Central Vestibular Disorders
Gail Ishiyama
Akira Ishiyama
A 48-year-old male has a 5- or 6-year history of gradually worsening gait disorder. He has had occasionally bouts of positional nystagmus that were called “benign positional vertigo.” However, the modified Epley maneuver failed to resolve the positional nystagmus. He has noted increasing difficulty when walking, and recently he noted a clumsiness of his hands and arms. On examination, he has a downbeat nystagmus that is noted when looking down or to either side, and he has a saccadic pursuit. Coordination testing reveals dysdiadochokinesis and dysmetria of his extremities. He is unable to tandem walk and cannot stand in the Romberg position with eyes open or closed. A magnetic resonance imaging (MRI) demonstrates atrophy of the cerebellar vermis.
A 64-year-old woman has a history of the sudden onset of spontaneous vertigo with a persistent tilting of the body to the left as if pulled by a strong external force. She was completely unable to walk at the onset. She has a Horner’s in the left pupil, large (hypermetric) saccades toward the left, and smaller (hypometric) saccades toward the right. She also had a skew deviation of the eyes with the left eye lower than the right and the upper poles rotated to the left. An MRI with diffusion-weighted imaging (DWI) was negative.
Both of these patients exhibit signs and symptoms of a central vestibular disorder. In this chapter, we discuss ways to distinguish central from peripheral vestibular disorders, the presentation of the common central vestibular disorders, the evaluation of a patient with dizziness, that is, the clinical examination, important questions to ask on history, and the audiologic and vestibular testing results in central vestibular disorders. In both patients, there are other neurologic symptoms noted in addition to the vertigo. Patient 1 has difficulty walking even when not having vertigo, and clumsiness of the extremities. Dysdiadochokinesis and dysmetria are cerebellar signs described below under cerebellar degeneration. Patient 2 has lateropulsion of the body (a sense of being pulled toward one side) and of the eye movements (bigger movements toward one side) associated with the vertigo.
From the history alone, there should be suspicion that these are not peripheral disorders. Patient 1 had been misdiagnosed with benign positional vertigo (BPV) on initial presentation, and patient 2 had been misdiagnosed with vestibular neuritis. Patient 1 had a history of cerebellar ataxia, and patient 2 had a history of a Wallenberg stroke. The negative MRI in a Wallenberg stroke may occur because the size of the stroke is too small to be detected. In central vestibular disorders, the inability to walk is oftentimes severe and cerebellar imbalance is often described as “clumsiness” or a “drunken feeling.” The following chapter reviews the central and vestibular anatomy briefly, describes the specialized portions of the examination and history pertinent to evaluation of central vestibular disorders, and reviews the most common central vestibular disorders that may present to the otolaryngologist with complaints of dizziness.
THE CENTRAL AND PERIPHERAL VESTIBULAR SYSTEM
The peripheral vestibular system refers to the labyrinthine organs of the inner ear, which includes the end organs of the semicircular canals (cristae ampullares) and of the utricle and saccule (maculae) that contain the hair cells, and the innervating primary afferent neuron and nerve (Scarpa ganglia). The central vestibular system refers to the secondary vestibular neurons and their projections. The secondary neurons are the vestibular nuclei in the brainstem, divided into the superior (angular or Bechterew), the lateral (Deiters), the medial, and the descending (inferior or spinal) (1). In primates, the vestibulocerebellar and vestibuloocular connections are relatively more prominent in comparison with vestibulospinal connections. The
vestibular nuclei play a large role in central compensation after a peripheral labyrinthine injury.
vestibular nuclei play a large role in central compensation after a peripheral labyrinthine injury.
Vertigo that is characterized by the sense of movement of the environment can result from lesions of the labyrinth, the vestibular nerve, or the interconnecting vestibular pathways in the brainstem and cerebellum. Vertigo is an illusion of movement, often of rotation, although the movement may be described as that of linear displacement (back and forth vertigo). Lesions of the labyrinth, the vestibular nerve, the vestibular nuclei, and the visual-vestibular interaction centers in the brainstem and cerebellum can produce a spontaneous vestibular nystagmus and vertigo. The production of spontaneous nystagmus requires an imbalance of tonic activity of the vestibuloocular pathways.
