Electrical Sensory Thresholds Research Articles

Conditioned pain modulation as a predictor of central sensitization in primary knee osteoarthritis patients

Aim of the workCentral sensitization (CS) is a nervous system disorder associated with chronic pain. This study aimed to quantify pain and evaluate conditioned pain modulation (CPM) and CS in knee osteoarthritis (KOA) patients with chronic pain. Patients and methodsThe study included 50 patients with primary KOA having chronic pain and 50 matched controls. The following assessment tools were used: visual analog scale (VAS)-pain, Western Ontario and McMaster Universities (WOMAC), pain DETECT questionnaire (PD-Q), and central sensitization inventory (CSI). Also, pressure pain threshold (PPT), electrical sensory threshold (EST), and electrical pain threshold (EPT) were assessed at both knees and remote sites. CPM was assessed using the submaximal effort tourniquet method, and the CPM ratio was measured (pre-to-post PPT). ResultsThe patients' mean age was 49.6 ± 9.7 years, 32 females and 18 males (F:M 1.2:1), and disease duration of 7.4 ± 3.6 years. Patients had a significantly higher CPM ratio (1.1 ± 0.21), PD-Q score (20.1 ± 9.1), CSI score (48.8 ± 21.4) compared to the control (0.9 ± 0.07; 8.3 ± 3.9 and 25.5 ± 9.4 respectively; p < 0.0001) and had a lower EPT and PPT in both knees and remote sites (p < 0.0001). CPM was significantly correlated with VAS-pain, WOMAC, CSI, PD-Q and inversely with EPT and PPT at both knees and remote sites and with EST at the right knee (p < 0.0001 each). CPM, PD-Q, and left knee EPT were significant predictors of CS tested with CSI (p < 0.0001, p < 0.0001, and p = 0.004, respectively). ConclusionThere is evidence of CS in KOA patients having chronic pain, and CPM and PD-Q can predict CS.

Applicability and tolerability of electrical stimulation applied to the upper and lower leg skin surface for cueing applications in Parkinson's disease

Due to possible sensory impairments in people with Parkinson's disease, several methodological aspects of electrical stimulation as a potential cueing method remain to be explored. This study aimed to investigate the applicability and tolerability of sensory and motor electrical stimulation in 10 people with Parkinson's disease. The study focused on assessing the electrical stimulation voltages and visual analogue scale discomfort scores at the electrical sensory, motor, discomfort, and pain thresholds. Results show that sensory electrical stimulation at the tibialis anterior, soleus, hamstrings, and quadriceps stimulation sites was applicable and tolerable for 6/10, 10/10, 9/10, and 10/10 participants, respectively. Furthermore, motor electrical stimulation at the tibialis anterior, soleus, hamstrings, and quadriceps stimulation sites were applicable and tolerable for 7/10, 7/10, 7/10, and 8/10 participants, respectively. Interestingly, the thresholds for the lower leg were higher than those of the upper leg. The data presented in this paper indicate that sensory and motor electrical stimulation is applicable and tolerable for cueing applications in people with Parkinson's disease. Sensory electrical stimulation was applicable and tolerable at the soleus and quadriceps sites. Motor electrical stimulation was not tolerable for two participants at any of the proposed stimulation sites. Therefore, future studies investigating motor electrical stimulation cueing, should apply it with caution in people with Parkinson's disease.

Trigeminal nociceptive function and oral somatosensory functional and structural assessment in patients with diabetic peripheral neuropathy

