Chapter 53: Dizziness and Vertigo
Approach to the patient: Dizziness or Vertigo
The term dizziness is used by pts to describe a variety of common sensations that include vertigo, light-headedness, faintness, and imbalance. With a careful history, distinguishing between faintness (presyncope; Chap. 52: Syncope) and vertigo (a sense of movement of the body or the environment, most often a feeling of spinning) is usually possible.
When the meaning of dizziness is uncertain, provocative tests to reproduce the symptoms may be helpful. Valsalva maneuver, hyperventilation, or postural changes leading to orthostasis may reproduce faintness. Rapid rotation in a swivel chair is a simple provocative test to reproduce vertigo.
Benign positional vertigo is identified by the Dix-Hallpike maneuver to elicit vertigo and the characteristic nystagmus; the pt begins in a sitting position with head turned 45°; holding the back of the head, the examiner gently lowers the pt to supine position with head extended backward 20° and observes for nystagmus; after 30 s the pt is raised to sitting position and after 1 min rest the maneuver is repeated on other side.
The most useful bedside test of peripheral vestibular function is the head impulse test, in which the vestibuloocular reflex (VOR) is assessed with small-amplitude (∼20 degrees) rapid head rotations. While the pt fixates on a target, the head is rotated to the left or right. If the VOR is deficient (e.g., in peripheral vertigo), the rotation is followed by a catch-up saccade in the opposite direction (e.g., a leftward saccade after a rightward rotation).
If a central cause for the vertigo is suspected (e.g., no signs of peripheral vertigo, no hearing loss, no ear sensations, or the presence of other neurologic abnormalities indicating central nervous system [CNS] disease), then prompt evaluation for central pathology is required. The initial test is usually an MRI scan of the posterior fossa. Distinguishing between central and peripheral etiologies can be accomplished with vestibular function tests, including videonystagmography and simple bedside examinations including the head impulse test and dynamic visual acuity (measure acuity at rest and with head rotated back and forth by the examiner; a drop in acuity of more than one line on a near card or Snellen chart indicates vestibular dysfunction).
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