Sensory function assessment of the human male lower urinary tract using current perception thresholds

Lower urinary tract electrical sensory assessment: A systematic review and meta-analysis

Objectives

To summarize the current literature on lower urinary tract electrical sensory assessment (LUTESA), with regard to current perception thresholds (CPTs) and sensory evoked potentials (SEPs), and to discuss the applied methods in terms of technical aspects, confounding factors, and potential for lower urinary tract (LUT) diagnostics.

Methods

The review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) statement. Medline (PubMed), Embase and Scopus were searched on 13 October 2020. Meta‐analyses were performed and methodological qualities of the included studies were defined by assessing risk of bias (RoB) as well as confounding.

Results

After screening 9925 articles, 80 studies (five randomized controlled trials [RCTs] and 75 non‐RCTs) were included, comprising a total of 3732 patients and 692 healthy subjects (HS). Of these studies, 61 investigated CPTs exclusively and 19 reported on SEPs, with or without corresponding CPTs. The recording of LUTCPTs and SEPs was shown to represent a safe and reliable assessment of LUT afferent nerve function in HS and patients. LUTESA demonstrated significant differences in LUT sensitivity between HS and neurological patients, as well as after interventions such as pelvic surgery or drug treatments. Pooled analyses showed that several stimulation variables (e.g. stimulation frequency, location) as well as patient characteristics might affect the main outcome measures of LUTESA (CPTs, SEP latencies, peak‐to‐peak amplitudes, responder rate). RoB and confounding was high in most studies.

Conclusions

Preliminary data show that CPT and SEP recordings are valuable tools to more objectively assess LUT afferent nerve function. LUTESA complements already established diagnostics such as urodynamics, allowing a more comprehensive patient evaluation. The high RoB and confounding rate was related to inconsistency and inaccuracy in reporting rather than the technique itself. LUTESA standardization and well‐designed RCTs are crucial to implement LUTESA as a clinical assessment tool.

Trigonal-sparing versus trigonal-involved Botox injection for treatment of idiopathic overactive bladder: A randomized clinical trial

OBJECTIVE

To evaluate safety and efficacy of trigone-involved Botox injections in comparison with trigone-sparing injections in refractory idiopathic overactive bladder (OAB).

MATERIALS AND METHODS

One hundred and three patients randomly received a 100-IU intradetrusal injection of Botox either sparing the trigone (52 patients) or involving the trigone (51 patients). Patients were prospectively evaluated at 1, 3, and 6 months. Efficacy was evaluated by 3-day voiding diaries, OAB symptom score (OABSS), and pressure flow study. Any complications were recorded. An ascending cystogram was done at 3 months for detection of vesicoureteral reflux. Urinary tract infection (UTI) was estimated on urine culture basis. Primary outcome was the difference of total OABSS at 3 months.

RESULTS

The mean age ± SD was 34.3 ± 10 years (range 18-59 years). There was a reduction of episodes of all components of OAB in both groups in comparison with baseline by the end of the study but without significant difference between both groups. The trigonal-sparing group had less score of frequency compared with the trigonal-involved group throughout the study period (P < .05). There was no difference in OABSS at 3 months (1.5 ± 0.4 vs 1.6 ± 0.3, P .875). Two patients in the trigonal-involved group out of 51 (3.9%) were in need of clean intermittent catheterization because of voiding difficulty and a postvoid residual > 200 mL. There was a higher rate of UTI in the trigonal-involved group ranging from 5.6% up to 11.7% at each follow-up visit. No patient had reflux.

CONCLUSION

Trigone injections are not superior to trigone-sparing injections. On the contrary, the incidence of UTI and voiding difficulty were higher. The concept of reflux induced by trigonal injection has not been proven.

Current Perception Threshold Testing in Pharyngeal Paresthesia Patients with Depression or Anxiety

PURPOSE

Satisfactory quantitative diagnostic approaches to pharyngeal paresthesia patients with depression or anxiety remain to be explored. This study investigated the plausibility of current perception threshold (CPT) testing in diagnosing pharyngeal paresthesia in patients with depression or anxiety.

PATIENTS AND METHODS

A total of 41 patients with pharyngeal paresthesia with depression or anxiety were recruited as the study group. Additionally, 60 healthy volunteers constituted the control group. The CPT values associated with 5-, 250-, and 2000-Hz electrical stimulation frequencies were measured at the palatal lingual arch and posterior third of the lingual body (two sensory nerve distribution sites in the pharynx). The normal range of CPT values of the above three frequencies was analyzed. The differences in the CPT values for sensory nerves were compared.