A lesion of the left vestibular labyrinth or nerve will produce a right-beating nystagmus with a torsional component. In lesions of the vestibular nuclei, the direction of spontaneous nystagmus that results is not as predictable and may be toward or away from the side of the lesion. Functional brain imaging demonstrates evidence for vestibular projections to the parietotemporal cortex and the thalamus in both normative controls and subjects with peripheral and central vestibular disorders (2). Because these vestibulo-thalamo-cortical projections do not carry tonic signals, a lesion in these cortical (within the brain) pathways will not produce vertigo but can produce an alteration of the body orientation (e.g., a sense of tilt or tendency to fall).
History of the dizzy patient: differentiating between a central versus peripheral cause of vertigo (Table 167.1). It is important for the clinician to distinguish the symptoms that the patient refers to as “dizziness.” This distinction can be a clinical decision of critical importance. In evaluation of the patient with dizziness, the clinician must obtain as accurate and thorough of a history as possible to aid in distinguishing probable peripheral versus central causes. Dizziness may refer to a light-headedness that feels as if nearly passing out, near faint dizziness. Typical causes include orthostatic hypotension or cardiac insufficiency, for example, aortic stenosis. Oftentimes, dizziness due to cardiac disease will worsen with exertion, and is not characterized by vertigo. When the patient describes a sense of movement of the environment, the symptom of vertigo, it is strongly suggestive of an imbalance within the vestibular system. Vertigo can occur due to either a peripheral or a central vestibular lesion. Typically, vertigo is an episodic phenomenon, whereas a nonvestibular dizziness is more likely to be a continuous nonspecific type of dizziness. Episodes that occur only in specific places, such as walking through the store aisles, are highly unlikely to be vestibular, and are more likely related to anxiety syndromes or to a migraine-associated sensitivity to visual stimuli. Gait imbalance is often described as “dizziness,” and the differential can include peripheral or central vestibular disorders, as well as neurodegenerative conditions such as Parkinson disease or spinal stenosis.
TABLE 167.1 DISTINGUISHING CENTRAL FROM PERIPHERAL CAUSES OF DIZZINESS | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Peripheral and central spontaneous nystagmus (Table 167.2). Spontaneous nystagmus occurs when there is an imbalance of the tonic firing and signals to the oculomotor neurons. Spontaneous nystagmus is in reference to a nystagmus that occurs with the eyes in primary position, without any external stimuli. The primary position is the eyes looking forward in midposition, and the patient in the seated position. Positional nystagmus is nystagmus that is not present in the sitting position but is present in other head or body (e.g., head-hanging) position. Both spontaneous and positional nystagmus can occur secondary to either peripheral or central vestibular disorders.
The type of nystagmus can oftentimes localize the lesion. The vestibular system, both peripheral and central, is the primary source of tonic signals for most types of spontaneous nystagmus. A peripheral vestibular lesion, a lesion of the labyrinth or vestibular nerve, results in a spontaneous nystagmus with combined torsional, horizontal, and vertical components with predominantly a horizontal component. A lesion of the vestibular nucleus can cause a horizontal torsional nystagmus that appears similar to a peripheral nystagmus. However, the direction does not indicate the side of the lesion, and the nystagmus is not suppressed with fixation because of the damage to the visual- vestibular pathways (3).
Spontaneous peripheral nystagmus. Whether the lesion is of the labyrinth or the vestibular nerve, the type of nystagmus is invariable: horizontal, torsional beating toward the contralateral side, increasing in frequency and amplitude
on gaze to the fast component side, inhibited by fixation. A peripheral nystagmus is inhibited by fixation because the suppression requires an intact brainstem and cerebellum. The clinician should check that the nystagmus follows Alexander law: gaze in the direction of the fast component will increase the frequency and amplitude in a peripheral nystagmus, whereas gaze in the opposite direction will cause a decrease in the nystagmus (4). A peripheral nystagmus does not change direction with changes in eye position or with changes in the head or body position.
on gaze to the fast component side, inhibited by fixation. A peripheral nystagmus is inhibited by fixation because the suppression requires an intact brainstem and cerebellum. The clinician should check that the nystagmus follows Alexander law: gaze in the direction of the fast component will increase the frequency and amplitude in a peripheral nystagmus, whereas gaze in the opposite direction will cause a decrease in the nystagmus (4). A peripheral nystagmus does not change direction with changes in eye position or with changes in the head or body position.
