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INTRODUCTION

APPROACH TO THE PATIENT Dizziness or Vertigo

The term dizziness is used by pts to describe a variety of head sensations or gait unsteadiness. With a careful history, distinguishing between faintness (presyncope; Chap. 56) and vertigo (an illusory or hallucinatory 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 degrees; holding the back of the head, examiner gently lowers pt to supine position with head extended backward 20 degrees 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.

If a central cause for the vertigo is suspected (e.g., signs of peripheral vertigo are absent or other neurologic abnormalities are present), 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 exams including the head impulse test (rapid, small amplitude head rotations while pt instructed to fixate on the examiner's face; if peripheral, a catch-up saccade is seen at the end of the rotation) and dynamic visual acuity (measure acuity at rest and with head rotated back and forth by examiner; a drop in acuity of more than one line on a near card or Snellen chart indicates vestibular dysfunction).

FAINTNESS

Faintness is usually described as light-headedness followed by visual blurring and postural swaying along with a feeling of warmth, diaphoresis, and nausea. It is a symptom of insufficient blood, oxygen, or, rarely, glucose supply to the brain. It can occur prior to a syncopal event of any etiology (Chap. 56) and with hyperventilation or hypoglycemia. Lightheadedness can rarely occur during an aura before a seizure. Chronic lightheadedness is a common somatic complaint with depression.

VERTIGO

Usually due to a disturbance in the vestibular system; abnormalities in the visual or somatosensory systems may also contribute to vertigo. Frequently accompanied by nausea, postural unsteadiness, and gait ataxia; may be provoked or worsened by head movement.

Physiologic vertigo results from unfamiliar head movement (seasickness) or a mismatch between visual-proprioceptive-vestibular system inputs (height vertigo, visual vertigo during motion picture chase scenes). True vertigo almost never occurs as a presyncopal symptom.

Pathologic vertigo may be caused by a peripheral (labyrinth or eighth nerve) or central CNS lesion. Distinguishing between these causes ...

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