New techniques in female pudendal somatosensory evoked potential testing.

OBJECTIVE: The primary nerves innervating the female genitalia are the dorsal nerve of the clitoris (DNC) and the perineal nerve, which innervate the clitoris and the external genitalia/distal vagina, respectively. We describe two novel electrodiagnostic techniques for evaluating the integrity of these female genital somatosensory pathways. SUBJECTS AND METHODS: Seventy-seven healthy women (mean age 29.3 years) were enrolled for this study. We performed DNC somatosensory evoked potentials (SEPs), stimulating through self-adhesive disk electrodes on either side of the clitoris. Perineal nerve SEPs were evoked through a vaginal probe. Cortical responses were measured through cup electrodes affixed to the scalp at Cpz and Fpz. Stimulus parameters were duration 0.1 ms, frequency 4.1 Hz, filters 5-5,000 Hz, at three times sensory threshold. RESULTS: DNC and perineal nerve SEPs from both the right and left sides were reproducible and easily discerned. The mean P1 latencies were: right DNC 39.4 ms (SD 2.8 ms), left DNC 39.3 ms (SD 3.3 ms), right perineal nerve 37.8 ms (SD 3.4 ms), left perineal nerve 37.6 ms (SD 3.1 ms). We recorded SEP responses from 90 to 92% of subjects for the DNC, and 69% for the perineal nerve. CONCLUSIONS: We are able to evoke somatosensory potentials from the four primary somatic nerves that mediate female genital cutaneous sensation. In healthy subjects, the DNC responses are robust and maintain laterality. The perineal nerve responses are less consistently obtained, but when recorded, are easily discerned. These preliminary data provide a foundation from which to study female genital innervation, particularly as it applies to sexual function.

Physiologic studies of male sexual dysfunction in multiple sclerosis.

OBJECTIVE: We conducted this investigation to better define the neural disruptions that result in sexual dysfunction in men with multiple sclerosis (MS), using genital electrodiagnostic testing and nocturnal penile tumescence and rigidity monitoring. METHODS: Thirteen men with MS and sexual dysfunction were recruited for the study. Twelve healthy, sexually potent men were enrolled as controls. All underwent pudendal somatosensory evoked potential (SEP) testing using standard methods, and a new modification to isolate the right and left dorsal nerves of the penis. RigiScan testing was performed on the MS subjects to assess nocturnal erectile function. RESULTS: Unilateral and bilateral DNP SEPs were able to be performed on the control subjects. In all but one MS subjects, DNP SEP abnormalities were found. Three men had normal latency bilateral DNP SEP latencies, but on unilateral DNP testing, abnormalities were identified. Seven men, including those with abnormal or absent SEP latencies, had normal nocturnal erectile activity. There was no correlation between overall functional status, presence of abnormal or absent SEP, and quality of nocturnal erectile activity. CONCLUSIONS: Genital SEP abnormalties are common in men with MS and sexual dysfunction. Unilateral DNP SEP testing was more sensitive in identifying abnormalities than the standard method of pudendal SEP testing. One of the causes of sexual dysfunction in men with MS may be due to genital somatosensory pathway disruption, with sparing of the efferent tracts in some men.

Neurophysiologic testing in chronic pelvic pain syndrome: a pilot study.

OBJECTIVES: Studies of male chronic pelvic pain syndrome (CPPS) have generally centered on the pathologic features of the prostate rather than on the neurology of pain. Electrodiagnostic studies examine the integrity of somatosensory nerve pathways consisting of large, group A fibers. Heat sensation and visceral (autonomic) pain is mediated through small, unmyelinated C fibers, which can be tested cutaneously by thermal sensory analysis. We hypothesized that CPPS pain is mediated by these small C fibers. METHODS: All subjects and controls had no history of neurologic disease and had normal neurologic examinations. Phase I: 14 patients with CPPS underwent electrodiagnostic testing using pudendal somatosensory evoked potentials and bulbocavernosus reflex latency measurements. Phase II: 31 patients with CPPS and 14 controls underwent thermal sensory analysis testing on the perineum and anterior thigh using noxious heat stimuli. Subjects used a computer-generated visual analog scale to dynamically report their discomfort. The peak and slope of the computer-generated visual analog scale were analyzed. RESULTS: Phase I: two patients had delayed latency of the somatosensory evoked potentials, but additional evaluation with magnetic resonance imaging revealed no definable lesion. Phase II: with thermal sensory analysis, men with CPPS reported higher intensity pain at lower temperatures (P = 0.03). Men with CPPS also had higher peak computer-generated visual analog scale scores on perineal testing. No difference in thermal testing on the anterior thigh was found between the two groups. CONCLUSIONS: Large, myelinated somatic fibers do not play a significant role in the pathophysiology of CPPS. Patients with CPPS have an altered sensation of perineal pain elicited by heat, which may represent a C-fiber-mediated effect.

Cortical evoked potentials of the dorsal nerve of the clitoris and female sexual dysfunction in multiple sclerosis.

PURPOSE: We evaluated whether disrupting genital central nervous system pathways is associated with subjective reports of sexual dysfunction in women with multiple sclerosis. MATERIALS AND METHODS: We performed pudendal somatosensory evoked potential testing in and had sexual questionnaires completed by 14 women with a mean age of 47 years who had multiple sclerosis. RESULTS: The mean expanded disability status score was 5. All but 1 woman reported the desire for sexual intercourse. There was a high rate of dissatisfaction with their sex life and all study participants had concomitant bladder and bowel function problems. The most common sexual complaint was difficult or no orgasm, which was statistically associated with abnormalities or absence of 1 or both pudendal cortical evoked potentials. Fatigue and arousal disorders were also common. CONCLUSIONS: Women with multiple sclerosis have a high self-reported rate of sexual dysfunction, which decreases quality of life. Electrodiagnostic data imply that pudendal somatosensory innervation is necessary for normal female orgasmic function. More study is needed to confirm these findings.

Cortical evoked responses from the perineal nerve.

PURPOSE: We characterize and determine normal reference latencies for the cortical evoked response from the perineal nerve. MATERIALS AND METHODS: A total of 15 healthy, potent men with a mean age of 31.3 +/- 6.8 years underwent genital electrophysiological testing. Square wave stimuli were applied to the perineal nerve at the ventral base of the penis and the perineal floor. Cortical evoked responses were recorded, and onset latencies were measured at baseline and after anesthetization of the dorsal nerve of the penis. RESULTS: In all 15 subjects a cortical evoked response was elicited after stimulation of the perineal nerve at the ventral base of the penis with a mean latency measured from the first positive deflection (P1) of 48.4 +/- 7.8 milliseconds. Penile block of the dorsal nerve of the penis did not change or abolish the cortical evoked response. A similar cortical evoked response was obtained, although less consistently, after stimulation of the perineal nerve through its course in the perineal floor. CONCLUSIONS: A cortical evoked response from the perineal nerve can be elicited reliably at the ventral penis. This neural pathway is independent of the dorsal nerve of the penis. The study of perineal somatic innervation may prove important in understanding the physiology of ejaculatory and erectile dysfunction.