Change of Current Perception Threshold of Median Nerve after Transcutaneous Electrical Nerve Stimulation

ABSTRACT

OBJECTIVE: We measured current perception threshold (CPT) with transcutaneous electrical nerve stimulation (TENS) to prove the selective increment of the threshold of C sensory fiber and to determine onset time and duration of effect for application of TENS. METHOD: TENS were applied to fifteen control volunteers for 20 minutes on hand three times per week for 2 weeks duration. The CPT was tested at the distal interphalangeal joint of the second finger with 5 Hz, 250 Hz, and 2,000 Hz in frequency, respectively. The test was repeated immediately and 30 minutes after cessation of TENS. These tests were performed on the first, eighth, and fifteenth day on application of TENS. RESULTS: The baseline CPT of C fiber was 32.7 +/- 6.4 10 2 mA, A gamma fiber 23.2 +/- 9.4 10(-2) mA, and A beta fiber 83.9 +/- 18.1 10(-2) mA. At 30 minutes after cessation of TENS in the fifteenth day, the CPT of C fiber increased markedly and that of A gamma fiber increased a little. The CPT of A beta fiber didn't increase for 2 weeks. CONCLUSION: With application of TENS, the threshold of C and A gamma fibers selectively increased, especially 30 minutes after removal of TENS application. This effect was outstanding after 2 weeks' application.