This case-control study primarily compared the trigeminal nociceptive function, the intraoral somatosensory profile and possible structural nerve changes between diabetic peripheral neuropathy (DPN, n = 12) patients and healthy participants (n = 12). The nociceptive blink reflex (nBR) was recorded applying an electrical stimulation over the entry zone of the right supraorbital (V1R), infraorbital (V2R) and mental (V3R) and left infraorbital (V2L) nerves. The outcomes were: individual electrical sensory (I0) and pain thresholds (IP); root mean square (RMS), area-under-the-curve (AUC) and onset latencies of R2 component of the nBR. Furthermore, a standardized full battery of quantitative sensory testing (QST) and intraepidermal nerve fibre density (IENFD) or nerve fibre length density (NFLD) assessment were performed, respectively, on the distal leg and oral mucosa. As expected, all patients had altered somatosensory sensitivity and lower IENFD in the lower limb. DPN patients presented higher I0, IP, RMS and AUC values (p < 0.050), lower warm detection thresholds (WDT) (p = 0.004), higher occurrence of paradoxical heat sensation (PHS) (p = 0.040), and a lower intraoral NFLD (p = 0.048) than the healthy participants. In addition, the presence of any abnormal intraoral somatosensory finding was more frequent in the DPN patients when compared to the reference group (p = 0.013). Early signs of trigeminal nociceptive facilitation, intraoral somatosensory abnormalities and loss of intraoral neuronal tissue can be detected in DPN patients.

Reliability of the nociceptive blink reflex evoked by electrical stimulation of the trigeminal nerve in humans.

The nociceptive blink reflex (nBR) can be useful to investigate trigeminal nociceptive function. The aim of this study was to estimate the reliability of the nBR evoked by electrical stimulation of the three branches of the trigeminal nerve under the following conditions: over time (test-retest and intrarater reliability) and by two examiners (interrater reliability). Twenty-one healthy participants were evaluated in two sessions (24h apart). The nBR was elicited by a so-called "nociceptive-specific" electrode placed over the entry zone of the right supraorbital (V1R), infraorbital (V2R), mental (V3R), and left infraorbital (V2L) nerve. The outcomes were individual electrical sensory (I 0) and pain thresholds (I P); root mean square (RMS), area-under-the-curve (AUC), and onset latencies of R2 responses (determined twice after a recalibration session); and stimulus-evoked pain on a 0-10 numerical rating scale. Intraclass correlation coefficients (ICCs) and Kappa statistics were computed (α=5%). ICCs were fair to excellent in 82% of the psychophysical measures (fair 21%, good 31%, excellent 30%) and in 86% of V1R, V2R, and V2L nBR parameters, whereas 52% of V3R showed poor reliability. ICCs for intrarater reliability were fair to good in 70% of measurements (fair 20%, good 50%) and in 75% of interrater measurements after the recalibration (fair 55%, good 20%). All kappa values showed at least fair agreement and the majority of the nBR measures (93%) presented moderate to excellent reliability. The nBR and its associated psychophysical measures can be considered a sufficiently reliable test. The nBR can be recommended as an electrophysiological technique to assess trigeminal nociceptive function.

Is the Nociceptive Blink Reflex Associated with Psychological Factors in Healthy Participants?

To evaluate the possible association between the nociceptive blink reflex (nBR) and various pain-related psychological measures: the Anxiety Sensitivity Index-3 (ASI-3), the Fear of Pain Questionnaire III (FPQ-III), the Pain Vigilance and Awareness Questionnaire (PVAQ), the Somatosensory Amplification Scale (SSAS), the Pain Catastrophizing Scale (PCS), and the Situational Pain Catastrophizing Scale (S-PCS). The nBR was evaluated in 21 healthy participants. It was elicited by a nociceptive-specific electrode placed over the entry zone of the right supraorbital nerve, infraorbital nerve, and mental nerve, as well as the left infraorbital nerve. The outcomes were (1) nBR measurements: (a) individual electrical sensory threshold (I0) and pain threshold (IP); (b) root mean square (RMS), area under the curve (AUC), and onset latencies of R2 responses; (c) stimulus-evoked pain on a 0 to 10 numeric rating scale (NRS); and (2) the ASI-3, the FPQ-III, the PVAQ, the SSAS, the PCS, and the S-PCS. Pearson correlation coefficient was used to evaluate the association between the means of nBR measurements from all sites and the questionnaires The significance level was set up after a Bonferroni correction (adjusted α = .8%). There was no correlation for any pair of variables at the adjusted significance level (P > .008). There was only a single significant correlation at the standard significance level (P < .05), where the pain intensity (NRS) at 50% of IP presented a positive and small to moderate correlation with the PCS (r = 0.43, P = .04). It appears that the nBR and its associated psychophysical measures are not associated with psychological factors in healthy participants.

