord syndrome

D. Anterior cord syndrome

Answer: B

Penetrating, compressive, or ischemic cord injury can lead to several characteristic presentations based on the anatomy of injury. The neurologic deficits may be deduced from the anatomy of the long sensory and motor tracts and understanding of their decussations. Four patterns are discussed.

First, injury to the entire cord at a given level results in anatomic or functional cord transaction with total loss of motor and sensory function below the level of the lesion. The typical mechanism is severe traumatic vertebral subluxation reducing spinal canal diameter and crushing the cord.

Second, injury to half the cord at a given level results in Brown-Sequard syndrome, with loss of motor control and proprioception ipsilaterally and loss of nociception and thermoception contralaterally. The typical mechanism is a stab or gunshot wound.

Third, injury to the interior gray matter of the cord in the cervical spine results in a central cord syndrome, with upper extremity worse than lower extremity weakness and varying degrees of numbness. The typical mechanism is transient compression of the cervical cord by the ligamentum flavum buckling during traumatic neck hyperextension. This syndrome occurs in patients with pre-existing cervical stenosis. Fourth, injury to the ventral half of the cord results in the anterior cord syndrome, with paralysis and loss of nociception and thermoception bilaterally. The typical mechanism is an acute disc herniation or ischemia from anterior spinal artery occlusion. (See Schwartz 9th ed., p 1529, and Fig. 42-1.)

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FIG. 42-1. Spinal cord injury patterns. a. = artery. (Adapted with permission from Hoff J, Boland M: Neurosurgery, from Principles of Surgery, 7th ed. New York: McGraw-Hill, 1999, p 1837.)

10. Which of the following is a criterion that must be met for the nonoperative management of an epidural hematoma?

A. Clot volume 30 cm3

B. Maximum thickness 2.5 cm

C. GCS >12

D. No previous history of systemic hypertension

Answer: A

Open craniotomy for evacuation of the congealed clot and hemostasis generally is indicated for EDH. Patients who meet all of the following criteria may be managed conservatively: clot volume 30 cm3, maximum thickness 1.5 cm, and GCS score >8.10. (See Schwartz 9th ed., p 1525.)

11. The most common origin for metastatic tumors to the brain is

A. Breast

B. Lung

C. Colon

D. Kidney

Answer: B

The sources of most cerebral metastases are (in decreasing frequency): lung, breast, kidney, GI tract, and melanoma. Lung and breast cancers account for more than half of cerebral metastases. Metastatic cells usually travel to the brain hematogenously and frequently seed the gray-white junction. Other common locations are the cerebellum and the meninges. Meningeal involvement may result in carcinomatous meningitis, also known as leptomeningeal carcinomatosis. (See Schwartz 9th ed., p 1537.)

12. Temporal lesions most commonly cause which of the following forms of brain herniation?

A. Subfalcine herniation

B. Uncal herniation

C. Central transtentorial herniation

D. Tonsillar herniation

Answer: B

Temporal lesions push the uncus medially and compress the midbrain. This phenomenon is known as uncal herniation. The posterior cerebral artery (PCA) passes between the uncus and midbrain and may be occluded, leading to occipital infarct. Masses higher up in the hemisphere can push the cingulate gyrus under the falx cerebri. This process is known as subfalcine herniation. The anterior cerebral artery (ACA) branches run along the medial surface of the cingulate gyrus and may be occluded, leading to medial frontal and parietal infarcts. Diffuse increases in pressure in the cerebral hemispheres can lead to central, or transtentorial, herniation. Increased pressure in the posterior fossa can lead to upward central herniation or downward tonsillar herniation through the foramen magnum. Uncal, transtentorial, and tonsillar herniation can cause direct damage to the very delicate brain stem. Figure 42-2 diagrams patterns of herniation. (See Schwartz 9th ed., p 1521.)

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FIG. 42-2. Schematic drawing of brain herniation patterns. 1. Subfalcine herniation. The cingulate gyrus shifts across midline under the falx cerebri. 2. Uncal herniation. The uncus (medial temporal lobe gyrus) shifts medially and compresses the midbrain and cerebral peduncle. 3. Central transtentorial herniation. The diencephalon and midbrain shift caudally through the tentorial incisura. 4. Tonsillar herniation. The cerebellar tonsil shifts caudally through the foramen magnum. (Reproduced with permission from Cohen DS, Quest DO: Increased intracranial pressure, brain herniation and their control, in Wilkins RH, Rengachary SS (eds): Neurosurgery, 2nd ed. New York: McGraw Hill, 1996, p 349.)

