Object: The isolated posterior femoral cutaneous nerve (PFCN) neuropathy has rarely been described in the literature and documented electrophysiologically, based on the paucity of published report. The purpose of this study was to assess the reference value of somatosensory evoked potentials (SSEP) in posterior femoral cutaneous nerve.

Method: Both legs of twenty healthy adults were tested. Somatosensory evoked potentials were obtained with the active recording electrode placed at Cz', 2 cm posterior to C_Z, and the reference electrode at F_Z (international 10∼20 system). The posterior femoral cutaneous nerve was excited 14 cm proximal to the midpopliteal fossa between the long head of the biceps femoris and the semitendinosus muscles.

Results: The mean latency of right P1 were 35.35⁑3.17 msec, N1 were 45.28⁑2.71 msec and mean peak amplitudes were 1.42⁑0.98 μV. In the left side, mean latency of P1 were 34.54⁑2.89 msec, N1 were 43.87⁑2.44 msec and mean peak amplitudes were 1.20⁑0.53 μV.

Conclusion: Based on the result of this study, the reference values could be used to differentiate and detect the lesion in the case of isolated dysfunction of the posterior femoral cutaneous nerve.

Medial femoral cutaneous nerve(MFCN), a sensory branch of the femoral nerve, supplies the skin over the anteromedial aspect of the thigh and knee. Posterior femoral cutaneous nerve(PFCN), comprised of fibers originating from the anterior and posterior divisions of the first three sacral segments, supplies the skin over the posterior aspect of the thigh.

Forty nerves of twenty healthy adults, ages from 20 to 58, were tested. The onset and peak latencies of MFCN were 2.3⁑0.2 ms and 2.9⁑0.2 ms respectively. The baseline to peak amplitude was 6.5⁑2.3 ㄍV. The onset and peak latencies of PFCN were 2.4⁑0.2 ms and 2.9⁑0.2 ms respectively. The baseline to peak amplitude was 7.1⁑1.7 ㄍV.