[L-arginine therapy on MELAS]

Neuropathological hallmarks in autopsied cases with mitochondrial diseases caused by the mitochondrial 3243A>G mutation

The mitochondrial (m.) 3243A>G mutation is known to be associated with various mitochondrial diseases including mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). Their clinical symptoms have been estimated to occur with an increased mitochondrial DNA (mtDNA) heteroplasmy and reduced activity of oxidative phosphorylation (OXPHOS) complexes, but their trends in the central nervous system remain unknown. Six autopsied mutant cases and three disease control cases without the mutation were enrolled in this study. The mutant cases had a disease duration of 1-27 years. Five of six mutant cases were compatible with MELAS. In the mutant cases, cortical lesions including a laminar necrosis were frequently observed in the parietal, lateral temporal, and occipital lobes; less frequently in the frontal lobe including precentral gyrus; and not at all in the medial temporal lobe. The mtDNA heteroplasmy in brain tissue samples of the mutant cases was strikingly high, ranging from 53.8% to 85.2%. The medial temporal lobe was preserved despite an inhospitable environment having high levels of mtDNA heteroplasmy and lactic acid. OXPHOS complex I was widely decreased in the mutant cases. The swelling of smooth muscle cells in the vessels on the leptomeninges, with immunoreactivity (IR) against mitochondria antibody, and a decreased nuclear/cytoplasmic ratio of choroidal epithelial cells were observed in all mutant cases but in none without the mutation. Common neuropathological findings such as cortical laminar necrosis and basal ganglia calcification were not always observed in the mutant cases. A high level of mtDNA heteroplasmy was observed throughout the brain in spite of heterogeneous cortical lesions. A lack of medial temporal lesion, mitochondrial vasculopathy in vessels on the leptomeninges, and an increased cytoplasmic size of epithelial cells in the choroid plexus could be neuropathological hallmarks helpful in the diagnosis of mitochondrial diseases.

Pearls & Oy-sters: Symmetric Numbness and Paresthesia Due to Stroke-like Episode in an Adolescent Male With MELAS

Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like episodes (MELAS) syndrome is a mitochondrial condition with a wide range of neurologic complications including migraines, seizures, and stroke-like episodes. This case report highlights a rare presentation of bilateral sensory changes related to MELAS and offers an opportunity to consider how a differential diagnosis may need to be modified in patients with underlying mitochondrial disorders. Neurologic symptoms in MELAS may defy classic localization patterns, and early neuroimaging is warranted.

Acute, reversible axonal energy failure during stroke-like episodes in MELAS

The pathophysiology of stroke-like episodes in MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) remains unresolved. Possible mechanisms include mitochondrial angiopathy, cytopathy, or both, collectively resulting in cellular energy depletion. To clarify disease mechanisms, axonal excitability properties were investigated in a 10-year-old child with MELAS. Serial assessments during a stroke-like episode revealed reversible depolarization of the axonal membrane consistent with disruption of energy-dependent processes. Axonal parameters correlated with the clinical assessment of central dysfunction and biochemical measures of acidosis. Novel axonal excitability techniques have established acute, reversible ischemic-like depolarization that may serve as a surrogate marker of central events that develop during stroke-like episodes in MELAS.