Does neuromuscular electrical stimulation increase pelvic floor muscle strength in women with urinary incontinence with an ineffective pelvic floor contraction?

Women’s health physiotherapists employ various techniques to treat urinary incontinence (UI) in patients who are attempting to restore function by improving the strength, stamina and coordination of their pelvic floor muscles (PFMs). Urinary incontinence can be subdivided into stress UI (SUI), urge UI (UUI) or mixed UI (MUI). Both the Chartered Society of Physiotherapy, and the National Institute for Health and Care Excellence advocate neuromuscular electrical stimulation (NMES) in patients whose PFM contractions register as grade 0 or l on the Modified Oxford Scale (MOS). A literature search was conducted to review the evidence supporting the use of NMES in this population. Twenty-two controlled trials were found, 10 of which used PFM strength as an outcome measure. Follow-up times ranged from 5 to 24 weeks. Five of the six studies of NMES in SUI found a statistically significant improvement in PFM strength following stimulation (mean increase=6.17–21.60 cmH2O, or +0.9 on the MOS), and the remaining paper reported a statistically insignificant improvement. Four of these studies described improvements in symptoms. Two of the three studies examining NMES in MUI elicited improved PFM strength, and two achieved statistical significance (mean increase=14.2–17.7 cmH2O, P<0.05). All three studies showed improvements in symptoms. There were inadequate data to allow conclusions to be drawn about the role of NMES in UUI. The clinical evidence supports the use of NMES, and the methodological irregularities in the literature are unlikely to obviate the study conclusions. However, the lack of subgroup analysis for baseline demographics or PFM strength preclude identifying the groups most likely to benefit from NMES, and call the guidelines’ limitation to a low MOS grade into question. Future research requires a multicentre randomized controlled trial of NMES in patients with UI, and subgroup analysis of PFM strength.