TABLE 167.2 DISTINGUISHING CHARACTERISTICS OF PERIPHERAL VERSUS CENTRAL NYSTAGMUS | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Spontaneous central nystagmus. The appearance of a central nystagmus can vary depending on the location of the lesion. Usually a central nystagmus will be prominent with or without fixation. Central spontaneous nystagmus occurs when there is an imbalance of the central vestibuloocular (VOR) or smooth pursuit pathways. In contrast to the peripheral vestibular pathways, the central horizontal and vertical pathways are separate, and thus a purely vertical or purely horizontal nystagmus is common in a central vestibular disorder. A central spontaneous nystagmus can be purely vertical, purely horizontal, or purely torsional, or some combination. Similarly to a peripheral nystagmus, gaze in the direction of the fast component may increase the amplitude and frequency of the nystagmus. However, gaze in the opposite direction will often cause a change in direction of a central vestibular nystagmus. A null region may be found several degrees off of the center beyond which the direction of the nystagmus changes. A direction-changing nystagmus is always central. An apparent direction-changing nystagmus can occur in one peripheral entity: horizontal variant of benign paroxysmal positional vertigo (5).
Positional nystagmus, central and peripheral disorders. A nystagmus that is triggered by a change in position can be either peripheral or central in etiology. BPV, a peripheral vestibular disorder due to loose otoliths, is by far the most common cause of recurrent attacks of positional vertigo. However, a positional nystagmus and vertigo can be due to a central vestibular finding. Common patterns of central positional nystagmus include a persistent downbeat nystagmus, or a horizontal direction-changing nystagmus. The patterns of nystagmus can appear similar to an anterior canal BPV, or a horizontal canal variant BPV, respectively. The common central disorders that present with a positional nystagmus that can mimic anterior (downbeat) or horizontal (direction-changing horizontal) nystagmus include Chiari malformation, tumors of the cerebellum or around the fourth ventricle, or spinocerebellar ataxia neurodegenerative conditions. There are no central vestibular disorders that induce a nystagmus that is characteristic of the classic and most common BPV, posterior canal BPV: a burst of upbeat, torsional geotropic nystagmus with a duration usually less than 30 seconds, and always less than 1 minute.
EXAMINATION OF EYE MOVEMENTS IN CENTRAL VESTIBULAR DISORDERS
The patient should be observed in all eye positions for nystagmus (a total of eight positions): gaze 30 degrees to the left and then 30 degrees to the right, and thereafter on upgaze and downgaze to the left, to the right, and at midline, with each position held for at least 20 seconds. Traditional terms used by otolaryngologists include the following: First degree nystagmus is present only on gaze in the direction of the fast component. Second degree nystagmus is present in the primary position (midposition, looking straight ahead). Third degree nystagmus is present even on gaze away from the fast component. These terms are most applicable to peripheral nystagmus patterns, and may not be relevant in central vestibular nystagmus. A peripheral nystagmus should not change direction with any positional change of the body or of the eyes.
Smooth pursuit, both horizontal and vertical, should be evaluated by having the patient follow the clinician’s pen or finger. The patient should be able to follow the target smoothly, without repeated “stops” that would be indicative of a “saccadic pursuit.” If the eyes follow the target
using a series of saccades rather than smoothly, then the central oculomotor pathway is unable to generate a smooth pursuit and is dysfunctional. A saccadic pursuit is nonspecific and can occur with normal aging, and is common in disorders such as multiple sclerosis (MS), Parkinson disease, or other neurodegenerative disorders. A severely saccadic pursuit may be seen in cerebellar conditions as in the 48-year-old patient initially described. Saccadic pursuit suggests central pathology.
using a series of saccades rather than smoothly, then the central oculomotor pathway is unable to generate a smooth pursuit and is dysfunctional. A saccadic pursuit is nonspecific and can occur with normal aging, and is common in disorders such as multiple sclerosis (MS), Parkinson disease, or other neurodegenerative disorders. A severely saccadic pursuit may be seen in cerebellar conditions as in the 48-year-old patient initially described. Saccadic pursuit suggests central pathology.
