Scalp topography of somatosensory evoked potentials following median and posterior tibial nerve stimulation in Down's syndrome.

The scalp topography of somatosensory evoked potentials (SEPs) following stimulation of the median and posterior tibial nerve of 39 patients with Down's syndrome was compared with that of age-matched normal controls using significance probability mapping (SPM). The maximal area of each potential in Down's syndrome was similar to that in normal controls, but the scalp distribution was wider. The amplitudes of all components, except the N45 and P59 potentials of the posterior tibial nerve SEPs, were greater in Down's syndrome, and the t values calculated by SPM were significantly greater. However, the difference of SEP maps between Down's patients and aged controls (over 65 years) was much smaller than that between Down's patients and age-matched controls. Therefore, we conclude that the generator sources and generating mechanisms of SEPs in Down's syndrome are not different from those of normal control, however SEP potentials in Down's syndrome are remarkably enhanced, resulting in a wider distribution, probably due to accelerated aging in Down's patients.