Evoked potentials in mitochondrial disorders.

Twenty-eight adult patients with mitochondrial disease were evaluated with muitimodal evoked potentials (EPs) to assess a possible CNS involvement The patients were classified into five groups: encephalopathy (two cases), progressive external ophthalmoplegia (PEO; four cases), pure myopatby (15 cases), cardiomyopathy (five cases) and asymptomatic relatives (two cases). EPs showed differences between encephalopathy (all EP modalities affected) and PEO groups (all patients with at least one EP altered), with lesser degrees of affection in pure myopathy and cardiomyopathy groups. The asymptomatics registered normal EPs. In view of these results, progressive CNS damage in mitochondriopathies, expressed by abnormal EPs, can be established as follows (from greatest to minor severity): encephalopathy, PEO, pure myopathy/cardiomyopathy and asymptomatic condition.