Effects of bilateral levator ani nerve injury on pelvic support in the female squirrel monkey

Alterations in pelvic floor muscles and pelvic organ support by pregnancy and vaginal delivery in squirrel monkeys

“…Later, at 4 months postpartum, portions of this injury may be repaired and portions may be modified with a high content of fat or connective tissue leading to MR changes. We have previously reported an evidence for this effect using histological evaluations in animals euthanized following MR where longer term injury of the levator ani muscles had been induced by nerve injury [15]. In this cohort of animal, no evidence of pelvic organ prolapse was observed during perineal inspection under anesthesia at the time of the MRI examination.…”

“…A bony reference line was created from the anterior aspect of the pubic symphysis to the anterior aspect of the first tail vertebra [15]. The bladder neck position in the relaxed state and with abdominal pressure descended ( p <0.04) relative to the reference line following vaginal delivery (Fig.…”

“…A dynamic series (using 2D FLASH with TR 6.22, TE 2.16, and flip angle of 10° gradient echo) of images was obtained during 25 s while inflating the cuff with a sufficient volume of air to reproduce prolapse as evaluated by perineal exam, if present, or voiding of bladder contents [15]. During this dynamic series, 20 sagittal images along the midline were obtained to evaluate the change of position of the bladder neck and cervix relative to bony landmarks as previously reported [15]. Animals were visually observed for motion of arms, feet, and tail as a monitor of sedation status during the entire MRI process.…”

“…Recording and analysis of images using 3D-Doctor software has been established in our laboratory with good inter-observer correlations for pelvic floor muscle volume measures [14]. A bony reference line was created from the anterior aspect of the pubic symphysis to the anterior aspect of the first tail vertebra [15]. The position of the bladder neck and cervix relative to this reference line in millimeter was measured as an objective description of the degree of prolapse of these pelvic structures.…”

The Role of Altered Connective Tissue in the Causation of Pelvic Floor Symptoms

“…One theory says that an important cause of prolapse and pelvic floor dysfunction is likely to be partial denervation (Swash et al 1985, Smith et al 1989). But Pierce et al (2008) demonstrated in nulliparous monkeys that bilateral transection of the levator ani nerve resulted in atrophy of denervated levator ani muscles but not in failure of pelvic support. This indicates that connective tissue components could compensate for weakened pelvic floor muscles.…”