Hyperexcitability of bladder afferent neurons associated with reduction of Kv1.4 α-subunit in rats with spinal cord injury

PURPOSE

To clarify the functional and molecular mechanisms inducing hyperexcitability of C-fiber bladder afferent pathways after spinal cord injury we examined changes in the electrophysiological properties of bladder afferent neurons, focusing especially on voltage-gated K channels.

MATERIALS AND METHODS

Freshly dissociated L6-S1 dorsal root ganglion neurons were prepared from female spinal intact and spinal transected (T9-T10 transection) Sprague Dawley® rats. Whole cell patch clamp recordings were performed on individual bladder afferent neurons. Kv1.2 and Kv1.4 α-subunit expression levels were also evaluated by immunohistochemical and real-time polymerase chain reaction methods.

RESULTS

Capsaicin sensitive bladder afferent neurons from spinal transected rats showed increased cell excitability, as evidenced by lower spike activation thresholds and a tonic firing pattern. The peak density of transient A-type K+ currents in capsaicin sensitive bladder afferent neurons from spinal transected rats was significantly less than that from spinal intact rats. Also, the KA current inactivation curve was displaced to more hyperpolarized levels after spinal transection. The protein and mRNA expression of Kv1.4 α-subunits, which can form transient A-type K+ channels, was decreased in bladder afferent neurons after spinal transection.

CONCLUSIONS

Results indicate that the excitability of capsaicin sensitive C-fiber bladder afferent neurons is increased in association with reductions in transient A-type K+ current density and Kv1.4 α-subunit expression in injured rats. Thus, the Kv1.4 α-subunit could be a molecular target for treating overactive bladder due to neurogenic detrusor overactivity.

Sacral neuromodulation in patients with idiopathic overactive bladder after initial botulinum toxin therapy

PURPOSE

We evaluated whether patients with overactive bladder and incontinence who discontinued intravesical botulinum toxin therapy can be successfully treated with sacral neuromodulation.

MATERIALS AND METHODS

All patients who were referred to our center after discontinuation of botulinum toxin-A between 2005 and 2010 were included in this observational study. All patients underwent test stimulation with sacral neuromodulation and were evaluated with voiding diaries. Success was defined as more than 50% improvement in leakage episodes. Successful test stimulation was subsequently followed by a definitive implant. Patient satisfaction with sacral neuromodulation therapy was evaluated 1 year after the definitive implant.

RESULTS

A total of 20 patients were included in the study. Of these patients 17 (85%) had discontinued botulinum toxin-A because of lack of efficacy and 3 had been treated successfully with botulinum toxin-A but requested a more permanent solution. The mean interval between the botulinum toxin-A and the sacral neuromodulation test stimulation was 23 months. In 14 patients (70%) the test stimulation was successful and they received a definitive implant. Of the 14 patients 5 even showed a decrease of greater than 90% in leakage episodes. One year after implantation 11 patients (79%) were satisfied with the sacral neuromodulation treatment.

CONCLUSIONS

Despite the small sample size, this study indicates that patients who are dissatisfied with or in whom botulinum toxin-A treatment fails can respond successfully to sacral neuromodulation. The success rate of the test stimulation was comparable to that of patients who have never been treated with botulinum toxin-A. The 1-year satisfaction rate was comparable that of patients without a history of botulinum toxin-A treatment.

Voiding diary might serve as a useful tool to understand differences between bladder pain syndrome/interstitial cystitis and overactive bladder

OBJECTIVES

To identify the voiding characteristics of bladder pain syndrome/interstitial cystitis and overactive bladder.

METHODS

Between September 2005 and June 2010, 3-day voiding diaries of 49 consecutive bladder pain syndrome/interstitial cystitis patients and 301 overactive bladder patients were prospectively collected at an outpatient clinic and retrospectively analyzed.

