Rafael H. Llinas
Constance J. Johnson
This chapter describes the approaches to history taking, physical examination, and laboratory evaluation that are most useful in ambulatory patients with neurologic symptoms. One or more of these approaches is appropriate for patients with each of the neurologic problems discussed in subsequent chapters (headache, seizures, dizziness, vertigo, syncope, tremor, Parkinson disease [PD], cerebrovascular disease [CVD], and peripheral neuropathy).
Neurologic History and Physical Examination
General Principles
To proceed with appropriate diagnostic and therapeutic actions, one must localize the lesion in the nervous system and determine the probable cause of the signs and symptoms. This requires knowledge of the presentation, epidemiology, and temporal profile of neurologic diseases. For example, new-onset central paralysis of an arm in a 20-year-old could be caused by multiple sclerosis, whereas in a 60-year-old stroke is far more likely; if the pattern is peripheral, then traumatic nerve injury is likely in the young but tumor is an important consideration in the old. Figures 86.1 and 86.2 summarize facts that are often needed for anatomic localization. Table 70.2 shows additional details regarding the anatomic relationships of peripheral nerves (cervical nerve roots) in Chapter 70, Table 71.3 (lumbar nerve roots) inChapter 71, and Figs. 92.1 (upper extremity), and 92.2 (lower extremity) in Chapter 92.
Localizing the part of the nervous system affected and then producing a differential diagnosis for a lesion in that area is the best way to address a neurologic sign or symptom. Most individual neurologic symptoms or signs are not specific for a single functional or anatomic disturbance or for a single cause. For example, loss of a reflex is not necessarily caused by motor nerve damage, a hemiparesis is not necessarily a result of cerebrovascular disease, and a resting tremor is not necessarily a symptom of PD. Nevertheless, the constellation of findings from the history and physical examination is often quite specific. Therefore, a thorough history and physical examination are adequate for making a working diagnosis for most neurologic problems encountered in office practice.
Depending on the hypotheses one is entertaining, a brief, general neurologic evaluation may be required; more often, only selected areas of the nervous system require evaluation.
Components of a General History
Higher Functions and Consciousness
Handedness
Is the patient right-handed or left-handed? Regardless of handedness, most people are left-hemisphere dominant
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for language; however, some left-handers are right- or mixed-hemisphere dominant. Knowledge of handedness is useful when localizing cortical versus subcortical lesions. A patient with right hemiparesis and intact language who is right-handed has a subcortical lesion. A patient with left hemiparesis and intact language who is left-handed may have a cortical or subcortical lesion.
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FIGURE 86.1. Schematic diagrams of neurologic localization—anterior series (A) and lateral series (B) views. Upper motor neuron signs and nonradicular sensory signs can define only the side of the lesion series (A); in general, they do not reveal the level of the lesion. The presence or absence of other neurologic signs or symptoms can help to specify the level of a localized neurologic problemseries (B). (Courtesy of Barry Gordon, M.D., Ph.D.) |
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FIGURE 86.2. Cutaneous innervation areas of dermatomes. The numbers correspond to the spinal cord level of the dermatome. C, Cervical; T, thoracic; L, lumbar; S, sacral. (From Haymaker W, Woodhall B. Peripheral nerve injuries. 2nd ed. Philadelphia: WB Saunders, 1953. ) |
Language
Has the patient had problems with thinking or speech? Minor difficulty in finding words is common in normal people, as are brief lapses of memory. A basic evaluation for aphasias should include determining whether patients can name, repeat, and comprehend normally.
Memory
How is the patient's memory? What kinds of things are forgotten? (Ask the family whether any problems with the patient's concentration, memory, or general abilities have been noted.) Can the patient work, drive, and do usual chores?
Acute Cerebral Dysfunction
Has the patient ever fainted, lost consciousness, felt dizzy, or had a seizure (fit, convulsion)? Does the patient have frequent or disabling headaches? How often?
Mood
How are the patient's spirits? Does he or she feel depressed? Worry a great deal? How does the patient feel
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about the future? About self (confident, hopeless, helpless, guilty)?
Hallucinations/Delusions
Has the patient seen or heard things that are unusual or things that are not there? Does the imagination seem to play tricks? What feels wrong? Does he or she perceive being controlled by anything or anybody?
Cranial Nerves
Nerve I (Olfactory)
Not tested in the brief history and physical examination unless the patient specifically mentions a loss of smell or has a history of head trauma with loss of consciousness.
Nerve II (Optic Nerve and Vision)
Is there impaired vision? Do things seem blurred, or are there patches where it is hard to see? Has vision ever been lost in one eye, or has the patient had trouble seeing out of one side or in one direction?
Nerves III, IV, and VI (Extraocular Motions)
Has there ever been double vision?
Double vision during reading or looking at objects close to the patient will often be an oculomotor palsy (III) because of a paresis of eye adduction. Double vision looking far away is often abducens (VI) palsy to paresis of eye abduction). Ask the following questions when doing a quick evaluation.
Nerve V (Trigeminal Nerve)
Has there been numbness over the face or difficulty chewing?
Nerve VII (Facial Nerve)
Has there been any weakness in the face or paralysis of the face?
Nerve VIII (Auditory–Vestibular Nerve)
How is the patient's hearing? Has there been any ringing in the ears or difficulty hearing out of one side? Any loss of balance, spinning sensations, or dizziness?
Nerves IX, X, and XII (Glossopharyngeal, Vagal, and Hypoglossal Nerves)
Have there been any problems swallowing food? Does it seem to get caught anywhere? Where? What kinds of food has the patient had problems with? (Liquids are often the most difficult foods for patients with neurologic problems.)
Other
Motor
Has there been any weakness in the arms or legs? Is it there all the time, or does it come and go? Has there been any twitching or cramps in the muscles? Where? How often? Any wasting of the muscles?
