We investigated surgical outcomes and changes of overactive bladder (OAB) symptoms after midurethral sling placement in female stress urinary incontinence (SUI) patients with or without neurological disease.

Medical records of patients who underwent midurethral sling operation for SUI between January 2009 and December 2018 at a single tertiary center were reviewed. Patients with previous anti-incontinence surgery and concurrent pelvic organ prolapse repair were excluded. Based on the presence of underlying neurological disease (cerebrovascular, neurodegenerative movement disorder, spinal cord disease, or peripheral neuropathy), patients were divided into two groups: the non-neurological disease (NND) group and the neurological disease (ND) group. 
Among patients who experienced complete dryness through the final follow-up examination, baseline demographics and changes in OAB symptoms were compared, including de novo OAB in the pure SUI group, resolution rate of urgency or de novo UUI in SUI in the urgency group, and resolution rate of UUI in the MUI group. OAB symptoms between postoperative month 6 and month 12evaluated to investigate the influence of midurethral sling operation. ND patients with MUI were categorized into three subsets based on the timeline of UUI symptoms and neurological condition as pre-existing UUI, UUI as sequela of a neurological condition, or not-identifiable. The resolution rate of UUI was compared between pre-existing and neurological sequela subsets. Next, to evaluate the association between postoperative OAB symptoms and neurological disease, we performed a 1:1 matched analysis between NND and ND groups in subsets of patients with pure SUI (de novo OAB) and MUI (resolution of UUI).

A total of 855 patients (median follow-up: 49.8 months; mean age: 57.9±9.3 years) were included. Complete dryness was achieved 95.0% of NND and 93.7% of ND patients (p=0.440). Among 797 patients (711 NND and 86 ND) who achieved complete dryness, 227 patients had pure SUI, 198 patients had SUI with urgency, and 372 patients had mixed urinary incontinence (MUI) preoperatively. The ND patients tended to be older older (57.2±9.0 years vs. 62.8±9.2 years) and had higher proportions of diabetes (8.0% vs. 24.4%), hypertension (26.7% vs. 47.7%), and MUI (44.6% vs. 64.0%) than NND patients (p<0.001 for all). The incidence of pure SUI was higher in ND patients (5.9% vs. 18.2%, p=0.032) than in NND patients. Specifically, de novo urgency developed in 5.4% of NND patients and 18.2% of ND patients and de novo UUI developed in 0.5% of NND patients and none of the ND patients. In patients with SUI with urgency, resolution rate of urgency was similar (72.0% vs. 77.8%, p = 0.703) and de novo UUI developed in 1.5% of patients. In patients with MUI, the overall resolution rate of UUI was significantly higher in NND patients than in ND patients (75.4% vs. 60.0%, p = 0.017). The rate was significantly higher in preoperative SUI predominant NND patients than in UUI predominant NND patients (80.9% vs. 55.0%, p < 0.001). There was no significant difference in resolution rates of UUI based on preoperative predominant type of incontinence in the ND group (62.9% vs. 50.0%, p = 0.387).
The chronological association of OAB symptoms with neurological conditions was clearly identified in 79.7% of MUI patients (43 out of 55). There was no significant difference in the resolution rates of UUI between patients whose storage symptoms were associated with a neurological condition and those whose storage symptoms were not associated with a neurological condition (17 out of 28: 60.7% vs. 9 out of 15: 60.0%, p = 0.964). In a 1:1 matched analysis of pure SUI patients, 19 patients were matched and de novo OAB was significantly higher in patients with ND than in patients with NND (5.26% vs. 21.05%, p < 0.001). In a 1:1 matched analysis of MUI group, 52 patients were matched but resolution of UUI did not significantly differ between ND and NND patients (53.9% vs. 57.7%, p = 0.414).

Comparable success rates in neurological patients might be due to the patients’ relatively high performance statuses. Most neurological patients in the study population were tolerable to monitored or general anesthesia and capable of caring for themselves or could perform normal activities with some difficulty. Our success rates of midurethral sling in neurological group are higher than previous literature, and this might have been becaute the etiology of SUI in our patient population was not purely due to impaired control of the external sphincter. In addition, the incidence of de novo OAB in neurological group is also higher than previous literature. This might be because our study population included 61.6% (53 out of 86) of patients with suprapontine lesions that might have influenced the tonic inhibition of the pontine micturition center, which can lead to spontaneous involuntary detrusor contractions. Significant difference in de novo OAB after 1:1 matched analysis might have occurred due to the natural course of neurological condition itself. Three-fourths of patients who developed de novo OAB had supra pontine lesion; cerebrovascular diseases (n = 2), Parkinson’s disease (n = 1). In a matched analysis of MUI patients, however, there was no significant difference in the resolution of UUI between non-neurological disease and neurological disease patients (53.9% vs. 57.7%, p = 0.414). This might be because patients included in the present study were in their early stage of neurodegenerative disease and had relatively high performance status.

Presence of neurological disease did not affect the success rate of midurethral sling placement. De novo OAB symptoms were more likely to develop and the resolution rate of UUI seemed to be lower in patients with neurological disease. However, after matching by baseline variables including age, diabetes and hypertension, there was no difference in the resolution rate of UUI in MUI group while de novo OAB symptoms were prevalent in neurological pure SUI group. In addition, the onset of preoperative UUI was irrelevant in patients with persistent postoperative UUI in neurological MUI group.

El-Azab AS, El-Nashar SA: Midurethral slings versus the standard pubovaginal slings for women with neurogenic stress urinary incontinence. Int Urogynecol J 2015; 26: 427.
Losco GS, Burki JR, Omar YA et al: Long-term outcome of transobturator tape (TOT) for treatment of stress urinary incontinence in females with neuropathic bladders. Spinal Cord 2015; 53: 544.
Ford AA, Taylor V, Ogah J et al: Midurethral slings for treatment of stress urinary incontinence review. Neurourol Urodyn 2019; 38 Suppl 4: S70.