Entubulization repair of severed cavernous nerves in the rat resulting in return of erectile function

Curcumin slow-release membrane promotes erectile function and penile rehabilitation in a rat model of cavernous nerve injury

Male erectile dysfunction (ED) caused by cavernous nerve injury is a common complication of pelvic surgery, radiotherapy, transurethral surgery or other operations. However, clinical treatment for iatrogenic or traumatic male ED is difficult and not satisfactory. Many studies have shown that curcumin can promote the repair and regeneration of peripheral nerves; however, whether curcumin can rescue cavernous nerve injury is unknown, and the poor bioavailability of curcumin limits its application in vivo. Hence, the study was conducted. A curved slow-release membrane was produced, and the properties were examined. In addition, the effects of the curcumin slow-release membrane on cavernous nerve-injured SD rats were studied. We found that polylactic acid-glycolic acid-polyethylene glycol (PLGA-PEG) can be used as a good carrier material for curcumin, and curcumin-loaded PLGA-PEG membranes can effectively rescue the cavernous nerve in SD rats, restore the continuity of the cavernous nerve, and increase the expression of nNOS mRNA and proteins in penile tissue, which can improve the penile erectile function of injured SD rats, reduce the degree of penile tissue fibrosis, and effectively promote penis rehabilitation. The curcumin slow-release membrane is proposed to be a new therapeutic approach for penile rehabilitation of cavernous nerve injury.

3D Printed Personalized Nerve Guide Conduits for Precision Repair of Peripheral Nerve Defects

The treatment of peripheral nerve defects has always been one of the most challenging clinical practices in neurosurgery. Currently, nerve autograft is the preferred treatment modality for peripheral nerve defects, while the therapy is constantly plagued by the limited donor, loss of donor function, formation of neuroma, nerve distortion or dislocation, and nerve diameter mismatch. To address these clinical issues, the emerged nerve guide conduits (NGCs) are expected to offer effective platforms to repair peripheral nerve defects, especially those with large or complex topological structures. Up to now, numerous technologies are developed for preparing diverse NGCs, such as solvent casting, gas foaming, phase separation, freeze-drying, melt molding, electrospinning, and three-dimensional (3D) printing. 3D printing shows great potential and advantages because it can quickly and accurately manufacture the required NGCs from various natural and synthetic materials. This review introduces the application of personalized 3D printed NGCs for the precision repair of peripheral nerve defects and predicts their future directions.

Cavernous nerve reconstruction with autologous vein graft and platelet-derived growth factors

In this study, we investigated the feasibility of using autologous vein graft and platelet-derived growth factors to bridge transected cavernous nerve in a rat model. A short defect in the bilateral cavernous nerve was created and repaired with vein graft from the right jugular vein or vein graft plus platelet-derived growth factors. The 32 rats were divided into four groups, namely Group 1 - no repair as a negative control, Group 2 - vein graft alone, Group 3 - vein graft plus platelet-derived growth factors, and Group 4 - sham operation as a positive control. We evaluated nerve regeneration and functional recovery using retrograde tracing study with FluoroGold, Toluidine blue staining of cavernous nerve, and the intracavernous pressure at 3 months. Three months after surgery, rich FluoroGold-positive cells were observed in the sham and vein graft plus platelet-derived growth factors group, but very few were found in the no repair group. The number of myelinated axons of regenerated cavernous nerve and intracavernous pressure were increased obviously in the two vein graft groups, especially in the vein graft plus platelet-derived growth factors group. These findings confirm the feasibility of using autologous vein as guides for cavernous nerve regeneration, and the regeneration can be further enhanced when the vein is filled with platelet-derived growth factors.

Newer concepts in neural anatomy and neurovascular preservation in robotic radical prostatectomy

With more than 60% of radical prostatectomies being performed robotically, robotic-assisted laparoscopic prostatectomy (RALP) has largely replaced the open and laparoscopic approaches and has become the standard of care surgical treatment option for localized prostate cancer in the United States. Accomplishing negative surgical margins while preserving functional outcomes of sexual function and continence play a significant role in determining the success of surgical intervention, particularly since the advent of nerve-sparing (NS) robotic prostatectomy. Recent evidence suggests that NS surgery improves continence in addition to sexual function. In this review, we describe the neuroanatomical concepts and recent developments in the NS technique of RALP with a view to improving the “trifecta” outcomes.

