Positional End-Point Nystagmus in Patients with Diagnosis of Acute Unilateral Vestibulopathy

Abstract

Introduction Recently, end-point nystagmus, traditionally observed in an upright position, has been identified in the Dix–Hallpike position among healthy subjects, suggesting a physiological origin. However, its characteristics in individuals with vestibular hypofunction remain unexplored. Objective To elucidate the impact of vestibular hypofunction on the characteristics of positional end-point nystagmus. Methods Thirty-one patients diagnosed with acute unilateral vestibulopathy according to Bárány Society criteria were selected. A video head impulse test was conducted in all participants, followed by McClure and Dix–Hallpike maneuvers with and without gaze fixation, and with the initial position of the eye in the straight-ahead position or in the horizontal end-point position. Nystagmus direction, sense, latency, slow-phase velocity, and duration were recorded. The relationship between these characteristics and video head impulse test values was analyzed. Results Positional end-point nystagmus was observed in 92.6% of subjects with vestibular hypofunction, significantly more than in healthy individuals. Nystagmus direction varied depending on the performed positional test and on the vestibulo-ocular reflex gains. Gaze occlusion and the initial horizontal end-point position increased its frequency. Conclusion Vestibular hypofunction influences the manifestation of positional end-point nystagmus. Recognizing this nystagmus can aid in resolving diagnostic uncertainties and preventing the misdiagnosis of benign paroxysmal positional vertigo in subjects with acute unilateral vestibulopathy.