Coordination/Cerebellar
Has there been any shaking or any difficulty in writing, drawing, buttoning, and so on?
Sensation
Has there been any numbness, tingling, or pain in the arms, legs, or feet? Where? Does position change or any other factor seem to bring it on?
Gait
Are there any problems with walking? What kind? Where or when does it happen (e.g., climbing up stairs, walking certain distances)? Is there unsteadiness when erect?
Bladder/Bowel
Have there been any problems in starting to urinate or in urinating? Any difficulty with constipation or diarrhea? Any uncontrolled urination or stool evacuation? If so, was it associated with the urge to urinate/defecate, or was it spontaneous?
Components of a General Examination
Higher Functions and Consciousness
Answers to the questions suggested, together with observations made throughout the history and physical examination, are usually sufficient to determine level of consciousness, language functioning, visual–spatial functioning, mood, level of intelligence, and memory.Chapters 19 and 26, respectively, describe the systematic mental status examinations appropriate for patients with psychiatric problems and for those with suspected cognitive impairments.
Cranial Nerves
Nerve II (Optic Nerve and Vision)
Check vision (make sure that patients wear their glasses, if needed) with the use of the Snellen chart or by having the patient read from a newspaper; test each eye separately. Check fields by confrontation (each eye separately) using finger wiggle. Examine fundi.
Nerves III, IV, and VI (Extraocular Movement and Pupils)
Have the patient move the eyes into all principal positions of gaze (horizontal, vertical, diagonal); observe for dysconjugate movements, and ask, while testing, about diplopia. Look for nystagmus, lid lag, and ptosis, and check pupils for size, symmetry, and reaction to light. The normal pupil size for young adults is 3 to 5 mm. In the elderly, normal pupils are often 2 to 3 mm. A slight degree of pupillary asymmetry, 1 mm or less, is present in about 5% of the normal population; it usually varies from hour to hour and day to day, and it decreases in bright light.
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Nerve V (Trigeminal Nerve)
With a pin, check for symmetry of perception over forehead, cheek, and chin. The corneal reflex is not routinely tested in the outpatient setting. There are wide variations in corneal sensitivity among normal individuals; some subjects, particularly those who have worn contact lenses, have virtually no response at all. To test corneal reflexes, touch corresponding points on the cornea of each eye with a cotton swab. Gauze should not be used because it is abrasive. Have the subject look up and away from the testing swab. Asymmetry is the most important clue to disease.
Nerve VII (Facial Nerve)
Inspect for asymmetry of the nasolabial folds when the face is not moving. Have the patient show teeth, close eyes, and frown. Normal people may have a slight degree of resting asymmetry of the face. Normally both sides should move briskly together on showing teeth, smiling, and other facial movements. Lag on one side may be a sign of a slight seventh nerve palsy, central or peripheral.
Nerves IX and X (Glossopharyngeal and Vagus Nerves)
Inspect the uvula for position and for motion when the patient says “Ahh.” Test the gag reflex on both sides of the pharynx, looking for asymmetry of response. Some people have asymmetry of the resting uvula. Visualize the palate. If it is unclear if it rises symmetrically, confirm if the uvula is deviated to one side or not. Also, bilaterally hyperactive to bilaterally absent gag responses are within the normal range.
Nerve XI (Accessory Nerve)
Observe shoulder shrug; it should be symmetric.
Nerve XII (Hypoglossal Nerve)
Inspect the tongue at rest in the mouth; have the patient protrude it and move it to both sides. It should protrude in the midline. In cases with a facial droop the lip should be pulled away slightly so the tongue is unimpeded.
Motor Examination
Adventitious Movements
Observe for tremor and other spontaneous movements (see Chapter 90).
Bulk
Examine for asymmetries of muscle mass. Denervation causes loss of muscle bulk, reaching a maximum by 4 months. Disuse over months to years also causes a decrease in muscle bulk (e.g., in the legs of patients who are permanently bedridden).
Muscle Tone (Resistance to Passive Motion)
Test tone by passively flexing and extending the upper and lower extremities. With normal tone there is a slight firmness of muscles and slight resistance to passive motion. In hypotonia the muscles are flaccid, without resistance to passive motion; this may indicate lower motor neuron (LMN) or cerebellar disease.
Hypertonia comprises several subtypes. Rigidity is increased resistance to passive motion throughout the whole range of motion around a joint. In spasticity, the initial passive motion is easy, but then there is a tightening of the muscle (spastic catch), possibly followed by a sudden release (clasp-knife effect). Spasticity usually affects only one set of muscles around a joint (in the upper extremities, the biceps, forearm pronators, and finger flexors; in the lower extremities, the quadriceps, hamstrings, and plantar flexors). In gegenhalten or paratonia, resistance is present in all directions but varies with the examiner's force and speed. It often seems to be voluntary (fighting back). Gegenhalten is seen normally in infants, but it appears pathologically in adults with dementias or with frontal lobe disease.
Voluntary Strength
Test voluntary strength in several major muscle groups. Survey proximal and distal muscles in each extremity. An adequate screen includes testing of shoulder abduction, elbow extension and flexion, wrist and finger extension, grip strength, hip flexion, knee flexion and extension, and foot dorsiflexion. Observe the patient's gait (discussed under Station and Gait).
For precise documentation, the following rating scale for strength can be used: 0: no movement; 1: flicker; 2: able to move with gravity eliminated (e.g., side-to-side movement on the bed.); 3: able to move against gravity; 4: able to move against resistance but less than expected; 5: normal strength.
In conversion reactions and malingering, strength on formal testing is usually jerky or giving. With sudden passive motions in the opposite direction, the examiner may find that the muscles produce normal resistive force. The examiner may find that the subject can do some voluntary activities (e.g., combing hair, reaching for objects, getting up or sitting down) with muscles that he or she states are too weak to use for such motions on formal testing.
