Concentric needle quantitative electromyography of pubovisceralis muscle group: Normative data from asymptomatic nulliparous women

The muscles of the pelvic floor closest to the vaginal opening are subject to the greatest degree of stretch during vaginal childbirth. We aim to define normative quantitative electromyography parameters for the pubovisceralis (PV) muscle in nulliparous women, and compare them with the external anal sphincter (EAS). Methods: In 31 asymptomatic nulliparous women, concentric needle electromyography of the PV and the EAS was performed. Multi-motor unit action potential and interference pattern algorithms were used to obtain quantitative electromyography parameters. We used paired t tests to compare PV and EAS parameters. Results: The motor units for the PV were of greater duration (P < 0.002) and had more turns (P = 0.03) than the paired motor units in the EAS. The EAS demonstrated more turns/s (P = 0.02), greater activity (P = 0.01), and more short segments (P = 0.009) than the PV. Conclusions: The PV has longer and more complex motor units than the EAS. This knowledge continues to improve our ability to detect neuropathic changes in this vulnerable muscle area after childbirth or in women with pelvic floor dysfunction. In addition, the PV muscle group appears less responsive to requests for increased neuromuscular activity than the EAS. This needs to be further evaluated, as it may be associated with understanding which portion of the muscle functionally shortens to maintain the closure of the levator hiatus.