Bilateral vestibulopathy with dissociated deficits in the superior and inferior vestibular systems.

OBJECTIVES: The aim of this study was to reveal the clinical characteristics of dissociated bilateral vestibulopathy (BV) affecting the superior vestibular nerve system on one side and the inferior vestibular nerve system on the other side. It is probable that BV does not always show bilateral deficits of the same vestibular nerve system. METHODS: In a retrospective study of 2,752 consecutive new patients, 1,560 patients had undergone both caloric testing and cervical vestibular evoked myogenic potential testing. All 1,560 patients had also undergone a battery of tests including standardized neurologic, neuro-otologic, neuro-ophthalmologic, and audiological examinations. RESULTS: Forty-three patients (2.8% of 1,560 patients) were given a diagnosis of dissociated BV. Among them, 10 patients (23%) had Meniere's disease and 6 patients (14%) had vestibular neuritis. Eighteen patients (42%) did not have any identifiable disease involving the peripheral vestibule, and 9 patients (21%) could be regarded as having a novel subtype of idiopathic BV. CONCLUSIONS: Although dissociated BV might be induced by some of the same causes that provoke bilateral vestibular dysfunction, a definite proportion of the patients did not have any identifiable causes of dissociated vestibular dysfunction. Idiopathic cases could be categorized into a novel subtype of idiopathic BV.

Assessment of postural stability using foam posturography at the chronic stage after acute unilateral peripheral vestibular dysfunction.

OBJECTIVE: To investigate the utility of foam posturography for assessing equilibrium at the chronic stage after acute unilateral peripheral vestibulopathy. METHODS: Thirty-four consecutive patients (16 patients at the chronic stage) with acute unilateral peripheral vestibulopathy and absent caloric responses unilaterally were recruited, along with 66 healthy control subjects. Two-legged stance tasks were performed in 4 conditions: with eyes open or closed, with or without using foam rubber. We adopted 6 parameters: the movement velocity of the center of pressure, the envelopment area traced by the movement of the center of pressure with eyes closed/foam rubber, Romberg's ratios of velocity and area with foam rubber, and the foam ratios (the ratio of a parameter measured with and without foam rubber) of velocity and area with eyes closed. RESULTS: All 6 parameters were significantly higher in the patients in the acute/subacute stage (<3 mo) than in the control subjects (p < 0.0001). Five parameters, excluding the foam ratio of the area with eyes closed, were still significantly higher in the patients at the chronic stage (>3 mo) than in the control subjects (p < 0.01). CONCLUSION: Foam posturography is useful for assessing equilibrium even at the chronic stage after acute unilateral peripheral vestibulopathy.