Penile rehabilitation after radical prostatectomy: what the evidence really says

The pathophysiology of erectile dysfunction after radical prostatectomy (RP) is believed to include neuropraxia, which leads to temporarily reduced oxygenation and subsequent structural changes in penile tissue. This results in veno-occlusive dysfunction, therefore, penile rehabilitation programmes focus on tissue oxygenation. Animal studies support the use of phosphodiesterase type 5 inhibitors (PDE5Is) after cavernous nerve damage but results from human studies are contradictory. The largest study to date found no long-term effect of either daily or on-demand PDE5I administration after RP compared with placebo. The effects of prostaglandin and vacuum erection devices are questionable and high-quality studies are lacking. Better documentation for current penile rehabilitation and/or better rehabilitation protocols are needed. One must be careful not to repeat the statement that penile rehabilitation improves erectile function after RP so many times that it becomes a truth even without the proper scientific backing.

Animal models of erectile dysfunction (ED): potential utility of non-human primates as a model of atherosclerosis-induced vascular ED

Erectile dysfunction (ED) is a prevalent medical condition affecting 18 million men and their sexual partners in the United States alone. In the majority of patients, ED is related to alterations in the flow of blood to or from the penis. Undeniably, significant progress has been made in understanding the multifactorial mechanisms that modulate erectile capacity and predispose one to ED, and this, in turn, has led to the availability of more effective treatment options. Nonetheless, all current therapies have untoward side effects, and moreover, there are still no satisfactory treatments for many patients with ED. Further enhancements in the treatment of ED would logically result from both early intervention and more detailed mechanistic insight into the characteristics of the disease process per se. This fact underscores the importance of improved understanding of the initiation, development and progression of ED. However, to do so requires longitudinal studies on animal models that more closely approximate the corresponding clinical features and time course of human disease. The goal of this report is twofold. First, to provide a brief general overview of the applicability of commonly used animal models for the study of ED. The second and primary goal is to highlight the scientific rationale for using non-human primates to evaluate the impact of atherosclerosis-induced vascular disease on the penile and systemic circulatory systems. This latter goal seems especially relevant in light of the recent literature documenting a link between ED and systemic vascular disease, a finding that has major implications in an aging US male population consuming a high fat diet.

Advances in the study of the peripheral nervous system for erection in animals and humans

Introduction

Since Walsh first emphasized the importance of preserving the neurovascular bundle n to protect the cavernous nerve during pelvic surgery, patients' sexual life quality has dramatically improved. Today, nerve-sparing radical prostatectomy is the established gold standard for organ-confined prostate cancer patients. Recent technical advances in functional assessment such as intraoperative electrical stimulation have unveiled new anatomical features and physiological roles. Basic research has advanced understanding of cavernous nerve function, while molecular biology has uncovered the crucial role of neuronal nitric oxide in mediating erection, and has led to new treatments such as phosphodiesterase type-5 inhibitors. A recent focus in cavernous nerve research concerns the nerve distribution external to the neurovascular bundle. The cavernous nerves in humans appear to be distributed more widely beneath the lateral pelvic fascia than in other animals, and electrical stimulation studies suggest possible involvement of these nerves in erection. These findings have prompted new surgical techniques such as the "veil of Aphrodite", or "intrafascial nerve-sparing" procedures.

Materials and Methods

These recent anatomical and physiological studies in humans and animals and their impact are reviewed in this article.

Conclusions

Further investigation should stimulate future advances in strategies to preserve erectile function in RP patients.

Future sexual medicine physiological treatment targets

INTRODUCTION

Sexual function in men and women incorporates physiologic processes and regulation of the central and peripheral nervous systems, the vascular system, and the endocrine system. There is need for state-of-the-art information as there is an evolving research understanding of the underlying molecular biological factors and mechanisms governing sexual physiologic functions.

AIM

To develop an evidence-based, state-of-the-art consensus report on the current knowledge of the major cellular and molecular targets of biologic systems responsible for sexual physiologic function.

METHODS

State-of-the-art knowledge representing the opinions of seven experts from four countries was developed in a consensus process over a 2-year period.

MAIN OUTCOME MEASURES

Expert opinion was based on the grading of evidence-based medical literature, widespread internal committee discussion, public presentation, and debate.

RESULTS

Scientific investigation in this field is needed to increase knowledge and foster development of the future line of treatments for all forms of biological-based sexual dysfunction. This article addresses the current knowledge of the major cellular and molecular targets of biological systems responsible for sexual physiologic function. Future treatment targets include growth factor therapy, gene therapy, stem and cell-based therapies, and regenerative medicine.

