Upbeat Nystagmus: Clinicoanatomical Correlations in 15 Patients

BACKGROUND AND PURPOSE: 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.

Two Cases of Bilateral Reversed Optokinetic Nystagmus / 대한이비인후과학회지

Normally, the fast phase of optokinetic nystagmus (OKN) beats on the opposite direction to the movement of an optokinetic stimulus. The fast component of OKN beating in the same direction are called "reversed OKN". Eventhough the mechanism of reversed OKN is still disputed, it is well known that reversed OKN occurs exclusively in patients with congenital nystagmus, or in some cases, with acquired neurologic disease. It is easy to diagnose the congenital nystagmus when the spontaneous nystagmus can be seen at birth. But when the congenital nystagmus can be seen only on eccentric gaze or when the patient has a wide neutral region around the primary position, the abnormal eye movement can not be detected until a medical examination is performed. It is thought that causes of reversed OKN may be the abnormal neural decussation of the visual system or spontaneous nystagmus. Recently, we experienced two cases of bidirectional reversed OKN as a congenital nystagmus. One patient had bilateral reversed optokinetic nystagmus and gaze evoked nystagmus, whereas the other patient had periodic alternative nystagmus and bilateral reversed OKN. Bilateral reversed OKN may be one of the pathognomic signs of congenital nystagmus.