Evaluation of the Vestibular System and Vestibular Disorders

Key Points

1.
Characteristics of Nystagmus in Benign Paroxysmal Positional Vertigo (BPPV): nystagmus in posterior canal BPPV is a torsional, up-beating positional nystagmus triggered by the Dix-Hallpike test with the affected ear down. It has a paroxysmal quality, building to a peak and then disappearing over several more seconds. There is a latency of a few seconds before it appears, and it fatigues with repeated Dix-Hallpike maneuvers.
2.
Vestibular Migraine: history of recurrent, severe, nauseating headaches or recurrent auras with vertiginous episodes. Vertigo spells vary in duration, from seconds or minutes up to hours or days. It is common in people <50 years of age, and there is an increased risk of BPPV, sleep apnea, and Ménière’s disease in this group.
3.
Ménière’s Triad: 1. Hearing loss that fluctuates, worsens during vertigo spells, and is associated with a sensation of fullness or pressure in the ear. 2. Tinnitus that fluctuates, can have a roaring quality, and is louder during vertigo spells. 3. Vertigo is usually hours in duration, severe, and associated with vomiting.
4.
Characteristics of the Normal Caloric Response: cold water irrigation causes nystagmus beating away from the irrigated ear, whereas warm water irrigation causes nystagmus beating toward the irrigated ear. A useful mnemonic for nystagmus direction is COWS ( C old O pposite, W arm S ame). The ear with the weakest response is the damaged ear.
5.
How to Test Each Inner Ear Sensory Organ
- a.
  Horizontal semicircular canal: horizontal head impulse test, caloric examination, rotational chair tests
- b.
  Anterior semicircular canal: vertical head impulse test, Dix-Hallpike test
- c.
  Posterior semicircular canal: vertical head impulse test, Dix-Hallpike test
- d.
  Utricle: ocular VEMP
- e.
  Saccule: cervical VEMP

Pearls

1.
Peripheral nystagmus becomes faster and more apparent when the patient gazes in the direction of the fast phase; for example, a right-beating nystagmus worsens on right gaze. This is called Alexander’s law .
2.
Multisensory imbalance can be improved using walking aids. Trekking poles are helpful early in the disorder, but as the disease progresses, a rolling walker with handbrakes is the most effective treatment.
3.
Patients with headaches and vertigo should be questioned about snoring. Sleep apnea is associated with morning headaches and worsened migraine and can be associated with recurrent brief dizziness and progressive inner ear disorders such as Ménière’s disease.
4.
Peripheral vestibular losses of less than 50% are usually hard to detect by impulse testing. Caloric testing is better able to detect these mild to moderate deficits.

Questions

1 When you evaluate a dizzy patient, what should your examination include?

Careful observation for nystagmus; examination of the ears and hearing assessment are always required. The neurologic examination should include an evaluation of cranial nerves and examination of cerebellar function by testing 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 ( Fig. 36.1 ) to rule out BPPV and head impulse testing to rule out vestibular loss.

2 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 and then focused to the left and right. Direct the patient to focus the eyes upward and then downward. Note the direction of nystagmus for each eye position.

3 How is the Dix-Hallpike maneuver performed?

The Dix-Hallpike maneuver is a test for BPPV ( Fig. 36.1 ). 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 or 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.

4 What constitutes an abnormal Dix-Hallpike maneuver?

Although this test has many implications, it is most commonly used to diagnose posterior semicircular canal BPPV. A rotatory nystagmus and sensation of vertigo that begins a few seconds after assuming the head-hanging position is characteristic of BPPV. The nystagmus fades in 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.

5 Can BPPV also affect the horizontal or anterior semicircular canals?

Yes, horizontal canal BPPV causes a violent, purely horizontal paroxysm of nystagmus on Dix-Hallpike testing 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 test 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.

6 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.

7 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 quickly. 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.

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