Evoked potentials in the evaluation of patients with mitochondrial myopathy.

Multimodality evoked potentials and pattern electroretinograms (PERGs) were performed in seventeen patients with histologically defined mitochondrial myopathy (MM). Brainstem auditory evoked potentials showed abnormalities in 47% and somatosensory evoked potentials in 76%. Visual evoked potentials were outside the normal range in 71%; PERGs exhibited a decreased amplitude or delayed P50 in 78%. These findings may be considered as an expression of impairment of the central nervous system in MM, even if the specific mechanism, 'structural' or 'functional', needs further investigation.