Akinetic-rigid syndrome due to extrapontine and pontine myelinolysis following appropriate correction of hyponatraemia

Abstract

Extrapontine myelinolysis in association with the more common central pontine variety is increasingly reported. Although typically associated with rapid correction of hyponatraemia, myelinolysis is also seen when sodium correction occurs at recommended rates. We present a 60-year-old man who developed hyponatraemia and hypokalaemia due to repeated vomiting. An acute symmetric akinetic-rigid syndrome followed correction of hyponatraemia, performed in line with current guidelines. There were no clinical features of pontine involvement even though a typical lesion was seen on MRI. Bilateral putaminal and caudate lesions were seen. He recovered well with only symptomatic treatment. Myelinolysis can present with features of extrapontine involvement with the pontine lesions remaining asymptomatic. Current guidelines for the correction of hyponatraemia do not prevent development of myelinolysis in all instances. In contrast to the generally expected poor outcome in this condition, patients do make a good recovery with symptomatic treatment and good nursing care.