Effects of aging on central conduction in somatosensory evoked potentials:evaluation of onset versus peak methods

Objectives: To investigate effects of aging on peripheral and central somat osensory conduction, and evaluate onset-to-onset and peak-to-peak measureme nts of each component and central conduction time (CCT) in somatosensory ev oked potentials (SEPs). Methods: We recorded SEPs with non-cephalic reference from the Erb's point, the posterior (cv 6) and anterior neck, and scalp (Fz and P4) after left m edian nerve stimulation in 138 normal subjects aged between 20 and 78 years . We determined onset or peak latencies of the Erb's potential (N9), the sp inal N13-P13 in cv 6-to-anterior neck montage and the N20-P20 in scalp lead s. Onset CCT was defined as a transit time from N13-P13 onset to N20-P20 on set. Ln each subject, interpeak latencies of the 'N13' component in cv 6-to -Fz montage and the N20-P20 in P4-to-Fz montage were also defined as conven tional peak CCT. Results: Using multiregression analysis, we found that the onset or peak la tencies of each SEP component were correlated with the subject's height and age. So were the onset CCTs: Onset CCT (in ms) = 2.549 + 2.041 x (height i n meters) + 0.005 x (age in years) (P < 0.0001) The conventional peak CCTs as well as onset-to-peak durations of the N20-P20 were correlated with the subject's age but not height: Peak CCT(in ms)= 5.458 + 0.012x(age in years) (P < 0.0005). Conclusion: Conductive function is affected by normal aging in the central as well as peripheral somatosensory pathways. The peak CCT is more affected by aging than the onset CCT. However, the onset-to-peak duration of the N2 0-P20 increased by 0.8 ms between the 4th and 7th decades, suggesting that the peak CCT increase in older people reflects the age-related changes in N 20-P20 profile but not in the fastest central conduction. We therefore conc lude that the onset CCT measurement is preferable to the peak CCT measureme nt when assessing the central somatosensory conduction. (C) 1999 Elsevier S cience Ireland Ltd. All rights reserved.