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Transition from upbeat to downbeat nystagmus observed in a patient with Wernicke's encephalopathy
Yasuo Suzuki1, Taisuke Matsuda, Noriaki Washio
1Department of Ophthalmology, Sapporo Medical University, School of Medicine, Sapporo, Japan. yasuzuki@sapmed.ac.jp
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, he 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 had 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.