CONCLUSIONS

Scientific discovery is critically important for developing new and increasingly effective treatments in sexual medicine. Broad physiologic directions should be vigorously explored and considered for future management of sexual disorders.

Udenafil enhances the recovery of erectile function and ameliorates the pathophysiological consequences of cavernous nerve resection

INTRODUCTION

Radical prostatectomy is the treatment of choice for prostate cancer patients. Despite the introduction of nerve-sparing surgical techniques, its success is not entirely guaranteed and the majority of patients report compromised erectile function following surgical procedures.

AIM

This study was performed to investigate the effect of repeated dosing of udenafil, a novel phosphodiesterase type 5 inhibitor, on penile hypoxia and fibrosis induced by bilateral cavernous nerve resection (BCNR) in rats.

METHODS

Thirty male Sprague-Dawley rats (300-320 g) were used in this study. The animals were divided into three groups; group I consisted of sham-operated animals (N = 10), animals in group II underwent BCNR alone (N = 10), and animals in group III were orally treated with 10 mg/kg udenafil b.i.d. for 8 weeks following BCNR (N = 10).

MAIN OUTCOME MEASURES

The expression of transforming growth factor-beta1, hypoxia-inducible factor-1 alpha, endothelial nitric oxide synthase, neuronal nitric oxide synthase, and endothelin B receptor in penile tissue was examined at gene level. Additionally, erectile function, measured by intracavernous pressure (ICP), and pathological changes in the corpus cavernosum were examined.

RESULTS

While fibrosis, apoptosis, and the expression of TGF-beta1, HIF-1 alpha, and ET(B) were significantly increased, and the expression of eNOS and nNOS were significantly decreased in group II, compared with the sham-operated animals, repeated dosing of udenafil significantly ameliorated these changes. Erectile function was profoundly impaired in animals that underwent BCNR alone, and udenafil treatment significantly attenuated this impairment as measured by ICP.

CONCLUSIONS

These results demonstrate that long-term administration of udenafil ameliorates penile hypoxia and fibrosis induced by cavernous nerve resection. This study also suggests the potential beneficial role of repeated dosing of udenafil in the recovery of erectile function in patients with neuronal erectile dysfunction.

Nerve Advancement with End-to-End Reconstruction after Partial Neurovascular Bundle Resection:A Feasibility Study

BACKGROUND AND PURPOSE

It is clear that some patients with prostate cancer require a total or partial neurovascular bundle (NVB) resection for oncologic safety to be guaranteed. Nerve grafting is an alternative for these patients to maintain erectile function; however, we report on a feasible option where the NVB is released, and both terminal nerve fibers are approximated; this is the "nerve advancement technique (NAT)."

PATIENTS AND METHODS

Since 2005, a total of 215 men aged 48 to 70 years (mean 59 years) with a Sexual Health Inventory for Men (SHIM) score of 22 have undergone robotic radical prostatectomy for cancer. We selected prospectively seven men to have NAT performed because of clinical high-risk criteria (serum prostate specific antigen [PSA] concentration >20 mg/dL, Gleason score = 8, and stage cT(2c) or higher), intraoperative criteria (difficulty separating the tissues around the prostate), and evidence of extracapsular extension (ECE) on magnetic resonance imaging. We performed unilateral partial resection, nerve advancement, and, finally, end-to-end anastomosis in six patients, whereas in one patient, we did a bilateral partial excision. We analyzed the results in terms of oncologic safety (positive surgical margins and PSA) and SHIM score after 18 months of follow-up.

RESULTS

Pathologic examination revealed stage T3 disease in six patients; one had a positive surgical margin. Two patients are receiving salvage radiotherapy for PSA relapse, and five continue to have undetectable PSA concentrations after a median follow-up of 20 months. Five of the seven men recovered erectile potency with or without a phosphodiesterase inhibitor, and their median SHIM score is 18.

CONCLUSIONS

We are encouraged by the initial results of NAT. The procedure may be an alternative for men who require extensive NVB dissection. However, further experience, longer follow-up, and independent trials are necessary.

