Idiopathic latent vestibulopathy: a clinical entity as a cause of chronic postural instability.

The objective of this study is to describe a new clinical entity of idiopathic latent vestibulopathy (ILV), in which patients have unilateral or bilateral vestibulopathy combined with unsteadiness but without episodic vertigo, auditory disturbance, or a medical history suggesting the presence of vestibulopathy. A retrospective study of 1,233 consecutive new outpatients was conducted. Two-legged stance tasks were performed by 11 patients identified as having ILV in four conditions: eyes open with and without foam rubber, and eyes closed with and without foam rubber. We examined six parameters: the velocity of movement of the center of pressure (COP) with eyes closed/foam rubber, the envelopment area traced by the movement of the COP with eyes closed/foam rubber, Romberg's ratio of velocity and area with foam rubber, and the foam ratios of velocity and area with eyes closed. Multiple regression analyses were performed in order to explore the relationship between the presence of ILV and the six parameters recorded during foam posturography, while adjusting for the subjects' gender and age. The presence of ILV had a significantly positive relationship with the values of 4 of the 6 parameters. Even though six patients showed only unilateral vestibulopathy, their median value in all 6 parameters was greater than that of healthy controls. ILV could be a clinical entity accountable for postural instability.