Reflexes
The most important reflexes to test can be recalled by simply counting from 1 to 8. These include the achilles tendon (S1–2), patellar (L3–4), biceps (C5–6), and triceps (C7–8). Activity of the reflexes varies widely among patients and can vary depending on a patient's emotional state and ability to relax muscles. As in the rest of the examination, asymmetries between the two sides generally carry more weight than symmetric reflex changes;
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comparison must be made with the muscles relaxed to a similar degree and with the two extremities in identical positions. A decrease in the reflex is usually caused by disruption of the sensory or motor nerves of the reflex loop itself. Sometimes decreased reflexes are seen immediately after an acute neurologic injury to be followed later by hyper-reflexia such as in acute cerebrovascular accident or acute spinal cord injury, in which case interpretation does not depend on the reflexes alone. Increased reflexes mean upper motor neuron (UMN) disease located anywhere from just above the anterior horn cell to the cerebral cortex.
A Babinski sign consists of dorsiflexion of the big toe after plantar stimulation; it may be associated with dorsiflexion and spreading of the other toes and dorsiflexion of the foot. The classic Babinski response is slow and deliberate. Nonspecific withdrawal may resemble the Babinski reflex, but it is usually rapid and the patient usually complains of subjective distress; a reliable Babinski sign should occur in the absence of any patient discomfort from the stimulus. A Babinski sign may be found as the sole indicator of UMN disease.
Sensation
The patient should be tested for symmetry and for differences in proximal and distal perception in all four extremities. Light touch (posterior columns) is not a well-delineated modality and can be normal when abnormalities of pinprick (lateral spinothalamic tract) or proprioception/vibration (posterior columns) are present; therefore, it should not be used as the sole screen of sensory function. Sensitivity to pinprick, proprioception, and vibratory sense should be tested. There are normal differences in pinprick perception over different areas of the body (e.g., it is decreased over the beard area), but patients usually ignore these differences. Particularly introspective or anxious patients can give very confusing responses and must be told to ignore small subjective differences. Repeated testing is often important to determine the reliability of a patient's response. Vibration sense should be tested with a 128-Hz tuning fork. Proprioception is tested in the most distal joint of the fingers and toes by moving the digit approximately 30 degrees to 45 degrees and then asking the patient to report the direction in which the digits have moved.
The Romberg test (patient stands with feet together and closed eyes while the ability to maintain balance is assessed) is a test of integrity of proprioception and the posterior columns through which proprioception is conveyed. The ability to stand with eyes closed must be interpreted with caution in patients with cerebellar ataxia. If the patient cannot stand steady with eyes open, the Romberg test may be altered to allow testing of posterior columns by having the patient stand with a wide base (to compensate for cerebellar ataxia) and then close the eyes. If the posterior columns are intact, the patient will not waver more than a slight amount.
Coordination/Cerebellar Function
The patient should be told to touch the thumb sequentially to each of the fingers of each hand separately; speed, effort, and rhythm of the movements should be observed. Finger-to-nose-to-finger movement should be tested (subject must touch examiner's moving finger, then touch his or her own nose, then touch the examiner's finger again) for speed, rhythm, intention tremor, and inaccuracy (dysmetria). The subject should be asked to tap each foot separately, and differences in speed, ease, and rhythm should be observed. In these tests, normal subjects show equal ability with either side or are slightly better on the side of their preferred hand. Slowness and subjective effort on repetitive movements, without a loss of rhythm, are characteristic of UMN lesions. Preserved speed with erratic movements and loss of rhythm may be seen in cerebellar disease. Finger–nose–finger testing may be affected by tremor of various types, as described in Chapter 90.
Station and Gait
Any tendency to list or any need for support while sitting, standing, or walking should be observed. The patient should be asked to walk normally and to walk on the heels and toes (to test strength and balance). Tandem gait testing (walking heel-to-toe) requires the patient to narrow the base of support and reveals abnormalities of balance in patients with ataxia not detected on normal walking.
In cerebellar disease, the patient exhibits a wide base (legs widely separated), unsteadiness, and lateral reeling. Lateral reeling can be evaluated by having the patient walk around a chair in both directions; the patient will tend to walk into the chair when it is on the affected side and to veer away from the chair when it is on the unaffected side. Because of fundamental abnormality of motor coordination, the patient with cerebellar disease affecting the lower extremities cannot participate in a standard Romberg test, which requires standing with the two feet together; a modified Romberg test for such patients was described earlier.
In sensory ataxia (loss of proprioception), there is uncertainty, slapping or stamping of the feet, and a positive Romberg test (the patient loses balance with eyes closed but can avoid falling when the eyes are open because of visually mediated vestibular or cerebellar compensation).
In a spastic gait (in UMN disease), the leg does not flex but circumducts, and there is foot dragging (the toe of the sole of the patient's shoe becomes disproportionately worn); there is also loss of arm swinging on the spastic side.
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In a parkinsonian gait, there is unilateral or bilateral loss of arm swinging, the patient is bent forward, and there is rigidity, shuffling, and festination (the upper part of the body advances ahead of the lower extremities; gait becomes faster, as if to catch up).
In LMN paralysis of the pretibial and peroneal muscles, foot-drop is seen; hip flexion is preserved, and the patient lifts the foot very high, advances it by swinging it forward, then slaps it down.
In frontal lobe disease, gait may be wide-based, shuffling, and slow, and turning is slow, but there is no weakness or loss of sensation.
Special Considerations in the Evaluation of Neurologic Symptoms and Signs
Neurologic signs are often subtle in ambulatory patients, compared with patients hospitalized for neurologic disease, and may be related to prior acute neurologic events. Two important considerations in the evaluation of ambulatory patients with neurologic symptoms and signs are the variability in performance over time and the difference between the manifestations of UMN and LMN lesions.
