Osmotic Demyelination Syndrome in Hyperosmolar Hyperglycemic State With Contrasting Initial Sodium Levels: A Report of Two Cases.

Osmotic demyelination syndrome (ODS) is typically associated with rapid correction of severe hyponatremia but is a rare complication of hyperosmolar hyperglycemic state (HHS). We describe two cases of ODS developing in HHS with contrasting initial sodium levels: one with profound hyponatremia (Na 112 mmol/L, corrected 167 mmol/L) and the other with hypernatremia (Na 149 mmol/L, corrected 177 mmol/L). Both patients exhibited severe hyperglycemia (2,398 and 1,277 mg/dL, respectively) and marked hyperosmolality (387 and 421 mOsm/kg) and were managed with cautious correction rates (1.2 and 1.0 mOsm/kg/hour). Despite this, each patient developed ODS diagnosed by MRI on days three and seven, respectively. Neurological function gradually improved in both, with final modified Rankin Scale scores of 2 and 1, respectively. To our knowledge, this is the first case report to directly compare hyponatremic and hypernatremic ODS in the context of HHS. Severe hyperosmolality can itself trigger ODS, regardless of measured and corrected sodium levels or the rate of correction. Clinicians should maintain a low threshold for timely MRI in HHS patients with persistent or unexplained neurological deficits.