We report a case of paroxysmal downbeat nystagmus, ataxia, and dysarthria in the context of a delirium in a patient with severe hypomagnesemia. Extensive workup did not provide alternative explanations. Her attacks subsided within 48 h after the start of magnesium substitution and the patient remained confused and ataxic with a gradual but full recovery over 6 weeks. Hypomagnesemia resulted most probably from long-term proton—pump inhibitor (PPI) intake. Paroxysmal downbeat nystagmus is rare and has so far only been consistently described in association with hypomagnesemia of various causes.
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