Somatosensory evoked potentials of median and tibial nerves in rhesus monkeys (Macaca mulatta) under captivity: influence of ontogenic status in neonatal, infant, young, adult, and senile stages

Background Somatosensory evoked potentials (SEPs) constitute a useful neurophysiologic tool commonly used to assess the functionality and developmental degree of the nervous system. Objective To analyze somatosensory pathways of the Macaca mulatta species throughout different ontogenetic statuses. Methods Twenty non‐human primates were divided into five age‐dependant groups. Recording of SEPs was executed by stimulation of lower limb at the tibial nerve and upper limb and recorded at the median nerve. Results Two wave series were observed for all groups for both limbs studied. Significant differences were found at the upper right limb at C4, C7 and also for the antecubital fossa site. The lower limbs showed a single significant right‐wing deflection. Conclusions Differences found in signals generated by the nervous system in response to somatosensory stimuli among the studied groups are thought to be developmental in origin, as the most remarkable deviations were seen in younger monkeys.     

Preliminary studies of neurosensory and cardiopulmonary health compromise in captive- bred Rhesus macaques (Macaca mulatta) suffering scoliosis

Background It has been widely documented that quadrupedal animals rarely display natural spontaneous scoliotic rachis deviations of the spinal column. The objective was to determine spinal deformities developed by geriatric monkeys of the Macaca mulatta species, by radiographical and tomographical studies of the vertebral column correlating morphological changes with altered physiological parameters and electrical neurosensorial conductivity of somatosensory‐evoked potentials (SEPs). Materials and methods A cohort of six geriatric monkeys was used: three non‐scoliotic subjects and three monkeys with naturally acquired true scoliosis. Results Radiographic and tomographic studies depicted a thoracic curvature displaying a left‐sided thoracic vertebral rotation. The evaluation of physiological parameters demonstrated significant differences in the respiratory rate, as it was observed for the diastolic blood pressures, which showed a decrease in the monkeys with scoliosis compared with healthy monkeys. Regarding the SEPs studies, the non‐parametric test for independent samples Mann–Whitney U test displayed a significant difference observed at the left and right thoracic derivative in P1; while regarding the study of upper limbs, a significant difference was seen at the Erb’s point derivative, left afferency in P1, showing in all the derivatives an increase in latency in monkeys with scoliosis versus monkeys in the control group. Conclusions This study has demonstrated that quadrupedal animals can develop true scoliosis showing an analogous way to that occurring in humans.     

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.