RESULTS

The characteristics of the two groups were not significantly different. However, all voiding variables including volume and frequency were significantly different except for the total voided volume: patients with bladder pain syndrome/interstitial cystitis showed significantly higher voiding frequencies, smaller maximal and mean voided volume, and more constant and narrower ranges of voided volume compared with overactive bladder patients (P < 0.005). Furthermore, mean intervals between voiding in bladder pain syndrome/interstitial cystitis were shorter and more consistent during the day and night (P < 0.001), although mean night-time variances were greater than daytime variances. Logistic regression analysis showed that total night-time frequency, maximal night-time voided volume and mean variance of daytime voiding intervals most significantly differentiated the two groups.

CONCLUSIONS

Some voiding characteristics of bladder pain syndrome/interstitial cystitis and overactive bladder patients differ significantly according to 3-day voiding diary records. These findings provide additional information regarding the differences between these two diseases in the outpatient clinical setting.

Treatment status and progression or regression of lower urinary tract symptoms in a general adult population sample

PURPOSE

We report progression and regression of lower urinary tract symptoms in a population based cohort by race/ethnicity, gender, age and lower urinary tract symptom medication use.

MATERIALS AND METHODS

The BACH (Boston Area Community Health) Survey enrolled 5,502 participants 30 to 79 years old of black, Hispanic or white race/ethnicity. The 5-year followup interviews were completed by 1,610 men and 2,534 women for a conditional response rate of 80%. Population weighted estimates of lower urinary tract symptoms severity were assessed using the AUASI (American Urological Association symptom index) and analyzed using multivariate models.

RESULTS

Symptom progression (increase in AUASI score of 3 or more points) was reported by 21% to 33% of participants and regression (decrease 3 or greater) by 30% to 44% of participants, most commonly women and Hispanic participants. Age and higher body mass index were associated with progression (p <0.01), but not with regression. Lower urinary tract symptom medication use at baseline only was associated with improved symptoms scores 5 years later (multivariate adjusted OR 3.10, 95% CI 1.28-7.51, compared to nonusers), whereas using medication at baseline and followup was associated with similar rates of progression and regression as observed among participants not using lower urinary tract symptom medication at either point.

CONCLUSIONS

Lower urinary tract symptoms persisted at followup for approximately half of the population experiencing symptoms at baseline, including many men and women using lower urinary tract symptom medications. However, overall lower urinary tract symptom medication use and surgical treatment appeared beneficial for symptom control at 5-year followup. Age and body mass index were associated with symptom worsening, and Hispanic ethnicity was associated with greater symptom fluctuation. Clinicians should consider the higher likelihood of lower urinary tract symptom progression for older or heavier patients, and monitor responsiveness to lower urinary tract symptom medication.

Dimensions of sensation assessed in urinary urgency: a systematic review

PURPOSE

Urinary urgency is an adverse sensory experience. Confirmation of the multidimensional nature of other adverse sensory experiences such as pain and dyspnea has improved the understanding of neurophysiological and perceptual mechanisms leading to innovations in assessment and treatment. It has been suggested that the sensation of urgency may include multiple dimensions such as intensity, suddenness and unpleasantness. In this systematic review we determine which dimensions of sensation have been assessed by instruments used to measure urinary urgency.

MATERIALS AND METHODS

A systematic search was undertaken of MEDLINE, Embase, AMED, CINAHL, Ageline, Web of Science, InformIT Health and Scopus databases to identify studies that included assessments of urinary urge or urgency. Articles were included in the analysis if they were primary studies that described the method used to measure urge/urgency in adults and published in English in peer reviewed publications since January 1, 2000. Articles were excluded from study if urgency was measured only in conjunction with other symptoms (eg frequency or incontinence) or if there was no English version of the instrument. Secondary analyses and systematic reviews were retained to hand search references for additional primary studies. Data were extracted for the instruments used to measure urge/urgency. For each instrument the items specific to urinary urgency were reviewed using a prospectively developed categorization process for the sensory dimension and the measurement metric. Items used to assess urinary urgency were collated in a matrix (sensory dimensions vs assessment metric). The most frequently used dimensions, metrics and combinations were descriptively analyzed.

