35 Evaluation of the Vestibular System & Vestibular Disorders Flashcards
When you evaluate a dizzy patient, what should your examination include?
When you evaluate a dizzy patient, what should your examination include?
Careful observation for nystagmus and a check of the ears and hearing are always required. The neurologic examination should include an evaluation of cranial nerves and examination of cerebellar function by testing of coordination, gait, and balance. The neck should be evaluated for carotid artery bruits. Examination of the legs and feet for sensory lesions or range-of-motion restrictions is important. At the end of the exam, you should always perform a Dix-Hallpike maneuver (Figure 35-1) to rule out benign paroxysmal positional vertigo (BPPV), and head impulse testing to rule out vestibular loss.
How do you properly examine a patient for nystagmus?
How do you properly examine a patient for nystagmus?
Nystagmus has slow and quick components. The slow component is generated by the vestibular system and causes the eye to smoothly rotate. The fast phase represents a corrective response, a saccade that quickly returns the eyes to their original position. By convention, the direction of the nystagmus is named by its fast component, since to the observer the eyes appear to be “beating” in the direction of the saccades. You should evaluate for spontaneous nystagmus by viewing the patient’s eyes with the eyes centered, then focused to the left and right. Direct the patient to focus the eyes upward, then downward. Note the direction of nystagmus for each eye position.
How is the Dix-Hallpike maneuver performed?
How is the Dix-Hallpike maneuver performed?
The Dix-Hallpike maneuver is a test for BPPV (Figure 35-1). The patient is seated on the examination table with the examiner on the side to be tested. Emphasize to the patient that the eyes should be kept open throughout the maneuver, so that you can observe nystagmus. To test the right ear, hold the patient’s head turned 45 degrees to the right and then swiftly move the patient into the supine position until the head overhangs the table edge. Continue to support the patient’s head throughout the test. After at least 30 seconds, assist the patient in reassuming the sitting position. The test is then repeated on the left. If the patient is elderly, frail, or has neck problems, the test can be done by lowering the head onto the table instead of allowing the head to overhang the edge of the table.
What constitutes an abnormal Dix-Hallpike maneuver?
What constitutes an abnormal Dix-Hallpike maneuver?
Although this test has many implications, it is most valuable when used to diagnose posterior semicircular canal BPPV. A rotatory nystagmus and sensation of vertigo that begins several seconds after assuming the head-hanging position is characteristic of BPPV. The nystagmus fades after less than 1 minute, reverses direction upon sitting, and “fatigues” or decreases in intensity with repeated testing. For example, if the patient has a left pathologic ear, he or she will manifest a mixed vertical and rotatory nystagmus when positioned with the left ear down, and the upper poles of the eyes will appear to you as if they are beating toward the floor.
Can BPPV affect the horizontal or anterior semicircular canals, too?
Can BPPV affect the horizontal or anterior semicircular canals, too?
Yes, horizontal canal BPPV causes a violent, purely horizontal paroxysm of nystagmus on Dix-Hallpike that can last for as long as a minute and often causes vomiting. Anterior canal BPPV causes a fine downbeating nystagmus that can be persistent for a few minutes on Dix-Hallpike testing. Repeating the Dix-Hallpike immediately after a BPPV treatment maneuver can cause particles to fall into the horizontal semicircular canal. Anterior canal BPPV is also more likely to appear in patients who have been recently treated with in-office or home maneuvers for posterior canal BPPV.
Do other disorders cause nystagmus with the Dix-Hallpike maneuver?
Do other disorders cause nystagmus with the Dix-Hallpike maneuver?
Other disorders of central or peripheral vestibular pathways may cause pathologic positional nystagmus. This kind of nystagmus usually does not fade away while the head remains in the hanging position, nor does it fatigue on repeated testing. It can appear when the patient is slowly brought to the supine position and does not require a quick movement like the Dix-Hallpike test to bring it out.
What are the usual symptoms of BPPV?
What are the usual symptoms of BPPV?
Typically, sudden episodes of vertigo are precipitated by specific head movements, usually in bed at night. For example, the patient may complain of vertigo precipitated by rolling over in bed, lying down into bed, or arising. These episodes are brief, lasting less than a minute. A change in hearing or tinnitus is not typical. Although BPPV becomes more frequent with age, it can occur in patients of any age group. This condition usually resolves spontaneously over a period of weeks to months. Failure to respond to treatment maneuvers is an indicator for formal vestibular testing.
How is BPPV treated?
How is BPPV treated?
This disorder usually disappears without treatment over several weeks, but the course can often be shortened dramatically by using therapeutic head maneuvers designed to rotate the particles out of the affected canal. The Epley maneuver, also called the canalith repositioning procedure, has proven very useful, with a success rate near 90%. Other liberatory maneuvers have also been described.
A patient returns after a third episode of BPPV. Is there a home exercise for this condition?
A patient returns after a third episode of BPPV. Is there a home exercise for this condition?