Association of neuropathic pain with ultrasonographic measurements of femoral cartilage thickness and clinical parameters in patients with knee osteoarthritis.

[Purpose] The aim of this study was to investigate whether neuropathic pain is associated with femoral condylar cartilage thickness, electrical pain threshold, and clinical parameters in patients with knee osteoarthritis. [Subjects and Methods] Sixty patients over the age of 40 diagnosed with knee osteoarthritis were enrolled. The PainDETECT questionnaire, Western Ontario and McMaster Universities Osteoarthritis Index, Hospital Anxiety and Depression Scale, and Short Form-36 questionnaire were completed for all patients. Electrical sensory threshold and electrical pain threshold measurements were obtained. Femoral condylar cartilage thickness was determined by means of ultrasound. [Results] PainDETECT scores of 13 or greater were observed in 28 (46.7%) patients, indicating the presence of neuropathic pain. These patients were found to have greater average pain severity, Western Ontario and McMaster Universities Osteoarthritis Index, and depression and anxiety scores and lower Short Form-36 scores than patients without neuropathic pain. Patients with neuropathic pain showed lower knee electrical sensory threshold and pain threshold values on average than patients without neuropathic pain. Femoral condylar cartilage thickness was not different between the two groups. [Conclusion] Neuropathic pain is associated with increased pain severity and decreased functional capacity and adversely affects quality of life and mood in patients with knee osteoarthritis.

Differences in two-point discrimination and sensory threshold in the blind between braille and text reading: a pilot study.

[Purpose] This study investigated two-point discrimination (TPD) and the electrical sensory threshold of the blind to define the effect of using Braille on the tactile and electrical senses. [Subjects and Methods] Twenty-eight blind participants were divided equally into a text-reading and a Braille-reading group. We measured tactile sensory and electrical thresholds using the TPD method and a transcutaneous electrical nerve stimulator. [Results] The left palm TPD values were significantly different between the groups. The values of the electrical sensory threshold in the left hand, the electrical pain threshold in the left hand, and the electrical pain threshold in the right hand were significantly lower in the Braille group than in the text group. [Conclusion] These findings make it difficult to explain the difference in tactility between groups, excluding both palms. However, our data show that using Braille can enhance development of the sensory median nerve in the blind, particularly in terms of the electrical sensory and pain thresholds.

Effects of thermal agents on electrical sensory threshold and current tolerance when applied prior to neuromuscular electrical stimulation

This study aimed to investigate the effects of thermal agents on electrical sensory threshold and current tolerance when applied prior to neuromuscular electrical stimulation. In this single-blind and cross-over trial, electrical sensory threshold and current tolerance of 24 healthy volunteers were evaluated by using biphasic symmetrical pulses (240 μsec, 50 pps), before and after thermal agent (cold pack, hot pack and ultrasound) applications. Electrical sensory threshold increased after cold-pack, and current tolerance reduced after hot-pack applications (p< 0.05). Inter-agent comparisons of pre and post-application differences of the investigated parameters revealed that the most obvious effects were caused by application of hot pack. Hot pack application prior to neuromuscular electrical stimulation (NMES) may reduce current tolerance and limit to reach the desired current intensity for strengthening the electrically induced contractions. Results are considered to be valuable for physiotherapists, who apply thermal agents and NMES consecutively, in their treatment programs.