Bilateral Cavernous Nerve Interposition Grafting During Radical Retropubic Prostatectomy: Memorial Sloan-Kettering Cancer Center Experience

PURPOSE

Cavernous nerve graft is an option for men requiring bilateral cavernous nerve resection for cancer control during radical prostatectomy. We determined the success rate and identified determinants of success of bilateral cavernous nerve grafting following resection of the 2 nerves during radical prostatectomy in patients who were potent preoperatively.

MATERIALS AND METHODS

We retrospectively reviewed the records of 44 consecutive patients who underwent bilateral nerve grafting from 1999 to 2004. Postoperative erectile function was defined as the achievement of erections satisfactory for intercourse with or without oral medication. We calculated cumulative erectile function recovery rates using Kaplan-Meier curves. The log rank test was used to compare variables affecting erectile function recovery with p <0.0083 considered significant after adjusting for the number of variables evaluated using the Bonferroni correction.

RESULTS

The overall 5-year cumulative recovery of erectile function permitting penetration was 34% and the rate of consistent penetration was 11%. None of the analyzed variables were significantly associated with recovery of postoperative erectile function, including patient age (p = 0.3), incomplete bilateral cavernous nerve resection (p = 0.045), sural nerve grafts compared to genitofemoral or ilioinguinal nerves as donor sites (p = 0.067), post-radiation salvage radical prostatectomy (p = 0.15), neoadjuvant hormone therapy (p = 0.7) and comorbidities (p = 0.15) or medications (p = 0.4) affecting EF.

CONCLUSIONS

Bilateral cavernous nerve grafts might be beneficial in select patients. A definitive answer awaits the performance of a multi-institutional, randomized, controlled trial.

Luminal fillers in nerve conduits for peripheral nerve repair

The use of nerve conduits as an alternative for nerve grafting has a long experimental and clinical history. Luminal fillers, factors introduced into these nerve conduits, were later developed to enhance the nerve regeneration through conduits. Though many luminal fillers have been reported to improve nerve regeneration, their use has not been subjected to systematic review. This review categorizes the types of fillers used, the conduits associated with fillers, and the reported performance of luminal fillers in conduits to present a preference list for the most effective fillers to use over specific distances of nerve defect.

Two-year outcome of unilateral sural nerve interposition graft after radical prostatectomy

OBJECTIVES

To study 41 men treated for prostate cancer with unilateral nerve-sparing radical prostatectomy and contralateral sural nerve grafting from January 2000 to September 2003.

METHODS

Patients were considered for sural nerve grafting if they were considered at high risk of extracapsular extension before or during surgery, were younger than 70 years of age with good preoperative erectile function, were sexually active, and had no significant risk factors for erectile dysfunction. Potency was assessed by patient-reported questionnaires, including the International Index of Erectile Function erectile domain and Rigiscan testing.

RESULTS

The mean follow-up was 27.4 +/- 14.5 months. At 24 months, 24 (63.2%) of 38 men had erections sufficient for intercourse, with or without phosphodiesterase type 5 inhibitor use. Four men had partial erections that were occasionally satisfactory (10.5%), and 10 men reported no sexual activity, no spontaneous erections, or partial erections unsatisfactory for intercourse (26.3%). In contrast, in a group of 49 men who underwent unilateral nerve-sparing prostatectomy without nerve grafting during the same period at our institution, 13 (26.5%) had rigid erections adequate for intercourse with or without phosphodiesterase type 5 inhibitor use at 24 months of follow-up.

CONCLUSIONS

At 24 months of follow-up, men who had undergone unilateral nerve-sparing prostatectomy with contralateral sural nerve interposition graft repair of a cut cavernosal nerve had a greater rate of return of erectile function than men undergoing unilateral nerve-sparing prostatectomy alone.

Neuromodulatory Therapy to Improve Erectile Function Recovery Outcomes After Pelvic Surgery

PURPOSE

Erectile dysfunction is a recognized, common adverse consequence of radical prostatectomy as well as various other pelvic surgeries. While a host of management options have been considered to decrease this complication, neuromodulatory therapy has recently been advanced as an intervention that may be applied for this purpose. We evaluated concepts regarding the neuropathic basis for erectile dysfunction following pelvic surgery, principles for establishing neuromodulatory therapy in this clinical context, evidence from preclinical studies supporting neuromodulatory approaches as a therapeutic strategy and the progress of early clinical developments in this field.

