Differences in Pain Perception Between Men and Women of Reproductive Age: A Laser-Evoked Potentials Study.

Objective: We investigated differences in pain perception between men and women of reproductive age by using Laser-Evoked Potentials (LEPs). Design, Setting, Subjects: Forty-four right-handed healthy volunteers (19 males/25 females), aged 30­40 years were studied. A CO2 laser generated three series of 10 thermal pulses (4.5 W) on the radial aspect of the dorsum of the left hand. A recording montage for late LEPs was used, and the potentials of each series of stimuli were averaged to calculate mean latency and amplitude for each subject. Volunteers scored verbally pain intensity (Numerical rating scale [NRS]; 0­10). Three series of 10 numbers were averaged for calculation of mean NRS score. Methods: LEP peak-to-peak amplitude, latency, and NRS scoring were compared between genders, and correlations between LEP amplitude/latency and NRS scores were assessed. Results: Data from 44 subjects were analyzed. LEP amplitudes differed significantly (P < 0.001) between men (24.2 ± 6.0 µV) and women (38.9 ± 15.28 µV), while no difference was found for latency (156.5 ± 8.6 versus 160.4 ± 19.8 ms, P = 0.42) or NRS score (2.6 ± 1.5 versus 2.4 ± 1.4, P = 0.63), respectively. Menstrual cycle phase did not influence LEP parameters (P = 0.59 for amplitude and P = 0.69 for latency) or NRS score (P = 0.95). No significant correlation was found between latency or amplitude and NRS score (P = 0.43 and P = 0.90, respectively). Conclusions: Our results demonstrate a significant gender-related difference in LEP amplitudes with lower mean values in men, while no difference was found in LEP latencies or in subjective pain ratings. Further research is required to clarify the clinical significance of the above experimental findings.

There is No Association between Cardiovascular Autonomic Dysfunction and Peripheral Neuropathy in Chronic Hemodialysis Patients.

BACKGROUND AND PURPOSE: The potential association between the severity of autonomic dysfunction and peripheral neuropathy has not been extensively investigated, with the few studies yielding inconsistent results. We evaluated the relationship between autonomic dysfunction and peripheral neuropathy in chronic hemodialysis patients in a cross-sectional study. METHODS: Cardiovascular autonomic function was assessed in 42 consecutive patients with chronic renal failure treated by hemodialysis, using a standardized battery of 5 cardiovascular reflex tests. Symptoms of autonomic dysfunction and of peripheral neuropathy were evaluated using the Autonomic Neuropathy Symptom Score (ANSS) and the Neuropathy Symptoms Score. Neurological deficits were assessed using the Neuropathy Disability Score. Conduction velocities along the sensory and motor fibers of the sural and peroneal nerves were measured. Thermal thresholds were documented using a standardized psychophysical technique. RESULTS: Parasympathetic and sympathetic dysfunction was prevalent in 50% and 28% of cases, respectively. Peripheral neuropathy was identified in 25 cases (60%). The prevalence of peripheral neuropathy did not differ between patients with impaired (55%) and normal (75%) autonomic function (p=0.297; Fisher's exact test). The electrophysiological parameters for peripheral nerve function, neuropathic symptoms, abnormal thermal thresholds, age, gender, and duration of dialysis did not differ significantly between patients with and without autonomic dysfunction. Patients with autonomic dysfunction were more likely to have an abnormal ANSS (p=0.048). The severity of autonomic dysfunction on electrophysiological testing was positively correlated with ANSS (r=0.213, p=0.036). CONCLUSIONS: The present data indicate that although cardiovascular autonomic dysfunction is prevalent among patients with chronic renal failure, it is not associated with the incidence of peripheral neuropathy.