Electronystagmographic (ENG) findings in paroxysmal positional vertigo (PPV) as a sign of vestibular dysfunction.

In 285 patients, the observed nystagmus during episodes of PPV was compatible with excitation of the posterior semicircular canal. In these cases, divided in two groups, routine ENG recordings were retrospectively reviewed. In Group A (n = 241), the ENG was performed during the time the vertigo could be elicited; in Group B (n = 44), during the time it could not. In Group A: 1) the velocity of positional nystagmus (not the paroxysmal) was less than 6 degrees/s in 93% of cases; 2) there was no statistical difference of positional nystagmus and post-caloric preponderance of opposite directions, with 66% of cases having symmetrical responses; 3) the velocity of positional nystagmus and the post-caloric preponderance were higher than in Group B. It is concluded that: (i) in most cases no concomitant vestibular dysfunction could be detected; (ii) there was a tendency to restore right-left asymmetricity when the episodes subsided; (iii) ENG recordings were not pathognomonic and did not localize the affected side; (iv) there were ENG findings suggestive of concomitant involvement of other vestibular sensors (canals), in a small number of cases.