Variability over Time
In patients who have abnormalities of the peripheral nerves, spinal cord, and brainstem, symptoms and signs remain about the same after the basic problem has stabilized; later alterations of the findings usually reflect a change in the patient's disease. On the other hand, cognitive and language impairment can vary greatly from minute to minute, hour to hour, or day to day. The variability affects the psychomotor domain (e.g., performance of everyday tasks, memory, speech and language, and mood). For example,
As a result of this type of variability, members of the patient's family may become confused and angry; they may inquire whether a change in behavior means that the disease is getting worse, or they may conclude that the patient is capable of doing certain tasks but is just not trying sometimes. When the pattern is clearly one of waxing and waning, the family should be reassured that, just as they have their good days and bad days, the patient does also, but in exaggerated and different ways. Chapters 26 (dementia) and 91 (stroke) discuss the evaluation and management of behavioral changes of patients with cerebral damage.
Differences between Upper Motor Neuron and Lower Motor Neuron Symptoms
The manifestations and the course of UMN and LMN damage differ fundamentally. UMN lesions affect the pathways that bring a command from the cortex to the anterior horn cell. UMN function depends on integrity of the cortex and of the corticospinal and corticobulbar tracts. LMN lesions affect the final common pathway for muscle movements. LMN function depends on the integrity of the anterior horn cell in the spinal cord and its nerve fiber for carrying impulses to the muscle cell. A number of points are helpful in recognizing or distinguishing these two patterns of motor abnormality when they are not overt, which is often the case in patients seen in office practice.
Upper Motor Neuron Lesion Syndrome
If a UMN lesion is total, movements are absent. However, there may be preservation of involuntary movements, such as those associated with yawning, laughing, crying, or anger. Classically a patient may have a dense facial weakness with volitional movements but with an emotional smile the face seems to move almost symterically. When there is weakness (paresis) rather than paralysis caused by UMN damage, the following patterns of weakness are seen.
In the face, the lower muscles are usually involved. There is variable but often some involvement of the orbicularis oculi, producing a widened palpebral fissure and weakness of eye closure, but the forehead may be completely spared. This is in contrast to LMN (peripheral) seventh nerve damage, in which both the upper and lower facial muscles are involved, although sometimes mild peripheral seventh nerve weakness (e.g., early Bell palsy, a LMN lesion) can mimic a UMN pattern. One additional differential point is that the LMN lesion produces the same amount of weakness with both a voluntary and an involuntary movement (e.g., laughing). A UMN seventh nerve paresis (e.g., from stroke) may not be apparent when the patient is laughing or crying involuntarily and may be present only when the patient is asked to smile voluntarily.
In the arm, extensors muscles are more affected by UMN lesions and flexor muscles are more affected in the lower extremities. This gives rise to the classic hemiplegic stance with the arm in hyperflexion and leg in hyperextension. Whether or not the muscles are weak in a UMN lesion, voluntary movements are typically slowed and require greater effort than usual, and the ability to make fine movements with the affected limb is lost. A patient with a very mild hemiparesis may be able to squeeze the
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examiner's hand with normal strength, but movements are slower and clumsier than usual; the patient may be unable to easily use fingers individually. They are likely to have weaker finger extensors and weakness of grip. Also, when the patient is asked to extend both arms with the eyes closed, there may be downward and inward drift of the weak arm (pronator sign). In the lower extremity, a patient with such a mild defect may be able to dorsiflex the foot voluntarily. However, the same patient may not be able to do this very rapidly (as revealed on attempted foot tapping), and the movement may not be automatically coordinated with walking, resulting in a foot-drop.
Typically (but not invariably), UMN lesions are accompanied by spasticity and hyperreflexia.
Lower Motor Neuron Lesion Syndrome
Weakness resulting from a permanent LMN lesion is fixed and unchanging. Only the muscles served by the involved spinal cord segment or peripheral nerve are weak. There are none of the widespread effects characteristic of a UMN lesion. Atrophy is usually apparent within several weeks after a LMN lesion, in contrast to UMN lesions, where atrophy is slight and late (many months). Pathologic fasciculations may be present in affected muscle groups, distinguishable from benign occasional muscle twitching by the fact that they are frequent and occur only in the denervated muscles. Muscles are usually flaccid and hyporeflexic or areflexic. If a peripheral nerve has been involved, there may be associated hypesthesia or anesthesia. In muscle disease (e.g., polymyositis, drug-induced myopathy), muscle tone, reflexes, and sensory function are normal. Weakness is typically proximal in the deltoids, iliopsoas, quadriceps, and neck flexor muscles. The patient complains of difficulty climbing steps or using the arms over the head.
In some situations, UMN and LMN lesions occur together. For instance, spinal cord injury typically gives signs of a LMN lesion at the level of the injury, caused by localized destruction of the anterior horn cells and their nerve roots; below the level of the injury, there may be a partial or complete UMN syndrome, with spasticity, hyperreflexia, and preserved involuntary reflexes. Likewise, amyotrophic lateral sclerosis, an idiopathic degenerative disease, affects both pyramidal tract cells and anterior horn cells. Along with LMN-type weakness, fasciculations, and wasting, these patients have hyperreflexia and may have Babinski signs.
Neurovascular Examination
This examination is especially important in patients in whom cerebrovascular disease or an increased risk of cerebrovascular disease is the problem (see Chapter 91). The examination includes an assessment of the heart and peripheral vasculature, with emphasis on the vessels of the head and neck.