MATERIALS AND METHODS

The exercise principally consisted of a current literature search using the National Library of Medicine PubMed Services, a survey of recent abstract proceedings from national meetings relevant to the topic and an Internet online search for current information on federally and privately supported clinical trials specific to this topic. References were made to such key words as neuroprotection, nerve regeneration, nerve growth factors, neurotrophic factors, cavernous nerves, nerve guides and penile erection.

RESULTS

Basic science research and clinical studies support the concept that erectile loss after pelvic surgery is frequently related to neuropathic effects, resulting in penile vascular impairment. An assortment of neurobiological studies using rodent models of cavernous nerve injury have shown nerve reconstitutive actions for a host of neurotrophic substances, including classic neurotrophins, growth hormone, cytokines and atypical neurotrophic mediators. Clinical trials of several proposed neuroprotective and neurotrophic applications have been done or are in progress.

CONCLUSIONS

Erectile dysfunction is a well recognized and yet ineffectively averted complication of pelvic surgery. Neuromodulatory therapy offers a therapeutic approach for addressing the neuropathic changes of the penis that occurs in this context with the goal of maximally preserving erectile function postoperatively. While several specific neuromodulatory applications have gained interest for their potential benefit with pelvic surgery, determining their actual roles awaits the completion of controlled clinical trials.

The Effects of Cavernous Nerve Grafting following Surgically Induced Loss of Erectile Function in a Large-Animal Model

BACKGROUND

Prostate cancer is the second most common cause of cancer deaths in men in the United States. Many patients experience partial or complete loss of erectile function following prostatectomy. The cavernous nerves can be reconstructed intraoperatively using sural nerve grafts in an attempt to restore erectile function.

METHODS

In this study, multiple anatomical dissections and neurologic assessments were used to define the position and histologic parameters of the cavernous nerve in a canine model. The subsequent experimental design included three groups of adult mongrel dogs followed for an 8-month period. Group 1, the control group, underwent bilateral nerve ablation to substantiate surgically induced loss of erectile function. Group 2, the "sham" group, underwent exploration only. Group 3 underwent bilateral cavernous nerve ablation with bilateral sural nerve graft reconstruction. Erectile function was evaluated with indirect electrical nerve and manual penile stimulation preoperatively and 1, 2, 4, 6, and 8 months postoperatively. Direct nerve stimulation and histologic analysis was preformed at the first operation and at the time the animals were euthanized at 8 months.

RESULTS

Bilateral cavernous nerve ablation resulted in a significant loss of erectile function for 8 months postoperatively in the control animals. The sham animals demonstrated preservation of erectile function immediately following exploration. The animals in the grafted group demonstrated a significant return of erectile function by 4 months compared with preoperative measurements and by 2 months compared with control animals.

CONCLUSIONS

This study establishes the first large-animal model for surgically induced loss of erectile function with successful cavernous nerve graft reconstruction, and it provides the unique opportunity to explore the effects of changes to this model in the future.

Hope springs eternal: cavernosal nerve regeneration

Erectile dysfunction after radical prostatectomy for prostate cancer remains a significant morbidity for a large group of patients. A large body of work suggests that disrupting the cavernosal nerves is central as a causative factor. Extensive research has focused on ways to increase potency rates after surgery, either by preserving neuro-integrity, or attempting to restore it using various approaches. Herein we discuss the neurophysiology of nerve injury and regeneration, and review the work to date on cavernosal nerve regeneration.

Neuroprotective strategies in radical prostatectomy

In this section, authors from New York give their views on the various neuroprotective strategies for patients having a radical prostatectomy, such as the use of nerve grafts and other approaches. A joint study from Korea, the USA, Canada and the UK is presented in a paper on the importance of patient perception in the clinical assessment and management of BPH. There is also a review of robotic urological surgery. Finally, authors from New York give a review on the life of Isaac Newton. This is a new historical review in the journal, but one that will be of general interest.

Current and Future Strategies for Preventing and Managing Erectile Dysfunction Following Radical Prostatectomy

INTRODUCTION AND OBJECTIVES

As radical prostatectomy remains a commonly used procedure in the treatment of clinically localized prostate cancer, we critically analyzed current and future strategies for preventing and managing postoperative erectile dysfunction.

METHODS

Systematic literature review using Medline and CancerLit from January 1997 to June 2003. Abstracts published in the journals European Urology, The Journal of Urology and the International Journal of Impotence Research as official proceedings of internationally known scientific societies held in the same time period were also assessed.

