Central pontine myelinolysis (CPM) is a demyelinating disease of the pons which is also associated with the demyelination of extrapontine areas of the central nervous system. Although the aetiology and pathogenesis are unclear, CPM is usually associated with hyponatremia or its rapid correction. Malnutrition and chronic alcoholism are also the common underlying conditions. Herein, we report a rare presentation of ODS, secondary to hyperosmolar hyperglycaemic state. We observed a 37-year-old female with diabetes type 1 and hypertension who presented with ataxia, dysarthria and pseudobulbar effect which evolved over a duration of few weeks at home with no evidence of hyponatremia or its rapid correction and no history of alcohol abuse or malnutrition.Key words: Central pontine myelinolysis, diabetes mellitus, extrapontine myelinolysis, hyperosmolar hyperglycaemic state, osmotic demyelination syndrome 37-year-old female with type 1 diabetes who developed osmotic demyelination syndrome (ODS) after rapid correction of osmolarity with normal serum electrolyte levels. This would be the first report of ODS in diabetic patient, associated with hyperosmolar hyperglycaemic state (HHS) with normal serum electrolytes. CASE REPORTA 37-year-old female with a history of type 1 diabetes mellitus (DM) and hypertension was admitted with a history of dysarthria, ataxia, behavioural changes which were gradual in onset and progressive with Glasgow Coma Scale (GCS) 12/15 (E4V4M4). Her neurological examination revealed normal cranial nerves, with grade 5/5 power in all 4 limbs with ataxic gait. Detailed history revealed progressively increasing ataxia with dysarthria, clumsiness with emotional lability and