The half somersault maneuver has been shown to be a useful home exercise (Figure 35-2). The head is inverted in the somersault position, turned to face the elbow on the affected side, and then is raised first to back level and then fully upright, pausing for 30 seconds in each position. Patients who cannot perform the half somersault can use the Epley maneuver or the Semont maneuver at home but will usually require an assistant to help. It is best to wait 15 minutes between repetitions of maneuvers to avoid displacing newly removed particles back into the semicircular canals.
You suspect that a patient’s vestibular symptoms are due to migraine. On what grounds do you base your diagnosis?
You suspect that a patient’s vestibular symptoms are due to migraine. On what grounds do you base your diagnosis?
Migraine-associated dizziness is the most common cause of chronic dizziness in young adults. Although this disorder often has a benign course between attacks, it can cause serious debility. Migraine is believed to be genetic in origin, and is the most common cause of dizziness in children and young adults. Vertigo may occur as part of an aura, as part of the headache phase, or between the headaches, and it varies in duration from seconds to days. Typically the headaches are moderate to severe, last for hours, and are associated with nausea, photophobia, or phonophobia. Headaches may be accompanied by an aura, often consisting of visual illusions such as a scintillating scotoma, or they may occur without aura. There is an association between migraine and other more serious vertigo disorders, particularly Ménière’s disease.
How is migraine-associated dizziness treated?
How is migraine-associated dizziness treated?
Migraine with vertigo can be treated with suppressants such as meclizine or promethazine if attacks are infrequent. However, prophylactic treatment is necessary if attacks are occurring more than once every few weeks. Tricyclic antidepressants such as amitriptyline are a good first-line choice; beta blockers, calcium channel blockers, topiramate, divalproex, and acetazolamide are also effective in some individuals. Medications should be tried for at least 1 month before another type is tried because the effect often builds over several weeks. Newer migraine treatments aimed at the headache phase, such as triptans, are generally not effective for migraine-associated vertigo spells.
Why do the elderly develop imbalance?
Why do the elderly develop imbalance?
Normal balance depends on a normal vestibular system, normal vision and visual tracking, and normal sensation and proprioception in the lower extremities. Usually vision, visual tracking, and sensation in the feet become impaired with age. When coupled with any vestibular disorder, or with a gradual age-related decline in vestibular function, multisensory imbalance occurs.
Affected people usually feel dizzy only when ambulating, and their dizziness is relieved when using a grocery store cart, for example.
What is the typical course of viral infections of the eighth nerve?
What is the typical course of viral infections of the eighth nerve?
This acute unilateral vestibulopathy can be preceded by a nonspecific viral illness. Within hours to days, the patient experiences the sudden onset of vertigo. The vertigo reaches a peak rapidly and then gradually declines over a few days to weeks. Cochlear symptoms vary, ranging from normal hearing to a mild high-frequency hearing loss to sudden profound deafness in one ear. If there is no hearing loss, the disease is called vestibular neuritis. Total destruction of all auditory and vestibular function in one ear can occur with certain viruses, such as measles, mumps, or herpes zoster. After the severe symptoms have subsided, the patient may experience mild light-headedness with sudden movement that can persist for months. With time, however, the patient’s vestibular system compensates, and the dizziness usually clears.
How are viral inner ear infections treated?
How are viral inner ear infections treated?
A brief course of steroids should be initiated within the first few days if possible. Vestibular suppressant medication, such as meclizine, diazepam, or promethazine, is used to control vomiting. Suppressants should be discontinued after a week because they interfere with the normal process of compensation to vestibular injuries. Patients who are still symptomatic at that time are good candidates for vestibular rehabilitation.
Describe the head impulse test.
Describe the head impulse test.
This test of the vestibular system, also called the “head thrust test” (in awake patients) or the “doll’s eye test” (in comatose patients) uses quick head rotation to demonstrate high-grade vestibular lesions in disorders such as vestibular neuritis. Awake patients should be asked to stare into your eyes during the test (Figure 35-3). Face the patient while holding the patient’s head and then briskly turn the head to the right and to the left. Normally, the patient’s gaze remains “locked” straight ahead on your eyes. The test is abnormal if the patient’s gaze can be jerked away from yours by the quick head turn. In patients with peripheral vestibular loss, a series of “catch-up” or refixation saccades (Halmagyi’s sign) may occur as the eyes attempt to regain focus on you. If the test results are abnormal with a right head turn, the patient has right vestibular injury; if abnormal to the left, the left ear is injured.
How can the otolith organs be tested?
How can the otolith organs be tested?
Vestibular evoked myogenic potential (VEMP) testing is able to assess the function of the otolith organs (Figure 35-3). Electrodes over the sternocleidomastoid muscles are able to detect electromyographic waveforms that result when the saccule is stimulated by loud sounds (cervical or cVEMP). Absence of the waveform on one side is a significant abnormality. However, the test is less reliable in patients over age 60, and in those with neck pain, stiffness or weakness.
Delays in the response can indicate a retrocochlear lesion on the affected side, and a lowered sound threshold for the response can be a sign of semicircular canal dehiscence. Electrodes positioned below the eyes can detect waveforms resulting from sound stimulation of the utricle (ocular or oVEMP).
