Secondary parkinsonism in a patient of psychogenic polydipsia

A 44-year-old man presented with history of slurring of speech, slowness in activities, abnormal posturing of the upper limbs and drooling of saliva from the mouth. He had a 5-yearlong history of compulsive water drinking, consuming 12-15 L of water every day. He was earlier evaluated for the same and found to have low serum sodium (126 mEq/L). Presently, he was admitted at a primary care facility with fever and altered sensorium. He was found to have serum sodium of 94 mEq/L. His sensorium improved with hypertonic saline infusion; however, after a lucid interval of 48 hours, he developed florid extrapyramidal symptoms. Contrast-enhanced MRI brain revealed bilaterally symmetric T2-weighted fluid-attenuated inversion recovery hyperintensity in caudate and lentiform nuclei. A diagnosis of extrapontine myelinolysis with secondary parkinsonism was made. He improved significantly with levodopa therapy.Psychogenic polydipsia is an important cause of hyponatraemia. Overzealous correction of hyponatraemia can be counterproductive.