Variation in course of cavernous nerve with special reference to details of topographic relationships near prostatic apex: Histologic study using male cadavers

Cavernous nerve mapping methods for radical prostatectomy

INTRODUCTION

Preserving the cavernous nerves, the main autonomic nerve supply of the penis, is a major challenge of radical prostatectomy. Cavernous nerve injury during radical prostatectomy predominantly accounts for post-radical prostatectomy erectile dysfunction. The cavernous nerve is a bilateral structure that branches in a weblike distribution over the prostate surface and varies anatomically in individuals, such that standard nerve-sparing methods do not sufficiently sustain penile erection ability. As a consequence, researchers have focused on developing personalized cavernous nerve mapping methods applied to the surgical procedure aiming to improve postoperative sexual function outcomes.

OBJECTIVES

We provide an updated overview of preclinical and clinical data of cavernous nerve mapping methods, emphasizing their strengths, limitations, and future directions.

METHODS

A literature review was performed via Scopus, PubMed, and Google Scholar for studies that describe cavernous nerve mapping/localization.

RESULTS

Several cavernous nerve mapping methods have been investigated based on various properties of the nerve structures including stimulation techniques, spectroscopy/imaging techniques, and assorted combinations of these methods. More recent methods have portrayed the course of the main cavernous nerve as well as its branches based on real-time mapping, high-resolution imaging, and functional imaging. However, each of these methods has distinctive limitations, including low spatial accuracy, lack of standardization for stimulation and response measurement, superficial imaging depth, toxicity risk, and lack of suitability for intraoperative use.

CONCLUSION

While various cavernous nerve mapping methods have provided improvements in identification and preservation of the cavernous nerve during radical prostatectomy, no method has been implemented in clinical practice due to their distinctive limitations. To overcome the limitations of existing cavernous nerve mapping methods, the development of new imaging techniques and mapping methods is in progress. There is a need for further research in this area to improve sexual function outcomes and quality of life after radical prostatectomy.

The male external urethral sphincter is autonomically innervated

INTRODUCTION

The aim of the present study was to describe autonomic urethral sphincter (US) innervation using specific muscular and neuronal antibody markers and 3D reconstruction.

MATERIAL AND METHODS

We performed en-bloc removal of the entire pelvis of three male human fetuses between 18 and 40 weeks. Serial whole mount sections (5 μm intervals) were stained and investigated. The sections were stained with Masson's trichrome and Eosin Hematoxylin, and immunostained with: anti-SMA antibody for smooth muscle; anti-S100 antibody for all nerves; and anti-PMP22 antibody, anti-TH antibody, anti-CGRP antibody, anti-NOS antibody for somatic, adrenergic, sensory and nitrergic nerve fibers, respectively. The slides were digitized for 3D reconstruction to improve topographical understanding. An animated reconstruction of the autonomic innervation of the US was generated.

RESULTS

The external and internal US are innervated by autonomic nerves of the inferior hypogastric plexus (IHP). These nerves are sympathetic (positive anti-TH antibody), sensory (positive anti-CGRP antibody), and nitrergic (positive anti-NOS antibody). Some autonomic fibers run within the neurovascular bundles, posterolaterally. Others run from the IHP to the posteromedial aspect of the prostate apex, above an through the rectourethral muscle. The external US is also innervated by somatic nerves (positive anti-PMP22 antibody) arising from the pudendal nerve, joining the midline but remaining below the rectourethral.

CONCLUSIONS

This study provides anatomical evidence of an autonomic component in the innervation of the external US that travels in the neurovascular bundle. During radical prostatectomy, the rectourethral muscle and the neurovascular bundles are to be preserved, particularly during apical dissection.

Surgical techniques to improve continence recovery after robot-assisted radical prostatectomy

Radical prostatectomy directly affects urinary continence dynamics with incontinence being a major factor in patients’ quality of life, social and psychological status. In order to help maintain continence after robot-assisted radical prostatectomy (RARP), a number of surgical techniques have been described. In the present narrative review, we summarize the surgical techniques that have been applied during RARP and their effects on incontinence rates and time to continence recovery.

Surgical techniques to improve continence recovery after robot-assisted radical prostatectomy

Radical prostatectomy directly affects urinary continence dynamics with incontinence being a major factor in patients' quality of life, social and psychological status. In order to help maintain continence after robot-assisted radical prostatectomy (RARP), a number of surgical techniques have been described. In the present narrative review, we summarize the surgical techniques that have been applied during RARP and their effects on incontinence rates and time to continence recovery.