Modulation of esophageal afferent pathways by 5‐HT3 receptor inhibition

The study aims were to investigate whether neural pathways involving 5-HT3 receptors mediate: (i) distension-induced upper esophageal sphincter (UES) relaxation reflex, (ii) esophageal sensitivity to acid and electrical stimuli, and (iii) viserosomatic sensitization following acid exposure. In Study I, in a double-blind crossover trial (n = 9) esophageal sensory and pain thresholds to electrical stimulation were measured in the esophagus, midsternum, and the foot, before subjects were randomized to receive either Ondansetron (8 mg i.v.) or NaCl (0.9% w/v). HCl (0.15 mol L(-1)) was then infused into distal esophagus and electrical thresholds were reassessed. Following electrical sensory threshold testing, subjects received a second esophageal infusion of HCl to evaluate esophageal sensitivity to acid. In Study II (N = 10), frequencies of distension-induced UES relaxation responses were scored before and after treatment with Ondansetron and NaCl in a double-blind crossover trial. In Study I, ondansetron had no effect on esophageal sensitivity to HCl or acid-induced sensitization. However, blockade of 5-HT3 receptors did reduce midsternum somatic pain thresholds. Sixty minutes after esophageal acid exposure, pain thresholds were significantly lower in the ondansetron arm (mean Δ-1.36 ± 0.4 mA) when compared with NaCl (mean Δ-0.14 ± 0.58 mA) (P < 0.05). In Study II, 5-HT3 receptor blockade had no significant effect on UES relaxation reflex. This study does not support the hypothesis that in health, 5-HT3 receptors play a significant role in esophago-UES distention-induced relaxation reflex and esophageal sensitivity to acid or electrical stimulation. It does provide new evidence for involvement of 5-HT3 receptors in viscerosomatic sensitization.

Acid Sensitization of Esophageal Mucosal Afferents

Sensitization of esophageal chemoreceptors, either directly by intermittent acid exposure or indirectly through esophagitis-associated inflammatory mediators, is likely to be the mechanism underlying the perception of heartburn. To compare basal esophageal sensitivity with electrical stimulation and acid, and to compare the degree of acid-induced sensitization in controls and in patient groups across the entire spectrum of gastroesophageal reflux disease: erosive oesophagitis (EO), nonerosive reflux disease (NERD), and functional heartburn (FH). Esophageal sensory and pain thresholds to electrical stimulation were measured before, 30, and 60 minutes after an intraesophageal infusion of saline or HCl. Patients received a 30-minute infusion of 0.15 M HCl and controls were randomized to receive either HCl (n = 11) or saline (n = 10). After electrical sensory threshold testing, participants received another 30-minute infusion of HCl to determine whether sensitivity to acid is increased by prior acid exposure All patient groups had higher basal sensory thresholds than healthy controls (controls, 13 ± 1.4 mA; FH, 20 ± 5.1 mA; NERD, 21 ± 5.1 mA; EO, 23 ± 5.4 mA; P < 0.05). Acute esophageal acid exposure reduced sensory thresholds to electrical stimulation in FH and NERD patients (P < 0.05). The level of acid sensitivity during the first HCl infusion was comparable between all patient groups and controls. The secondary infusion caused increased discomfort in all participants (P < 0.01). This acid-induced sensitization to HCl was significantly elevated in the patient groups ( P < 0.05). (1) Esophageal acid infusion sensitizes it to subsequent electrical and chemical stimulation. (2) The acid-related sensitization is greater in gastroesophageal reflux disease than in controls and may influence in part symptom perception in this population. (3) Acid-related sensitization within the gastroesophageal reflux disease population is not dependant on mucosal inflammation.

Analysis of the sensory threshold between paretic and nonparetic sides for healthy rehabilitation in hemiplegic patients after stroke

The purpose of this study was to investigate the differences in the sensory threshold between the paretic and nonparetic sides of hemiplegic patients. 28 patients who were hemiplegic post-stroke (14 men and 14 women) participated in the electrical sensory and pain thresholds study; 22 patients who were hemiplegic post-stroke (13 men, 9 women) participated in a study measureing the sensory threshold with light touch. Electrical sensory and pain thresholds were measured in the forearm via transcutaneous electrical nerve stimulation. The light-touch threshold was measured in the forearm using monofilaments. The light-touch, electrical sensory, and pain thresholds for the paretic side were significantly higher than for the nonparetic side in our population, respectively. In both the nonparetic and paretic sides, the male group generally showed higher thresholds for pain and sensation than did the female group. These results suggest that the different evaluations of sensory thresholds performed in this study for healthy rehabilitation will be a valuable clinical tool in hemiplegic patients after stroke.