13. The initial dose of methylprednisolone that should be given to a patient with an acute spinal cord injury is

A. 5 mg/kg

B. 15 mg/kg

C. 30 mg/kg

D. 50 mg/kg

Answer: C

The National Acute Spinal Cord Injury studies (NASCIS I and II) provide the basis for the common practice of administering high-dose steroids to patients with acute SCI. A 30-mg/kg IV bolus of methylprednisolone is given over 15 minutes, followed by a 5.4-mg/kg per hour infusion begun 45 minutes later. The infusion is continued for 23 hours if the bolus is given within 3 hours of injury, or for 47 hours if the bolus is given within 8 hours of injury. The papers indicate greater motor and sensory recovery at 6 weeks, 6 months, and 1 year after acute SCI in patients who received methylprednisolone. However, the NASCIS trial data have been extensively criticized, as many argue that the selection criteria and study design were flawed, making the results ambiguous. Patients who receive such a large corticosteroid dose have increased rates of medical and ICU complications, such as pneumonias, which have a deleterious effect on outcome. A clear consensus on the use of spinal-dose steroids does not exist. A decision to use or not use spinal-dose steroids may be dictated by local or regional practice patterns, especially given the legal liability issues surrounding SCI. Patients with gunshot or nerve root (cauda equina) injuries or those who are pregnant, 14 years old, or on chronic steroids were excluded from the NASCIS studies and should not receive spinal dose steroids. (See Schwartz 9th ed., p 1531.)

14. Which of the following is the most common mechanism of spinal cord injury following a dive into shallow water?

A. Compression

B. Flexion

C. Extension

D. Rotation

Answer: C

Arching the neck and back extends the spine. Extension loads the spine posteriorly and distracts the spine anteriorly. High extension forces occur during rear-end motor vehicle collisions (especially if there is no headrest), frontward falls when the head strikes first, or diving into shallow water.

Bending the head and body forward into a fetal position flexes the spine. Flexion loads the spine anteriorly (the vertebral bodies) and distracts the spine posteriorly (the spinous process and interspinous ligaments). High flexion forces occur during front-end motor vehicle collisions, and backward falls when the head strikes first.

Force applied along the spinal axis (axial loading) compresses the spine. Compression loads the spine anteriorly and posteriorly. High compression forces occur when a falling object strikes the head or shoulders, or when landing on the feet, buttocks, or head after a fall from height. A pulling force in line with the spinal axis distracts the spine. Distraction unloads the spine anteriorly and posteriorly. Distraction forces occur during a hanging, when the chin or occiput strikes an object first during a fall, or when a passenger submarines under a loose seat belt during a front-end motor vehicle collision.

Force applied tangential to the spinal axis rotates the spine. Rotation depends on the range of motion of intervertebral facet joints. High rotational forces occur during off-center impacts to the body or head or during glancing automobile accidents. (See Schwartz 9th ed., p 1527.)

15. Findings in an anterior cerebral artery stroke include

A. Language deficits

B. Contralateral leg weakness

C. Contralateral homonymous hemianopsia

D. Horner’s syndrome

Answer: B

The anterior cerebral artery (ACA) supplies the medial frontal and parietal lobes, including the motor strip, as it courses into the interhemispheric fissure. ACA stroke results in contralateral leg weakness.

The middle cerebral artery (MCA) supplies the lateral frontal and parietal lobes and the temporal lobe. MCA stroke results in contralateral face and arm weakness. Dominant-hemisphere MCA stroke causes language deficits.

The posterior cerebellar artery (PCA) supplies the occipital lobe. PCA stroke results in a contralateral homonymous hemianopsia.

The posterior inferior cerebellar artery (PICA) supplies the lateral medulla and the inferior half of the cerebellar hemispheres. PICA stroke results in nausea, vomiting, nystagmus, dysphagia, ipsilateral Horner’s syndrome, and ipsilateral limb ataxia. The constellation of symptoms resulting from PICA occlusion is referred to as the lateral medullary or Wallenberg’s syndrome. (See Schwartz 9th ed., p 1533.)

16. In decorticate posturing, the patient’s extremities

A. Withdraw to pain

B. Extend in response to pain

C. Flex in response to pain

D. None of the above

Answer: C

Characteristic motor reactions to pain in patients with depressed mental status include withdrawal from stimulus, localization to stimulus, flexor (decorticate) posturing, extensor (decerebrate) posturing, or no reaction (in order of worsening pathology). (See Schwartz 9th ed., p 1518.)

17. The most common intramedullary spinal tumor in adults is

A. Hemangioma

B. Ependymoma

C. Astocytoma

D. Osteoblastoma

Answer: B

Ependymomas are the most common intramedullary tumors in adults. There are several histologic variants. The myxopapillary type occurs in the conus medullaris or the filum terminale in the lumbar region and has the best prognosis after resection. The cellular type occurs more frequently in the cervical cord.