RESULTS

Patient selection and surgical technique are the major determinants of postoperative erectile function. Apoptosis of corporeal smooth muscle cells plays a role in the development of cavernous veno-occlusive dysfunction following radical prostatectomy. Pharmacological prophylaxis and treatment of postoperative erectile dysfunction is effective and safe. The concepts of cavernous nerve reconstruction and neuroprotection have been associated to promising results.

CONCLUSIONS

In the hands of experienced surgeons, properly selected patients undergoing a nerve sparing radical prostatectomy should achieve unassisted or medically assisted erections postoperatively.

Cavernous nerve graft reconstruction during radical prostatectomy or radical cystectomy: safe and technically feasible

High local stage prostate and bladder cancers frequently require wide local resection and sacrifice of one or both cavernous nerves to achieve a negative surgical margin, thus resulting in erectile dysfunction. This is a report on preliminary experience with cavernous nerve graft reconstruction using sural nerve grafts with radical prostatectomy or radical cystectomy.Pre-operative evaluation was performed and consent was obtained in 14 potent men with prostate (11) or bladder (three) cancer. Sural nerve grafts of resected cavernous nerves were performed using a microsurgical technique. Post-operative treatment (Sildenafil or Alprostadil) was pursued until return of spontaneous function, documented by interview and adequate scores (>20) in the erectile function (EF) domain of the International Index of Erectile Function (IIEF).Twelve unilateral nerve grafts were performed, 10 during radical prostatectomy and two during radical cystoprostatectomy. Two procedures were technically not possible because of locally advanced disease. Mean age was 57.5 y (36-68 y). Mean follow up was 16.1 months (7-28 months). Pathological stage of prostate cancer was pT2 in 2, pT3 in 7 and pT4 in one. Surgical margins were positive in five out of 10 (50%), and two (20%%) had positive lymph nodes. Four patients (three post prostatectomy and one post cystectomy) were fully potent. Additionally, one patient post prostatectomy had improving partial erections. Six patients post prostatectomy and one patient post cystectomy had no erections. The only complication was one superficial wound infection in the sural nerve donor site. Preliminary experience shows that sural nerve grafts are feasible and safe after radical prostatectomy and cystectomy. However, candidates usually present with high stage disease, high risk for recurrence and frequent requirement for adjuvant therapy that further compromises erectile function. Randomized studies with more patients and long follow-up periods are necessary in order to define the ideal candidate for nerve graft procedures.

Neuroprotection and nerve grafts in the treatment of neurogenic erectile dysfunction

PURPOSE

The rationale for protecting the nerve supply of the penis derives mainly from the fact that neurological injury or disease states involving this organ commonly result in erectile dysfunction. Novel directions in the management of neurogenic erectile dysfunction that pertain specifically to sustaining penile neuronal function are described.

MATERIALS AND METHODS

The review constitutes a summary of neuroprotective strategies for penile erection that are under investigation at the basic science level or have been brought to clinical practice. The basic exercise consisted primarily of a literature search using the National Library of Medicine PubMed Services, with references made to such keywords as nerve grafts, nerve growth factors, neuroprotection and nerve regeneration.

RESULTS

Primary advances in this field have centered on repairing structural defects and restoring the functional integrity of the cavernous nerves of the penis. In the former autologous nerve conduits, such as sural nerve grafts, have been explored and used prominently in the context of radical prostatectomy. In the latter diverse neurotrophic treatments have been investigated, with progress mostly limited to animal models of cavernous nerve injury. Basic concepts and ongoing developments in the neurobiology of axonal regeneration were identified as being applicable to this area of neurourology.

CONCLUSIONS

Because neurogenic origins represent a leading categorical cause of erectile dysfunction, the importance of developing and applying treatment approaches to alleviate neuropathic effects on the erectile tissue of the penis is certain. Medical and surgical innovations for preserving and reconstituting the functional nerve supply of the penis offer great promise in the management of erectile dysfunction.

