117. Lumbosacral dermatomal somatosensory evoked potential of pelvic floor: Stimulation and recording techniques and normative data

The aim of this study is to develop the better stimulation and recording protocol of D-SEP to study pelvic floor dermatomal (L1/L2, S2, S3 and S4), and to collect normative data in healthy subjects. We paid attention to place stimulation electrode in specific dermatomal region but not to stimulate directly sensitive nerve. Stimulation sites: L1/L2 internal face of anterior side of thigh, 5–6 cm distal to pubic symphysis, S2 posterior side of thigh, 2 cm medial to the midline and 7 cm distal to gluteal fold, S4 perianal zone. Stimulation of S3 was different for male and female: male: each side of penis, female: on clitoris. We recorded from L2 and Cz′. Stimulation parameters: duration 0,2 ms, rate 0,1 Hz, intensity 4× sensory threshold. Subjects: 12. Studied parameters: peak latency of P40, N50 and P60, side-to-side difference latency, peak to peak amplitude of P40. Results (mean ± SD): P40 latency: L1/L2 (n. 22) 37,78 ± 13,56 ms, S2 (n. 19) 39,56 ± 8,85 ms, S3 (n.16) 43,81 ± 11,2 ms, S4 (n. 22) 39,72 ± 8,11 ms; mean side to side difference latency of P40: L1/L2 (n.10) 2,7 + 7,1 ms, S2 (n.9) 2,3  + 7,6 ms, S3 (n. 5) 1,6 + 1,1 msec, S4 (n.10) 2,4 + 5,2 ms. Peak to peak amplitude L1/L2 (n. 22) 2.10 + 3.67 microV, S2 (n. 19) 1,70 + 1,70 microV, S3 (n. 16) 2,91 + 4,85 microV, S4 (n. 22) 1,85 + 4,18 microV. These normative data could be useful for a careful neurophysiological evaluation of pelvic floor, in addition to standard tests.