Extrapontine Myelinolysis in the Context of Hypernatremia and Hyperosmolar Hyperglycemic State

Introduction: Osmotic Demyelination Syndrome (ODS) is a devastating but infrequent complication associated with overly rapid correction of hyponatremia. It has less commonly been reported in the setting of other osmotic challenges. We present a case of ODS following correction of hypernatremia and Hyperosmolar Hyperglycemic State (HHS). Case Description: A 54-year-old man with a diet almost exclusively comprised of high sugar drinks presented with lethargy and generalized weakness. The patient was awake, alert and had no focal neurological deficits. Labs were notable for serum glucose of 966 mg/dL, serum osmolality of 406 mOsm/kg and serum sodium of 173 mmol/L. HHS was treated with Lactated Ringer's and an insulin infusion, complicated by hypoglycemia of 66 mg/dL within 24 hours. Fluid was changed to 0.45% Normal Saline, then Dextrose 5% for hypernatremia. Sodium initially rose to 196 mmol/L, plateaued >180 mmol/L for 3 days, then fell to 156 mmol/L over 27 hours by hospital day 6. Beginning from the first day of plateau, the patient became progressively more altered until hospital day 9, when he became non-verbal and responsive only to painful stimuli with subsequent hypoxic respiratory failure. A brain MRI revealed symmetric areas of diffusion abnormalities involving the corpus callosum splenium, internal capsule, basal ganglia and middle cerebellar peduncles with high suspicion for extrapontine myelinolysis (EPM). The patient was started on a 3-day course of steroids and received plasmapheresis. He was subsequently extubated and discharged with improved mental status, alert and regaining verbal ability, but with limited strength of his bilateral lower extremities. Discussion: ODS includes central pontine myelinolysis and EPM. It can occur in the setting of osmotic challenges and their corrections such as hyponatraemia, hypernatraemia and HHS. Prevention is attempted by maintaining a slow rate of osmotic correction, although recent data indicates that this may not apply to the correction of hypernatremia. Treatment suggested by published reports include steroids, plasmapheresis and IVIG. Our case illustrates that not only should rapid correction in the setting of hyperosmolar states be monitored closely, but that treatments such as steroids, plasmapheresis and/or lVlG can improve prognosis like they did in our patient.