Comparison between sensory testing modalities for the evaluation of afferent nerve functioning in the genital area

The role of the neurometer CPT/C in sacral neuromodulation

Objective

The aim of the current research project was to study the role of the Neurometer^® as a tool to predict responders to sacral neuromodulation therapy (SNM).

Material and methods

This was a prospective, open study in male and female patients, aged 18 and over with voiding dysfunction [non-obstructive retention and/or frequency/ urgency syndrome]. The first group underwent a screening test to evaluate percutaneous nerve functions (PNE) and to determine whether they are candidates for SNM with the InterStim^®. Prior to PNE testing, all patients were evaluated with the pain tolerance test (PTT) using the electro-diagnostic Neurometer^® CPT/C device. An InterStim^® implant was placed in patients who were responders to PNE testing underwent. On the other hand, non-responders underwent a staged implant placement. The second group consisted of patients who already had InterStim^® implanted for voiding dysfunction. During the routine office follow-up, the patients implanted with Interstim^® underwent a PTT using the Neurometer^® CPT/C device. All the testing using the Neurometer CPT/C was performed on the day of the PNE for the first group, and the day of the routine follow-up visit for the second group. All of the results for the Neurometer^® testing were kept blinded from the PNE results, and those of the outcome of the follow-up visit. The study received approval by the Research Ethics Board of the University Health Network (No. 14-8196).

Results

We recruited a total of 123 patients. The results presented here include 110 patients who completed the study, 48 of whom were in the first group, and 62 in the second group. The statistical analysis used was as follows: Group 1: Simple linear regression analysis and the linear discriminate analysis were preformed. It was found that for patients without the InterStim^® implant with a combined CPT/CPD of 800 and above, the Neurometer^® could predict the test screening results with an accuracy of 71%. Group 2: Same analysis and tests were conducted for patients with the InterStim^® implant, and the results showed that if the patient had a combined CPT/CPD of 600 and above, the Neurometer^® could predict the patients satisfaction or dissatisfaction with an accuracy of 72%.

Conclusion

Neurometer^® may play a role in predicting test trial positive responders and patient satisfaction after the placement of InterStim^® implant.

The assessment of sensory detection thresholds on the perineum and breast compared with control body sites

INTRODUCTION

Few studies explored multiple sensory detection thresholds on the perineum and breast, but these normative data may provide standards for clinical conditions such as aging, genital and breast surgeries, pathological conditions affecting the genitals, and sexual function.

AIMS

The aim of this study was to provide normative data on sensory detection thresholds of three sensory modalities on the perineum and breast.

METHODS

Thirty healthy women aged between 18 and 35 years were assessed on the perineum (clitoris, labia minora, vaginal, and anal margin), breast (lateral, areola, nipple), and control body locations (neck, forearm, abdomen) for three sensory modalities (light touch, pressure, vibration).

MAIN OUTCOME MEASURES

Average detection thresholds for each body location and sensory modality and statistical comparisons between the primary genital, secondary sexual, and neutral zones were the main outcome measures.

RESULTS

Average detection thresholds for light touch suggest that the neck, forearm, and vaginal margin are most sensitive, and areola least sensitive. No statistical difference is found between the primary and secondary sexual zones, but the secondary sexual zone is significantly more sensitive than the neutral zone. Average detection thresholds for pressure suggest that the clitoris and nipple are most sensitive, and the lateral breast and abdomen least sensitive. No statistical difference is found between the primary and secondary sexual zone, but they are both significantly more sensitive than the neutral zone. Average detection thresholds for vibration suggest that the clitoris and nipple are most sensitive. The secondary sexual zone is significantly more sensitive than the primary and neutral zone, but the latter two show no difference.

CONCLUSION

The current normative data from sensory detection threshold are discussed in terms of providing standard values for research and clinical conditions. Additional analysis from breast volume, body mass index, hormonal contraception, menstrual cycle, and sexual orientation do not seem to influence the results. Sexual abstinence and body piercing may have some impact.

