Activation of C-fiber nociceptors by low-power diode laser

Objective: The evaluation of selective activation of C-fibers to record evoked potentials using the association of low-power diode laser (810 nm), tiny-area stimulation and skin-blackening. Method: Laser-evoked potentials (LEPs) were obtained from 20 healthy young subjects. An aluminum plate with one thin hole was attached to the laser probe to provide tiny-area stimulation of the hand dorsum and the stimulated area was covered with black ink. Results: The mean intensity used for eliciting the ultra-late laser-evoked potential (ULEP) was 70 +/- 32 mW. All subjects showed a clear biphasic potential that comprised a negative peak (806 +/- 61 ms) and a positive deflection (1033 +/- 60 ms), corresponding to the ULEP related to C-fiber activation. Conclusion: C-fiber-evoked responses can be obtained using a very low-power diode laser when stimulation is applied to tiny areas of darkened skin. This strategy offers a non-invasive and easy methodology that minimizes damage to the tissue.Univ Fed Sao Paulo, Dept Psicobiol, Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Setor Neurofisiol Clin, Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Dept Psicobiol, Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Setor Neurofisiol Clin, Sao Paulo, SP, BrazilWeb of Scienc

Pudendal nerve latency time in normal women via intravaginal stimulation

INTRODUCTION & OBJECTIVES: Studies of motor conduction for the efferent functional assessment of the pudendal nerve in women with pelvic dysfunctions have been conducted through researching distal motor latency times. The transrectal approach has been the classic approach for this electrophysiological examination. The objective of the present study is to verify the viability of the transvaginal approach in performing the exam, to establish normal values for this method and to analyze the influence of age, stature and parity in the latency value of normal women. MATERIALS AND METHODS: A total of 23 volunteers without genitourinary pathologies participated in this study. In each, pudendal motor latency was investigated through the transvaginal approach, which was chosen due to patient s higher tolerance levels. RESULTS: The motor response represented by registering the M-wave was obtained in all volunteers on the right side (100%) and in 13 volunteers on the left side (56.5%). The mean motor latency obtained in the right and left was respectively: 1.99 ± 0.41 and 1.92 ± 0.48 milliseconds (ms). There was no difference between the sides (p = 0.66). Latency did not correlate with age, stature or obstetric history. The results obtained in the present study were in agreement with those found by other researchers using the transrectal approach. CONCLUSION: The vaginal approach represents an alternative for pudendal nerve distal motor latency time, with similar results to those achieved through the transrectal approach. Normative values obtained herein might serve as a comparative basis for subsequent physiopathological studies.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Universidade Federal de São Paulo (UNIFESP), Escola Paulista de Medicina (EPM) Departments of Urology and NeurologyUNIFESP, EPM, Departments of Urology and NeurologySciEL

Cortical correlates of response time slowing in older adults: ERP and ERD/ERS analyses during passive ankle movement

Objectives: The response time (RT) to kinesthetic perception has been used as a proprioceptive measurement, for example, in older individuals. However, the RT cannot provide information on impairments at specific stages of the respective sensorimotor processing. In the present study, electroencephalographic (EEG) signals were recorded during passive ankle movement with and without an associated perceptual task of movement detection. The main purpose was to analyze differences between young and older adults both in terms of RT and cortical responses. Putative differences in the latter were expected to point to changes in the processing associated with neural pathways or cortical regions in the older subjects. Methods: The EEG activity of nineteen older (OA, 65-76 years) and 19 young adults (YA, 21-32 years) was recorded during passive ankle movement, without motor voluntary response (NVR, sensory condition), and during a condition with voluntary motor response (VR, with measurement of the RT). Event-related potentials (ERP) and beta event-related desynchronization/synchronization (ERD/ERS) were recorded and analyzed in both experimental conditions. Results: The RT in OA was larger than in YA (P < 0.0001). EEG analyses showed that the N1 amplitude was larger in the VR than in the NVR condition (P = 0.006), whereas no difference for latency was obtained between conditions (P = 0.376). Comparisons between the groups revealed attenuated (P = 0.019) and delayed (P = 0.001) N1 in the OA group, irrespective of the condition (no interaction group vs condition). Only OA showed correlations between RT and N1, with significant correlation for both amplitude (r = -0.603, P = 0.006) and latency (r = 0.703, P = 0.001). The ERD/ERS analyses revealed a task-dependent group effect: in NVR, significant differences were obtained only for the ERS amplitude, which was attenuated in OA (P = 0.003). In VR, larger (P = 0.004) and delayed (P = 0.003) ERD and attenuated (P = 0.029) and delayed (P = 0.017) ERS peaks were observed in the older group. Conclusions: The results suggest that a larger response time to proprioceptive stimuli in older adults is associated with a weaker and delayed proprioceptive afferent inflow to the cortex. In this scenario, older adults would need a higher cognitive effort (larger ERD) to process the sensory inputs when attempting to properly perform a sensorimotor task. Significance: ERP and ERD/ERS measurements during kinesthetic assessment provide new insights on identification of the origin of sensorimotor slowing in older adults. (C) 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Univ Sao Paulo, Neurosci Program, EP USP, PTC, BR-05508900 Sao Paulo, SP, BrazilUniv Sao Paulo, Biomed Engn Lab, EP USP, PTC, Ave Prof Luciano Gualberto,Travessa 3,158, BR-05508900 Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Div Neurol, Sao Paulo, BrazilUniv Cruzeiro Sul, Inst Phys Act & Sport Sci, Sao Paulo, BrazilUniv Cruzeiro Sul, Grad Program Human Movement Sci, Sao Paulo, BrazilSao Paulo State Univ, Inst Biosci, Rio Claro, BrazilUniv Fed Sao Paulo, Div Neurol, Sao Paulo, BrazilFAPESP: 2011/17193-0CNPq: 303313/2011-0CNPq: 2009/09286-9FAPESP: 2013/14667-7Web of Scienc

