Nystagmus of Paroxysmal Positional Vertigo: Some New Insights

Abstract

In most of our patients with paroxysmal positional vertigo, the paroxysm was usually short (< 25 or 30 seconds). With the eyes deviated toward the lowermost ear, the observed nystagmus was rotatory-linear and the fast phases beat toward this ear. When the eyes were deviated to the opposite side, the fast phase of nystagmus was mainly upward linear-oblique. In a small number of patients, however, some unusual findings were observed: 1) the nystagmus was the usual rotatory-linear, but the duration was much longer; or 2) the nystagmus was purely horizontal; or 3) the nystagmus was rotatory-linear, but the fast phases were in opposite direction to that usually observed. These data suggest that: 1) the observed paroxysmal nystagmus seems compatible with excitation of the posterior or horizontal semicircular canal of the lowermost ear, or the superior canal of the uppermost ear; and 2) singular nerve section is an appropriate treatment only if the observed paroxysmal nystagmus is compatible with excitation of a posterior semicircular canal.