Which pattern of findings suggests central vestibular involvement?

• A. Direction-changing, vertical or pure torsional nystagmus without corrective saccades; VOR gain may be normal.
• B. Unidirectional, horizontal nystagmus that does not change direction and may have reduced VOR gain.
• C. Absent nystagmus and normal hearing.
• D. Nystagmus that is suppressed by fixation.

Answer: (B)

Central vestibular involvement often shows eye movement patterns that differ from a simple, peripheral ear problem. The pattern described—nystagmus that stays in one direction and is horizontal, with the possibility of reduced VOR gain—points to disruption in the brainstem–cerebellar networks that hold gaze and calibrate the vestibulo-ocular reflex. When these central pathways are affected, the eye drift can persist in a single direction and the reflex gain can weaken, reflecting impaired gaze stabilization rather than a peripheral labyrinth issue. This contrasts with peripheral patterns, which typically show a consistent direction with corrective catch-up saccades and strong fixation suppression, or gaze-evoked changes that raise concern for central involvement. The presence of direction-changing, vertical, or torsional nystagmus, or a pattern that is markedly improved with fixation, would steer the interpretation toward different aspects of central or peripheral pathology, but the described unidirectional horizontal nystagmus with potentially reduced VOR gain most directly aligns with central involvement in this context.