The value and function of the vestibular system may often be underestimated when considering the various special senses that we possess. However, of all the special senses, unilateral loss of the vestibular system may cause the most significant determent for our daily function and survival. Millions of people present annually to their physician with the complaint of dizziness. The goal of this chapter is to discuss the common disorders that affect the vestibular system and provide a framework for the evaluation, diagnosis, and treatment of patients with vestibular disorders.
Injury to the peripheral or central vestibular system causes asymmetry in the baseline input into the vestibular centers and this causes vertigo, nystagmus, vomiting, and a sense of falling toward the side of the injury. Vertigo is defined as the illusion of movement. However, the chief complaint of patients with injury to the vestibular system is usually not vertigo but dizziness. If the complaint is clarified to be vertigo, the duration, periodicity, and circumstance of the vertigo and the presence of other neurological signs or symptoms allow for categorization of the vertigo.
The proximity of the vestibular system to the auditory system often causes vertigo to be coupled with hearing loss. The role of the otolaryngologist includes clarifying the subset of patients who have vertigo due to injury to the vestibular system and differentiating central from peripheral vestibular disorders. The evaluation includes a complete head and neck and vestibular examination (Table 56–1). The diagnostic evaluation includes audiology, vestibular testing, and imaging. Knowing the duration of the vertigo or disequilibrium and the presence or absence of hearing loss allows for a narrowing of the differential diagnosis (Table 56–2). The vertigo may be due to injury of the peripheral or central vestibular system. Often, the presence of other neurological abnormalities leads to an investigation for a central cause of the vertigo. However, central vestibular injury due to a lesion or stroke may mimic a peripheral vestibular disorder.
Table 56–1. Steps in a Vestibular Evaluation. |Favorite Table|Download (.pdf)
Table 56–1. Steps in a Vestibular Evaluation.
Head and neck examination, including cranial nerves
Spontaneous and gaze-evoked nystagmus with Frenzel glasses
- Direction: fixed-peripheral, changing-central
- Form: jerk-peripheral, pendular-central
- Fixation: suppression-peripheral, enchanced-central
Smooth pursuit–“Follow my fingers.”
Saccades–“Look to my left or right finger when I say to.”
- Dysmetric: cerebellar
- Slow: brainstem
- Late: frontal lobe
- Disconjugate: multiple sclerosis
- Normal: no refixation saccade
- Abnormal: refixation saccade (peripheral)
Headshake–“10 degrees, 2 cycles/second, 20 seconds.”
- Normal: no nystagmus
- Abnormal: horizontal, nystagmus-peripheral; vertical, nystagmus-central (brainstem)
Dynamic visual activity–“Look at Schnell chart with head shake.”
- Normal: <3 line drop
- Abnormal: 3 or more line drop-bilateral vestibular loss
Fixation suppression–“Look at your thumb during rotation.”
- Normal: no nystagmus
- Abnormal: nystagmus-central (flocculus)
- Normal: no nystagmus
- Abnormal: downbeating, fatigable, rotatory nystagmus
Cerebellum–finger to nose, rapid alternating movements, heel to shin
Table 56–2. Differential Diagnosis of ...
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