Heart and Peripheral Vessels
The radial arteries should be simultaneously palpated at the wrists to determine any asymmetry in pulse amplitude or timing (pulse delay). The brachial arterial blood pressure should be measured in the supine, sitting, and standing positions. Blood pressure should be measured in both arms to check for asymmetry. Unequal blood pressure in the two arms (20 mm Hg or more difference in systolic pressure, more than 10 mm Hg in diastolic pressure) suggests a stenotic lesion of the subclavian or innominate artery on the side with the lower pressure. Orthostatic hypotension, defined as a fall in systolic pressure of more than 15 mm Hg on moving from a supine to an upright position, is common in autonomic neuropathy and may be important in explaining symptoms in patients with severe stenotic lesions of carotid or vertebral–basilar arteries.
A detailed cardiac examination can provide evidence of cardiomegaly, valvular disease, or arrhythmia, each of which may predispose a patient to a stroke. Finally, a complete assessment of the peripheral vasculature, for evidence of widespread atherosclerosis, should include palpation and auscultation of the femoral arteries and palpation of the arterial pulses in the feet.
Vessels of Head and Neck
Evaluation of the vessels of the head and neck may include inspection, palpation, and auscultation.
Inspection
Prominence of the superficial temporal artery with erythema and, occasionally, ulceration of the overlying skin in a patient with persistent malaise is suggestive of giant cell arteritis, an inflammatory process that can lead to retinal or cerebral infarction (see Chapter 87).
Dilation of the episcleral arteries of an eye can result from occlusion of the ipsilateral internal carotid artery; in this instance, the hemisphere on the side of the occlusion is being supplied in a retrograde fashion by the external carotid artery through dilated ophthalmic arteries. The funduscopic examination allows direct visualization of the retinal vessels, and changes resulting from atherosclerosis, hypertension, or diabetes mellitus can be detected. Moreover, the absence of an expected change can be informative, as in the case of the hypertensive patient with normal retinal vessels on the side of a severely stenosed carotid artery; in this instance, occlusive disease of the ipsilateral carotid artery protects the retina from the effects of chronic hypertension. A detailed funduscopic examination may also demonstrate emboli, seen as white or refractile elements in the retinal arterioles
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(see Fig. 91.1 in Chapter 91). These emboli may be composed of cholesterol, platelets and fibrin, or calcium and are suggestive of atherosclerotic carotid occlusive disease or cardiac valve disease.
Palpation
Reports of embolic stroke after firm palpation of a diseased carotid artery have left some clinicians with a sense of trepidation regarding manipulation of this vessel. The current consensus, however, is that gentle palpation of the carotid artery can be performed with limited risk and occasionally provides useful information about the status of the vessel. Perhaps more valuable, and without risk, is palpation of the superficial temporal and facial arteries, which are branches of the external carotid artery. A weak or absent pulse in these arteries on one side of the head is suggestive of ipsilateral occlusive disease of the external or common carotid artery. In contrast, an increase in pulsation in these vessels may result from stenosis or occlusion of the ipsilateral internal carotid artery that causes collateral flow through the external system. Finally, the finding of a tender superficial temporal artery with decreased pulsation may support other data consistent with the diagnosis of giant cell arteritis (see Chapter 87).
Auscultation
After auscultation of the heart to check for transmitted cardiac murmur, the examiner should proceed to the supraclavicular regions over the subclavian arteries and to the carotid arteries up to their bifurcation at the angle of the jaw; a cervical bruit is suggestive, but not diagnostic, of atherosclerotic occlusive disease. Auscultation may at times be useful over the occipital, temporal, and parietal regions of the cranium, and over the orbits. The finding of a cephalic bruit in an adult raises the possibility of an arteriovenous malformation; an orbital bruit suggests intracranial internal carotid artery disease.
Use of Diagnostic Procedures
Patients may be referred for any of a number of diagnostic procedures in the evaluation of a neurologic problem. The principles described inChapter 2 are especially important in deciding which of these procedures to select. Costs of neurodiagnostic tests vary widely from region to region and within a region because fee profiles are individually determined. Charges for many of these tests are in the range of $200 to $2,000; however, practitioners should become aware of costs in their own regions. For most of the procedures currently available for ambulatory application, the definition, principal indications, limitations, and a description of the patient experience are provided here.Chapter 92 provides this information for nerve conduction tests and electromyography.
Radiography of the Skull
Definition of Procedure
The term routine skull radiographs refers to a set of films that include three standard views: lateral, anteroposterior (AP), and inclined AP. Many other views are possible and may be indicated in specific conditions (e.g., basal skull views for a patient with atypical trigeminal neuralgia).
Principal Indications
The principal indications are suspected skull fracture and problems involving the bones, such as metastatic tumor (osteoblastic or osteolytic), myeloma, or Paget disease.
Limitations
The skull radiograph has little value as a screening or diagnostic test for intracranial disease because few intracranial neurologic conditions are associated with bony changes. It has been almost entirely replaced by computed tomography (CT) imaging of the head.
Patient Experience
The patient will be asked to keep his or her head in several uncomfortable positions for short periods of time; accurate positioning might be impossible for elderly patients or for those who have neck problems.
Radiography of the Spine
Definition of Procedure
Standard spine films are usually AP and lateral views; oblique and flexion–extension views usually must be ordered specifically.
Principal Indications
The principal indications are suspected cervical spondylitic radiculopathy (in which case, oblique films are necessary to examine the intervertebral foramina through which the roots pass); suspected cervical or lumbar stenosis, spondylolisthesis, luxation, or subluxation; suspected vertebral fracture; and suspected metastatic tumor.
Limitations
Asymptomatic cervical spondylosis and interspace narrowing caused by disc degeneration are so common after 40 years of age (seeChapters 70 and 71) that their presence has limited usefulness in the absence of more specific findings from the history and physical examination. Negative films provide good evidence against spondylosis as the cause of radicular symptoms.