Smooth muscle of the male pelvic floor: An anatomic study

Knowledge of the anatomy of the male pelvic floor is important to avoid damaging the pelvic floor muscles during surgery. We set out to explore the structure and innervation of the smooth muscle (SM) of the whole pelvic floor using male fetuses. We removed en-bloc the entire pelvis of three male fetuses. The specimens were serially sectioned before being stained with Masson's trichrome and hematoxylin and eosin, and immunostained for SMs, and somatic, adrenergic, sensory and nitrergic nerve fibers. Slides were digitized for three-dimensional reconstruction. We individualized a middle compartment that contains SM cells. This compartment is in close relation with the levator ani muscle (LAM), rectum, and urethra. We describe a posterior part of the middle compartment posterior to the rectal wall and an anterior part anterior to the rectal wall. The anterior part is split into (1) a centro-levator area of SM cells localized between the right and left LAM, (2) an endo-levator area that upholsters the internal aspect of the LAM, and (3) an infra-levator area below the LAM. All these areas are innervated by autonomic nerves coming from the inferior hypogastric plexus. The core and the infra-levator area receive the cavernous nerve and nerves supplying the urethra. We thus demonstrate that these muscular structures are smooth and under autonomic influence. These findings are relevant for the pelvic surgeon, and especially the urologist, during radical prostatectomy, abdominoperineal resection and intersphincteric resection. Clin. Anat., 2019. © 2019 Wiley Periodicals, Inc.

Novel Concept Enabling an Old Idea: A Flexible Electrode Array to Treat Neurogenic Erectile Dysfunction

INTRODUCTION

Many studies have shown that electrostimulation of the cavernosal nerve can induce and maintain penile erection. Based on these discoveries, neurostimulation to activate the erectile response has been considered a potential solution to treat erectile dysfunction (ED). However, despite recognized potential, this technology has not been further developed. The barrier is the complex anatomy of the human cavernous nerve, which challenges the intraoperative identification of the cavernosal nerves for electrode placement.

AIM

To overcome this major barrier, we proposed a practical solution: a 2-dimensional flexible electrode array that can cover the entire plexus area, ensuring that at least 1 of the electrodes will be in optimal contact with the cavernosal nerve, without the need of intraoperative identification. The present study aims to evaluate this concept intraoperatively.

METHODS

24 patients enrolled for open radical prostatectomy were recruited. During the surgical procedures, the electrode array was positioned on the pelvic plexus (on the prostatic apex or pelvic wall) and electrical stimulation was applied to induce penile erection. Penile erectile response was assessed by (i) visual change of penile tumescence and (ii) by a penile plethysmograph system.

MAIN OUTCOME MEASURE

Ability and success rate of evoking penile response were measured by applying electrical stimulation using the developed electrode array.

RESULTS

Electrical stimulation produced immediate penile response in all cases when tested before (on prostatic apex) or after prostate removal (on pelvic wall). Clear visual penile engorgement was observed in 75% of the cases, whereas 25% showed minimal to moderate penile tumescence. As expected, patients with lower International Index of Erectile Function-5 score presented a reduced response, whereas stimulation before prostate removal showed greater response than following removal. Interestingly, erectile response was potentiated by bilateral stimulation (circumference increase [mm]: 2.7 ± 1.02 vs. 8.2 ± 1.9, P = .01).

CLINICAL IMPLICATIONS

These data bring sufficient proof of concept of a conceivable novel medical implant for the treatment of ED caused by mechanical nerve injury, such as prostatectomy and spinal cord injury.

STRENGTH & LIMITATIONS

This is the first approach that can ensure the optimal site stimulation of the erectogenic neuronal path within the lower pelvic area and overcome the major barrier of individual anatomic variability. However, because this study was performed intraoperatively in an acute scenario, further studies are needed to evaluate its chronic efficacy for clinical practice.

CONCLUSION

The flexible electrode array concept can ensure the electrostimulation of erectogenic neuronal path when positioned on the prostate apex or pelvic floor. Skoufias S, Sturny M, Fraga-Silva R, et al. Novel concept enabling an old idea: A flexible electrode array to treat neurogenic erectile dysfunction. J Sex Med 2018;15:1558-1569.