Cavernous nerve reconstruction to preserve erectile function following non-nerve-sparing radical retropubic prostatectomy: a prospective study

Erectile dysfunction following radical prostatectomy for treatment of clinically localized prostate cancer remains a problem that deters many men from seeking surgical treatment. Sparing the cavernous nerves has been popularized as a method of preserving potency, but men with locally advanced disease may be at increased risk for positive margins with this technique. In this study, sural nerve grafting of the cavernous nerve bundles, to preserve postoperative potency while potentially maximizing cancer control, was examined. Thirty men were enrolled in this prospective phase I study and underwent non-nerve-sparing radical prostatectomy performed by one of two protocol surgeons. Preoperative erectile function was assessed both objectively, using a RigiScan (Timm Medical Technologies, Inc., Eden Prairie, Minn.), and subjectively. The cavernous nerves were identified and resected during the operation with the use of an intraoperative mapping device (CaverMap; Alliant Medical Technologies, Norwood, Mass.). Bilateral autologous sural nerve grafting to the cavernous nerve stumps was performed by one of two protocol plastic surgeons. Postoperative erectile dysfunction therapy, using intracorporeal injection, a vacuum pump, and/or oral sildenafil therapy, was instituted 6 weeks after the operation. Spontaneous erectile activity was subjectively and objectively measured every 3 months after the operation. Follow-up periods ranged from 13 to 33 months (mean, 23 months). Overall, 18 of 30 patients (60 percent) demonstrated both objective and subjective evidence of spontaneous erectile activity. Of those 18 men, 13 (72 percent) were able to have intercourse (seven unassisted and six with the aid of sildenafil). No disease or biochemical recurrences have been noted in this group of patients with locally advanced disease. In conclusion, autologous sural nerve grafting after non-nerve-sparing radical prostatectomy is an effective means of preserving spontaneous erectile activity after the operation while maximizing cancer control potential.

Bilateral nerve grafting during radical retropubic prostatectomy: extended follow-up

OBJECTIVES

To confirm the benefit of using an interposition sural nerve graft at the time of radical retropubic prostatectomy in an extended series of men with at least 1 year of follow-up. We previously reported the return of erectile function after resection of both cavernous nerves.

METHODS

Twenty-eight potent men with clinically localized prostate cancer underwent radical retropubic prostatectomy with deliberate wide bilateral neurovascular bundle resection and the placement of bilateral nerve grafts. Erectile dysfunction questionnaires and patient interviews were completed at 6-month intervals. A minimum of 12 months of follow-up (mean 23 +/- 10 months) was obtained for 23 men (mean age 58 +/- 6 years). A control group of 12 men who underwent bilateral nerve resections, but declined nerve graft placement, was also followed up.

RESULTS

Of the 23 men, 6 (26%) had spontaneous, medically unassisted erections sufficient for sexual intercourse with vaginal penetration. An additional 6 men (26%) described "40% to 60%" spontaneous erections (fullness, no rigidity, not able to penetrate). Ten men (43%) had intercourse with sildenafil. No demonstrable erections occurred before 5 months postoperatively. The greatest return of function thus far was observed at 18 months after surgery.

CONCLUSIONS

This surgical technique continues to show promise as an advance in prostate cancer surgery. The results of this study demonstrated recovery of erectile function in men who underwent bilateral nerve graft placement during radical retropubic prostatectomy when both cavernous nerves were deliberately resected.

Bilateral nerve graft during radical retropubic prostatectomy: 1-year followup

PURPOSE

With the interposition of a sural nerve graft to replace resected cavernous nerves at radical retropubic prostatectomy, we have previously reported the return of effective erectile function. We determine the efficacy of this procedure in a series of men with at least 1-year followup.

MATERIALS AND METHODS

A total of 12 potent men (mean age plus or minus standard deviation 57 +/- 6 years) with clinically localized prostate cancer underwent radical retropubic prostatectomy, with deliberate wide bilateral neurovascular bundle resection and placement of bilateral nerve grafts. A series of patient and partner erectile dysfunction questionnaires, and patient interviews were performed at 3, 6, 12 and 18 months postoperatively. Only results for those men with a followup of 12 months or greater (mean 16 +/- 4) are presented. A control group of 12 men who had undergone bilateral nerve resection but declined nerve graft placement, was also followed.

RESULTS

Of the 12 men 4 (33%) had spontaneous medically unassisted erections sufficient for sexual intercourse with vaginal penetration. An additional 5 (42%) men describe "40 to 60%" spontaneous erections, with fullness, no rigidity and not able to penetrate. Overall, 9 (75%) men had return of erectile activity. No demonstrable erections occurred before 5 months postoperatively. The greatest return of function was observed at 14 to 18 months after surgery.

CONCLUSIONS

This surgical technique has minimal morbidity and represents a significant advance in prostate cancer surgery in men requiring bilateral nerve resection. Our study clearly demonstrates recovery of erectile function in men who underwent bilateral nerve graft placement during radical retropubic prostatectomy when both cavernous nerves were deliberately resected.

