The aetiology of sensory changes seen in women with pelvic floor dysfunction

Abstract

The pathophysiology of pelvic floor dysfunction is incompletely understood but involves injury to pudendal motor nerves during childbirth. Pelvic organ prolapse (POP), urinary and sexual dysfunction are associated with pudendal sensory nerve impairment. I hypothesised this sensory injury also occurs during childbirth and aimed to investigate the impact of childbirth on female genital sensation. I included an evaluation of sensation of vaginal tone, by developinga protocol for quantitative sensory testing (QST) of stretch sensation for Aα and Aβ nerves at the vagina and introitus in 100 non-pregnant women with good reproducibility. Logistic regression found an association between age and sensation, and this was used to create nomograms. Next, 150 pregnant women underwent vibration QST at the vagina and clitoris (Aβ nerves), stretch QST at the vagina and introitus (Aα and Aβ nerves), prolapse examination and symptom questionnaire. This was repeated at 8-12 weeks postnatal (PN1) and six months postnatal (PN2). Vibration sensation in pregnancy was reduced but improved postnatally. Stretch sensation was normal in pregnancy, deteriorated at PN1 but recovered by PN2. Vibration sensation in women delivered by caesarean section (CS) at PN1 showed greater improvement than following a normal (NVD) or instrumental delivery. By PN2 the NVD group were comparable to the CS group, but the same recovery was not evident in the instrumental group. There was a transient deterioration in stretch sensation at PN1 after a vaginal birth, with no difference at PN2 across mode of delivery. Postnatal pudendal sensorineuropathy was associated with objective POP, urinary, bowel and sexual dysfunction. Finally, a pilot study was performed to evaluate temperature and vibration QST with neurohistology in 16 women with POP and three controls. Vaginal mucosa was immunostained for neural markers. There was no association, however this is likely to represent the small sample size in this exploratory study. In conclusion, measurement of stretch sensation thresholds of the vaginal and introitus is valid and repeatable. Whilst it appears vaginal birth is associated with injury to Aα and Aβ nerves compared to CS, the greatest impact on Aβ nerves was pregnancy itself with all modes of delivery improving compared to AN values. Neurohistology of vaginal mucosa is feasible and can be correlated with clinical neurophysiology.

Date of Award	1 Aug 2020
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Fiona Reid (Supervisor) & Jenny Myers (Supervisor)