Extrapontine myelinolysis in a patient with systemic lupus erythematosus: a case report

Syndrome of inappropriate secretion of antidiuretic hormone (SIADH) in systemic lupus erythematosus (SLE) is rare and related pathologic changes in brain images have not been reported. We report the case of a 49-year-old woman with SLE who developed extrapontine myelinolysis (EPM) following gradual correction of marked hyponatremia caused by SIADH. EPM was caused by the hyponatremia, which resulted in cerebral hypoxia and brain swelling. SIADH was most likely induced by the occult vasculitis of SLE. After partial correction of hyponatremia, she regained consciousness, but gradually developed parkinsonism including rigidity, bradykinesia, and tremors 1 week later. Magnetic resonance imaging revealed bilateral symmetrical brain lesions at the putamen, globus pallidus, and part of the thalamus. These symptoms improved gradually after administration of levodopa. Mild jerky tremors of both hands persisted 4 months later. The EPM lesions differ from those observed in central pontine myelinolysis (CPM), which is immediately induced by acute correction of hyponatremia. Therefore, hyponatremia in lupus-related SIADH should be carefully corrected to prevent CPM or EPM.