Overactive bladder (OAB) is common in Multiple Sclerosis (MS), characterised by urinary frequency, urgency, and incontinence (1). Conservative treatments include Transcutaneous Tibial Nerve Stimulation (TTNS) and Parasacral Nerve Stimulation (PNS), which are non-invasive neuromodulation options for OAB. TTNS stimulates the sacral nerve indirectly via the tibial nerve, while PNS targets it directly. Both methods work by inhibiting the detrusor muscle (2, 3). This study investigates the effectiveness of TTNS and PNS in managing OAB symptoms in women with MS to provide clinicians with viable treatment options and evidence for choosing the best method.

This study was a single-blind sham randomized controlled trial. Participants were randomly assigned to three groups using a computer-generated randomization scheme: TTNS (tibial nerve stimulation with behavioural treatment), PNS (parasacral nerve stimulation with behavioural treatment), and a sham group (sham stimulation with behavioural treatment). Each group used the application for 30 minutes twice weekly over six weeks.
The inclusion criteria included female MS patients with an Expanded Disability Status Scale (EDSS) score below 7.0, Patients with neurogenic overactive bladder owing to MS who had not responded to medication, self-reported urgency confirmed by a score of 8 or higher on the Overactive Bladder – Validated 8-Question Awareness Tool (OAB-V8), individuals aged 18 and older, no relapse for at least one month, and all types of MS. Exclusion criteria included urinary tract infections, diabetes, those on diuretics or using intermittent catheters, prior urological conditions, pacemakers or brain stimulators, epilepsy, and pregnant or postpartum individuals. 
The primary outcomes were uroflowmetry results, including maximum flow rate (Qmax) and voided volume (VV). Secondary outcomes included post-void residual volume (PVR), Three-Day Bladder Diary (3-day BD), and the OAB-V8 questionnaire. A one-way ANOVA assessed the effects of three interventions. The Tukey test identified differences in measurements. Assessments were repeated after six weeks. Randomized controlled trials showed a between-group effect size of d = 1.55 for Qmax. A priori power analysis indicated that 42 (14 for each group) participants are needed, allowing for a 10% dropout rate, 5% Type I error rate, and aiming for 95% power. The project planning followed the guidelines of the Consolidated Standards of Reporting Trials (CONSORT).

This is a preliminary report of 30 patients with three groups (TTNS: n=11, PNS: n=9, Sham: n=10). No significant baseline differences were found (p>0.05). Demographic characteristics are given in Table 1.
At week 6, in intergroup comparisons, mean uroflowmetry voided volume (VV) scores differed significantly (p=0.022), with the TTNS group scoring higher than the sham group (p=0.016). Other factors, such as Qmax and PVR, showed no significant differences.
The OAB-V8 score improved more in the TTNS and PNS groups than in the sham group (p=0.002; p=0.004). In the 3-day BD, subscores for urinary frequency, nocturia, urgency, and incontinence decreased more in the PNS than in the sham group (p=0.003, p=0.006, p=0.007, p=0.002). The urgency subscore also decreased more in TTNS compared to sham (p=0.002) (Table 2).

The TTNS and PNS groups showed significant improvements in 3-day BD subscores and OAB-V8 values compared to the sham group. However, no superiority was found between the two treatment groups in terms of bladder diary and OAB-V8 values, and no significant difference was found between the three groups in uroflowmetry subscores.

TTNS is a promising treatment option for alleviating MS-related overactive bladder symptoms and is commonly used in clinical practice. However, due to the nature of MS, some patients may experience sensory loss in the lower extremities or develop sensitivity in the tibial nerve region. In such situations, or when patients do not respond well to treatment, PNS can serve as an alternative treatment modality to TTNS.

Polat Dunya C, Tulek Z, Kürtüncü M, Panicker JN, Eraksoy M. Effectiveness of the transcutaneous tibial nerve stimulation and pelvic floor muscle training with biofeedback in women with multiple sclerosis for the management of overactive bladder. Mult Scler. 2021;27(4):621-9.
Wang ZH, Liu ZH. Treatment for overactive bladder: A meta-analysis of tibial versus parasacral neuromodulation. Medicine (Baltimore). 2022;101(41):e31165.
de Sèze M, Raibaut P, Gallien P, Even-Schneider A, Denys P, Bonniaud V, et al. Transcutaneous posterior tibial nerve stimulation for treatment of the overactive bladder syndrome in multiple sclerosis: results of a multicenter prospective study. Neurourol Urodyn. 2011;30(3):306-11.