Astrocytomas are the most common intramedullary tumors in children, although they also occur in adults. They may occur at all levels, although more often in the cervical cord. The tumor may interfere with the CSF-containing central canal of the spinal cord, leading to a dilated central canal, referred to as syringomyelia (syrinx).

Hemangiomas and osteoblastomas are extramedullary tumors. (See Schwartz 9th ed., p 1543.)

18. A patient who localizes to pain, is confused, and opens his eyes to pain has a Glasgow Coma Scale score of

A. 9

B. 10

C. 11

D. 12

Answer: C

The GCS is determined by adding the scores of the best responses of the patient in each of three categories. The motor score ranges from 1 to 6, verbal from 1 to 5, and eyes from 1 to 4. The GCS therefore ranges from 3 to 15, as detailed in Table 42-1. (See Schwartz 9th ed., p 1522.)

TABLE 42-1 The Glasgow Coma Scale scorea

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19. Patients with symptoms from a Chiari I malformation may complain of

A. Seizures

B. Extremity weakness

C. Eye pain

D. Ataxia

Answer: B

Chiari I malformation is the caudal displacement of the cerebellar tonsils below the foramen magnum. It may be seen as an incidental finding on MRI scans in asymptomatic patients. Symptomatic patients usually present with headache, neck pain, or symptoms of myelopathy, including numbness or weakness in the extremities. A syrinx may be associated, but the brain stem and lower cranial nerves are normal in Chiari I malformations. Chiari II malformations are more severe and involve caudal displacement of the lower brain stem and stretching of the lower cranial nerves. Symptomatic patients may be treated with suboccipital craniectomy to remove the posterior arch of the foramen magnum, along with removal of the posterior ring of C1. Removal of these bony structures relieves the compression of the cerebellar tonsils and cervicomedullary junction, and may allow reestablishment of normal CSF flow patterns. (See Schwartz 9th ed., p 1554, and Fig. 42-3.)

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FIG. 42-3. T1-weighted sagittal magnetic resonance imaging of a patient with a Chiari I malformation. The large arrowhead points to the cerebellar tonsils. The small arrowhead points to the posterior arch of the foramen magnum.

20. Unilateral loss of visual acuity and pulsatile proptosis is suggestive of

A. Retinal artery aneurysm

B. Carotid-cavernous fistula

C. Hypertensive crisis

D. Carotid artery dissection

Answer: B

Traumatic vessel wall injury to the portion of the carotid artery running through the cavernous sinus may result in a carotid-cavernous fistula (CCF). This creates a high-pressure, high-flow pathophysiologic blood flow pattern. CCFs classically present with pulsatile proptosis (the globe pulses outward with arterial pulsation), retro-orbital pain, and decreased visual acuity or loss of normal eye movement (due to damage to cranial nerves III, IV, and VI as they pass through the cavernous sinus). Symptomatic CCFs should be treated to preserve eye function. Fistulae may be closed by balloon occlusion using interventional neuroradiology techniques. Fistulae with wide necks are difficult to treat and may require total occlusion of the parent carotid artery. (See Schwartz 9th ed., p 1527.)

21. Hemorrhagic strokes most commonly involve the

A. Cerebellum

B. Basal ganglia

C. Pons

D. Brain stem

Answer: B

Hemorrhagic stroke typically occurs within the basal ganglia or cerebellum [Table 42-2]. The patient is usually hypertensive on admission and has a history of poorly controlled hypertension. Such patients are more likely to present with lethargy or obtundation, compared to those who suffer an ischemic stroke. Depressed mental status results from brain shift and herniation secondary to mass effect from the hematoma in deep structures. Ischemic stroke does not cause mass effect acutely; and therefore, patients are more likely to present with normal consciousness and a focal neurologic deficit. Hemorrhagic strokes tend to present with a relatively gradual decline in neurologic function as the hematoma expands, rather than the immediately maximal symptoms caused by ischemic stroke. (See Schwartz 9th ed., p 1534.)

TABLE 42-2 Anatomic distribution of intracranial hemorrhages and correlated symptoms

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22. The most common primary malignant tumor of the brain is

A. Oligodendoglioma

B. Ependymoma

C. Astrocytoma

D. Ganglioglioma

Answer: C

Astrocytoma is the most common primary CNS neoplasm. The term glioma often is used to refer to astrocytomas specifically, excluding other glial tumors. Astrocytomas are graded from I to IV. Grades I and II are referred to as low-grade astrocytoma, grade III as anaplastic astrocytoma, and grade IV as glioblastoma multiforme (GBM).

Oligodendroglioma accounts for approximately 10% of gliomas. They often present with seizures. Calcifications and hemorrhage on CT or MRI suggest the diagnosis.

The lining of the ventricular system consists of cuboidal/columnar ependymal cells from which ependymomas may arise. Although most pediatric ependymomas are supratentorial, two thirds of adult ependymomas are infratentorial.

