Shafik A, Mostafa R M, Shafik A A, El-Sibai O
Cairo University, Cairo.
Int Urogynecol J Pelvic Floor Dysfunct. 2002;13(5):294-8. doi: 10.1007/s001920200064.
The bulbocavernosus muscle (BCM) surrounds the vaginal introitus and covers the vestibular bulb. Its role in erection is known. However, as it surrounds the vaginal introitus, it may also have a role in intravaginal pressure regulation and in the pathogenesis of uterovaginal prolapse. We investigated the effect of increased intra-abdominal pressure (IAP) on the BCM, aiming to assess its possible function in supporting the uterus, vagina and anorectum. The intrarectal (representative of the IAP) and intravaginal pressures were measured by manometric catheters in 19 healthy women volunteers (mean age 46.2 +/- 10.4 years). The EMG activity of the BCM and its response to straining at different pressures were recorded by a concentric needle electrode. Two types of straining were tested: sudden momentary and slow sustained. The procedure was repeated in 11 of the women after individual anesthetization of the BCM, rectum and vagina. Sudden straining (coughing) produced a significant increase in intrarectal ( P<0.0001) and intravaginal ( P<0.0001) pressure as well as BCM EMG activity. Slow straining effected a similar but lower response: the BCM responded gradually with pressure elevation, whereas the latency exhibited a gradual decrease. The BCM did not react to straining after individual anesthetization of the BCM, vagina and rectum, but did respond to saline administration. The results were reproducible. BCM contraction on straining postulates a reflex relationship, which we call the 'straining-bulbocavernosus reflex'. We hypothesized that this reflex is evoked by straining and results in BCM contraction and closure of the vaginal introitus. The vagina is believed to become a closed cavity, counteracting the increased intra-abdominal pressure and the uterine tendency to prolapse. The high pressure in the closed vaginal cavity presumably supports the rectovaginal septum against the high intrarectal pressure, and is suggested to share in the prevention of rectocele. The role of BCM in the pathogenesis of uterovaginal prolapse and rectocele needs further study.
球海绵体肌（BCM）围绕阴道口并覆盖前庭球。其在勃起中的作用已为人所知。然而，由于它围绕阴道口，它可能在阴道内压力调节以及子宫阴道脱垂的发病机制中也发挥作用。我们研究了腹内压（IAP）升高对球海绵体肌的影响，旨在评估其在支撑子宫、阴道和直肠方面的可能功能。通过测压导管在19名健康女性志愿者（平均年龄46.2±10.4岁）中测量直肠内（代表腹内压）和阴道内压力。通过同心针电极记录球海绵体肌的肌电图活动及其在不同压力下对用力的反应。测试了两种类型的用力：突然瞬间用力和缓慢持续用力。在对球海绵体肌、直肠和阴道进行个体麻醉后，对11名女性重复了该过程。突然用力（咳嗽）导致直肠内压力（P<0.0001）和阴道内压力（P<0.0001）以及球海绵体肌肌电图活动显著增加。缓慢用力产生了类似但较低的反应：球海绵体肌随着压力升高逐渐反应，而潜伏期逐渐缩短。在对球海绵体肌、阴道和直肠进行个体麻醉后，球海绵体肌对用力没有反应，但对注射生理盐水有反应。结果具有可重复性。用力时球海绵体肌收缩假定存在一种反射关系，我们称之为“用力 - 球海绵体反射”。我们假设这种反射是由用力引起的，导致球海绵体肌收缩和阴道口闭合。阴道被认为变成一个封闭的腔，抵消腹内压升高和子宫脱垂的趋势。封闭阴道腔内的高压大概支撑直肠阴道隔抵抗直肠内的高压，并被认为有助于预防直肠膨出。球海绵体肌在子宫阴道脱垂和直肠膨出发病机制中的作用需要进一步研究。
