Myoclonic epilepsy with ragged-red fibers (MERRF) – clinical and electrophysiological analysis

Abstract

© by Wydawnictwo Continuo. Myoclonic epilepsy with ragged-red fibers (MERR F) is an ultra-rare mitochondrial disease, typically associated with a point mutation of nucleotide 8344 of the mitochondrial DNA. In patients with MERR F also other mutations, eg. T8356C, G8361A, G8363A, a mutation in the polymerase gamma (POL G) nuclear DNA are described. The underlying disease processes are disturbances in the functioning and structure of mitochondria, resulting in the inefficiency of oxidative phosphorylation and AT P deficiency. Biochemical studies have demonstrated isolated or combined damage of I and IV of the respiratory chain. The main symptoms of MERR F relate to organs with a high demand for AT P, especially the nervous system and muscles. The classic clinical picture includes myoclonus, seizures, progressive cerebellar ataxia and distinctive skeletal muscle damage. Less common symptoms include–deafness, dementia, short stature, cardiomyopathy, ophthalmoplegy. In the most cases in MERR F ragged fibers (RR F, ragged-red fibers) in muscle biopsy were revealed. Imaging of the brain (CT and MRI) show atrophy of the brain, cerebellum and the brain stem, which is due to loss of neurons. In patients with MERR F and the asymptomatic family members they found at a standstill elevated levels of lactic acid in the serum and cerebrospinal fluid. The authors present the current knowledge on MERR F, with particular emphasis on clinical diagnostic with electrophysiology methods such as EE G, EMG and evoked potentials.