Site-dependent differences in the composite fibers of male pelvic plexus branches: an immunohistochemical analysis of donated elderly cadavers

Background

Although the pelvic autonomic plexus branches are considered to be a mixture of sympathetic and parasympathetic nerves, little is known regarding the composite fibers of the pelvic plexus branches. This study aimed to investigate the immunohistochemical features of sympathetic and parasympathetic nerves in the pelvic autonomic plexus branches.

Methods

Using 10 donated elderly male cadavers, the detailed topohistology of nerve fibers at and around the bladder, seminal vesicle, prostate, and rectum was examined. Neuronal nitric oxide synthase (nNOS) and vasoactive intestinal polypeptide (VIP) were used as parasympathetic nerve markers; tyrosine hydroxylase (TH) was used as a sympathetic nerve marker. The myenteric plexus of the colon was utilized as a positive control.

Results

Most nerve fibers in the bladder, seminal vesicle, prostate, and rectum were both nNOS- and TH-positive. Thus, pelvic plexus branches were classified into two types: 1) triple-positive mixed nerves (nNOS+, VIP+, TH+, thick myelinated fibers + or -) and 2) double-positive mixed nerves (nNOS+, VIP-, TH+, thick myelinated fibers + or -). Notably, triple-positive nerves were localized within the posterosuperior part of the plexus (near the rectum) and travelled anteroinferiorly toward the posterolateral corner of the prostate. The posteriorly and inferiorly located nerves were predominantly composed of parasympathetic, rather than sympathetic, fibers. In contrast, nerve fibers within and along the bladder and seminal vesicle contained either no or few VIP-positive nerves. These superiorly located nerves were characterized by clear sympathetic nerve dominance.

Conclusions

The nerves of the pelvic plexus branches were clearly classified into nerves around the bladder and seminal vesicle (VIP-negative) and nerves around the prostate (VIP-positive). Although nNOS- and VIP-positive nerve fibers are candidate cavernous nerves, cavernous nerve identity cannot be definitively concluded for these nerves in the periprostatic region.

Penile neurovascular structure revisited: immunohistochemical studies with three-dimensional reconstruction

Penile erection is a neurovascular phenomenon that requires well coordinated and functional interaction between penile vascular and nervous systems. In order to provide a useful tool to examine pathologic changes in the erectile tissue, mainly focusing on penile neurovascular dysfunction, we established the technique to determine the differential distribution of endothelial cells, smooth muscle cells, pericytes, and nerve fibers in the mouse penis using immunohistochemical staining with three-dimensional reconstruction. Immunofluorescent staining of penile tissue was performed with antibodies against CD31 (an endothelial cell marker), smooth muscle α -actin (SMA, a smooth muscle cell marker), NG2 (a pericyte marker), or βIII-tubulin (a neuronal marker). We reconstructed three-dimensional images of penile vascular or neurovascular system from stacks of two-dimensional images, which allows volume rendering and provides reliable anatomic information. CD31-positive endothelial cells, SMA-positive smooth muscle cells, and NG2-positive pericytes were evenly distributed and composed sinusoidal or venous wall. However, the endothelial layer of the cavernous artery or dorsal artery was mainly covered with smooth muscle cells and rarely associated with pericytes. The reconstructed three-dimensional images clearly visualized typical wavy appearance of nerve fibers that evenly innervate to cavernous sinusoids, cavernous artery, dorsal vein, and dorsal artery. We observed a significant decrease in CD31-positive endothelial cells, NG2-positive pericytes, and βIII-tubulin-positive nerve fibers in the penis of diabetic mice compared with those in normal condition. Our protocol for immunofluorescent staining with three-dimensional reconstruction will allow a better understanding of the penile neurovascular anatomy and may constitute a standard technique to determine the efficacy of candidate therapeutics targeting therapeutic angiogenesis or neural regeneration.

Role of Schwann cells in the regeneration of penile and peripheral nerves

Schwann cells (SCs) are the principal glia of the peripheral nervous system. The end point of SC development is the formation of myelinating and nonmyelinating cells which ensheath large and small diameter axons, respectively. They play an important role in axon regeneration after injury, including cavernous nerve injury that leads to erectile dysfunction (ED). Despite improvement in radical prostatectomy surgical techniques, many patients still suffer from ED postoperatively as surgical trauma causes traction injuries and local inflammatory changes in the neuronal microenvironment of the autonomic fibers innervating the penis resulting in pathophysiological alterations in the end organ. The aim of this review is to summarize contemporary evidence regarding: (1) the origin and development of SCs in the peripheral and penile nerve system; (2) Wallerian degeneration and SC plastic change following peripheral and penile nerve injury; (3) how SCs promote peripheral and penile nerve regeneration by secreting neurotrophic factors; (4) and strategies targeting SCs to accelerate peripheral nerve regeneration. We searched PubMed for articles related to these topics in both animal models and human research and found numerous studies suggesting that SCs could be a novel target for treatment of nerve injury-induced ED.

