Neurophysiologic studies of the penilo-cavernosus reflex: normative data

To determine normative values for the penilo-cavernosus reflex on single and double pulse electrical, and mechanical stimulation.

All men without neurologic disorder, with normal neurologic examination, and with bilaterally normal quantitative electromyography of the external anal sphincter muscles referred for sacral neurophysiologic studies in the years 2003-2005 were included. The penilo-cavernosus reflex was studied on single and double electrical, and mechanical stimulation. Responses were detected by a needle electrode inserted consecutively into the left and right bulbocavernosus muscle. In each subject, latency of the response, and using electrical stimulation, the sensory threshold, reflex threshold and stimulation strength, were determined. Normative values were calculated using parametric statistics and optimal data transformations.

In all 26 men with minor non-neurogenic sacral dysfunction reflex responses were recorded using each stimulation technique. Minimal latencies of reflex responses (in msec) were 29.88 +/- 5.65 (upper limit: 39.4), 30.00 +/- 4.11 (36.0), 28.16 +/- 5.80 (35.5) on single electrical, double electrical and mechanical stimulation, respectively. Sensory thresholds (in mA) were 7.80 +/- 2.73 (upper limit: 14.5) and 6.08 +/- 2.30 (10.5), and reflex thresholds (in mA) 25.36 +/- 11.04 (upper limit: 49.6) and 12.78 +/- 6.06 (26.9) on single and double electrical stimulation, respectively.

The obtained normative values for latency on single electrical and mechanical stimulation were similar to those previously published. Additional data on latency on double electrical stimulation, and on the sensory and reflex thresholds on single and double electrical stimulation are expected to increase the diagnostic utility of the penilo-cavernosus reflex.