Radiographs do not show soft tissue, brain, spinal cord, or nerve roots. In patients with herniated intervertebral discs, films are usually normal or show only nonspecific
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intervertebral narrowing. However, patients with congenitally small bony canals (cervical or lumbar stenosis) are at risk for neurologic problems occurring secondary to degenerative changes in the disc and ligaments; the radiologist should be asked specifically about these possibilities if they are important diagnostic considerations.
Patient Experience
The patient must cooperate for several views. Patients with neck problems and those who are elderly may be unable to position themselves for adequate cervical spine films.
Electroencephalography
Definition of Procedure
The electroencephalogram (EEG) is a record of the (1- to 50-mV) electrical rhythms of the brain.
Principal Indications
One principal indication is known or suspected seizure disorder (see Chapter 88). Recording during sleep or after sleep deprivation significantly increases the chances of a useful diagnostic examination; for complex partial seizure, sleep deprivation or extended EEG can increase the yield of the study.
The procedure is also used for confirmation of focal brain lesions in the absence of other evidence (e.g., in the diagnosis and localization of stroke) and for confirmation of diffuse brain disease, such as dementia, delirium, cerebral vasculitis, or drug effect or withdrawal. The EEG may at times be helpful in differentiation of the dementia syndrome of depression from organic dementia (see Chapter 26). For sleep disorders (see Chapter 7), routine and special EEG recording techniques are often indicated.
Limitations
The EEG records cortical activity and, although it is sensitive for processes affecting the cortex, it is not useful for delineation of subcortical processes. However, this property can be useful in investigating vascular lesions when a cortical lesion is not identified on CT or magnetic resonance imaging (MRI).
Negative Electroencephalogram
A single negative EEG is not evidence for the absence of a seizure disorder. For example, up to 50% of patients with known epilepsy have normal interictal records. Serial or repeated negative EEGs may be far more significant (see Chapter 88). A normal EEG in a patient with suspected delirium suggests psychiatric illness.
“Mildly Abnormal” Electroencephalogram
Depending on the reader and the classification scheme, some adult EEGs (5% to 30% or more) can be classified as minimally or mildly but nonspecifically abnormal. The relevance of these interpretations must be judged in the context of the patients’ problems but should not be given undue weight because of the broad range of normal findings. This is particularly true in infancy, childhood, adolescence, and old age. For instance, temporal slow activity is present after 40 years of age in as many as 30% to 40% of subjects.
Patient Experience
Subjects are asked to lie down or recline while surface electrodes are attached with electrode paste. The total procedure takes an average of 40 to 60 minutes, with 20 to 30 minutes of actual recording time. For most of the actual recording, the patient is simply asked to lie calmly with eyes closed. Additional studies that most laboratories routinely perform include recording during hyperventilation (for 3 to 5 minutes) and during photic simulation with a repetitive flash. For many tracings, subjects are encouraged to fall asleep. Some laboratories induce sleep with oral chloral hydrate if permitted by the referring physician; if this is planned in advance, the patient should be told to bring someone who can drive the patient home.
The EEG is extremely sensitive to patient movement, sweating, and muscle tension, any of which can make a tracing uninterpretable.
For sleep-deprived EEGs, the patient is asked to stay up the night before, and the EEG is done in the laboratory first thing in the morning.
Lumbar Puncture
Definition of Procedure
Lumbar puncture is performed to obtain cerebrospinal fluid (CSF) for analysis and to measure intracranial pressure. A normal opening pressure does not exceed 200 mm. Normal CSF is crystal clear and contains no more than five mononuclear cells; the normal glucose concentration is two thirds that of a simultaneously determined serum glucose level, and the protein concentration is less than 45 mg/dL. Xanthochromia is a yellowish discoloration of the spinal fluid that is present in red cell breakdown (indicating previous subarachnoid hemorrhage), in hyperbilirubinemia, and with extreme elevations of protein.
Principal Indications
Elevated intracranial pressure must be documented to diagnose idiopathic intracranial hypertension (see Chapter 87). The low-pressure headache syndrome (see Chapter 87) can be documented by lumbar puncture but may be exacerbated by the procedure.
Lumbar puncture is used in the evaluation of patients with suspected meningitis; those with suspected or known chronic infection of the CNS, such as syphilis, acquired immunodeficiency syndrome (AIDS), Lyme disease,
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cryptococcus, or tuberculosis; those with subarachnoid hemorrhage; those with suspected demyelinating or inflammatory disease, such as multiple sclerosis or inflammatory neuropathy (e.g., Guillain–Barre syndrome); and those with undiagnosed CNS disease.
Limitations
The opening pressure depends on the intracranial pressure, which can be elevated by measures that increase venous pressure, such as straining and tightening of the abdominal musculature. A tense patient with an elevated opening pressure should be encouraged to relax, and pressure should be remeasured before fluid is removed. The closing pressure depends on the pressure/volume dynamics, which are influenced by the amount of fluid removed and the intracranial compliance. Abnormalities of CSF are nonspecific; however, when they are interpreted in the context of the clinical presentation and further evaluation in the laboratory, diagnostic accuracy can be increased.
The procedure is completely safe if infection of the skin overlying the puncture site, an intracranial mass lesion, and bilateral brain edema are ruled out. Neurologic consultation and CT or MRI of the brain before the lumbar puncture will eliminate the potential for complications caused by the latter two problems. If papilledema is present, an imaging study to rule out a mass lesion before lumbar puncture is always mandatory in an outpatient.
