Maturational study of short-latency somatosensory evoked potentials after posterior tibial nerve stimulation in infants and children

Abstract

SSEPs produced in response to PTN stimulation were studied in 41 normal infants and children from 4 months to 16 years in age. SSEPs were recorded on the scalp with reference electrodes attached to the contralateral knee, shoulder and earlobe. Four positive SSEPs, PI, PII, PIII and PIV, named in order of appearance, and one negative SSEP, N0, were recorded as FFPs on the scalp with the cKn reference. Following these FFPs, the cortical component P1 which corresponded to P37 in adults was recorded. Preceding P1, another negative wave, N1, could be recognized solely at Cz' mainly at the onset of P1. P1 and N1 could be identified in all children with derivations with noncephalic references, although they could not be identified in 5 of 41 children with a Cz' - Fpz derivation. PI, bilobed in configuration, was considered to originate at the sacral plexus or entry to the spinal canal. PII was the least reproducible potential and was considered to originate at the dorsal root, dorsal horn or conus medullaris. PIII, PIV and N0 were considered to originate at the cervical cord, brain stem and thalamus, respectively. With the peak latencies of PI, PII, PIII, PIV, N0, N1 and P1, the RV was calculated in order to eliminate the influence of body height. The RV of the later appearing components leveled off in the older age categories. The RV of P1 reached a steady level at 3 years of age. RVs of PII and PIII appeared to level off by the age of 6 years. The RV of PIV leveled off by the age of 9 years. RVs of N0 and N1 leveled off by the age of 12 years, and that of P1 decreased until over 12 years of age. Furthermore, to eliminate the influence of naturation in the peripheral nerves, the RV was obtained from PI-PIV, PI-P1, PIV-P1 and N1-P1 interpeak latencies. The RVs of these 4 interpeak latencies all decreased until over 12 years of age. Accordingly, the maturation of afferent conduction in the central nervous system after PTN stimulation appeared to be complete after 12 years of age.