Managing perineal trauma after childbirth

Webb et al have raised an important issue regarding post- partum morbidity, and the need for early identification and treatment. Important inter-partum neurological injury was not high-lighted.
The pudendal nerve is frequently compromised during child birth, with incidence of 32% of all vaginal deliveries being reported [1]. 20% of vaginal births have symptoms requiring medical intervention at 6 weeks, with 80% resolving physiologically [2].
The pudendal nerve emanates from Onuf`s nucleus, and is made up of the S2,3 and 4 nerve roots. It travels a circuitous course into the pelvis via the greater sciatic foramen, before returning through the lesser sciatic foramen, and travelling through Alcock`s Cannal, as it splits into its terminal divisions: the rectal branch [ external anal sphincter ]; the perineal branch [urethral sphincter] and the clitoral branch [ perineal sensation, and sexual function].The nerve can be injured at any location along its route, but is frequently injured during the second stage of labour at the ischial spine. Injury to the nerve can result in flatal and faecal incontinence, urinary incontinence as well as perineal pain and sexual dysfunction. 4 patterns of neuropathy have been reported [2], with patients presenting in the first 3 months or frequently many decades after child birth. This second group often presents after the menopause. This is thought to be due to further age related atrophy, which has been accelerated by a hormonal loss, on a previously compromised pudendal nerve sphincter complex, resulting in the late onset symptoms. Occasionally other pathologies are identified as associated aetiologies [Diabetes Mellitus, Multiple Sclerosis; Multi System Atrophy, Spondylolisthesis and Lumbar-Sacral spine pathology]
Over the past decade the assessment of this nerve has advanced to assess the full length of the nerve with quantitative needle EMG to the sphincter muscles, as well as the Clitoral Anal Sacral Reflex [3]. This methodology is now the recommended standard [4]. Early detection of a pudendal nerve injury will ensure appropriate action takes place before muscle atrophy becomes critical. Continence seems to be maintained at a recruitment pattern of 55% or greater. Needle EMG allows this important kinesiological measurement to be made in the sphincter muscles. This is essential if deciding on surgical intervention, as a denervated muscle or atrophic muscle .will not recover in the same way as a muscle with normal neurological function
Once a nerve injury has been established treatment includes: targeted rehabilitation of the atrophic muscles. Neuromodulation either directly to the sacral plexus, or remotely using the tibial nerve [5]. Oral medication such as pregablin and sildenafil can be used for pain, as well as nerve blocking injection .Growth hormone and gene therapy have been considered as a treatment option for the atrophic muscles [6], but stem cell therapy looks certain to have a role in improving the atrophic sphincter muscles.
Early detection is an essential component for a good outcome, and hence specific questions should be asked of the mother relating to pudendal nerve injury symptoms at the 3 month check-up. There is also current work being undertaken to specifically monitor the pudendal nerve inter-partum, and thus identify the problem at source .
When considering cases of post-partum morbidity, the pudendal nerve should always be considered

References

1.Abnormalities in central and peripheral nerve conduction in patients with anorectal incontinence. J R Soc Med. Apr 1985; 78(4): 294–300.S J Snooks, M Swash, and M M Henry
Fitzpatrick O Brien
2 Fitzpatrick M, O’Brien C, O’Connell PR, O’Herlihy C. Patterns of abnormal pudendal nerve conduction associated with postpartum faecal incontinence. Am J Obstet Gynecol 2003;189(3):730-735
3.Pudendal neuropathy is best determined by full neurophysiological assessment.
Am J Obstet Gynecol. 2004 Nov;191(5):1836 , O’Brien C, O’Connell PR, O’Herlihy C.
4 Executive Summary: The International Consultation on Incontinence 2008--Comittee on: "Dynamic Testing"; for urinary or fecal incontinence. Part 3: Anorectal physiology studies.Rosier PF, Hosker GL, Szabó L, Capewell A, Gajewski JB, Sand PK; International Consultation on Incontinence 2008 Committee on Dynamic Testing.
Neurourol Urodyn. 2010;29(1):153-8.

5 Peters, K. M., Carrico, D. J., MacDiarmid, S. A., Wooldridge, L. S., Khan, A. U., McCoy, C. E., Franco, N. and Bennett, J. B. (2013), Sustained therapeutic effects of percutaneous tibial nerve stimulation: 24-month results of the STEP study. Neurourol. Urodyn., 32: 24–29.

6 Effects of IGF-I gene therapy on the injured rat pudendal nerve.
J M Kerns;S Shott,L Brubaker;K Sakamoto;J T Benson ;A E Fleischer;M E Coleman
International Urogynecology Journal 03/2003; 14(1):2-7;