Older women with urge urinary incontinence (UUI) display two distinct patterns of brain reaction to bladder filling, which can predict their response to pelvic floor muscle training (PFMT), according to a study published in the Journal of Urology.

The mechanisms underlying UUI are not well understood, although they are often attributed to detrusor overactivity. This lack of understanding has retarded the development of effective treatments for UUI, and those that are available are not curative. PFMT is recommended for behavioural treatment, but urodynamic factors are not predictors of PFMT response, nor do they mediate the effect. Thus, central mechanisms of urinary control have now come under the spotlight.

62 women aged >60 years, who were functionally intact with ≥5 UUI episodes per week were included in the study, with 11 continent controls recruited under the same criteria. Women kept a 3-day bladder diary, received urodynamic assessment and functional brain imaging (fMRI) both before and after an 8–12-week course of PFMT. Those who reported a ≥50% reduction in incontinence episodes were deemed responders.

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PFMT reduced the mean frequency of UUI episodes from 3.5 to 1.9 per 24 h, reflecting a change of 3.5 to 1.9 episodes in responders, versus 3.5 to 3.0 in nonresponders. 28 women (46%) were deemed responders. PrePFMT fMRI showed a weak brain reaction in normal controls, but activation of the dorsal anterior cingulate cortex/supplementary motor area (dACC/SMA) and deactivation of the medial prefrontal cortex (mPFC) in women with UUI. When these women were stratified according to their eventual response to PFMT, it became clear that responders displayed activation of the dACC/SMA and insula, whereas nonresponders exhibited deactivation of the mPFC and part of the posterior brain. PostPFMT fMRI showed small changes in both responders and nonresponders, with mPFC deactivation becoming significant in the responders group and dACC/SMA activation significantly smaller after treatment.

...mPFC changes mediate the PFMT response, increasing executive control of the lower urinary tract

The authors suggest that the differences in brain activation between responders and nonresponders reflect their different response to the threat of incontinence. PrePFMT, nonresponders react to bladder filling with strong mPFC deactivation, likely demonstrating a willed decision to suppress voiding, whereas those who respond to therapy activate the dACC and SMA, which is likely accompanied by urgency and sphincter tightening, temporarily averting leakage. The response is not seen in healthy controls. Changes in the brain activation of responders postPFMT are towards that of normal controls, suggesting compensation to the reduction in UUI severity. However, the trend towards de novo mPFC deactivation is towards abnormality, suggesting that mPFC changes mediate the PFMT response, increasing executive control of the lower urinary tract.

This increased understanding of the neural mechanisms involved in UUI confirms the belief that a population of women with therapy-resistant UUI exists. These women need a treatment option that is better targeted to the underlying abnormality of their disorder.