Hyponatremia in Acute Polyneuropathy

HYPONATREMIA is a widely recognized complication of several central nervous system (CNS) disorders. Recent reports of hyponatremia in subarachnoid hemorrhage¹and herpes simplex encephalitis²have added to a long list which includes meningitis,³head injuries,⁴brain tumors,⁵and a variety of other CNS illnesses.⁶⁻⁸The recognition of this complication is clinically important since hyponatremia per se may cause delirium, tremor, and convulsions, and thus create a problem in diagnosis or additionally insult an already damaged nervous system. It is less widely recognized that hyponatremia complicates "acute para-infectious" polyneuropathy, an illness usually considered to be restricted to the peripheral nervous system.⁹To our knowledge, only three such cases have been reported;¹⁰⁻¹²and in all, the lowered serum sodium produced no symptoms. This paper reports four cases of severe hyponatremia associated with, and complicating the course of, pareinfectious polyneuropathy. The evidence suggests that