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Evoked cavernous activity: neuroanatomic implications.

Yilmaz U, Vicars B, Yang CC - Int. J. Impot. Res. (2009)

Bottom Line: All the PS patients had reproducible ECA and SSRs, both preoperatively and postoperatively.There was no difference in the latency and amplitude measurements of ECA and SSRs in the postoperative compared with that of the pre-operative period (P>0.05).In conclusion, ECA is absent in men with SCI above the sympathetic outflow to the genitalia.

View Article: PubMed Central - PubMed

Affiliation: Department of Urology, University of Washington, Seattle, WA 98195-6510, USA.

ABSTRACT
We investigated the autonomic innervation of the penis by using evoked cavernous activity (ECA). We recruited seven men with thoracic spinal cord injury (SCI) and sexual dysfunction, and six men who were scheduled to have pelvic surgery (PS), specifically non-nerve-sparing radical cystoprostatectomy. In the PS patients, ECA was performed both pre- and postoperatively. The left median nerve was electrically stimulated and ECA was recorded with two concentric electromyography needles placed into the right and left cavernous bodies. We simultaneously recorded hand and foot sympathetic skin responses (SSRs) as controls. In the SCI group, all but one patient had reproducible hand SSRs. None of these patients had ECA or foot SSRs. All the PS patients had reproducible ECA and SSRs, both preoperatively and postoperatively. There was no difference in the latency and amplitude measurements of ECA and SSRs in the postoperative compared with that of the pre-operative period (P>0.05). In conclusion, ECA is absent in men with SCI above the sympathetic outflow to the genitalia. In men, after radical pelvic surgery, ECA is preserved, indicating the preservation of sympathetic fibers.

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The surgical field of a radical cystoprostatectomy is schematically presented. Autonomic fibers innervating the penis are known to travel on the postero-lateral aspects of the prostate gland. Based on the ECA responses, we posit that the sympathetic fibers lie lateral to the area of resection, and thus are spared, as compared to the more medial parasympathetic fibers, which are resected.
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Figure 3: The surgical field of a radical cystoprostatectomy is schematically presented. Autonomic fibers innervating the penis are known to travel on the postero-lateral aspects of the prostate gland. Based on the ECA responses, we posit that the sympathetic fibers lie lateral to the area of resection, and thus are spared, as compared to the more medial parasympathetic fibers, which are resected.

Mentions: The persistence of ECA following the radical pelvic surgery can possibly be explained by the highly variable course of the parasympathetic and sympathetic fibers through the pelvic plexus to the erectile tissue. One study showed the distribution of autonomic fibers to be wider than expected, extending posterolaterally on the rectal wall, separate from the neurovascular bundle immediately adjacent to the prostate.7 It was also suggested that the cavernous nerve had interindividual variations in its course near the apex of the prostate and the surgically defined neurovascular bundle is often likely to differ from the actual axial course of the cavernous nerve fibers passing through the pararectal space and the rectourethral muscle. Therefore, an axial course of the cavernous nerve fibers lateral to the surgical field seemed to provide “unexpected nerve-sparing” after non-nerve-sparing radical prostatectomy, because the fibers are likely to be located outside the surgical margin.8 Terada et al reported that of 16 instances in which the neurovascular bundle was macroanatomically resected, a positive intracavernous pressure increase after intraoperative electrical stimulation was detected in 5 cases (31%).9 We think the persistence of ECA in the subjects in our study also suggests a lateral location of the sympathetic nerves to the penis, away from the main surgical site, thereby preserving sympathetically mediated neural activity (Figure 3). The autonomic fibers in the neurovascular bundle immediately adjacent to the prostate are likely primarily parasympathetic fibers. This finding of differentially located autonomic fibers may also explain erectile dysfunction with shortening of penile length following non-nerve-sparing radical prostatectomy procedures.10 Injury of parasympathetic fibers but preservation of more laterally located sympathetic fibers can cause an autonomic imbalance within the penis, resulting in the dominance of sympathetically-mediated smooth muscle contraction of the corpus cavernosum, and subsequent erectile dysfunction and penile shortening. All these findings further support the concept that the cavernous nerve is not a singular structure within a neurovascular bundle, but a “net” or “layer” of fibers extending from the anterior surface of the prostate, and extending posterolaterally to the lateral rectal wall.11 Another explanation for the presence of ECA can be based on an alternate route of penile sympathetic innervation, such as through the dorsal nerve of the penis.12


Evoked cavernous activity: neuroanatomic implications.

