To describe a severe neurological manifestation of an unusual type of osmotic demyelination syndrome (ODS).

A 32-year-old woman with history of an apendicectomy, in the immediate postoperative period she had a prolonged confusion state associated with natremia of 156 mg/dl, which was corrected in less than 24 hours to 121 mg/dl. Five days later the patient had dysarthria, tongue dyskinesias and dysphagia. One week later, and lasting until two months after operation, she presented with masked facies, shuffling gait, and pill-rolling tremors suggestive of acute-onset parkinsonism. Brain magnetic resonance imaging was with symmetrical hyperintense lesions on T2 weighted images involving bilateral basal ganglia; central pontine myelinolysis (CPM) was also present. She was treated with levodopa/carbidopa 62.5 mg PO every six hours. Three days later, she had clinical improvement in axial tremor, with full recovery after a week.

ODS can occur with slow rates of sodium correction, but the most common manifestation is a flaccid quadriparesis; rarely, ODS can manifest with acute-onset parkinsonism. Following an initial stage of diffuse encephalopathy, the neurological sequelae are usually of diffuse cognitive deficits and extrapyramidal or cortico­bulbo­spinal disorders; however, the patient was definitively asymptomatic after short therapy with low-dose levodopa-carbidopa.