Side-to-Side Amplitude Ratio in SEP : Comparisons of Three Measurement Methods in Normal Adults

J Korean Assoc EMG Electrodiagn Med 2000;2(1):39-43.
Published online May 9, 2000.

Abstract

Objective : To evaluate clinical utility of amplitude of lower extremity SEP in lumbosacral radiculopathy, we tried to know side to side amplitude ratios in normal adults. Methods : In 20 healthy men, we calculated amplitude ratios of lower extremity SEP according to 3 different amplitude decision methods on both sides and compared both sides with 3 different methods. All subjects was studied with posterior tibial nerve, sural nerve and S1 dermatomal SEPs. Results : In posterior tibial nerve, amplitude ratio was 41.8~93.4% and 43.5~98.6% in sural nerve and 21.2~93.2% in S1 dermatome. Conclusion : When comparing amplitudes on both sides in lower extremity SEP studies, P1/N1 amplitude is recommended and comparing of mean of 2 different tests is recommended. Also, amplitude ratio with less than 40% is considered abnormal in posterior tibial nerve or sural nerve SEP studies.

Key Words: Lower extremity somatosensory potential study, Side to side comparison, Amplitude ratio, Amplitude decision method