Saccades. Saccadic eye movements are examined by asking the patient to fixate alternately between two fixed targets. The first target is usually in the primary position, “Look at my nose.” Then, the patient is asked to look quickly to a target placed 15 degrees to the right, “Quickly look to my pen,” and then placed 15 degrees to the left. Saccades that repeated “overshoot,” for example, when attempting to look at a target on the right, the patient saccades further to the right, or “undershoot” is a sign of central vestibuloocular motor dysfunction (hypermetric or hypometric saccades, respectively), that usually localize to cerebellar or cerebellar peduncle lesions. Slow saccades may indicate a brainstem lesion, and delayed saccades can be seen in cerebral hemispheric lesions.
Saccadic intrusions include square wave jerks, ocular flutter, and opsoclonus. Saccadic intrusions occur when unwanted saccades disrupt steady fixation. A differential of these entities is beyond the scope of this chapter. All of these entities are associated with central vestibular pathology, and would warrant referral to a neurologic specialist. These entities are common with cerebellar lesions, progressive supranuclear palsy, Huntington disease, Friedreich ataxia, or paraneoplastic syndromes.
Ocular tilt reaction. If a normal subject tilts the head toward the right, then the eyes will reflexively counterroll and skew to allow for visual stabilization. Traditionally, a skew deviation, which clinically is described as a diplopia with two images split both slightly horizontally, and vertically, was considered to be a central finding. However, the ocular tilt reaction is a labyrinthine reflex, and can be seen by stimulation of the contralateral utricular nerve (6). The ocular tilt reaction can be seen in peripheral labyrinthine lesions (7), in which case the head tilt and lower eye are toward the ipsilateral lesion. An ocular tilt reaction can also be seen in lateral medullary infarcts (Wallenberg syndrome) (8), in which case it is also toward the ipsilateral side. In mesencephalic lesions (of the midbrain), the tilt is toward the contralateral side. Skew deviation and the ocular tilt reaction are noted following ablative procedures of the vestibular periphery (labyrinthectomy or vestibular nerve section) and in association with idiopathic sudden unilateral peripheral vestibular or cochleovestibular loss (9). This also can occur following resection of acoustic neuroma, another form of acute deafferentation. The skew deviation is often the earliest to compensate, disappearing within a few days.
Positional nystagmus. The patient should be evaluated for nystagmus in the head-hanging right and left (Dix-Hallpike maneuver). In BPV, the nystagmus fatigues, has a few seconds or more of latency, and will be a torsional upbeat nystagmus if the particles fell into the posterior semicircular canal. Positioning in a central positional nystagmus may induce a downbeat nystagmus that persists as long as the head-hanging position is held. Other central nystagmus include a direction-changing nystagmus or rebound nystagmus. Two positional maneuvers can be conducted. The Dix-Hallpike maneuver is conducted by placing the patient in right or left head-hanging position very quickly. In the side-lying test, the patient moves slowly into the side-lying position and then the clinician evaluates for a slow persistent nystagmus that would be indicative of a central vestibular disorder.
Fixation suppression means that the removal of ability to focus, as with Frenzel glasses, is associated with an increasing of the nystagmus. A peripheral nystagmus is usually inhibited by fixation. If Frenzel glasses are not available, the clinician can observe the nystagmus using an ophthalmoscope and covering the patient’s other eye. If the nystagmus increases, then the nystagmus was inhibited by fixation, a characteristic of peripheral nystagmus.
Vibration-induced nystagmus. The other maneuver that can be used in the clinical setting is application of vibration to the mastoid, which can elicit a peripheral nystagmus in a compensated peripheral vestibulopathy from vestibular neuritis, Ménière disease, or anterior semicircular canal dehiscence (using vibration over the suboccipital cranium) (10, 11).
Head-shaking nystagmus. The clinician should examine for head-shaking induced nystagmus. In this maneuver, the patient is asked to turn the head quickly from right to left about 20 times at 2 to 3 Hz, and the eye movements are then examined, ideally with the suppression of fixation using Frenzel lenses. Head shaking nystagmus indicates a latent asymmetry of the velocity-storage that can be due to a peripheral or a central vestibular disorder. In peripheral disorders, the nystagmus induced will be of the peripheral type: horizontal with a torsional component. In central disorders, the nystagmus induced can be vertical, downbeating or upbeating, or can be horizontal. In a study of 16 patients with lateral medullary infarction (vestibular nuclei infarction), a central vestibular disorder, head-shaking nystagmus was observed in 87.5%, and was ipsilesional in all cases. Even in patients with a contralesional nystagmus spontaneously, the head-shaking nystagmus was ipsilesional (12).