RESULTS

There were no significant differences in age and sex between the study and control groups. The CPT values of the pharynx at the two tested sites were not significantly correlated with age and gender. The CPT value of the study group was significantly lower than that of the control group in the palatal lingual arch and posterior third of the lingual body at an electrical stimulation of 5 Hz (p<0.05). No significant differences in the CPT values at other frequencies were found between the two groups.

CONCLUSION

CPT testing is effective in determining pharyngeal paresthesia in patients with depression and anxiety. Paresthesia of the pharyngeal sensory nerve region is caused by damaged C fibers.

Optimized Measurement Parameters of Sensory Evoked Cortical Potentials to Assess Human Bladder Afferents - A Randomized Study

Overactive bladder and voiding dysfunction are highly prevalent and often associated with malfunction of the bladder afferent pathways. Appropriate diagnostic tools for an objective assessment of afferent nerve function of the human bladder are currently missing. One promising possibility is the assessment of sensory evoked potentials (SEP) during repetitive electrical bladder stimulation, which proved feasible in healthy subjects. For an implementation into clinical practice, however, further refinements for efficient and reliable data acquisition are crucial. The aim of this randomized study was to find the optimal measurement settings regarding stimulation frequency, repetition number, and data acquisition. Forty healthy subjects underwent two visits of SEP (Cz-Fz) assessments using repetitive (500 stimuli) electrical stimulation of 0.5 Hz, 1.1 Hz, and 1.6 Hz and pulse width of 1 ms at the bladder dome or trigone. SEP analyses revealed higher amplitudes and better signal-to-noise ratio (SNR) with lower stimulation frequencies, while latencies remained unchanged. Decreasing amplitudes and SNR were observed with continuing stimulation accompanied by decreasing responder rate (RR). When applying stimuli at a frequency of 0.5 Hz, averaging across 200 stimuli revealed optimal reliability with best SNR, RR and sufficiently high amplitudes. This constitutes an optimal compromise between the duration of the assessment and SEP peak-to-peak amplitudes.

Quantitative electrical pain threshold assessment in the lower urinary tract

AIMS

Assessing the reliability of electrical pain threshold (PT) and evaluating the impact of stimulation frequency at different locations in the healthy lower urinary tract (LUT).

METHODS

Ninety subjects (age: 18.3-35.8 years, 40 females, 50 males) were randomly allocated to one stimulation site (bladder dome [BD], trigone, proximal, membranous (only males), or distal urethra). Using 0.5 Hz/1.1 Hz/1.6 Hz electrical stimulation (square wave, pulse width:1 ms), current perception thresholds (CPTs), PTs and tolerance thresholds were assessed at two visits. Analyses were performed using linear mixed models, intraclass correlation coefficients (ICC) and Bland-Altman method.

RESULTS

PTs vary in relation to stimulation frequency, location and between genders. PT decreased with higher stimulation frequency. The highest PTs were measured at the BD and membranous urethra with males reporting higher PTs than females. Reliability of PT assessments according to ICC was good to excellent across all frequencies, locations, and genders (ICC = 0.61-0.97), except for BD and distal urethra in females showing poor to fair reliability (BD: all frequencies, distal urethra: 0.5 Hz).

CONCLUSIONS

PTs can be safely and reliably assessed from bladder and urethral locations. Semi-objective PT assessment may provide additional information on functionality and sensitivity of the LUT slow fiber afferents and complement findings from urodynamic investigations and CPT assessments. In conclusion, the developed methodology may open new opportunities for using electrical stimulation paradigms for LUT PT assessments and diagnostics. All this allows a more precise, location-specific characterization of pain origin and pain reaction towards therapy.

Sensory evoked cortical potentials of the lower urinary tract in healthy men

AIMS

To assess the afferent innervation of various locations in the male lower urinary tract (LUT) using sensory evoked cortical potentials (SEPs).

METHODS

Twelve healthy men (mean age: 29.6 ± 7.2 years, mean height: 1.8 ± 0.1 m) underwent repetitive slow (0.5 Hz/1 ms) and fast (3 Hz/0.2 ms) electrical stimulations of bladder (dome/trigone) and urethral (proximal/membranous/distal) locations with simultaneous cortical SEP recording (Cz-Fz). Latencies (ms) and peak-to-peak amplitudes (μV) for SEP components P1, N1, and P2 were analyzed. Tibial SEPs were assessed as methodological control. The reproducibility was investigated from between visits and inter-rater assessments using Bland-Altman plots. Statistical tests comprised analysis of variance (ANOVA), linear regressions, and paired t-tests. Values are given as mean ± standard deviation.