RESULTS

After removal of duplicate articles 1,048 full text articles were screened and 411 were excluded, leaving 637 eligible articles from which data were extracted. A total of 216 instruments were identified which were 1 of 6 types, namely 1) wider symptom questionnaires, 2) urgency specific questionnaires, 3) ordinal scales, 4) visual analog scales, 5) event records or 6) body maps. These 216 instruments contained a total of 309 urgency specific items. Of the instruments 51% did not define a dimension of sensation and 26% did not define the metric used. From the remaining instruments 8 dimensions of sensation and 5 types of metrics were identified. From most common to least common, the sensory dimensions assessed were behavioral response, intensity, suddenness, bother, affective response, unpleasantness, quality (descriptors) and problems associated with sensation. Metrics were magnitude, frequency, presence, time frame or location. The most common sensory dimension/metric combinations were frequency of a behavioral response (14% of items) and magnitude of bother caused by the sensation (8% of items).

CONCLUSIONS

The hypothesis that urinary urgency is multidimensional is supported by the range of dimensions assessed with available instruments. To clarify the nature of urinary urgency compared with the normal desire to void, prospective studies are required to determine whether sensory dimensions are distinct, and which may delineate between normal and pathological sensation.

Onabotulinum toxin a (botox®) in the treatment of neurogenic bladder overactivity

Botulinum toxin (BT) is a potent presynaptic neuromuscular blocking agent which induces selective, reversible muscle weakness for months when injected intramuscularly. During recent years BT has revolutionized the treatment of previously intractable symptoms of detrusor overactivity. Based on a systematic search of the PubMed database, a review of the current literature on the use of onabotulinum toxin A (Botox®) in the treatment of neurogenic detrusor overactivity is presented.

Onabotulinum toxin A proved to be highly effective in the majority of studies, even though a wide range of injection techniques and dosages were described. The onset of the effect usually appeared before 2 weeks, and reached a peak within 2-6 weeks, with the clinical effect being maintained for approximately 6-8 months, or even longer. Depending on the dose, a number of patients developed high residual volume and clean intermittent self/helper catheterization (CIC) may become necessary. Only a few side effects were described, and intravesical onabotulinum toxin A injection seems to be well tolerated. However, details on injection technique, dose interval between injections, etc. are still under debate and only a few randomized, placebo controlled studies have been published.

Dorsal genital nerve stimulation for the treatment of overactive bladder symptoms

AIM

To evaluate percutaneous placement of electrodes adjacent to the dorsal genital nerve (DGN) and measure the effects of electrical stimulation on symptoms of urge incontinence during 1 week of home use.

METHODS

Prospective, multicenter study. Subjects with urge incontinence underwent percutaneous placement of an electrode using local anesthetic. Test stimulation was applied to confirm electrode placement and cystometry was conducted with and without application of electrical stimulation. A 7-day testing period with the electrode connected to an external pulse generator was performed and was followed by a 3-day post-treatment test period. Bladder diaries, 24 hr pad tests, and adverse event queries were obtained.

RESULTS

Twenty-one women were enrolled with an average age of 52.7 years and average duration of incontinence of 6 years. Percutaneous electrode placement required 5-10 min and was well tolerated. There was no relationship between the acute effects of stimulation on cystometry and the results during home use. Pad weight was reduced by >or= 50% in 13 of 17 subjects (76%) (4 did not complete 24 hr pad testing) and 47% of subjects reported >or=50% reduction in incontinence episodes. Of the subjects who reported severe urgency at baseline, 81% experienced a 50% or greater improvement. Seven subjects experienced nine adverse events ranging from skin irritation to pain and bruising around the electrode exit site.

CONCLUSIONS

Electrodes to stimulate the DGN can be placed percutaneously and a home testing period showed a reduction in overactive bladder symptoms with DGN stimulation.