title: Upbeat nystagmus: clinicoanatomical correlations in 15 patients.
abstract: 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.
authors.affiliation: Department of Neurology, College of Medicine, Seoul National University, Seongnam, Korea.
authors.forename: Ji Soo
authors.initials: JS
authors.lastname: Kim
authors.forename: Bora
authors.initials: B
authors.lastname: Yoon
authors.forename: Kwang-Dong
authors.initials: KD
authors.lastname: Choi
authors.forename: Sun-Young
authors.initials: SY
authors.lastname: Oh
authors.forename: Seong-Ho
authors.initials: SH
authors.lastname: Park
authors.forename: Byung-Kun
authors.initials: BK
authors.lastname: Kim
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