RESULTS

Typical LUTSEPs with P1, N1, and P2 components were successfully detected (100% responder rate) for slow but less successfully for fast stimulation. The slow stimulation provided reproducible LUTSEPs with position specific N1 latencies: dome 125.6 ± 21.3 ms, trigone 122.9 ± 20.5 ms, proximal- 116.1 ± 21.4 ms, membraneous- 118.8 ± 29.3 ms, and distal urethra 108.8 ± 17.8 ms. Despite good inter-rater agreement, latency variability between and within subjects was higher for LUTSEPs than for tibial SEPs. N1 latencies became shorter (P < 0.01) with increasing subject age for bladder dome and distal urethra stimulation.

CONCLUSIONS

LUTSEPs can be successfully obtained for different LUT locations in men using slow electrical stimulation. Location specific differences in N1 latencies may indicate different local afferent innervation. Larger variability of LUTSEPs versus tibial SEPs may be related to the more challenging approach and afferent fibre access within the LUT. Further studies optimizing measurement and analysis approach are required.

Possible role of hyposensitivity of C-fiber afferents at the proximal urethra in the development of urge urinary incontinence in patients with detrusor overactivity

OBJECTIVE

The aim of the present study was to investigate associations between urethral sensation and urge urinary incontinence (UUI) in patients with and without detrusor overactivity (DO).

METHODS

The medical records of 80 consecutive patients who underwent filling cystometry and urethral current perception threshold (CPT) tests were examined retrospectively. Following the exclusion of 4 patients not eligible for analysis, patients were classified into neurogenic DO, idiopathic DO, or DO-negative groups based on neurological and cystometric findings (n = 30, 12, and 34, respectively). Eleven DO-negative patients were defined as normal controls on cystometrograms (CMG) using the following exclusion criteria: bladder compliance <12.5 mL/cmH₂ O, volume >275 mL at first filling sensation, and comorbidities possibly affecting lower urinary tract function. Thus, 53 patients were finally included in the study. Proximal urethral CPT was evaluated with intraurethral square-wave stimulation at 3 Hz to activate C-fiber afferents.

RESULTS

Median CPT was higher in neurogenic and idiopathic DO than in the normal CMG group (11.3 and 9.0 vs. 2.8 mA, respectively; P < .05), as well as in patients with UUI (n = 19) compared with non-UUI patients (n = 34; 12.5 vs. 5.4 mA, respectively; P < .05). The proportion of UUI patients was significantly greater in the DO-positive groups than in the normal CMG group (P < .05). CPTs were not associated with bladder capacity at the first filling sensation (r = 0.11).

CONCLUSION

Hyposensitive C-fibers of the proximal urethra may contribute to the development of urodynamic DO as well as UUI in patients complaining of lower urinary tract symptoms.

Protocol for a prospective, randomized study on neurophysiological assessment of lower urinary tract function in a healthy cohort

Background

Lower urinary tract symptoms are highly prevalent and a large proportion of these symptoms are known to be associated with a dysfunction of the afferent pathways. Diagnostic tools for an objective and reproducible assessment of afferent nerve function of the lower urinary tract are missing. Previous studies showed first feasibility results of sensory evoked potential recordings following electrical stimulation of the lower urinary tract in healthy subjects and patients. Nevertheless, a refinement of the methodology is necessary.

Methods

This study is a prospective, randomized trial conducted at Balgrist University Hospital, Zürich, Switzerland. Ninety healthy subjects (forty females and fifty males) without lower urinary tract symptoms are planned to be included in the study. All subjects will undergo a screening visit (including standardized questionnaires, 3-day bladder diary, urinalysis, medical history taking, vital signs, physical examination, neuro-urological examination) followed by two measurement visits separated by an interval of 3 to 4 weeks. Electrical stimulations (0.5Hz-5Hz, bipolar, square wave, pulse width 1 ms) will be applied using a custom-made transurethral catheter at different locations of the lower urinary tract including bladder dome, trigone, proximal urethra, membranous urethra and distal urethra. Every subject will be randomly stimulated at one specific site of the lower urinary tract. Sensory evoked potentials (SEP) will be recorded using a 64-channel EEG cap. For an SEP segmental work-up we will place additional electrodes on the scalp (Cpz) and above the spine (C2 and L1). Visit two and three will be conducted identically for reliability assessment.

Discussion

The measurement of lower urinary tract SEPs elicited by electrical stimulation at different locations of the lower urinary tract has the potential to serve as a neurophysiological biomarker for lower urinary tract afferent nerve function in patients with lower urinary tract symptoms or disorders. For implementation of such a diagnostic tool into clinical practice, an optimized setup with efficient and reliable measurements and data acquisition is crucial. In addition, normative data from a larger cohort of healthy subjects would provide information on variability, potential confounding factors and cut-off values for investigations in patients with lower urinary tract dysfunction/symptoms.

Trial registration

Clinicaltrials.gov; Identifier: NCT02272309.