Neurophysiological evidence of aging in Down's syndrome.

Fifteen subjects with Down's syndrome had measurements of peripheral and central nervous system conduction parameters. Conventional nerve conduction studies revealed evidence of peripheral nerve dysfunction consistent with an axonal degeneration. Upper limb somatosensory evoked potentials were delayed compared with age-matched controls in both young and older age groups of Down's subjects. Lower limb somatosensory evoked potentials were also delayed when correction for height was made; furthermore the 'central conduction time' was prolonged in young and older groups. These results suggest that both peripheral and central nervous system function is impaired in Down's syndrome and the pattern of change is similar to that found with aging in normal individuals.