A thin 50-year-old man with a history of diabetes and deafness and a family history of hearing dysfunction presented with new-onset headaches, psychiatric symptoms, and a seizure. He was found to have a right temporal lesion (Figure, A). Three months later, he developed aphasia, complained of headache, and had a convulsive seizure. This was followed by gradual improvement in his language and cognitive function throughout several months. A subsequent magnetic resonance image (Figure, B) showed a new lesion in the left temporal lobe. The results of magnetic resonance angiography of the head and carotid ultrasound were unrevealing. Transthoracic echocardiography revealed no thrombus or patent foramen ovale. Proteins C and S and antithrombin III levels were within the reference range. Factor V Leiden was not present and anticardiolipin antibody concentrations were not elevated. No cerebrospinal fluid pleocytosis was identified, and polymerase chain reaction was negative for herpes. The serum lactate level was within the reference range. Mitochondrial DNA analysis revealed mutation A3243G, the most common mutation in patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS).2
Kisanuki YY, Gruis KL, Smith TL, Brown DL. Late-Onset Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Strokelike Episodes With Bitemporal Lesions. Arch Neurol. 2006;63(8):1200–1201. doi:10.1001/archneur.63.8.1200
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