Patients and the ProPep AdvantageThe Role of Somatic Nerves in Sexual Function & Continence
It is common knowledge that literature reports up 38% - 40% of patients are impotent [6] and up to 20% - 44% are incontinent at 12 months following “successful” nerve-sparing, robotic-assisted, radical prostatectomy [1]. It is also well known that nerve sparing (neurovascular bundle (NVB) sparing), as it is performed today, is primarily an autonomic nerve sparing surgical technique. What is less well known is the role somatic nerves play in sexual function and continence (see chart below). Specifically in regard to sexual function, it is typically not well understood is that penile erection is a two phase process – one parasympathetic nerve-mediated and one somatic nerve-mediated.
- The initial or vascular phase is a parasympathetic nerved-mediated event which involves vasodilation of the penile arteries; the filling of the corpus cavernosa; and subsequent compression of the penile veins resulting in penile tumescence.
- The second or muscular phase is a somatic nerve-mediated event which involves the contraction of the bulbospongiosus and ischiocavernosus muscles which further compresses the deep dorsal vein of the penis and compresses the crux of the penis which together result in full tumescence and penile rigidity.
What is also not well understood is the fact that these critical somatic nerves, that lie outside the NVB, vary significantly in their course through the pelvis (see footnotes [2,3,4]). So much so that anatomical landmarks are not reliable in identifying where they are.
Muscles Innervated by the Perineal Nerve
MuscleBulbospongiosus
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Course & InsertionSurrounds lateral aspects of bulb of penis and most proximal part of body of penis, inserting into perineal membrane, dorsal aspect of corpora spongiosum and cavernosa, and fascia of bulb of penis.
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InnervationMuscular (deep) branch of perineal nerve, branch of pudendal nerve (S2–S4)
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Main Action(s)Compresses bulb of penis to expel last drops of urine/semen.
Assists erection by compressing outflow via deep dorsal vein and by pushing blood from bulb into body of penis. [5] |
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Ischiocavernosus
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Embraces crus of penis, inserting onto inferior and medial aspects of crus and to perineal membrane medial to crus.
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Muscular (deep) branch of perineal nerve, branch of pudendal nerve
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Maintains erection of penis by compressing deep dorsal vein and pushing blood from root of penis into body of penis.
Increases intracavernosal pressure 3 – 5 fold. Elevates penis past horizontal position and pulls penis against ischial tuberosity to assist vaginal penetration. [2,3] |
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External urethral sphincter
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Surrounds urethra superior to perineal membrane
Also ascends anterior aspect of prostate |
Muscular (deep) branch of perineal nerve, branch of pudendal nerve (S2–S4)
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Compresses urethra to maintain urinary continence.
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Levator ani
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Forms the main part of the pelvic diaphragm, the cranial layer of the pelvic floor.
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Perineal nerve; inferior rectal nerve, branches of pudendal nerve.
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Controls opening and closing of the levator hiatus. By this means, plays a crucial role in the preservation of urinary and bowel continence.
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1Sabine Geiger-Gritsch, Wilhelm Oberaigner, Nikolai, et al. Patient-Reported Urinary Incontinence and Erectile Dysfunction Following Radical Prostatectomy: Results from the European Prostate Centre Innsbruck. Urologia Internationalis. 2015; 419-427. DOI: 10.1159/000369475.
2 Zvara P, Carrier S, Kour N-W, Tanagho EA. The detailed neuroanatomy of the human striated urethral sphincter. BJU. 1994; 74: 182 – 187.
3 Akita K, Sakamoto H, Sato T. Origins and courses of the nervous branches to the male urethral sphincter. Surg Radiol Anat. 2003; 25: 387 – 392.
4 Schraffordt SE, Tjandra JJ, Eizenberg N, Dwyer PL. Anatomy of the pudendal nerve and its terminal branches: a cadaver study. ANZ J. Surg. 2004: 74: 23 – 265 Lavoisier P, Proulx J, Courtois F, De Carufel F, Durand L-G. Relationship between muscle contractions, penile tumescence, and penile rigidity during nocturnal erections. J Urol. 1988 Jan; 139: 176 -9.
5 Zvara P, Carrier S, Kour N-W, Tanagho EA. The detailed neuroanatomy of the human striated urethral sphincter. BJU. 1994; 74: 182 – 187.
6 Rafael F. Coelho, M.D., Bernardo Rocco, M.D., Manoj B. Patel, M.D., et al. Retropubic, Laparoscopic, and Robot-Assisted Radical Prostatectomy: A Critical Review of Outcomes Reported by High-Volume Centers. JOURNAL OF ENDOUROLOGY Vol. 24, No.12, December 2003-2015.
Dr. Randy Fagin presentation at 2013 Prostate Cancer World Congress