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, 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.