Up to 85% of women with interstitial cystitis/bladder pain syndrome (IC/BPS) have pelvic floor dysfunction and hypertonicity. Current evaluation methodologies lack objective measures of pelvic floor muscle (PFM) activity. We examined the ability of utilizing intravaginal high-density surface electromyography (HD-sEMG) to quantitatively, objectively and non-invasively map PFM activity and innervation zone (IZ) locations in IC/BPS patients.
Fifteen IC/BPS women and fifteen controls underwent two sessions of digital pelvic exams and HD-sEMG assessments. The root mean squared (RMS) amplitude of HD-sEMG was first calculated, and the resting RMS ratio was then calculated by normalizing the resting EMG RMS to the peak EMG amplitude during maximum voluntary contraction. IZ distributions were obtained from decomposed HD-sEMG signals. The correlation between the RMS ratio and IC/BPS symptom scores and PFM alignment were investigated in IC/BPS patients and healthy controls.
IC/BPS Women demonstrated significantly increased resting RMS ratios compared to controls (0.155±0.048 vs. 0.099±0.041, p=0.0019). Significant correlations were found between resting RMS ratio and patient-reported pain (rs=0.523, p=0.003), IC symptom (rs=0.521, p=0.003) and problem indices (rs=0.60, p<0.001). In addition, women with IC/BPS were more likely to have shortened PFMs (80% (12/15) vs. 13.3% (2/15), p<0.01). Women with shortened PFMs demonstrated significantly higher resting RMS ratio compared to those with normal PFM length (0.155±0.046 vs. 0.107±0.040, p=0.0058).
Intravaginal HD-sEMG offers an objective and quantitative strategy to non-invasively assess PFM dysfunction in women with IC/BPS. Abundant spatiotemporal muscle activity information captured by HD-sEMG allows for mapping IZ distributions for major PFMs.
The Journal of urology. 2020 Jul 06 [Epub ahead of print]
Nicholas Dias, Chuan Zhang, Theresa Spitznagle, H Henry Lai, Yingchun Zhang
University of Houston, Department of Biomedical Engineering, Houston, Texas., Department of Physical Therapy, Washington University School of Medicine, St Louis, Missouri., Departments of Surgery (Urology) and Anesthesiology, Washington University School of Medicine, St Louis, Missouri.