Abstract

Department of Otolaryngology, Head and Neck Surgery1, and Neurology2, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea Background and Objectives : Central positional nystagmus is induced by positional changes from brainstem or cerebellar lesions. Differentiation central from peripheral positional nystagmus is important in clinical practice. To delineate characteristics of the positional nystagmus observed in central lesions, we analyzed the parameters of positional nystagmus from focal brain lesions. Materials and Methods : Ten patients with central positional nystagmus were recruited from the dizziness clinic of Seoul National University Bundang Hospital. All the patients had focal brainstem or cerebellar lesions documented by magnetic resonance imaging. The nystagmus was observed with and without fixation by using Frenzel glasses or Video Goggles. The nystagmus was videotaped or recorded with video-oculography. Provoking positional maneuvers, direction, latency, duration, phase reversal, and fatigue phenomenon of the nystagmus were analyzed.
Results
: Of the 10 patients, seven had infarctions in the lateral medulla or inferior cerebellum while two experienced cerebellar hemorrhage and remaining one showed a compression of the ventrolateral medulla by cavernous malformation of the vertebral artery. The directions of the positional nystagmus were variable depending on the lesions and provoking maneuvers. Most patients exhibited direction-changing nystagmus without latency, direction-reversal and fatigue phenomenon. However, some of the patients also showed patterns of nystagmus characteristic of peripheral positional nystagmus. In two of the four patients with infarction in the territory of medial posterior inferior cerebellar artery, the positional nystagmus was the only abnormal findings.
Conclusions
: Central positional nystagmus may share many characteristics with peripheral type of positional nystagmus. In individual cases, the patterns of nystagmus should be interpreted with caution in differentiating central from peripheral positional nystagmus. Considering the isolated positional nystagmus in some patients with caudal cerebellar lesions, systematic positional maneuvers should be applied to all the patients with vertigo Key Words : Positional nystagmus, Medulla, Cerebellum

• Keywords: Positional nystagmus;Medulla;Cerebellum;