General use of animal models for investigation of the physiology of erection

In review, animal models have accounted significantly for the amazing strides made in the field of sexual dysfunction research. Fundamentally, they have offered a unique experimental approach to test many hypotheses regarding sexual function. Since their early use for sexual physiology research, there has been increasing sophistication using animals involving techniques for stimulating and monitoring sexual responses. One specific area that has been advanced is the use of conscious animal models to obtain a better sense of the natural contexts for sexual physiology and to avoid pharmacological interference associated with anesthetics. Another area of interest is the increasing use of simple but valid techniques to record and assess sexual responses. Efforts to develop and evaluate animal models that replicate disorders of sexual function have also been most advantageous. In the future, animal models will remain useful. The expanded applications of animal models include the study of predisposing disease states associated with sexual dysfunction and the study of all aspects of sexual dysfunction, in both male and female subjects. Continued judgment must be applied, understanding the advantages of one or another animal model, to explore questions and provide answers that are most scientifically relevant to the human condition. The promise of advancing therapies in this field indicates the additional prominent role for animals for the purposes of drug development.

Intraoperative electrical stimulation of cavernosal nerves with monitoring of intracorporeal pressure in patients undergoing nerve sparing radical prostatectomy

OBJECTIVE

To explore the utility of intraoperative cavernosal nerve stimulation in facilitating atraumatic nerve dissection during radical prostatectomy, and thus help predict postoperative erectile function.

PATIENTS AND METHODS

Fourteen patients (aged 51-72 years) underwent nerve-sparing radical retropubic prostatectomy (NSRRP); 10 were potent before surgery (group 1), and four had erectile dysfunction (group 2). A multi-acquisition system (MacLab/8e) with a Macintosh computer was used for real-time display and recording of intracavernosal pressure (ICP) during surgery. Nerves were stimulated with a bipolar probe (monophasic rectangular pulses, 10 mA, 20 Hz, 0.22 s) before and after removal of the gland. The follow-up consisted of interviews with patients and their partners' 12-18 months after treatment.

RESULTS

The mean (sem) basal ICP of 8. 0 (2.0) cmH2O remained unchanged during nerve dissection. The mean increase in ICP during electrical stimulation was >50 cmH2O in seven potent patients (group 1) and was sustained as long as the nerve was stimulated. Postoperatively, these seven patients reported erections sufficient for sexual intercourse. However, the three remaining patients in group 1 had pressure rises of <30 cmH2O, of whom two reported partial erections and one reported total impotence postoperatively. The recovery time for erectile function was 6-12 months after surgery. Two patients from group 2 had transient increases in ICP to <40 cmH2O; one had an increase to 20 cmH2O and one had no response at all. All four patients remained totally impotent postoperatively. There were no complications.

CONCLUSIONS

Intraoperative electrical stimulation of the cavernosal nerves with ICP monitoring before and after NSRRP is a safe and reliable method for documenting nerve continuity and its functional status. Patients who have normal preoperative erectile function and show an adequate rise in ICP upon electrical nerve stimulation during NSRRP will almost certainly be potent after surgery. This tool may be used to facilitate atraumatic nerve dissection during NSRRP.

Electrical stimulation of the dorsal nerve of the penis evokes reflex tonic erections of the penile body and reflex ejaculatory responses in the spinal rat

An animal model using the spinal rat was characterized. Electrical stimulation of the dorsal nerve of the penis elicited reflex tonic erections of the penile body and reflex bulbospongiosus muscle activity, flips and ejaculations. The tonic erections of the penile body are independent from contractions of the bulbospongiosus muscle and appear to be the result of a neurovascular process. Our observations suggest that reflex bulbospongiosus muscle activity, flips and ejaculations are a single complex reflex response, which we define as reflex ejaculatory response. Two parameters predicted the occurrence and type of reflex response. The visualization of bulbospongiosus muscle activity during surgical isolation of the dorsal nerve of the penis was sufficient to anticipate the elicitability of reflex ejaculatory responses. The latter, together with a systemic systolic pressure > or = 73 mmHg., warranted the elicitability of reflex tonic erections. The similarities found in the physiology of rat tonic penile body erections and of human erections make this model promising for further elucidation of sexual function. Moreover, the present model may prove useful for the investigation of neurogenic erectile dysfunction, and of neurogenic ejaculatory disorders.