Spontaneous downbeat nystagmus. A downbeat nystagmus has a fast phase beating vertically downward and typically will increase in vertical amplitude with horizontal gaze deviation (13). A downbeat nystagmus is always a central vestibular nystagmus. Lesions of the uvula and flocculonodular lobes of the cerebellum in the monkey will induce a downbeat nystagmus (14). In humans, a downbeat nystagmus often localizes to the cervicomedullary junction, including the midline cerebellum (vermis) and associated
pathologies include cerebellar ataxias, vertebrobasilar ischemia (VBI), MS, and Arnold-Chiari (AC) malformation (15). AC is a malformation associated with increased pressure on the flocculonodular region of the cerebellum (see Arnold-Chiari malformation). Decompression surgery may allow for reversal to normal (13).
pathologies include cerebellar ataxias, vertebrobasilar ischemia (VBI), MS, and Arnold-Chiari (AC) malformation (15). AC is a malformation associated with increased pressure on the flocculonodular region of the cerebellum (see Arnold-Chiari malformation). Decompression surgery may allow for reversal to normal (13).
Other types of central vestibular nystagmus. Other pathologic nystagmus patterns include gaze-evoked nystagmus, which is seen when the patient tries to move eyes away from primary (midline) position. In normal subjects, a nystagmus can be seen at the outermost peripheral positions of gaze. This normal physiologic variant is termed, “end-point nystagmus” and is normal. Typically, physiologic gaze-evoked nystagmus can be distinguished from pathologic forms in that it has lesser amplitude and frequency, is unsustained, is relatively symmetrical, and is not associated with any other ocular movement abnormalities. However, it has been noted that a gaze-evoked nystagmus can be seen in up to 50% of the normal population (16). Furthermore, a recent study evaluating 56 subjects for gaze-evoked nystagmus reported that normal subjects have a high incidence of physiologic gaze-evoked nystagmus at even smaller angles of gaze: 93% at extreme gaze, 73% at 40 degrees, 43% at 30 degrees, and even at the lowest angle tested 21% at 10 degrees (17). In the clinical setting, the most common cause of a pathologic gaze-evoked nystagmus is drugs such as phenobarbital, phenytoin, alcohol, and benzodiazepines. Central vestibular pathologies associated with a gaze-evoked nystagmus include MS and cerebellar atrophy, and these diseases would usually be associated with other eye movement abnormalities.
Rebound nystagmus. Rebound nystagmus is a type of gazeevoked nystagmus that disappears or reverses as the lateral gaze is held. After an attempted prolonged eccentric gaze of 20 or 30 seconds, upon returning to the primary position, a rebound nystagmus appears with the fast phase toward the center and the slow phase toward the side of attempted gaze-holding. Rebound nystagmus usually indicates cerebellar pathology, such as olivopontocerebellar atrophy (18). Tumors at the cerebellopontine angle, such as acoustic neuromas, may cause a Bruns’ nystagmus. This presents with a low-frequency, large amplitude nystagmus when looking ipsilaterally, and a high-frequency, low amplitude nystagmus when looking contralaterally. In a study of 984 patients with acoustic neuroma, Bruns’ nystagmus was present in 11% and was associated with larger tumor size, with 92% of patients with larger than 3.5 cm tumor having Bruns nystagmus (19).
OTHER FOCAL NEUROLOGIC EXAMINATION FINDINGS IN CENTRAL VESTIBULAR DISORDERS
As noted above, a careful examination of eye movements is important.
Examine the patient for head tilt (seen ipsilateral to a Wallenberg infarct) and the body for lateropulsion (also seen in central vestibular disorders, such as ipsilateral to a Wallenberg infarct). The lateropulsion may be so severe that the patient is unable to stand, which would usually be an indication of a central vestibular disorder. There may be concomitant lateropulsion of the eyes, with larger saccades toward the ipsilateral lesioned side in Wallenberg syndrome (20).
Facial weakness (CN VII): a peripheral weakness will include the upper and lower facial muscles, whereas a central weakness will spare the upper facial muscles (i.e., raising the eyebrows). Of note, both a peripheral and a central type of facial weakness can occur in association with a Wallenberg dorsolateral medullary stroke.
