Dizziness is an imprecise symptom used to describe a variety of common sensations that include vertigo, light-headedness, faintness, and imbalance. Vertigo refers to a sense of spinning or other motion that may be physiological, occurring during or after a sustained head rotation, or pathological, due to vestibular dysfunction. The term light-headedness is classically applied to presyncopal sensations resulting from brain hypoperfusion but as used by patients has little specificity, as it may also refer to other symptoms such as disequilibrium and imbalance. A challenge to diagnosis is that patients often have difficulty distinguishing among these various symptoms, and the words they choose do not reliably indicate the underlying etiology.
There are many causes of dizziness. Vestibular dizziness (vertigo or imbalance) may be due to peripheral disorders that affect the labyrinths or vestibular nerves, or it may result from disruption of central vestibular pathways. It 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) due to loss of normal vestibular reflexes.
Presyncopal dizziness occurs when cardiac dysrhythmia, orthostatic hypotension, medication effects, or another cause leads to brain hypoperfusion. 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. 18, should always be considered when one is evaluating patients with brief episodes of dizziness or dizziness that occurs with upright posture. Other causes of dizziness include non-vestibular imbalance and gait disorders (e.g., loss of proprioception from sensory neuropathy, parkinsonism), and anxiety.
When 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? (3) If vestibular, is it peripheral or central? A careful history and examination often provide sufficient information to answer these questions and determine whether additional studies or referral to a specialist is necessary.
APPROACH TO THE PATIENT Dizziness HISTORY
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. Vertigo, an illusion of self or environmental motion, implies asymmetry of vestibular inputs from the two labyrinths or in their central pathway that 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 characteristics is typically unreliable. Thus, the history should focus closely on other features, including whether this is the first ...