Dizziness is a common, vexing symptom, and epidemiologic data indicate that more than 20% of adults experience dizziness within a given year. The diagnosis is frequently challenging, in part because patients use the term to refer to a variety of different sensations, including feelings of faintness, spinning, and other illusions of motion, imbalance, and anxiety. Other descriptive words, such as light-headedness, are equally ambiguous, referring in some cases to a presyncopal sensation due to hypoperfusion of the brain and in others to disequilibrium and imbalance. Patients often have difficulty distinguishing among these various symptoms, and the words they choose do not describe the underlying etiology reliably.
Vascular disorders cause presyncopal dizziness as a result of cardiac dysrhythmia, orthostatic hypotension, medication effects, or another cause. Such presyncopal sensations vary in duration; they may increase in severity until loss of consciousness occurs, or they may resolve before loss of consciousness if the cerebral ischemia is corrected. Faintness and syncope, which are discussed in detail in Chap. 20, should always be considered when one is evaluating patients with brief episodes of dizziness or dizziness that occurs with upright posture.
Vestibular causes of dizziness may be due to peripheral lesions that affect the labyrinths or vestibular nerves or to involvement of the central vestibular pathways. They may be paroxysmal or due to a fixed unilateral or bilateral vestibular deficit. Acute unilateral lesions cause vertigo due to a sudden imbalance in vestibular inputs from the two labyrinths. Bilateral lesions cause imbalance and instability of vision when the head moves (oscillopsia). Other causes of dizziness include nonvestibular imbalance and gait disorders (e.g., loss of proprioception from sensory neuropathy, parkinsonism) and anxiety.
In evaluating patients with dizziness, questions to consider include the following: (1) is it dangerous (e.g., arrhythmia, transient ischemic attack/stroke)? (2) is it vestibular? and (3) if vestibular, is it peripheral or central? A careful history and examination often provide enough information to answer these questions and determine whether additional studies or referral to a specialist is necessary.
Approach to the Patient: Dizziness
When a patient presents with dizziness, the first step is to delineate more precisely the nature of the symptom. In the case of vestibular disorders, the physical symptoms depend on whether the lesion is unilateral or bilateral and whether it is acute or chronic and progressive. Vertigo, an illusion of self or environmental motion, implies asymmetry of vestibular inputs from the two labyrinths or in their central pathways and is usually acute. Symmetric bilateral vestibular hypofunction causes imbalance but no vertigo. Because of the ambiguity in patients' descriptions of their symptoms, diagnosis based simply on symptom character is typically unreliable. The history should focus closely on other features, including whether dizziness is paroxysmal or has occurred only once, the duration of each episode, any provoking factors, and the symptoms that accompany the dizziness.