Evoked potentials in children with oxidative metabolic defects leading to Leigh syndrome.

We studied evoked potentials in 15 children (age range: 2 wks to 4 yrs; mean: 10 mos) with metabolic disturbances that led to Leigh syndrome. These disturbances included deficiencies of pyruvate dehydrogenase (N = 5), complex 1 (N = 7), complex 4 or cytochrome oxidase (N = 2), and complex 5 (N = 1) deficiencies. Subsequent studies were performed in 11 children. All of the children with pyruvate dehydrogenase deficiency had abnormal brainstem auditory evoked potentials (BAEPs) due to poor morphology and reproducibility of the waveforms; central conduction time was normal in 4 of 5 initial studies. The patients with complex 4 or cytochrome oxidase deficiency had abnormal BAEPs, due to increased interpeak latencies and low amplitude or absent waves IV/V. Six of 7 of the children with complex 1 deficiency had normal BAEPs. The remaining patient (the youngest, age 6 wks) had only waves I and II bilaterally and suffered from the rapidly progressive form of complex 1 deficiency; the other 6 with complex 1 deficiency had the slowly progressive form. The one patient with complex 5 deficiency had normal BAEPs when first tested at 4 mos; abnormal BAEPs with loss of later waves were observed 10 weeks later. The visual evoked potentials and somatosensory evoked potentials usually were abnormal in these patients, but the findings were not specific to the patient subgroups. In all but one patient, subsequent studies disclosed a lack of normal maturational changes and/or deterioration across all 3 modalities. The BAEPs appeared to covary with the specific metabolic findings in these patients and with the patient's clinical course, but no BAEP could be considered characteristic of Leigh syndrome.