Chronic unilateral vestibular loss.

Chronic unilateral vestibular loss is a condition defined by the presence of reduced function of the peripheral vestibular system on one side, which has generally persisted for 3 or more months. The deficit is demonstrated by a reduction of the vestibular-ocular reflex either at the bedside or on laboratory testing. Though some patients with chronic vestibular loss have disabling symptoms, others are asymptomatic. Causes include a viral/postviral disorder, Menière's disease, structural lesions, ischemia, and trauma. Any other systemic or genetic disorder would be expected to involve both sides at some point.