Upbeat nystagmus: clinicoanatomical correlations in 15 patients.
OBJECTIVE
The mechanism of upbeat nystagmus is unknown and clinicoanatomical correlative studies in series of patients with upbeat nystagmus are limited.


METHODS
Fifteen patients with upbeat nystagmus received full neuro-ophthalmological evaluation by the senior author. Nystagmus was observed using video Frenzel goggles and recorded with video-oculography. Brain lesions were documented with MRI.


RESULTS
LESIONS RESPONSIBLE FOR NYSTAGMUS WERE FOUND THROUGHOUT THE BRAINSTEM, MAINLY IN THE PARAMEDIAN AREA: in the medulla (n=8), pons (n=3), pons and midbrain with or without cerebellar lesions (n=3), and midbrain and thalamus (n=1). Underlying diseases comprised cerebral infarction (n=10), multiple sclerosis (n=2), cerebral hemorrhage (n=1), Wernicke encephalopathy (n=1), and hydrocephalus (n=1). Upbeat nystagmus was mostly transient and showed occasional evolution during the acute phase. In one patient with a bilateral medial medullary infarction, the upbeat nystagmus changed into a hemiseesaw pattern with near complete resolution of the unilateral lesion. Gaze and positional changes usually affected both the intensity and direction of the nystagmus. A patient with a cervicomedullary lesion showed a reversal of upbeat into downbeat nystagmus by straight-head hanging and leftward head turning while in the supine position. Gaze-evoked nystagmus (n=7), ocular tilt reaction (n=7), and internuclear ophthalmoplegia (n=4) were also commonly associated with upbeat nystagmus.


CONCLUSIONS
In view of the responsible lesions and associated neuro-ophthalmological findings, upbeat nystagmus may be ascribed to damage to the pathways mediating the upward vestibulo-ocular reflex or the neural integrators involved in vertical gaze holding.
Kim
Ji Soo
JS
Department of Neurology, College of Medicine, Seoul National University, Seongnam, Korea.
Yoon
Bora
B
Choi
Kwang-Dong
KD
Oh
Sun-Young
SY
Park
Seong-Ho
SH
Kim
Byung-Kun
BK
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