SUBJECT-BASED P1 LATENCY INTERROOT COMPARISON, A METHOD TO EVALUATE P1 LATENCY IN SCALP RECORDED SOMATOSENSORY-EVOKED POTENTIALS OBTAINED WITH SENSORY NERVE-STIMULATION IN THE LOWER-EXTREMITIES
E. Pape, SUBJECT-BASED P1 LATENCY INTERROOT COMPARISON, A METHOD TO EVALUATE P1 LATENCY IN SCALP RECORDED SOMATOSENSORY-EVOKED POTENTIALS OBTAINED WITH SENSORY NERVE-STIMULATION IN THE LOWER-EXTREMITIES, Electroencephalography and clinical neurophysiology. Evoked potentials, 96(4), 1995, pp. 329-337
The purpose of the present study was to establish a method that allows
the general use of subject-based criteria to evaluate P1 latency in s
calp recorded somatosensory evoked potentials obtained with stimulatio
n of the sural (S1), superficial peroneal (L5) and saphenous (L4) nerv
es bilaterally. The nerves were stimulated at the same distance from t
he registration electrode. Two groups of normal nerve roots were studi
ed: (1) nerve roots on both sides in 20 asymptomatic volunteers, and (
2) neuroradiologically normal nerve roots on the asymptomatic side in
22 patients with unilateral sciatica. The results presented show that
the P1 latencies after stimulation of the 6 different nerves in the sa
me person can be regarded as equal. On this basis 2 criteria to evalua
te P1 latency by within-subject pi latency inter-root comparison were
defined. They were the difference between P1 latency of 1 registration
and (1) that of any one of the other 5 registrations and (2) the mean
P1 latency of the other registrations. The variability of these subje
ct-based criteria and the width of their reference limits were compare
d to those of the population-based criteria of height- and height-age-
corrected PI latency. This comparison showed that the use of within-su
bject P1 latency inter-root comparison should enhance the ability to d
emonstrate small bilateral P1 latency prolongations at the same segmen
tal level.