Transition from upbeat to downbeat nystagmus observed in a patient with Wernicke's encephalopathy

Background: We report an unusual case of Wernicke's encephalopathy presenting with transient upbeat nystagmus that changed to a persistent downbeat nystagmus. Case: A 27-year-old man presented with upbeat nystagmus. Three months earlier, lie had been diagnosed with Wernicke's encephalopathy after fasting for a month. Observations: This diagnosis was supported by his symptoms (ataxia, a confused state). Clinical recovery followed thiamine therapy. His upbeat nystagmus had linear slow phases with average amplitude and frequency (+/- SD) during fixation straight ahead of 2.8 +/- 0.7 degrees and 4.6 +/- 2.2 Hz, respectively. Two months later, the primary position upbeat nystagmus had diminished and downbeat nystagmus (0.9 +/- 0.5 degrees and 3.2 +/- 0.7 Hz on average) for a 20 degrees downward gaze It ad developed. Then, 8 months later, he showed only downbeat nystagmus, which obeyed Alexander's law. His primary position downbeat nystagmus was completely suppressed by clonazepam, a gamma-aminobutyric acid (GABA) agonist. Conclusions: Owing to an underlying central vestibular imbalance, even after the recovery of acute neurological symptoms, Wernicke's encephalopathy can be complicated by persistent downbeat nystagmus, which can be treated by a GABA agonist. (c) Japanese Ophthalmological Society 2005.