Fatal neurological complications in anorexia nervosa: a case report of osmotic demyelination syndrome in the binge-eating/purging subtype.

BACKGROUND: Anorexia nervosa (AN) is associated with high mortality due to severe complications. Osmotic demyelination syndrome (ODS), although rare, is a severe neurological complication that has been associated with rapid correction of chronic hyponatremia. The occurrence of ODS in patients with AN, particularly the binge-eating/purging subtype (AN-BP), remains poorly recognized despite their increased susceptibility arising from chronic malnutrition and multiple electrolyte disturbances. CASE PRESENTATION: A 33-year-old woman was treated in the intensive care unit of an outside hospital on July 7, 2025, for severe hyponatremia, with a serum sodium level of 103.52 mmol/L. Her serum sodium increased from 103.52 mmol/L to 123.34 mmol/L over approximately 20.5 h, corresponding to a correction rate of 23.2 mmol/L per 24 h. When she presented to the emergency department of our hospital on July 10, 2025, she exhibited marked psychiatric and behavioral abnormalities. After psychiatric consultation, supplementary history obtained from her family revealed a 10 month history of untreated anorexia nervosa.Serial brain MRI examinations demonstrated both central pontine myelinolysis (CPM) and extrapontine myelinolysis (EPM), with lesions involving the pons, basal ganglia, and cerebellum. During hospitalization at our institution, she received corticosteroid therapy in combination with multidisciplinary supportive care. At the 1-month post-discharge follow-up(September 2025), she remained dependent on others for activities of daily living. With sustained participation in rehabilitation training, her condition markedly improved, at a 7 month telephone follow up (March 2026), her Functional Independence Measure (FIM) total score was 126, and she had resumed normal work and daily life. CONCLUSIONS: This case describes ODS occurring after correction of severe hyponatremia in a patient with previously unrecognized AN-BP and multiple electrolyte abnormalities. Although causality cannot be established from a single case, the temporal association highlights the importance of cautious electrolyte correction, close neurological monitoring, and early MRI evaluation when new neuropsychiatric symptoms emerge. Further studies are needed to clarify the factors contributing to ODS risk in patients with eating disorders.