Primary position upbeat nystagmus in Wernicke's encephalopathy.

for morbid obesity. In the subsequent 4 months, he suffered from recurrent and intense vomiting, losing 40 kg. Asymptomatic hypokalemia and hypomagnesemia were discovered and supplemented. At this time, systematic oral vitamin therapy was begun. One month later, he started to describe blurred vision and vertical oscillopsia. Neurological examination revealed ataxia and nystagmus. Standard biological screening and vitamin dosage were normal except for thiamine, which was just above the inferior limit. His CT scan and brain MRI were normal. Wernicke’s encephalopathy was suspected and ataxia improved following the introduction of parenteral vitamin therapy. Because of persisting oscillopsia, the patient was referred to our unit. Neuro-ophthalmological examination disclosed upbeat nystagmus in the primary position of gaze and gaze-evoked nystagmus in lateral gaze, with an oblique direction due to upbeat nystagmus. PPUN was rapid, persistent in up-and-down gaze, and absent in the supine position. Examination disclosed a postural ataxia originating in both a somatosensorial deficit with abolished tendon reflexes and cerebellar syndrome. ElectroneuromyogDear Sir, Primary position upbeat nystagmus (PPUN) is a rare nystagmus observed in neurological diseases. Although Wernicke’s encephalopathy is one of the classical etiologies of PPUN [1] , clinical reviews of this pathology do not precisely describe PPUN as a frequent neuro-ophthalmological manifestation [2] . The neuro-ophthalmological signs reported more frequently are bilateral abduction deficits due to VI nerve palsies, and vertical or horizontal gaze-evoked nystagmus. We report here two cases in which PPUN was the predominant manifestation of Wernicke’s encephalopathy.