Alternate-Sided Homonymous Hemianopia as the Solitary Presentation of Mitochondrial Encephalomyopathy, Lactic Acidosis, Stroke-Like Episodes Syndrome

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS)syndrome has various presentations. We report on a case of MELAS in which alternate-sidedhomonymous hemianopia was the main symptom of recurrent neurological defects. A 19-year-old woman suffered from blurred vision, headaches, vomiting, and fever that subsidedwithin days. The ophthalmic examination demonstrated right homonymous hemianopia.One month later a similar episode occurred again. Computed tomography (CT) and magneticresonance imaging (MRI) of her brain revealed an infarct in the left temporo-occipitallobes. Exercise tests showed lactic acidosis, and a muscle biopsy confirmed the diagnosis ofmitochondrial myopathy. Half a month later, a third episode occurred. Visual field examinationdemonstrated left homonymous hemianopia and partial recovery of the right visualfield. The infarct in the brain, as revealed by CT and MRI, was compatible with the visualfield changes. MELAS should be ruled out in young patients who present with homonymoushemianopia accompanied by recurrent headaches or other recurrent symptoms.