Functional electrical stimulation (FES) is a highly effective treatment for the management of foot drop in patients with central neurological disorders such as Multiple sclerosis (MS) and stroke, and consists of intermittent electrical stimulation of the common peroneal nerve (CPN). Percutaneous electrical stimulation of the tibial nerve (PTNS), which shares a common innervation with the CPN, is associated with improvements in overactive bladder (OAB) symptoms, and it is therefore  possible that CPN stimulation can influence LUT symptoms.  Anecdotally, some patients have reported improvements in lower urinary tract (LUT) symptoms after commencing FES, however this has never been systematically evaluated in the literature.  The purpose of this study was to therefore explore changes in OAB symptoms in a group of patients undergoing FES of the CPN.

Consecutive patients attending a dedicated FES unit at a tertiary level teaching hospital over six months in 2016-2017 were enrolled in a prospective exploratory assessment of LUT functions.   A validated questionanire, the ICIQ-OAB, was adminstered at baseline and 3 months during their routine physiotherapy appointments, alongside conventional measures of walking speeds over 10 metres, and an 11 point Visual Analogue Scale (VAS) of satisfaction with walking, where 0 is extremely dissatisfied and 10 is extremely satisfied. Patients used the Odstock Dropped Foot Stimulator (ODFS®) Pace device, a single channel, foot switch triggered, stimulator designed to elicit dorsiflexion and eversion of the foot by stimulation of the common peroneal nerve (maximum amplitude 100mA, 350s pulse, 40Hz).  Skin electrodes are typically placed over the common peroneal nerve as it courses around the head of the fibula and over the motor point of tibialis anterior and the device is used when the patient requires to ambulate. The service evaluation was reviewed and registered with the Quality and Clinical Governance Department. Data was analysed using SPSS; the Wilcoxon Signed-Rank Test was used to compare walking speeds and ICIQ-OAB scores at baseline and 3 months and Spearman’s Rank Correlation Coefficient to assess the relationship between baseline walking speed and A scores with change in the ICIQ-OAB score.

Analysis revealed a significant improvement in walking speed at 3 months both in the whole cohort (p<0.001) and in the MS cohort (p=0.001). Additionally, satisfaction of gait improved significantly in all groups (p<0.001) (Table).  There was a significant improvement of the ICIQ-OAB scores in the MS population over the 3 month period (p=0.043).  When individual LUT symptoms were separately analysed, significant improvements were seen in urinary urgency and urinary urge incontinence (p< 0.05).   There were no significant side effects reported.  There was a significant negative correlation of moderate strength within the MS cohort between baseline walking speed and the subsequent change in ICIQ-OAB score (correlation coefficient r=-0.40, p=0.046), ie. greater improvments in OAB symptoms were seen in patients with lower baseline walking speeds. A significant negative correlation of moderate strength was shown between baseline ICIQ-OAB score and change in ICIQ-OAB score in the whole cohort and within MS patients; Ie. those with worse OAB symptoms at baseline showed smaller improvements in OAB symptoms (whole group r=-0.466, p=0.001; MS group r=0.442, p=0.008).

The results of this prospective observational study suggest that electrical stimulation of the CPN, results in significant improvements of OAB scores after 3 months of stimulation in patients with MS. Moreover, the one unit reduction in ICIQ-OAB score represents a clinically important difference which is recognized to constitute evidence for clinicians and patients to continue treatment [1].  Improvements in incontinence could reflect changes in mobility and walking speed when accessing toileting facilities, however additionally the urinary urgency score improved and therefore the results of this preliminary study suggest a direct improvement on the OAB.  Studies have demonstrated the efficacy and safety of PTNS for MS-related OAB symptoms [2], and therefore a larger study is required to confirm the findings of this preliminary study exploring CPN stimulation.  Moreover, urodynamic testing should be included to explore whether improvements in LUT symptoms following CPN stimulation are associated with objective changes in LUT dysfunction such as detrusor overactivity.

The results of this exploratory study suggest that FES of the common peroneal nerve, a commonly used neurostimulation treatment for managing foot drop, may result in improvements in OAB symptoms in neurological patients.

Verghese T S, Tryposkiadis K, Arifeen K, Middleton L, Latthe P M. Minimal clinically important difference (MCID) for the international Consultation on Incontinence Questionnaire- Overactive Bladder (ICIQ- OAB). Abstract 638, ICS Florence 2017 https://www.ics.org/Abstracts/Publish/349/000638.pdf
Canbaz Kabay S, Kabay S, Mestan E, Cetiner M, Ayas S, Sevim M, Ozden H, Karaman HO. Long term sustained therapeutic effects of percutaneous posterior tibial nerve stimulation treatment of neurogenic overactive bladder in multiple sclerosis patients: 12-months results. Neurourol Urodyn. 2017 Jan;36(1):104-110.