Patient Experience
Patients are often reluctant to undergo lumbar puncture, based on widespread belief that it is dangerous and very painful. The patient should be reassured that, after neurologic evaluation or an imaging study, the procedure is safe. Under adequate local anesthesia, the discomfort is mild. When lumbar puncture is done properly under aseptic conditions, the most common complication is a postprocedure headache (see Chapter 87). The probability of postprocedure headache can be decreased by using the smallest-gauge needle that is practical (20-gauge in most adults). Newer, blunt-tipped “atraumatic” lumbar puncture needles are postulated to result in a smaller dural hole and have been demonstrated to reduce headache after the procedure. The flow rate through the needle may be compromised with a needle of 22 gauge or higher, but it is adequate with the 20-gauge needle. For most patients, a 20-gauge atraumatic needle is ideal. Performing the tap with the patient in a sitting position also increases the likelihood of a first-pass nontraumatic tap; however, the lateral decubitus position is necessary to obtain a precise opening pressure measurement. After the lumbar puncture, the patient is instructed to lie flat for 5 to 60 minutes and to drink copious amounts of fluid over the ensuing 6 hours. A minority of patients complain of pain at the puncture site, which may be treated with nonnarcotic analgesics.
Duplex Scan
Definition of Procedure
Duplex scanning combines B-mode ultrasonic scanning of the carotid bifurcation with spectral analysis of a Doppler signal to assess plaque disease. The extent of plaque is classified into categories that vary among laboratories but usually approximate the following categories: 0% to 15%, 16% to 40%, 41% to 60%, 61% to 80%, 81% to 99%, and occluded. The percentage of stenosis approximates angiographic measurements; however, some discrepancy occurs because duplex scanning approximates area, whereas angiography is usually a linear measurement. Plaque characteristics such as calcification, hemorrhage, and ulceration can be determined. Plaque distribution in common, internal, and external carotid arteries is delineated.
Principal Indications
This noninvasive screening technique may be used in the evaluation of patients with asymptomatic carotid bruits, transient ischemic attacks (TIAs), or stroke. Duplex ultrasonography compares favorably with MRI angiography (see Cerebral Angiography) in predicting 100% carotid artery occlusion and 70% carotid artery stenosis (1,2). With use of this procedure, stroke-prone patients may be selected for arteriography (see Chapter 91).
Limitations
No more than 3 cm of the internal carotid artery can be imaged above the bifurcation. The proximal common carotid is imaged for a variable distance, depending on its tortuousity. This technique cannot distinguish complete occlusion from a very-high-grade stenosis. No information about intracranial disease is obtained.
Patient Experience
A comprehensive duplex examination of the carotid arteries takes approximately 45 minutes. The transducer head is held over the carotid bifurcation at the angle of the mandible. There is no appreciable discomfort or risk.
Cerebral Angiography
Definition of Procedure
Cerebral angiography provides imaging by intra-arterial injection of a contrast agent, by magnetic resonance technique (magnetic resonance angiography [MRA]), or by helical CT (see Computed Tomography).
For intra-arterial angiography a flexible catheter is placed in an artery, usually the femoral artery, and passed
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to the aortic arch, where it is selectively advanced into the arteries of interest, including the common carotid or vertebral arteries, which are then injected with a contrast agent. Serial radiographs are taken.
MRA is a noninvasive procedure that uses radiofrequency signals to construct images of the cerebral vessels.
Principal Indications
Cerebral angiography can be used in the delineation of a number of intracranial processes. Since the advent of CT and MRI, the principal indication for angiography has been the definitive diagnosis of cerebrovascular diseases including extracranial and intracranial arterial stenosis, vascular malformations, aneurysms, and vasculitis.
Limitations
Intra-arterial Angiography
Adequate renal function is a prerequisite. Serious complications (approximately 1% to 2% of patients) occur related to femoral puncture, manipulation of the catheter, and reactions to the contrast agent. Serious complications include femoral artery clot with embolization, stroke, and anaphylactic reaction to the contrast agent. The ionic load of the contrast agent may precipitate heart failure in susceptible patients.
Magnetic Resonance Angiography
Resolution with MRA is not yet as acute as with intra-arterial angiography; this limitation is related to disturbances of laminar flow and to the multiplanar course of cerebral vessels. This can lead to intracranial and extracranial arteries appearing more stenotic or artifactually occluded on MRA. The hazards associated with MRA are the same as those listed later for MRI. MRA may be used to noninvasively image the intracranial vessels and the carotid and vertebral arteries in the neck.
Patient Experience
For intra-arterial angiography, the patient lies on a radiography table and a femoral artery puncture is made after local anesthesia with lidocaine. The major discomfort is a burning sensation, which can be intense, that is felt with the injection of contrast material. Less stressful reactions are a metallic taste in the mouth, itching, and occasionally hives. Mild or severe bronchospasm, although uncommon, can occur. The patient must be able to lie still for the radiographs. After the procedure, patients are instructed to drink a large amount of fluid, limit activity, and monitor for signs of bleeding or obstruction at or distal to the site of arterial puncture. Instructions usually include limiting ambulation, no lifting or other strenuous activity for 24 hours, and no bathing for at least 12 hours. For MRA, the patient experience is the same as for MRI (see Magnetic Resonance Imaging).
Computed Tomography Scanning of the Head
Definition of Procedure
CT uses narrow x-ray beams to exploit differences in x-ray absorption between different kinds of intracranial tissues. Without contrast, the CT scanner can distinguish the densities of bone, calcified tissue, blood, gray matter, white matter, CSF, and air. Its resolving power is proportional to the differences in the densities of these tissues. Although CT scanning results are typically presented as horizontal slices through the brain, present technology allows slices to be reconstructed in the vertical plane or in any other plane to give a better perspective on abnormal findings. Helical CT reduces scanning time with some loss of resolution. It is useful for CT angiography.
Intravenous injection of contrast material is used to enhance the x-ray contrast of vascular lesions such as tumors and abscesses; contrast material diffuses into an area where the blood–brain barrier has broken down to increase the x-ray absorption density.
