Osmotic demyelination syndrome despite appropriate gradual correction of moderate hyponatraemia.

Osmotic demyelination syndrome characteristically follows rapid correction of hyponatraemia. We present a young woman with a subacute progressive brainstem syndrome and diffuse pontine signal abnormality on MR imaging, diagnosed as osmotic demyelination syndrome. The case posed a diagnostic challenge due to comorbid Behçet's disease and the absence of significant fluctuation in her serum sodium concentration. Osmotic demyelination syndrome is not limited to patients with rapidly corrected hyponatraemia, especially when there are other risk factors. These factors, all present in this patient, include hypokalaemia, hypophosphataemia, malnutrition, harmful alcohol use and liver dysfunction.