Facial sensory loss (CN V): the clinician should check the upper (V1), mid (V2), and lower chin area (V3) for light touch using a cotton wisp, and temperature sensation using a cold tuning fork (can be cooled under water). Avoid the angle of the jaw as it is innervated by upper cervical roots. Although some clinicians recommend pinprick testing, patients may find it unpleasant. Initial examination with a cotton wisp and cold tuning fork serves as a screening evaluation for additional methods of physical examination. The clinician can also check the corneal reflex which tests V1 (afferent) and VII (efferent). Ask the patient to look up and toward the opposite side and using a cotton wisp, lightly touch the cornea. This should elicit a blink response, which should be consensual. An absent corneal reflex supplements the findings of a trigeminal sensory deficit.
Visual fields testing the temporal and nasal upper, middle, and lower quadrants of each eye. Most infarcts in the posterior cerebral artery distribution will cause a visual field deficit.
Crossed sensory loss: a key indication for brainstem involvement, for example, facial sensory loss on the side ipsilateral to the infarct and extremity sensory loss on the contralateral side. A crossed sensory loss often localizes the insult to the dorsolateral medullary (Wallenberg infarct), and can be variably associated with vertigo, ipsilateral Horner’s, hiccoughs, and dysarthria and dysphagia.
Horner syndrome consists of miosis (pupillary constriction) and ptosis, secondary to loss of sympathetic innervation. The difference in pupil size is termed anisocoria. The clinician should evaluate the patient in relative darkness since the abnormal miotic (small) pupil cannot dilate properly in a low light setting. In the Wallenberg syndrome, the Horner syndrome is ipsilateral to the infarct. Because the sympathetic pathway in the brainstem is close to the spinothalamic tract (pain and temperature) for the contralateral body, Horner syndrome due to brainstem lesions is often associated with contralateral loss of pain and temperature.
Head thrust test or Halmagyi maneuver (21): when positive, patients will have catch-up saccade because
they are unable to keep their eyes on the clinician’s nose when the head is rapidly, passively turned to the side with the lesion. In bilateral vestibulopathy (e.g., gentamicin ototoxicity), the test will reveal catchup saccades to both sides. In a right-sided vestibular neuritis, there may be a catch-up saccade when the head is turned passively by the clinician to the patient’s right side.
Romberg: ask the patient to stand with the feet together with eyes open and eyes closed. A positive Romberg occurs when the patient’s imbalance significantly increases with eye closure. The accentuation of imbalance with eye closure is a sign of either vestibular imbalance or proprioceptive loss. A patient with a central vestibular disorder such as a cerebellar stroke will likely be unable to stand in the Romberg position (feet together) and will be unsteady whether the eyes are open or closed. Strictly speaking, the inability to stand with the feet together (Romberg position) with the eyes open, as well as closed, is not a positive Romberg.
Always ask the patient to try to walk. Patients with lateropulsion will lean strongly toward one side (usually toward the lesion). Severe lateropulsion that interferes with walking or standing is usually a sign of central vestibular disorder.
Tandem walk: when performed with the eyes open, tandem walking is predominantly a test of cerebellar function. Vision and proprioceptive (position sense) will allow for a relatively normal tandem walk in a compensated peripheral vestibular loss (e.g., vestibular neuritis in the past). An acute vestibular lesion will usually impair the tandem walk, even with eyes open. Patients with cerebellar lesions will oftentimes have a wide-based gait and are unable to tandem walk even taking a single step.
Testing for coordination (cerebellar or central vestibular pathways) and other clinical manifestations of cerebellar dysfunction.
Hypotonia: a diminished deep tendon reflex, oftentimes more prominent in the upper extremities or a “pendular” reflex. After tapping the patella, the patient’s leg swings to and fro like a pendulum. This sign is indicative of large cerebellar hemispheric damage.
Dysarthria: a slurring of the speech, abnormal articulation, and prosody (rhythm) is common in cerebellar syndromes.
Eye movements as noted above. Common cerebellar eye movement findings include downbeat nystagmus, hypermetric saccades, and rebound nystagmus. d) Ataxia: inability to coordinate movements of the voluntary motor acts, which err in rate, range, force, and duration.
Appendicular coordination: Finger-to-nose. Ask the patient to touch the tip of the index finger to their nose with the eyes closed. Finger-to-finger. Ask the patient to touch the tip of their index finger to yours. An intention tremor is missing the target and increasing the amplitude of tremor as the target is approached. Dysmetria occurs when the patient overshoots or undershoots the target.