An initial exploration of the perceptual threshold test using electrical stimulation to measure arm sensation following stroke

Objective: To explore the viability of the perceptual threshold test using electrical stimulation to measure light touch sensation in the hands of stroke survivors. Design: Descriptive study. Setting: University research laboratory. Subjects: Twenty-nine adult community-dwelling chronic stroke survivors. Main measure(s): Perceptual threshold test using electrical stimulation, stroke rehabilitation assessment of movement, Nottingham sensory assessment for stereognosis, action research arm test, Fugl-Meyer assessment of sensation and motor activity log 14. Results: Perceptual threshold test using electrical stimulation mean threshold values were 1.23 (0.6) milliamperes (range 0.5–3.5) for the uninvolved side and 1.68 (0.91) milliamperes (range 0.5–4.5) for the involved side. The perceptual threshold test using electrical stimulation demonstrated excellent intra-rater reliability (intraclass correlation coefficient = 0.896 – uninvolved; 0.829 – involved). There was a statistically significant difference between the perceptual threshold test using electrical stimulation mean threshold values for the uninvolved and involved arms (P = 0.003), but this significance did not hold for subjects who had normal sensation as measured by the Fugl-Meyer assessment of sensation (P = 0.083). Low to nonexistent correlations were found between the perceptual threshold test using electrical stimulation and other measures of sensation, arm movement, activity and participation. Conclusions: The perceptual threshold test using electrical stimulation is a reliable and clinically feasible test with the potential to identify sensory capacity in stroke survivors with substantial sensory loss. Electrical sensory thresholds do not reflect overall sensory function or motor capabilities in stroke survivors.

On the threshold - evaluation of variability in effects of acupuncture in a gender perspective

Variable results of pain alleviation in response to acupuncture have been reported, complicating its interpretation. Sources of variability are probably multi-factorial, including the contribution of gender related effects. Gender related variation in perceived pain has been discussed frequently, but documented effects of acupuncture referring to gender are sparse. Furthermore, factors such as operationalisation of the outcome variable and the statistical method for evaluation could also be sources of variability. When pain is regarded as subjective, the produced data should be treated as ordinal. The rank-based method by Svensson, taking the non-metric qualities of the ordinal data into account as well as the variability at the group and the individual level, is therefore an alternative. The present commentary aims to (1) evaluate changes in electrical sensory thresholds and electrical pain thresholds after low frequency electro-acupuncture separately in healthy women and men; (2) introduce and exemplify the method by Svensson in a user-friendly approach. To analyze the systematic patterns of change in thresholds, indicating evidence of treatment on a group level, the relative position (RP) and relative concentration (RC), were measured. The variation related to the individual, the relative rank variation (RV) was also measured. The results were divergent between women (n = 23) and men (n = 22), i.e. unchanged sensory threshold after acupuncture at the group level in women while changed in men. The assessed pain threshold after acupuncture on the other hand was changed towards higher levels in women and unchanged in men. The individual variation was apparent in both women and men but larger in women. For statistical analysis of the variability for both group and individual related effects, the rank-based method by Svensson could be used. The present study indicates that evaluation of sensory and pain threshold response should be analysed separately in women and men.

