Hypothesis / aims of study
Sacral neuromodulation (SNM) has been extensively investigated as a therapeutic intervention for non-neurogenic overactive bladder, particularly when conservative and pharmacologic approaches have proven unsuccessful. Conditions such as detrusor underactivity, fecal incontinence, and chronic pelvic pain also warrant consideration for this treatment, with demonstrated success in numerous trials. Recent research indicates outstanding safety and effectiveness of SNM in neurogenic patients. Nevertheless, the implantation of SNM devices in individuals with neurogenic lower urinary tract dysfunction remains a topic of debate, given the limited availability of high-quality evidence in this area. The objective of this study was to evaluate the efficacy of SNM therapy in a cohort of patients with neurogenic lower urinary tract dysfunction, all treated by a single surgeon, and whether urodynamic parameters could help in predicting SNM response in this cohort of patients.
Study design, materials and methods
We retrospectively reviewed a single surgeon experience with sacral neuromodulation in patients with neurogenic lower urinary tract dysfunction treated at a tertiary hospital from 2019 to 2023. All procedures, namely test-phase and 2nd stage (SNM device implantation) were performed under local anesthesia. We compared the Bladder Diary data of patients before neuromodulation and at 6-12 months after treatment, as well as the Urodynamic or Video-Urodynamic exams before treatment. The medical records of these patients were also reviewed regarding adverse events and treatment efficacy. The ICIQ Bladder Diary was used, in its validated translation to Portuguese.
Results
We reviewed a total of 31 patients with neurogenic lower urinary tract dysfunction who underwent implantation of a SNM device. 7 patients were excluded from the analysis due to lack of data (unavailability of Bladder Diary or Urodynamic study data). 24 patients were included in the analysis: 12 women and 12 men, mean age of 45.7 ± 16.0 years. 8 patients were performing intermittent self-catheterization (ISC), 2 of them twice daily and the other 6 patients 5-8 times per day (minimal or no spontaneous voiding). The neurologic conditions were: spinal cord injury (6 patients), multiple sclerosis (4), myelomeningocele (4), encephalitis (2), stroke (2), herniated disk (1), caudal regression syndrome (1), cerebral glioblastoma (1), Parkinson’s (1), miastenia gravis (1) and cauda equina syndrome (1). Of the 24 patients that underwent the test-phase, 19 proceeded to the implantation of the permanent implant, while the other 5 failed to demonstrate a reasonable improvement after the 1st stage.
The mean change in Bladder Diary parameters before vs. 6-12 months after SNM were: daily micturitions: -3.2; nocturnal micturitions: -1.0; average volume per micturition: +61 mL; incontinence episodes/24h (Bladder sensation scale 4): -3.3; urgency without incontinence episodes/24h (Bladder sensation scale 3): -1.1. Of the 8 patients performing ISC, 5 patients proceeded to the 2nd stage of the procedure, while the other 3 did not have sufficient improvement in the test-phase. One of these 5 patients stopped performing ISC, while the other 4 still need self-catheterization, although reporting less urinary incontinence between ISC. Change in Bladder Diary data was not different in males vs females, nor variable with age.
Regarding urodynamic evaluation and its correspondence with SNM response, there was no statistically significant covariance in bladder diary parameters with urodynamic parameters. We assessed whether cystometric capacity, presence of non-inhibited detrusor contractions, urgency, incontinence, Qmax, PdetQmax, post-micturition residue, Bladder Contractility Index and Bladder Outlet Obstruction index had any correlation with change in daily micturitions, nocturia, average volume, incontinence episodes or urgency episodes. There was a statistically significant greater decrease in nocturia in patients with higher BCI (r2=0.209, p=0.019), and a tendency for a greater decrease in the number of daily micturitions (r2=0.106, p=0.077), as well as a stronger increase in volume of micturitions in patients with a higher BCI (r2=0.141; p=0.070).
Interpretation of results
Despite not formally recommended in most guidelines, emerging evidence suggests a potential utility for sacral neuromodulation in the management of neurogenic lower urinary tract dysfunction. This is a consequence of a lack of studies including neurogenic patients with the only existing evidence primarily relying on a few case-reports or small non-controlled cohorts.
The prediction of SNM efficacy remains very challenging, especially in neurogenic patients, and so far no studies have been conducted in this field. Urodynamic studies are routinely performed in patients who are candidates for SNM, and these enable the assessment of bladder contractility, volume, obstruction, etc. These parameters could have a correlation to SNM response. In this study, only Bladder Contractility Index has shown a tendency to predict a bigger increase in micturition volumes, suggesting that the preservation of bladder contractility is a good prognostic factor for patients undergoing treatment with SNM. In other words, SNM seems to be more successful at decreasing bladder overactivity than underactivity, a finding already reported regarding non-neurogenic cohorts.
We examined a cohort of patients with neurogenic lower urinary tract dysfunction who underwent SNM. A total of 21% of patients did not experience sufficient improvement during the test phase to proceed to permanent device implantation, a proportion similar to the observed in the literature for non-neurogenic patients. Among those who received the permanent device, there was a notable reduction in symptom severity, as evidenced by changes in the Bladder Diary. We consider the ICIQ Bladder Diary an excellent tool for assessing patient-reported outcomes, given its validation and non-invasive nature. Additionally, SNM appeared to positively impact other important outcomes such as the need ISC, bowel-related symptoms, and quality of life. Interestingly, improvements in bowel-related symptoms were reported to occur more rapidly than urinary symptoms, which sometimes require SNM reprogramming.