Appendicular coordination: check rapid alternating movements, for example, turning the hand alternating palm and back of the hand or a rhythmic slapping of the knee. An inability to conduct rapid alternating movements smoothly is called dysdiadochokinesis.
Appendicular coordination: check heel-to-shin. While lying down, ask the patient to “draw” a perfectly straight line with the back of the heel, up and down the opposite shin.
Tandem walk: a sensitive but nonspecific test for balance. In central vestibular disorders, the patient may be completely unable to tandem, and when severe the patient may be unable to stand. Patients with spinal stenosis or strokes causing motor weakness would also be unable to tandem walk. Similarly, patients with neurodegenerative conditions such as Parkinson disease would be unable to tandem walk. The quality of the walk can provide clues to the etiology. Spinal stenosis may be associated with a “scissoring” quality of the walk, and Parkinson may be associated with a shuffling gait and a pill-rolling tremor.
ASSOCIATED SYMPTOMS IN CENTRAL VESTIBULAR DISORDERS
In central vestibular disorders, the symptoms associated with the vertigo or onset of imbalance will be dictated by the location of the pathology. Central vestibular disorders generally localize to the brainstem or the cerebellum. Clinical examples of central vestibular disorders that can present with vertigo and imbalance include Wallenberg syndrome (an infarct of the dorsolateral medullary), MS, brainstem tumors or encephalitis, cerebellar ataxias, AC malformation, and cerebellopontine angle tumors.
Important Questions to Ask the Patient
“Do you feel as if you are about to pass out?” This would be consistent with global hypoperfusion, which can occur in orthostasis, cardiac insufficiency, or vasovagal reactions.
“If you are seated still when the dizziness occurs, do you feel as if the world or you are moving?” This would be consistent with true vertigo.
“How long is the vertigo spell, and is the onset abrupt or gradual?” Vertebrobasilar transient ischemic attacks (TIAs) often present with vertigo of abrupt onset, lasting 3 to 4 minutes in duration. The duration of the vertigo is critical in determining the differential diagnoses (see Table 167.3).
TABLE 167.3 LENGTH OF VERTIGO IN COMMON VESTIBULAR DISORDERS | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
“Are the spells provoked by positional changes of the head?” BPV is characterized by spells of vertigo induced by tilting the head back or rolling over while prone. It is important to note that vertigo of any etiology is associated with increased sensitivity to head movement.
“Have you had loss of consciousness or confusion with the spells of dizziness?” Peripheral vestibular disorders are not associated with a loss of consciousness. Some patients may have a vasovagal response to the nausea and vomiting. However, sudden spells of falls with loss of consciousness would be characteristic of vertebrobasilar insufficiency, brainstem disorders affecting the reticular activating system, or as a diagnosis of exclusion, basilar migraine.
“In between the spells of dizziness or vertigo, do you feel imbalanced when walking or clumsy with your extremities? Some but not all cerebellar disorders are characterized by spells of vertigo. However, nearly all cerebellar disorders are characterized by persistent ataxia and/or clumsiness of the extremities. Notably, a cerebellar syndrome may affect the gait (truncal ataxia) without affecting the limbs (appendicular ataxia).
“Are there accompanying otologic signs with the spells of vertigo, such as aural fullness, hearing loss, or tinnitus?” These may indicate Ménière disease, but can also be seen in basilar migraine and TIAs in the anterior inferior cerebellar artery (AICA) distribution.
“Are there accompanying focal neurologic signs with the spells of vertigo, or in isolation?” (Box 167.1). The presence of focal neurologic signs would be highly suspicious for vertebrobasilar TIAs, indicating a high risk for stroke.
“Is there a personal history of hypertension, hyperlipidemia, diabetes mellitus, cancer, coronary artery disease, peripheral vascular disease, migraines with aura or complicated migraine, strokes or TIAs in the past?” Vascular risk factors should alert the clinician to the possibility of vertebrobasilar insufficiency as the cause of spells of vertigo. Additionally, chronic nonspecific imbalance may be secondary to microvascular ischemic changes in a patient with vascular risk factors. Both require evaluation with an MRI of the brain and preventative treatment.
BOX 167.1 NEUROLOGIC REVIEW OF SYSTEMS
Have you experienced any of the following symptoms? Please check yes or no and indicate if constant or in episodes.