Electrical pain thresholds of face and finger in patients with chronic masticatory muscle pain

To compare electrical sensory threshold (EST) and electrical pain threshold (EPT) of bilateral masseters, temporal muscles and finger region of chronic masticatory muscle pain (MMP) patients and the controls, and to analyze the mechanism of pain threshold change. Twelve patients with MMP and 12 matched controls participated in this study. EST and EPT of bilateral masseters, bilateral temporal muscles, and left middle finger were recorded and compared within group and between groups. Compared to the controls, the EPTs of patients significantly decreased [left masseter (5.9 +/- 1.1) mA,right masseter (5.7 +/- 1.0) mA, left temporal muscle (5.3 +/- 1.4) mA, right temporal muscle (5.5 +/- 1.7) mA,finger (5.2 +/- 1.0) mA] (P < 0.001). There was no significant difference in EST between patients and the controls. No relationship was found among VAS, ESP, and EPT. Decreased pain thresholds of masseters, temporal muscles and fingers in MMP indicated that peripheral sensitization was induced in MMP patients. Decreased pain threshold in patients meant that MMP might influence the central modulation of nervous system.

Lateral ligament division during rectopexy causes constipation but prevents recurrence: Results of a prospective randomized study

Denervation of the rectum during rectopexy has been suggested as a reason for postoperative constipation. Bowel symptoms and anorectal function have been examined in a prospective randomized study of rectopexy with (n = 14) or without (n = 12) division of the lateral ligaments. Incontinence improved in both groups of patients. Division of the lateral ligaments increased the number of patients with constipation (three before operation, ten after operation, P less than 0.01). Mean and canal pressures were higher after operation in all patients. Rectal electrical sensory threshold increased significantly in those in whom the ligaments had been divided (preoperative 27.6 mA versus postoperative 56.7 mA; P less than 0.01) but not in those in whom they were preserved (39.0 versus 34.9 mA; P greater than 0.05). Prolapse recurred in six patients who did not undergo division of the lateral ligaments, but in none of the group in whom the ligaments were divided.

Evaluation of variations in sensory and pain threshold assessments by electrocutaneous stimulation

Assessed sensory and pain thresholds can change consequently to disturbances associated with ongoing pain. Such assessments could be an additional method in the daily clinical evaluation of perceived pain. To study the test–retest variability within-day and between-day of such procedures a newly developed instrument producing electrocutaneous stimulation, PainMatcher (PM), was used to assess the electrical sensory thresholds (EST) and pain thresholds (EPT) in healthy volunteers and in patients with pain. The produced data were considered ordinal and analyzed with rank-invariant statistics with properties of analyzing systematic disagreement, bias, and individual variations.The percentage agreements within ±1PM value for EST were in the two groups of healthy volunteers and patients in pain 94% and 92%, and for EPT assessments 49% and 78%, respectively. The variability in the EST assessments is possibly explained by a slight bias while the individual variations were negligible between the two occasions. The assessed EPT were unbiased in both groups while individual variations were significant among the healthy volunteers but negligible among the patients in pain. The EST was found to be increased in pain patients compared to healthy volunteers, p < 0.03, and the EPT decreased in pain patients compared to healthy volunteers, p < 0.001.The results in this study indicate stable and reliable assessments of EST and EPT except for a possible bias. The threshold assessment procedure followed in this study may be a valuable tool in the clinical evaluation of sensory and pain assessments in pain patients.

Gender differences in electrical pain threshold responses to transcutaneous electrical nerve stimulation (TENS)

Gender differences in pain perception have been frequently discussed, but the documented gender-related pain-alleviating effects of non-pharmacological methods are sparse. In this study we aimed to investigate changes in electrical sensory thresholds and electrical pain thresholds, in response to high frequency transcutaneous electrical nerve stimulation, TENS, for 20 min in healthy women ( n = 29) and men ( n = 29). The thresholds were assessed pre-, during-, and post-TENS. The pattern of change in thresholds was evaluated with a rank-based statistical method regarding the level of systematic change, expressed as relative position (RP) and additional individual changes, expressed as relative rank variance (RV), with its 95% confidence intervals. Equal levels of systematic changes towards increased electrical sensory thresholds were seen in women and men post-TENS (RP, 0.35; 95% CI, 0.07, 0.63, and RP, 0.36; 95% CI, 0.17, 0.53, respectively). At the same point of time, systematic changes towards increased electrical pain thresholds were only seen in women (RP, 0.43; 95% CI, 0.27, 0.60), while they were unchanged in men (RP, −0.01; 95% CI, −0.13, 0.10). Significant additional individual variations were found in the women's responses of assessed electrical sensory and pain thresholds but not in the men's. It is concluded that both women and men responded with a significant increase of the electrical sensory threshold to high frequency TENS, but only women responded with increase of the electrical pain thresholds. The individual variation of the responses was greater in the women than in the men.

