Which finding most strongly suggests a peripheral vestibular lesion rather than a central one?

• A. Unidirectional and fatigable nystagmus
• B. Nystagmus that changes direction with gaze
• C. Marked cognitive slowing
• D. Bilateral symmetry on caloric testing

Answer: (A)

The thing being tested is how eye movements reveal where a vestibular problem lies. A finding that points most strongly to a peripheral vestibular lesion is unidirectional nystagmus that fatigues with repetition. When the inner ear on one side is damaged, the imbalance drives the eyes with a fast phase in a single direction in primary gaze, and the response tends to lessen with repeated testing or fixation. This fatigue and single-direction pattern fit the peripheral input problem and the intact central pathways that produce a stable, direction-fixed nystagmus.

In contrast, central lesions often produce nystagmus that can change direction with gaze, can be vertical or torsional, and is typically not fatigable, and they’re more likely to be accompanied by other neurologic signs like cognitive slowing or limb abnormalities. Bilateral symmetry on caloric testing doesn’t strongly indicate a peripheral lesion because it could reflect normal variation or bilateral involvement rather than a unilateral peripheral deficit.