The effects of total and REM sleep deprivation on laser-evoked potential threshold and pain perception

We investigated the effects of total and rapid eye movement (REM) sleep deprivation on the thermal nociceptive threshold and pain perception using the objective laser-evoked potential (LEP) and the subjective visual analogue scale (VAS). Twenty-eight male adult volunteers were assigned into Control (CTRL), Total (T-SD), and REM (REM-SD) Sleep Deprivation groups. the T-SD and REM-SD volunteers were totally or selectively deprived of sleep for 2 and 4 consecutive nights, respectively. Pain parameters were measured daily during the experimental period. Volunteers were stimulated on the back of the hand by blocks of 50 diode laser pulses. Intensities increased between successive blocks, ranging from nonnoxious to noxious levels, and the LEP threshold was identified based on the evoked-response onset. Both the LEP threshold and VAS ratings were significantly increased after the second night of T-SD. No significant variations were observed in the REM-SD group, suggesting a predominant role for slow wave sleep rather than selective REM-SD in pain perception. Also, for both sleep-deprived groups, the mean values of the LEP threshold and VAS ratings showed a gradual increase that was proportional to the SD deprivation time, followed by a decrease after 1 night of sleep restoration. These findings demonstrate a hyperalgesic modification to pain perception (as reflected by the augmented VAS) and a concomitant increase in the LEP threshold following T-SD, an apparently contradictory effect that can be explained by differences in the ways that attention affects these pain measurements. (C) 2011 Published by Elsevier B.V. on behalf of International Association for the Study of Pain.AFIPFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Universidade Federal de São Paulo, Dept Psicobiol, São Paulo, SP, BrazilUniversidade Federal de São Paulo, Dept Neurofisiol Clin, São Paulo, SP, BrazilUniversidade Federal de São Paulo, Dept Psicobiol, São Paulo, SP, BrazilUniversidade Federal de São Paulo, Dept Neurofisiol Clin, São Paulo, SP, BrazilFAPESP: 98/14303-3FAPESP: 06/03444-3FAPESP: 06/58276-8Web of Scienc

Urethral sensory threshold and urethro-anal reflex latency in continent women

Aims the sensory evaluation of the lower urinary tract is summarized in the bladder proprioceptive sensitivity during cystometry. Experimental studies suggest that abnormalities of the urethral innervation and micturition reflex can be related to the presence of continence disturbances. This study aimed to measure the urethral sensory threshold and the urethro-anal reflex latency in healthy volunteers, establishing reading criteria, comparing the results and technique used with the literature and verifying the effect of physiological factors.Materials and methods Thirty healthy female volunteers were studied. They had an absence of genital or urinary complaints and had undergone no previous pelvic or vaginal procedures. the measurement of the urethral sensory threshold and urethro-anal reflex latency were performed as described.Results the determination of the urethral sensory threshold and urethro-anal reflex latency were obtained in 96.6% of the volunteers. the electrophysiological parameters did not correlate with age, parity or number of vaginal deliveries. There was a positive association of the urethral sensory threshold with height. Technical aspects were considered and compared with those in the literature as well as the advantages and limitations of the method.Conclusions the measurement of the urethral sensory threshold and urethro-anal reflex latency presented consistent recordings. the urethral sensory threshold should be analyzed carefully in individuals with height above the population average. Subsequent observations are necessary to clarify their function in patients with continence disturbances and to measure the urethral function, but these values can be used as normal parameters for comparison.Universidade Federal de São Paulo, Dept Surg, Div Urol, BR-01308000 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Neurol & Neurosurg, Div Clin Neurol, BR-04023062 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Surg, Div Urol, BR-01308000 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Neurol & Neurosurg, Div Clin Neurol, BR-04023062 São Paulo, BrazilWeb of Scienc

