Postural disturbances in paroxysmal positional vertigo

Postural sway was computed in 14 patients suffering from paroxysmal positional vertigo, before and after the paroxysm. In all patients, the nystagmus elicited during the paroxysm was compatible with excitation of the posterior semicircular canal. Patients stood on a force plate for 20 s while the anteroposterior and mediolateral projections of the center of force were recorded and standard deviations computed. Recordings were made after placing the patient's head in the opposite (healthy) and the provocative position. Vertigo was elicited and the nystagmus was observed in 10 of 14 patients. Analysis of the sway data in these patients (N = 10), using the Wilcoxon matched pairs test, showed that the mediolateral sway remained unchanged, while the anteroposterior sway increased, following the provocative maneuver (p less than 0.01). It is concluded that paroxysmal positional vertigo, in which the elicited nystagmus is compatible with excitation of the posterior semicircular canal, increases the anteroposterior rather than the mediolateral sway immediately following the paroxysm.