Study design, materials and methods
We included all patients with a neurogenic bladder who started PTNS between January 2008 and July 2018. PTNS patients without neurogenic bladder but with OAB where used as controls. Our group of neurogenic bladder patients contained a variety of neurological diseases. The severity of the neurogenic disease was staged by a neurologist before starting and after discontinuing PTNS for probable bias purposes. We used the Expanded Disability Status Scale (EDDS) for multiple sclerosis patients, modified Rankin Scale (mRS) for post-CVA and the Hoehn and Yahr Scale (HY) for Parkinson’s disease. Statistical analysis was done by using the Paired T-test for differences between the mentioned pre and post PTNS neurological performance scales. Kaplan-meier curves in combination with log rank test (SPSS) were used to describe the survival of the PTNS treatment between the neurogenic bladder group as a whole, as well as the idiopathic group. Separately, we evaluated patients considered a success and the reasons for them to stop. This resulted in a subgroup of patients who had initially a good response to the treatment (PTNS) but had to quit because of death, moving, a successful switch to TENS, persistent disappearance of problems of OAB after 12 weeks of treatment, physical strain or problems visiting the hospital. These were considered successful patients instead of failure to therapy.
We included 55 patients with neurogenic bladder (53% female, mean age 64 years (SD17)) Neurologic diseases were as follows: MS 11 patients, post-CVA 10 patients, Parkinson’s disease 10 patients, others 24 (see table 1). Baseline scores at the start of PTNS were as follows: EDSS mean 4.4, range 1-7; EDSS cat mean 1.7, range 1-3. HY mean 2.4, range 1-4. MRS mean 1.5, range 1-2. The control group consisted of 347 patients. Median follow-up (mFU) of the neurogenic bladder group was 4 months, maximum follow up 69 months. After 12 weeks of PTNS 53% continued to maintenance PTNS, compared to 57% in idiopathic OAB (not significant). There was no difference in neurologic performance/severity of the disease after starting and discontinuing PTNS (EDSS no difference, HY p= 0.341, mRS p=0.336). Figure 1A shows no significant difference (p=0.566) between the groups (neurogenic bladder versus control group) in failure of the treatment (PTNS). In the group of patients who had initially a good response but had to quit because of reasons not to be considered a failure of stimulation itself (as described above) there was also no significant difference in survival of the treatment (figure 1B): mFU 35 in neurogenic bladder patients versus 46 months in controls (p=0.825).
Interpretation of results
Neurological disease is almost always an exclusion criterium for PTNS research, therefore results regarding efficacy and long-term follow up in patients with neurogenic bladder are not well known. Our results show that there is no significant difference in failure of the treatment (PTNS) for OAB in selected patients with neurogenic bladder compared to patients treated for idiopathic OAB. However the total number of patients in the neurogenic bladder group is small and differences between the neurologic diseases (i.e., MS, post-CVA, Parkinson’s disease) could not be evaluated because of small sample sizes. Nevertheless we do think PTNS is a viable treatment option for selected neurological patients with OAB symptoms. Discontinuation of the therapy is not based on deterioration of the severity of the neurologic disease. We hope this study will path the way to further research in the future in patients with neurogenic bladder and treatment of PTNS in OAB. Development of an implant to replace percutaneous treatment could even be more successful as some patients stopped because of physical strain or too many visits.