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Original Contributions
December 1983

Downbeating Nystagmus: A Review of 62 Cases

Author Affiliations

From the Eye and Ear Unit, Department of Neurology, Royal Prince Alfred Hospital, Australia (Dr Halmagyi); and the Medical Research Council Neuro-Otology Unit, Institute of Neurology (Drs Rudge and Gresty), and the Neuroophthalmology Department (Dr Sanders), National Hospital, London.

Arch Neurol. 1983;40(13):777-784. doi:10.1001/archneur.40.13.777
Abstract

We reviewed the clinical and oculomotor findings in 62 patients with down-beating nystagmus (DBN). Only those patients whose DBN was enhanced in lateral gaze were included. Apart from gait ataxia, few patients had additional neurologic signs. The two most common causes of DBN were cerebellar ectopia (25%) and cerebellar degeneration (25%) with another 10% having a variety of conditions. In about 40% the cause remained undiagnosed. In some patients with idiopathic DBN and in others with DBN due to cerebellar ectopia, the disease progressed slowly, If at all. In DBN the slow-phase velocity is dependent on vertical head position and head velocity in pitch; vertical pursuit, particularly downward pursuit, is defective and vertical vestibulo-ocular reflexes are intact. We concluded that at least some cases of DBN were due to an imbalance in otolith-ocular reflexes. The lesion causing DBN appears to be in the vestibulocerebellum, perhaps the nodulus, a structure that normally inhibits otolith-ocular reflexes.

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