Central Pontine Myelinolysis in a Patient with Hyperosmolar Hyperglycemia and Consistently Normal Serum Sodium

Abstract

Central pontine myelinolysis (CPM) is almost always described in association with a disturbance in sodium homeostasis, most commonly rapid correction of chronic hyponatremia. It has only rarely been described in patients with disturbances of serum osmolality in the absence of abnormal serum sodium concentrations. Case report. A 93 year-old-man developed marked gait ataxia 2 days after the diagnosis and treatment of hyperosmolar hyperglycemia. MRI demonstrated a symmetric lesion in the central pons consisting of increased T2 signal intensity and restricted diffusion, consistent with CPM. Calculated serum osmolality on admission was 344 mOsm/kg and fell to 300 mOsm/Kg over 20 h. Serum sodium concentration stayed between 137 and 140 mEq/l throughout the admission. One month after admission, his ataxia had nearly completely resolved and the MRI changes had improved. CPM can develop in the setting of hyperosmolar hyperglycemia without abnormalities of sodium homeostasis. This supports the theory that the pathogenesis of CPM is dependent on a relatively hypertonic insult, which may occur independently of sodium abnormalities. CPM can present as isolated gait ataxia. Clinical manifestations of the disorder may show significant improvement despite a dramatic initial presentation.