Pudendal somatosensory evoked potentials in normal women

OBJECTIVE: Somatosensory evoked potential (SSEP) is an electrophysiological test used to evaluate sensory innervations in peripheral and central neuropathies. Pudendal SSEP has been studied in dysfunctions related to the lower urinary tract and pelvic floor. Although some authors have already described technical details pertaining to the method, the standardization and the influence of physiological variables in normative values have not yet been established, especially for women. The aim of the study was to describe normal values of the pudendal SSEP and to compare technical details with those described by other authors. MATERIALS AND METHODS: The clitoral sensory threshold and pudendal SSEP latency was accomplished in 38 normal volunteers. The results obtained from stimulation performed on each side of the clitoris were compared to ages, body mass index (BMI) and number of pregnancies. RESULTS: The values of clitoral sensory threshold and P1 latency with clitoral left stimulation were respectively, 3.64 &plusmn; 1.01 mA and 37.68 &plusmn; 2.60 ms. Results obtained with clitoral right stimulation were 3.84 &plusmn; 1.53 mA and 37.42 &plusmn; 3.12 ms, respectively. There were no correlations between clitoral sensory threshold and P1 latency with age, BMI or height of the volunteers. A significant difference was found in P1 latency between nulliparous women and volunteers who had been previously submitted to cesarean section. CONCLUSIONS: The SSEP latency represents an accessible and reproducible method to investigate the afferent pathways from the genitourinary tract. These results could be used as normative values in studies involving genitourinary neuropathies in order to better clarify voiding and sexual dysfunctions in females

The Role of Membranous Urethral Afferent Autonomic Innervation in the Continence Mechanism After Nerve Sparing Radical Prostatectomy: A Clinical and Prospective Study

Purpose: We evaluated the somatic and autonomic innervation of the pelvic floor and rhabdosphincter before and after nerve sparing radical retropubic prostatectomy using neurophysiological tests and correlated findings with clinical parameters and urinary continence. Materials and Methods: From February 2003 to October 2005, 46 patients with prostate cancer were enrolled in a controlled, prospective study. Patients were evaluated before and 6 months after nerve sparing radical retropubic prostatectomy using the UCLA-PCI urinary function domain and neurophysiological tests, including somatosensory evoked potential, and the pudendo-urethral, pudendo-anal and urethro-anal reflexes. Clinical parameters and urinary continence were correlated with afferent and efferent innervation of the membranous urethra and pelvic floor. We used strict criteria to define urinary continence as complete dryness with no leakage at all, not requiring any pads or diapers and with a UCLA-PCI score of 500. Patients with a sporadic drop of leakage, requiring up to 1 pad daily, were defined as having occasional urinary leakage. Results: Two patients were excluded from study due to urethral stricture postoperatively. We evaluated 44 patients within 6 months after surgery. The pudendo-anal and pudendo-urethral reflexes were unchanged postoperatively (p = 0.93 and 0.09, respectively), demonstrating that afferent and efferent pudendal innervation to this pelvic region was not affected by the surgery. Autonomic afferent denervation of the membranous urethral mucosa was found in 34 patients (77.3%), as demonstrated by a postoperative increase in the urethro-anal reflex sensory threshold and urethro-anal reflex latency (p<0.001 and 0.0007, respectively). Six of the 44 patients used pads. One patient with more severe leakage required 3 pads daily and 23 showed urinary leakage, including 5 who needed 1 pad per day and 18 who did not wear pads. Afferent autonomic denervation at the membranous urethral mucosa was found in 91.7% of patients with urinary leakage. Of 10 patients with preserved urethro-anal reflex latency 80% were continent. Conclusions: Sensory and motor pudendal innervation to this specific pelvic region did not change after nerve sparing radical retropubic prostatectomy. Significant autonomic afferent denervation of the membranous urethral mucosa was present in most patients postoperatively. Impaired membranous urethral sensitivity seemed to be associated with urinary incontinence, particularly in patients with occasional urinary leakage. Damage to the afferent autonomic innervation may have a role in the continence mechanism after nerve sparing radical retropubic prostatectomy