Vestibular dysfunction has rarely been reported in MELAS syndrome. A 40-year-old male with long-term diabetes and hearing loss experienced a stroke-like episode with hemisensory disturbance and lactic acidosis. Brain MRI showed temporo-parieto-occipital cortical lesions, and a final diagnosis was made of MELAS syndrome with the mitochondrial 3243A>G mutation. Neuro-otologic evaluations revealed anterior-canal-sparing bilateral impairments of the vestibulo-ocular reflex in the video head impulse test and no caloric paresis. This unique pattern of vestibular dysfunction may aid in diagnosing MELAS syndrome.

We describe the case of a 22-year-old female complaining of ophthalmoplegia, which deteriorated with seizure. Leigh syndrome (LS) was diagnosed by identifying the m.9176T>C mutation. She improved with vitamin cocktail therapy plus intravenous methylprednisolone, and had an excellent prognosis. This was the first case of an adult patient with LS presenting with the m.9176T>C mutation and reporting cortical symptoms, which in this case comprised cortical vision loss, and cortical, basal ganglia, and brainstem signal changes on magnetic resonance imaging.

The MELAS (Mitochondrial Encephalomyopathy with Lactic Acidosis, and Stroke-like episodes) syndrome is one of the inherited mitochondrial disorder. We have experienced a 16-year-old girl with headaches and left hemianopsia. Diagnosis of MELAS syndrome with multiple brain parenchymal lesions was confirmed by gene study. The stroke-like lesion of MELAS syndrome showed significant improvement in radiological follow up study. Therefore, MRI findingsin MELAS could be interpreted as metabolic cellular dysfunction rather than ischemic vasculopathy