Houston M, Dias N, Peng Y, et al. Gamma-band intermuscular connectivity is associated with increased neural drive to pelvic floor muscles in women with interstitial cystitis/bladder pain syndrome J Urol. 2023;210(3):465-471.

Study Need and Importance

Patients suffering from chronic pelvic pain conditions such as interstitial cystitis/bladder pain syndrome (IC/BPS) can exhibit pelvic floor muscle (PFM) dysfunction including elevated activity at rest. While an abnormally elevated neural drive has previously been identified in IC/BPS patients, further efforts to characterize this phenomenon have not directly assessed common shared neural input to the PFM, but rather cortical correlates via functional neuroimaging. Intermuscular connectivity (IMC) of the PFM is one way to quantify and assess impaired neural drive in a more direct fashion.

What We Found

The gamma-band IMC between the left and right sides of the PFMs was found to be significantly different for healthy controls when contrasting the resting and contraction conditions, but no such difference was identified in IC/BPS patients (see Figure). This phenomenon was accompanied by an expectedly higher than normal resting root mean squared amplitude in patients. Other typical frequency bands (alpha and beta frequency-bands) associated with sensorimotor paradigms were unremarkable.

Figure. Visual summary. A, Vaginal probe and high-density surface electromyography (HD-sEMG) grid with 2D mapping of resting pelvic floor muscle amplitude used to identify peak activation on the left and right sides of the pelvic floor musculature. B, Signals from areas previously determined for intermuscular connectivity analysis. C, Comparison of average gamma-band intermuscular connectivity across rest and contraction conditions for both groups. Dashed horizontal line indicates zero.

Limitations

Study limitations include limited sample size (N=15) and data length for connectivity analysis, although statistical significance was still identified across groups. Further studies are needed to evaluate the negative consequences of lower urinary tract symptoms in general on IMC. Additionally, the functional interactions between the PFM and other synergistically coactive muscles in the abdomen and other supporting muscles should be explored.

Interpretations for Patient Care

IMC is an easily calculable and readily deployable myoelectric biomarker for clinical use. Physicians can benefit from the methodology and results of this study by using IMC to determine whether a patient’s case of chronic pelvic pain involves neurogenic PFM dysfunction or not, which in turn may influence the decision-making process of differential diagnoses and ultimately treatment plans. For example, patients with abnormal PFM IMC may benefit more from myofascial therapy targeting PFM myofascial pain, whereas those patients with normal IMC may respond better to movement pattern training.