Early cortical median nerve somatosensory evoked potentials. Prognostic value in anoxic coma
H. Walser, H. Mattle, H. M. Keller and R. Janzer
Subcortical and early cortical median nerve somatosensory evoked potentials
(SEPs) were examined in 26 patients in hypoxic coma. The amplitude ratio
between the negative slope of the scalp response and the following positive
trough was determined. The latency difference between the major negative
component recorded from the upper neck, N14, and the initial negative
potential from the scalp, N20, was also measured. The mean of these
parameters in both hemispheres was referred to as mean central conduction
time (MCCT) and mean amplitude ratio (MAR). There was a significant
difference in MAR in patients with a bilaterally recordable scalp response
between those with a good and those with a bad outcome, but no difference
in MCCT. Comparison of SEP findings with postmortem examinations suggests
that a reduced MAR may yield an estimate of cortical damage in hypoxic
coma.