Yilmaz U, Vicars B, Yang CC - Int. J. Impot. Res. (2009)

The surgical field of a radical cystoprostatectomy is schematically presented. Autonomic fibers innervating the penis are known to travel on the postero-lateral aspects of the prostate gland. Based on the ECA responses, we posit that the sympathetic fibers lie lateral to the area of resection, and thus are spared, as compared to the more medial parasympathetic fibers, which are resected.
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Related In: Results  -  Collection

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Figure 3: The surgical field of a radical cystoprostatectomy is schematically presented. Autonomic fibers innervating the penis are known to travel on the postero-lateral aspects of the prostate gland. Based on the ECA responses, we posit that the sympathetic fibers lie lateral to the area of resection, and thus are spared, as compared to the more medial parasympathetic fibers, which are resected.
Mentions: The persistence of ECA following the radical pelvic surgery can possibly be explained by the highly variable course of the parasympathetic and sympathetic fibers through the pelvic plexus to the erectile tissue. One study showed the distribution of autonomic fibers to be wider than expected, extending posterolaterally on the rectal wall, separate from the neurovascular bundle immediately adjacent to the prostate.7 It was also suggested that the cavernous nerve had interindividual variations in its course near the apex of the prostate and the surgically defined neurovascular bundle is often likely to differ from the actual axial course of the cavernous nerve fibers passing through the pararectal space and the rectourethral muscle. Therefore, an axial course of the cavernous nerve fibers lateral to the surgical field seemed to provide “unexpected nerve-sparing” after non-nerve-sparing radical prostatectomy, because the fibers are likely to be located outside the surgical margin.8 Terada et al reported that of 16 instances in which the neurovascular bundle was macroanatomically resected, a positive intracavernous pressure increase after intraoperative electrical stimulation was detected in 5 cases (31%).9 We think the persistence of ECA in the subjects in our study also suggests a lateral location of the sympathetic nerves to the penis, away from the main surgical site, thereby preserving sympathetically mediated neural activity (Figure 3). The autonomic fibers in the neurovascular bundle immediately adjacent to the prostate are likely primarily parasympathetic fibers. This finding of differentially located autonomic fibers may also explain erectile dysfunction with shortening of penile length following non-nerve-sparing radical prostatectomy procedures.10 Injury of parasympathetic fibers but preservation of more laterally located sympathetic fibers can cause an autonomic imbalance within the penis, resulting in the dominance of sympathetically-mediated smooth muscle contraction of the corpus cavernosum, and subsequent erectile dysfunction and penile shortening. All these findings further support the concept that the cavernous nerve is not a singular structure within a neurovascular bundle, but a “net” or “layer” of fibers extending from the anterior surface of the prostate, and extending posterolaterally to the lateral rectal wall.11 Another explanation for the presence of ECA can be based on an alternate route of penile sympathetic innervation, such as through the dorsal nerve of the penis.12

Bottom Line: All the PS patients had reproducible ECA and SSRs, both preoperatively and postoperatively.There was no difference in the latency and amplitude measurements of ECA and SSRs in the postoperative compared with that of the pre-operative period (P>0.05).In conclusion, ECA is absent in men with SCI above the sympathetic outflow to the genitalia.

View Article: PubMed Central - PubMed

Affiliation: Department of Urology, University of Washington, Seattle, WA 98195-6510, USA.

ABSTRACT
We investigated the autonomic innervation of the penis by using evoked cavernous activity (ECA). We recruited seven men with thoracic spinal cord injury (SCI) and sexual dysfunction, and six men who were scheduled to have pelvic surgery (PS), specifically non-nerve-sparing radical cystoprostatectomy. In the PS patients, ECA was performed both pre- and postoperatively. The left median nerve was electrically stimulated and ECA was recorded with two concentric electromyography needles placed into the right and left cavernous bodies. We simultaneously recorded hand and foot sympathetic skin responses (SSRs) as controls. In the SCI group, all but one patient had reproducible hand SSRs. None of these patients had ECA or foot SSRs. All the PS patients had reproducible ECA and SSRs, both preoperatively and postoperatively. There was no difference in the latency and amplitude measurements of ECA and SSRs in the postoperative compared with that of the pre-operative period (P>0.05). In conclusion, ECA is absent in men with SCI above the sympathetic outflow to the genitalia. In men, after radical pelvic surgery, ECA is preserved, indicating the preservation of sympathetic fibers.

Show MeSH
Related in: MedlinePlus