Reproducibility of electrical sensory testing in lower urinary tract at weekly intervals in healthy volunteers and women with non-neurogenic detrusor overactivity

OBJECTIVE

To evaluate the reproducibility of a standardized technique of current perception threshold measurements with square wave and sine wave current, with monopolar and bipolar electrodes in a cohort of patients with overactive bladder (OAB) and healthy volunteers.

METHODS

We enrolled 6 female nulliparous healthy volunteers and 11 female patients with OAB. Current perception threshold measurements of the bladder were performed using several techniques. The same sequence was used for all 3 measurements performed at weekly intervals to assess the reproducibility. An intraclass correlation coefficient >0.75 was considered as very good reproducibility.

RESULTS

All the different stimulation forms were well tolerated by all participants and all experienced stimulation at 2.5-Hz and 95-Hz square wave current. The results with sine wave current showed less uniform results. The intraclass correlation showed the greatest reproducibility with bipolar stimulation at a current of 95 Hz. Sine wave current at 5 Hz and 250 Hz showed low reproducibility. Bipolar stimulation had significantly lower thresholds than monopolar stimulation (P < .0001). No significant differences were found between the healthy subjects and the patients with OAB for the 4 settings.

CONCLUSION

In the healthy volunteers and patients with OAB, the determination of the current perception threshold in the bladder using a standardized method is feasible and well tolerated, with both bipolar and monopolar stimulation. In our study, square wave current showed strong reproducibility at weekly intervals at 2.5 Hz and 95 Hz. However, sinusoid current gave weak reproducibility.

Measuring Urinary Sensation with Current Perception Threshold: A Comparison between Method of Limits and Method of Levels

Purpose. To determine the association between the two methods of obtaining current perception thresholds (CPTs) in the lower urinary tract (LUT). Materials and Methods. Twenty-one women undergoing pelvic surgery underwent CPT determinations of the urethra. CPTs were measured at 2,000, 250, and 5 Hz (corresponding to A-β, A-δ, and C fibers, resp.) both pre- and postoperatively. Threshold values were obtained in all patients by using the method of limits and the method of levels. Results. CPT values obtained by using the method of levels and the methods of limits were highly correlated at all frequencies before and after surgery (ρ = 0.93–0.99, P < 0.0001). The mean threshold values obtained by the method of levels were significantly lower at all frequencies compared with those obtained by the method of limits. Conclusions. Our findings suggest that the method of levels is more sensitive for the detection of CPTs compared to the method of limits.

Antimuscarinic effects on current perception threshold: a prospective placebo control study

AIMS

To evaluate the effect of Tolterodine on urethral and bladder afferent nerves in women with detrusor overactivity (DO) in comparison to placebo, by studying the changes in the current perception threshold (CPT).

METHODS

Women with overactive bladder symptoms and idiopathic DO were recruited and randomized in a double-blind manner between placebo and tolterodine extended release. All women underwent CPT testing of the bladder and urethra using a Neurometer constant current stimulator. CPT values were determined at three frequencies, including 2,000 Hz (corresponding to Aβ-fibers), 250 Hz (corresponding to Aδ-fibers), and 5 Hz (corresponding to C fibers) before and 7 days on treatment. CPT values before and on treatment were compared using a Wilcoxon Signed Rank test.

RESULTS

Twenty women (mean age 46 years) were studied. There was no statistical difference between the two groups in terms of age, ethnicity, severity of symptoms and pre-treatment CPT values. Only in the tolterodine group there was a significantly increased CPT value at 5 and 250 Hz upon both urethral and bladder stimulation after 1 week of treatment. When compared with placebo, women taking tolterodine had significantly increased Bladder CPT values at 5 Hz (P-value <0.05). The electrical stimulation with 5 Hz was described as urgency.

CONCLUSIONS

This is a randomized placebo control study evaluating the effect of antimuscarinics on sensory nerve function in women with DO. Our results support the animal studies that antimuscarinics have an effect on sensory function.