Ganglioglioma is a mixed tumor in which both neurons and glial cells are neoplastic. They occur in the first three decades of life, often in the medial temporal lobe, as circumscribed masses that may contain cysts or calcium and may enhance. (See Schwartz 9th ed., p 1540.)

23. Eccymosis behind the ear (“Battle sign”) is indicative of which of the following?

A. Parietal skull fracture

B. Temporal skull fracture

C. Basilar skull fracture

D. Occipital skull fracture

Answer: C

Fractures of the skull base are common in head-injured patients, and they indicate significant impact. They are generally apparent on routine head CT, but should be evaluated with dedicated fine-slice coronal-section CT scan to document and delineate the extent of the fracture and involved structures. If asymptomatic, they require no treatment. Symptoms from skull base fractures include cranial nerve deficits and CSF leaks. A fracture of the temporal bone, for instance, can damage the facial or vestibulocochlear nerve, resulting in vertigo, ipsilateral deafness, or facial paralysis. A communication may be formed between the subarachnoid space and the middle ear, allowing CSF drainage into the pharynx via the eustachian tube or from the ear (otorrhea). Extravasation of blood results in ecchymosis behind the ear, known as Battle’s sign. A fracture of the anterior skull base can result in anosmia (loss of smell from damage to the olfactory nerve), CSF drainage from the nose (rhinorrhea), or periorbital ecchymoses, known as raccoon eyes. (See Schwartz 9th ed., p 1523.)

24. Which of the following is standard treatment for a significant posttraumatic CSF leak?

A. Placement of a lumbar drain

B. Lumbar blood patch

C. Endoscopic sinus exploration with mucosal repair

D. Craniotomy and closure of the dural tear

Answer: A

Many CSF leaks will heal with elevation of the head of the bed for several days. A lumbar drain can augment this method. A lumbar drain is a catheter placed in the lumbar CSF cistern to decompress the cranial vault and allow the defect to heal by eliminating normal hydrostatic pressure. There is no proven efficacy of antibiotic coverage for preventing meningitis in patients with CSF leaks. (See Schwartz 9thed., p 1523.)

25. A patient presents to the ER with a sudden, severe headache. Based on the CT scan in Fig. 42-4, what is the most likely diagnosis?

A. Subarachnoid hemorrhage

B. Subdural hematoma

C. Diffuse axonal injury

D. Epidural hematoma

Answer: A

The image shown is a computed tomography scan of a patient who experienced a sudden, severe headache. Subarachnoid hemorrhage is visible as hyperdense signal in the interhemispheric fissure (1), bilateral sylvian fissures (2shows the left fissure), and in the ambient cisterns around the midbrain (3). This gives the classic five-pointed-star appearance of a subarachnoid hemorrhage. Visible temporal tips of the lateral ventricles indicate hydrocephalus. (See Schwartz 9th ed., p 1536.)

FIG. 42-4.

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26. A patient with a crush injury to the arm has motor and sensory deficits that indicate a radial nerve injury. The most appropriate management is

A. Immediate operative exploration and repair

B. EMG 5-7 days after injury; surgical exploration if nerve conduction is decreased

C. EMG 3-4 weeks after injury; surgical exploration if nerve conduction is decreased

D. Surgical exploration if there is no functional improvement after 3 months

Answer: D

The sensory and motor deficits [in a patient with a peripheral nerve injury] should be accurately documented. Deficits are usually immediate. Progressive deficit suggests a process such as an expanding hematoma and may warrant early surgical exploration. Clean, sharp injuries may also benefit from early exploration and reanastomosis. Most other peripheral nerve injuries should be observed. EMG/NCS studies should be done 3 to 4 weeks postinjury if deficits persist. Axon segments distal to the site of injury will conduct action potentials normally until Wallerian degeneration occurs, rendering EMG/NCS before 3 weeks uninformative. Continued observation is indicated if function improves. Surgical exploration of the nerve may be undertaken if no functional improvement occurs over 3 months. If intraoperative electrical testing reveals conduction across the injury, continue observation. In the absence of conduction, the injured segment should be resected and end-to-end primary anastomosis attempted. However, anastomoses under tension will not heal. A nerve graft may be needed to bridge the gap between the proximal and distal nerve ends. The sural nerve often is harvested, as it carries only sensory fibers and leaves a minor deficit when resected. The connective tissue structures of the nerve graft may provide a pathway for effective axonal regrowth across the injury. (See Schwartz 9th ed., p 1532.)

27. The motor scoring system is a 5-point scale to assess motor strength. A patient who is able to move only against gravity (but not against resistance) would have a motor score of

A. 2

B. 3

C. 4

D. 5

Answer: B

(See Schwartz 9th ed., p 1518, and Table 42-3.)

TABLE 42-3 Motor scoring system

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