MELAS is a mitochondrial disorder caused by mutations in mitochondrial DNA. It is characterized by:
- Stroke-like episodes affecting brain function that predominantly involve the temporal, parietal and occipital lobes.
- Additional neurological manifestations including seizures, headaches, hearing loss and dementia.
- Diagnosis requires evidence of elevated lactate levels as well as mitochondrial abnormalities on muscle biopsy and identification of a pathogenic gene mutation.
- Neuroimaging during episodes shows lesions in areas not corresponding to vascular territories.