[A case of MELAS showing CSF pleocytosis associated with stroke-like episodes]

A 55-year-old woman, who had two episodes of difficulty in putting a key into a keyhole probably due to optic ataxia at age 52 and 54 years old, developed speaking errors and was admitted to our hospital. She was 152.5 cm in height and 52.5 kg in weight. Neurological examination revealed right homonymous hemianopsia and sensory aphasia. A CSF examination revealed lymphocytic pleocytosis of 88/microliter. Serum lactate and pyruvate were remarkably increased after an aerobic exercise test. A few ragged-red fibers were present in the biopsied brachial biceps muscle. Brain MRI by FLAIR method showed scattered high signal lesions in the left temporal lobe, bilateral parieto-occipital lobes, left insular cortex and left thalamus. The left superficial temporal lesion was enhanced by gadolinium-DTPA. The proton MRS demonstrated the lactic acid peak as well as the decrease of NAA/choline ratio (0.38) in the left parieto-occipital region. Thus, she was diagnosed as a case of MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) and successfully treated with ubidecarenone (150 mg/day). Six months later, she again developed seizure, right hemiparesis and deterioration of aphasia and presented again CSF lymphocytic pleocytoses of 15/microliter. Brain MRI demonstrated new lesions in the left temporoparietal lobes, left insular cortex and left corona radiata. Therefore, CSF pleocytosis appeared to be associated with stroke-like episodes in this case. Although the mechanism of CSF pleocytosis remains to be elucidated, it may involve the breakdown of blood-brain barrier caused by mitochondrial dysfunction. Otherwise, an inflammatory process similar to that in cases of Leber disease, who developed multiple sclerosis-like additional lesions in the central nervous system, may also take place in MELAS.