Repetitive Transcranial Magnetic Stimulation (rTMS) on Neurogenic Overactive Bladder in Stroke

A Mixed-methods Evaluation of the Clinical and Cost-effectiveness of Repetitive Transcranial Magnetic Stimulation (rTMS) on Neurogenic Overactive Bladder in Stroke

Neurogenic overactive bladder (NOAB) presents with urgency incontinence. Existing NOAB management is expensive, lacks standardized regimens, or is invasive. Therefore, evaluating the effectiveness of non-invasive repetitive transcranial magnetic stimulation (rTMS) for NOAB management among stroke survivors remains crucial. Objectives: Evaluate the effects of active-rTMS compared to sham-rTMS among stroke survivors with NOAB, the interventions' cost-effectiveness and explore their experiences qualitatively.

Summary Background: Neurogenic overactive bladder (NOAB) presents with urgency incontinence. Existing NOAB management is expensive, lacks standardized regimens, or is invasive. Therefore, evaluating the effectiveness of non-invasive repetitive transcranial magnetic stimulation (rTMS) for NOAB management among stroke survivors remains crucial. Objectives: Evaluate the effects of active-rTMS compared to sham-rTMS among stroke survivors with NOAB, the interventions' cost-effectiveness and explore their experiences qualitatively. Hypothesis: Active-rTMS will reduce NOAB symptom severity for stroke survivors, interventions' cost and assist in gaining insight into the NOAB patients' experiences. Methods: This study will be a randomised-sham-controlled, double-blinded trial, with embedded qualitative and cost-effectiveness studies. Snowball-convenience sampling technique and computer-generated randomisation will be adopted to recruit 30 participants into active-rTMS and sham-rTMS groups each. Active-rTMS participants will receive a continuous 1 pulse per second 1200 pulses of low-frequency rTMS to the pelvic floor muscle representation in the contralesional primary motor cortex (M1) for 20 minutes thrice weekly. Sham-rTMS participants will receive the same parameters as the active-rTMS group, however, the coil will be rotated 90° away from the scalp. Fifteen active-rTMS participants will be invited for 45-60 minutes focus group discussions. The primary and secondary outcomes will be urinary incontinence severity and quality of life evaluated using the Overactive Bladder Symptom Score and Incontinence-Quality of life Questionnaire, respectively. Quality-adjusted life-years (QALY) will be the cost-effectiveness outcome. The EQ-5D-5L responses will estimate the gain or loss of QALY. A follow-up assessment will be conducted one-months post-intervention. The Client Service Receipt Inventory (CSRI) will be used to collect information on the whole range of services and support required by the study participants. Statistical analysis: Normality will be evaluated using Shapiro-Wilk test. To determine active-rTMS and sham-rTMS group differences, between-groups analysis of covariance (ANCOVA) will be conducted using R software. Bonferroni correction will be applied for multiple comparisons. Thematic analysis will be used for analysing the qualitative data. For the cost-effectiveness analysis, the unadjusted mean costs and cost differences between active-rTMS and the sham-rTMS group will be calculated.

The therapist and the participants will be blinded in the recruitment, randomization and treatment allocation

The active rTMS group will receive a 1 Hz inhibitory low-frequency rTMS protocol hotspot of the contra-lessional primary motor cortex (M1), will deliver a continuous pulse of 1 pulse per second totalling 1200 pulses of 80% active motor threshold stimulation. The duration of the stimulation will last for 20 minutes thrice a week for four weeks (12 sessions). The motor threshold will be the minimum single-pulse TMS intensity necessary to elicit a motor-evoked potential greater than 50μV in more than 5 out of 10 consecutive trials. The standard 70 mm figure-of-eight air-cooled coil handle (MagPro) will be held at right angle to the skull for effective M1 stimulation. The participants in the active rTMS groups will receive a subthreshold stimulation intensity for muscle contraction with no painful peripheral sensation

The sham rTMS will be applied using the same parameters as the active rTMS but the coil will be rotated 90° away from the scalp so that minimal or no flow of current will be induced

The OABSS is reported to be a reliable and valid questionnaire for the quantitative evaluation of overactive bladder symptoms in the Hong Kong population (ICC score: 0.82). The measure comprised four questions on OAB symptoms with domain maximum scores ranging from 2 to 5: daytime frequency (two points), night-time frequency (three points), urgency (five points), and UUI (five points). The OABSS total score ranges from 0 to 15 points, with higher scores indicating higher symptom severity. According to severity, mild is defined as a score of 3 to 5 points, moderate as a score of 6 to 11 points, and severe as a score of 12 or more points.

The I-QoL is reported to be a psychometrically robust incontinence-specific outcome measure for the evaluation of OAB quality of life. The I-QoL measure has 22 items subdivided into 3 subscale scores. The total scores is 100 with 0 representing worst quality of life and 100 means absence of problem (intraclass correlation coefficient [ICC] = 0.93). The measure is tested among Chinese population and found to be of sound psychometric properties; high internal consistency (Cronbach's α: 0.963; excellent test-retest reliability (ICC: 0.74-0.96, P<0.01) and acceptable construct validity.

The Brief Resilience Scale has been reported to provide unique and critical information regarding "people coping with health-related stressors". Items 1, 3, and 5 on the scale are positively worded. In contrast, items 2, 4, and 6 are negatively worded. Resilience represents coping strategy of individuals to stressed environment and negative life events. The resilience is observed to be lacking in people with urinary incontinence of all age groups

The 5-level EQ-5D (EQ-5D-5L) version developed by the EuroQol Research Foundation will be used to estimate the Quality-adjusted life-years (QALY) gain or loss.

Inclusion Criteria: Stroke survivors aged between 18-80 years diagnosed with NOAB Urodynamic findings confirming detrusor overactivity Experience moderate (OABSS scores: 6-11 points) to severe NOAB (OABSS scores: 12 points and above) Obtain a Mini-Mental State Examination (MMSE) score of ≥ 24 Be willing to be randomized Exclusion Criteria: Presence of metals in the cranium, intracardiac lines, increased intracranial pressure, heart diseases, or cardiac pacemaker, use of sacral neuro-modulation Pregnancy or less than six months postpartum stage Patients with a family history of epilepsy or seizures Patients taking tricyclic antidepressants or neuroepileptics Participation in any other research project related to urinary incontinence; contra-indicated to MRI, urologic cancer, prostatic pathology, severe pelvic pain, six weeks post-surgery and non-neurogenic bladder

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