1. Double vision, blurred vision, or blindness
2. Numbness of the face or extremities
3. Weakness in arms or legs
4. Clumsiness in arms or legs
5. Confusion or loss of consciousness
6. Difficulty with speech
7. Difficulty swallowing
8. Pain in neck or shoulder
Imaging modalities.
There are now excellent noninvasive imaging technology to evaluate the cerebrovascular arteries including the vertebrobasilar arteries, and the arch of the aorta, and takeoff of vessels. Contrast-enhanced magnetic resonance angiography (CE-MRA) can identify arterial stenosis with nearly the same sensitivity as traditional cerebral angiography (28). MRI with FLAIR (fluid-attenuated inversion recovery) imaging is especially sensitive for demyelinating lesions in MS. A sagittal MRI that includes the posterior fossa is excellent to evaluate for AC malformation. DWI is highly sensitive to ischemia or infarcts (strokes), but can be negative when the lesion is small.
VERTEBROBASILAR ISCHEMIA AND INFARCTS
Vertebrobasilar TIAs are likely to recur and to progress to stroke. It is critical to recognize the first vertebrobasilar TIA. There appears to be as high or even higher risk of stroke after VBI TIAs than after carotid TIAs. Identifying a basilar stenosis is critical as there is a very high incidence of stroke or TIA recurrence (28). Referral to a stroke center is often indicated as interventions may range from anticoagulation, stenting, angioplasty, or clot retrieval angiography.
VBI is associated with the traditional vascular risk factors. If a patient presents with vertigo or hearing loss as a TIA, then the localization is in the posterior circulation, that is, VBI. The incidence of vascular risk factors in patients with posterior circulation strokes is high. In a study of consecutive patients presenting to a large stroke center, the New England Medical Center Posterior Circulation Registry, the group of patients with extensive atherosclerotic disease involving the basilar artery had a very high incidence of stroke risk factors. Hypertension was present in 70%, and coronary artery disease was present in 60%. The incidence of stroke risk factors was also high in 300
consecutive patients presenting with posterior circulation strokes or TIAs of any cause: 58% had hypertension, 25% had diabetes mellitus, 42% tobacco abuse, 33% had coronary artery disease, 19% had hyperlipidemia. Other important modifiable lifestyle factors included alcohol abuse (13%), obesity (11%), and use of oral contraceptive pills (2%). Hyperlipidemia was more common in intracranial vertebral artery disease and basilar disease (31% and 35%, respectively) in comparison with extracranial vertebral artery disease (18%) (23).
consecutive patients presenting with posterior circulation strokes or TIAs of any cause: 58% had hypertension, 25% had diabetes mellitus, 42% tobacco abuse, 33% had coronary artery disease, 19% had hyperlipidemia. Other important modifiable lifestyle factors included alcohol abuse (13%), obesity (11%), and use of oral contraceptive pills (2%). Hyperlipidemia was more common in intracranial vertebral artery disease and basilar disease (31% and 35%, respectively) in comparison with extracranial vertebral artery disease (18%) (23).
Isolated vertigo as transient VBI. Both the central and peripheral vestibular pathways are fed by the posterior circulation: the vertebrobasilar arteries. The vertebrobasilar system represents about 20% of cerebral blood flow, and posterior circulation TIAs and strokes represent about 20% of all TIAs and strokes. In fact, isolated spells of vertigo are likely the most common presentation of vertebrobasilar TIA first described by Williams and Wilson, 1962 (Table 167.4) (29). In that study, 48% of the patients with VBI had vertigo. In the guinea pig, occlusion of the internal auditory artery causes cessation of cochlear potentials and degeneration within minutes (30). However, clinically in humans, the predominant first symptom and most common symptom reported is vertigo. In a posterior circulation TIA, the onset of vertigo is usually very abrupt and spontaneous, rather than being induced by position, and there may be a flurry of spells within a few weeks’ time. The duration of the vertigo is critical. In the case of VBI, the duration of vertigo is 3 to 4 minutes in length. A comprehensive discussion of this topic is provided by the authors in another reference (31).
Some neurologists have stated that isolated vertigo is an unlikely presentation of VBI given that there are multiple neurologic structures packed closely together within the brainstem, making isolated vestibular nuclei ischemia unlikely. However, the clinical data clearly demonstrate that isolated vertigo can be a TIA in the posterior circulation. Grad and Baloh (24
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
