Encephalopathy With Alternating Hemispheric MRI Abnormalities
A 21-year-old woman with a long-standing history of migraine sought care at her local provider for a 1-week history of confusion and mixing up her words. She then had a witnessed seizure, with dyscognitive features and secondary generalization. On hospitalization, electroencephalography demonstrated left temporal theta slowing and sharp waves. Magnetic resonance imaging showed patchy T2-signal abnormality, nonenhancing, in the left temporal region (only a report was available). Thyroid peroxidase antibodies were increased at 271 IU/mL. A diagnosis of an autoimmune encephalopathy was made, and the patient was treated with phenytoin, levetiracetam, and high-dose corticosteroids, followed by a slow oral prednisone taper. The patient improved cognitively but had considerable emotional lability and an increase in headache frequency and severity and, thus, sought a second opinion. Blood was drawn for genetic testing. The patient died in her sleep a short time later, most likely in the context of sudden unexplained death in epilepsy. Her genetic testing results became available 1 month later, which showed findings consistent with MELAS syndrome: heteroplasmic sequence variation m.3243A>G (tRNA Leu) and homoplasmic rare variant m.2294A>G (16S rRNA). Encephalopathy or encephalitis of subacute onset with fluctuating course is not unique to autoimmune encephalitis. Common acquired metabolic disorders must be considered and excluded in all cases, such as deficiencies of vitamin B12 and folate, hypothyroidism, sepsis, and central nervous system–active medications.