Clinical Manifestations of Benign Paroxysmal Positional Vertigo of the Horizontal Semicircular Canal: Pathophysiology of Atypical Manifestations

Abstract

The presence of a direction changing positional nystagmus (DCPN) in a patient with vertigo is the characteristic sign to diagnose a benign paroxysmal positional vertigo of the horizontal semicircular canal (HSC-BPPV). If a persistent DCPN is observed when positional tests are performed, a light or heavy cupula phenomenon must be suspected. In order to differentiate between these clinical phenomena, a null plane test should be considered for diagnosis. On the other hand, when a paralytic or irritative fixed direction nystagmus is found, then a complete or incomplete jamming within the HSC may be involved. In this particular situation a head shaking nystagmus test may be clarifying. When persitent DCPN or paralytic-irritative nystagmus are found in positional testing, ENT clinicians must keep alert to search for atypical clinical forms of HSC-BPPV.