CT scanning is highly sensitive and often diagnostic; therefore, it has a place in both screening and specific investigations. Use of a contrast agent is not necessary for screening studies. CT angiography is becoming a very quick and efficient method for evaluating intracerebral and extracerebral arteries. It does not appear to lead to “over call” stenosis the way MRA can.
Principal Indications
CT is used in the evaluation of patients with intracranial problems when structural alteration is known or suspected, such as tumor, cerebrovascular disease, degenerative disease (e.g., Alzheimer disease, Huntington disease), hydrocephalus, subdural hematoma, or unexplained headache. CT is superior to MRI in identifying calcification and hemorrhage. CT is safe for patients with aneurysm clips, pacemakers, and implanted defibrillators. The imaging time and noise are much less than with MRI, which makes CT useful for uncooperative or confused patients. Many conditions can be assessed without the use of a radiographic contrast agent; this should be strongly considered for patients who have conditions for which the most common causes do not require contrast for visualization (i.e., dementia, remote stroke) and for elderly persons, in whom the risks associated with contrast studies are somewhat greater. CTA can quickly evaluate vascular stenosis with a high degree of accuracy.
Limitations
A negative CT scan does not exclude a structural lesion or damage. The damage may not have caused enough change in local absorption density to produce contrast with its
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surroundings. This is not uncommon in cases of cerebral infarction within 1 week after the initial insult, when the original edema has cleared and new vessel formation and phagocytosis have not yet begun to affect brain density. A CT scan can also be negative because the damage is in an area of the brain that is poorly visualized, such as the brainstem or spinal cord. Additionally, a CT scan is typically negative after transient ischemia, but this finding does not detract from the significance of the event and the need for further study. CT is less sensitive than MRI for stroke, vascular malformation, tumor, abscess, and demyelinating lesions.
When it is performed without contrast injection, CT scanning is essentially free of risk. When contrast material is used, the risk is that of the contrast agent itself—often a warm flush in the face, nausea, or sometimes vomiting. In approximately 1 case in 100,000 there is the possibility of death from anaphylaxis. The serum creatinine concentration should be measured before the infusion of contrast material. If it is abnormal, the risks and precautions related to renal insult from contrast media must be considered (see Chapter 52).
Patient Experience
The patient is asked to lie down with his or her head inside what looks somewhat like a large doughnut. Straps are usually applied over the forehead to prevent motion. The procedure takes 5 to 20 minutes, depending on the scanner. Contrast material may be given intravenously, by single bolus, or by intravenous drip.
Computed Tomography Scanning of the Spine
The definition of the procedure and the patient experience are the same as for CT scanning of the head.
Principal Indications
CT of the spine is the preferred technique for evaluation of acute fractures and bony impingement on the central canal. It does not visualize the spinal cord or nerve roots and has therefore been replaced by MRI for visualization of the spinal cord and disc disease. CT of the spine can be used for patients with aneurysm clips, pacemakers, and debrillators.
Limitations
If the spinal region to be studied spans three or more vertebrae, MRI is more practical than CT because MRI can visualize an entire region of the spine. Diagnostic accuracy of CT presupposes use of a localizer image for accurate selection of the plane and angle of the slice, as well as a thin slice for optimal resolution.
Magnetic Resonance Imaging of the Central Nervous System
Definition of Procedure
MRI is a noninvasive imaging technique that yields better contrast and sensitivity for most CNS lesions than does radiographic CT. It uses radio waves of a specific (resonance) frequency. No ionizing radiation is required. MRI studies usually are substantially more expensive than CT studies.
Principal Indications
The high tissue contrast achieved with MRI makes it the imaging technique of choice for most CNS diseases, including tumors (especially posterior fossa tumors), cerebral infarctions, vascular malformations, abscesses, white matter disease (e.g., multiple sclerosis), and spinal cord abnormalities including herniated nucleus pulposus.
In several aspects of brain imaging, MRI has been shown to be superior to CT. MRI provides better imaging of the posterior fossa than does CT because the surrounding bone causes no streak artifacts. Tissue contrast with MRI is superior to that obtained with CT. As a result, gray matter and white matter are better delineated and the extent of certain diseases is better appreciated. For example, MRI can reveal many more of the lesions of multiple sclerosis than can CT. Major blood vessels can be identified with MRI without the need for contrast media because the flowing blood, as a result of its velocity, appears dark. The common carotid, internal carotid, external carotid, and vertebral and basilar arteries are easily seen. Aneurysms of the internal carotid artery have been detected, and a thrombus in the lumen of the artery can be identified. Disc disease is easily evaluated without injection of contrast material, as is required for myelography. Diffusion weighted MRI can show strokes within minutes where conventional CT and MRI may not show acute strokes for 6 to 24 hours.
Limitations
MRI has high sensitivity for disease detection in the CNS but is limited and may be less useful than CT in the evaluation of acute hemorrhages, calcified lesions, and bony structures, each of which is easily detected by CT. Because the scanning time is longer than that for CT studies, MRI studies are more subject to artifact caused by patient motion. Some claustrophobic patients cannot undergo the procedure without sedation.
The known hazards of MRI result from the force and torque exerted by the field on ferromagnetic objects brought into the vicinity of the magnet and on patients’ prostheses, such as surgical clips, pacemakers, cochlear implants, metal in the eye, and joint replacements. Cardiac pacemaker and implanted defibrillator function can
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be disrupted and false signals produced. Ferromagnetic metal clips, such as those on cerebral aneurysms, may be dislodged.
Patient Experience
The patient lies supine on a table identical to the CT scanner, but the head holder consists of a plastic coil that passes very close to the patient's face. The entire table is then moved into a larger tunnel. The patient may experience claustrophobia. A loud knocking sound is heard during data collection, during which time the patient must remain absolutely still. The test lasts about 45 minutes.
Specific References*
For annotated General References and resources related to this chapter, visit http://www.hopkinsbayview.org/PAMreferences.