DETRUSOR OVERACTIVITY. DOES IT REPRESENT A DIFFERENCE IF PATIENTS FEEL THE INVOLUNTARY CONTRACTIONS?

We evaluated the differences between patients with overactive bladder (OAB) who felt involuntary detrusor contractions during cystometry (detrusor overactivity [DO]) and those who did not feel them. We prospectively studied 45 patients with symptoms of nonneurogenic, nonobstructed overactive bladder and with DO on cystometry. All patients underwent videourodynamics, the ice water test and electrical perception threshold determination. Continence, urodynamic parameters, data from specific sensory evaluation and outcome of drug treatment were examined. Almost half of our patients did feel the contractions of DO and half did not. The groups differed significantly. Those without DO sensation were more frequently incontinent, had more involuntary detrusor contractions and these occurred earlier during bladder filling. They had involuntary start of voiding more frequently, more pathological sensation of bladder filling and lower electrical sensory thresholds. The results of drug treatment were better in the group who felt DO. Contractions of DO are felt by some of the patients and they differ from those patients who do not feel such contractions. It is likely that this finding reflects the existence of different OAB conditions with a different neuropathological cause and a different treatment outcome. Therefore, we suggest that specific tests for the evaluation of sensation in the lower urinary tract should be part of the diagnosis of patients with DO and symptoms of OAB.

Urinary retention after hysterectomy for benign disease: extended diagnostic evaluation and treatment with sacral nerve stimulation

To detect prospectively neurogenic damage in patients with urinary retention responding to sacral nerve stimulation (SNS) after hysterectomy for benign disease. From August 1995 to February 2002, 13 of 15 patients (mean age 43 years, sd 7) with urine retention for a mean (sd, range) of 25 (22, 6-240) months after hysterectomy for benign disease, were prospectively evaluated and treated with SNS. They were assessed using urodynamics at baseline and during the test stimulation. Sensory evoked potentials (SEPs), electrical sensory threshold (EST) measurements of the pudendal nerve, bladder neck and the bladder (2 Hz, 0-300 V), and needle electromyography of the external urethral sphincter (EUS) were undertaken in all patients. De-afferentiation (EST >/= 200 V) was limited to the bladder in four of the 13 patients and extended to the bladder neck in one other, and was matched by no response at the SEP. Relative ESTs of the bladder neck correlated inversely with residual urine (r = - 0.76, P = 0.01, x = 546, fx = 1.22) and bladder capacity (r = - 0.77, P = 0.01, x = 611, fx = 1.26) at diagnosis. Complex repetitive discharges and decelerating bursts of the EUS were seen in these five patients. Unilateral SNS was applied in 10 patients (bilateral in three). A revision was needed in six patients. Uroflowmetry at the last follow-up showed a mean (sd) maximum urinary flow rate of 22 (18) mL/s (not significantly different from during trial stimulation) with residual urine of 50-100 mL in two and 200-400 mL in three patients. Intermittent catheterization was needed in four patients. Urinary retention after hysterectomy for benign disease is associated with de-afferentiation of the bladder wall in some patients and is correlated inversely with the relative EST of the bladder neck. A Fowler syndrome was detected in five patients. For residual urine, about half the patients have a good and a third a partial long-term effect; we now offer SNS as a further treatment option.

Lidocaine Infusion Test Does Not Change Mechanical and Electrical Sensory Threshold in Healthy Volunteers

Lidocaine Infusion Test Does Not Change Mechanical and Electrical Sensory Threshold in Healthy Volunteers