Hypoglycemic Encephalopathy Caused by Insulinoma With Reversible High Signals in the White Matter on Diffusion-Weighted MRI: A Case Report.

Hypoglycemic encephalopathy can result in reversible, and sometimes irreversible, lesions within the brain that need prompt recognition and treatment. The disease is relatively uncommon, but radiologists must keep in mind the rare radiologic findings of this disease. Although the most common cause is insulin, insulinoma is a rare etiology, and hypoglycemia is often misdiagnosed as epilepsy. A 66-year-old man presented with recurrent involuntary movements and impaired consciousness with neuropsychiatric symptoms without a history of antidiabetic therapy. Initial blood glucose was critically low at 29 mg/dL. Diffusion-weighted imaging (DWI) revealed reversible high signals in the white matter, involving the bilateral posterior limbs of the internal capsule, corona radiata, cerebral peduncle, and splenium of the corpus callosum. A fasting test and contrast-enhanced computed tomography confirmed the diagnosis of insulinoma. Intravenous glucose was administered immediately, resulting in rapid clinical improvement. Laparoscopic distal pancreatectomy was subsequently performed. Clinical symptoms resolved completely within 1 day of glucose administration. Follow-up DWI performed 2 months after onset demonstrated complete resolution of all white matter hyperintensities without recurrence. The patient reported feeling well without recurrence of the symptoms. We report a case of hypoglycemic encephalopathy caused by insulinoma with reversible high signals in the white matter on DWI, presenting with neuropsychiatric symptoms mimicking epilepsy. We also discuss findings of magnetic resonance imaging in hypoglycemic encephalopathy with emphasis on the time course of the findings.