Electroencephalographic findings in patients with chronic progressive external ophthalmoplegia

Utility of multimodal evoked potential study and electroencephalography in mitochondrial encephalomyopathy

We performed electroencephalography (EEG) and multimodal evoked potential (EP) studies in 16 patients with various forms of mitochondrial encephalomyopathy (ME). The electrophysiological investigations revealed signs of involvement of the peripheral and central nervous system (CNS) in 14 patients, with a high incidence of visual-EP (VEP) alterations, indicative of visual pathway vulnerability in mitochondrial diseases. No specific pattern of abnormalities emerged and, in particular, clinical and laboratory findings did not correlate with each other. EP (particularly VEP and electroretinogram) investigations should be part of the diagnostic work-up of patients with mitochondrial disorders in order to better characterize the clinical picture, disclose involvement of specific sensory systems of the CNS, and assess patients with atypical clinical presentations.

EEG and evoked potential findings in mitochondrial myopathies

Electroencephalograms (EEGs) and evoked potentials (EPs) were studied in 43 patients with mitochondrial myopathies. Abnormalities were found most frequently in patients who presented predominantly or exclusively with central nervous system (CNS) dysfunction (abnormal EEGs in 18 of 21 patients, abnormal EPs in 9 of 11 patients). However, of patients presenting with ocular myopathy or proximal muscle weakness who had little or no CNS involvement clinically, 8 of 22 had abnormal EEGs and 5 of 10 had abnormal EPs, suggesting that electrophysiological tests are of value in demonstrating subclinical CNS disease in mitochondrial myopathy, although the abnormalities are not specific.