Transient downbeat nystagmus from West Nile virus encephalomyelitis

Abstract

Most human West Nile virus (WNV) infections are asymptomatic, but a minority of patients develops neuroinvasive disease, including a poliomyelitis-like syndrome.1 Reported ophthalmologic manifestations include optic neuritis, uveitis, multifocal choroiditis, ocular motor palsies, and opsoclonus.2–4 We cared for a patient with WNV who developed downbeat nystagmus and ocular flutter with acute areflexic quadriparesis. A 64-year-old previously healthy retired steel mill worker presented after 7 days of leg and arm pain and 4 days of progressive weakness. He reported horizontal binocular diplopia, decreased strength, mild dyspnea, and arm tremor. On admission, temperature was 39.2 °C. He was oriented and followed requests. Visual fields were full. Pupils were equal and reactive. He had a mild esotropia in the primary position, with a partial right abduction deficit with right lateral gaze. Downbeat nystagmus was present in primary gaze, and the amplitude increased in up gaze and lateral gaze (video, on the Neurology Web site at www.neurology.org). Pursuit was saccadic in all directions, but particularly in vertical gaze. He had intermittent …