Novel methods for mapping the cavernous nerves during radical prostatectomy

The cavernous nerves, which course along the surface of the prostate gland, are responsible for erectile function. During radical prostatectomy, urologists are challenged in preserving these nerves and their function. Cavernous nerves are microscopic and show variable location in different patients; therefore, postoperative sexual potency rates are widely variable following radical prostatectomy. A variety of technologies, including electrical and optical nerve stimulation, dye-based optical fluorescence and microscopy, spectroscopy, ultrasound and magnetic resonance imaging have all been used to study cavernous nerve anatomy and physiology, and some of these methods are also potential intraoperative methods for identifying and preserving cavernous nerves. However, all of these technologies have inherent limitations, including slow or inconsistent nerve responses, poor image resolution, shallow image depth, slow image acquisition times and/or safety concerns. New and emerging technologies, as well as multimodal approaches combining existing methods, hold promise for improved postoperative sexual outcomes and patient quality of life following radical prostatectomy.

Improved Intraoperative Visualization of Nerves through a Myelin-Binding Fluorophore and Dual-Mode Laparoscopic Imaging

The ability to visualize and spare nerves during surgery is critical for avoiding chronic morbidity, pain, and loss of function. Visualization of such critical anatomic structures is even more challenging during minimal access procedures because the small incisions limit visibility. In this study, we focus on improving imaging of nerves through the use of a new small molecule fluorophore, GE3126, used in conjunction with our dual-mode (color and fluorescence) laparoscopic imaging instrument. GE3126 has higher aqueous solubility, improved pharmacokinetics, and reduced non-specific adipose tissue fluorescence compared to previous myelin-binding fluorophores. Dosing and kinetics were initially optimized in mice. A non-clinical modified Irwin study in rats, performed to assess the potential of GE3126 to induce nervous system injuries, showed the absence of major adverse reactions. Real-time intraoperative imaging was performed in a porcine model. Compared to white light imaging, nerve visibility was enhanced under fluorescence guidance, especially for small diameter nerves obscured by fascia, blood vessels, or adipose tissue. In the porcine model, nerve visualization was observed rapidly, within 5 to 10 minutes post-intravenous injection and the nerve fluorescence signal was maintained for up to 80 minutes. The use of GE3126, coupled with practical implementation of an imaging instrument may be an important step forward in preventing nerve damage in the operating room.

The urethral rhabdosphincter, levator ani muscle, and perineal membrane: a review

Detailed knowledge of the anatomy of the rhabdosphincter and adjacent tissues is mandatory during urologic surgery to ensure reliable oncologic and functional outcomes. To characterize the levator ani (LA) function for the urethral sphincter, we described connective tissue morphology between the LA and urethral rhabdosphincter. The interface tissue between the LA and rhabdosphincter area in males contained abundant irregularly arrayed elastic fibers and smooth muscles. The male rhabdosphincter was positioned alongside the LA to divide the elevation force and not in-series along the axis of LA contraction. The male perineal membrane was thin but solid and extends along the inferior margin or bottom of the rhabdosphincter area. In contrast, the female rhabdosphincter, including the compressor urethrae and urethrovaginal sphincter muscles, was embedded in the elastic fiber mesh that is continuous with the thick, multilaminar perineal membrane. The inferomedial edge of the female LA was attached to the upper surface of the perineal membrane and not directly attached to the rhabdosphincter. We presented new diagrams showing the gender differences in topographical anatomy of the LA and rhabdosphincter.

Topohistology of sympathetic and parasympathetic nerve fibers in branches of the pelvic plexus: an immunohistochemical study using donated elderly cadavers

Although the pelvic autonomic plexus may be considered a mixture of sympathetic and parasympathetic nerves, little information on its composite fibers is available. Using 10 donated elderly cadavers, we investigated in detail the topohistology of nerve fibers in the posterior part of the periprostatic region in males and the infero-anterior part of the paracolpium in females. Neuronal nitric oxide synthase (nNOS) and vasoactive intestinal polypeptide (VIP) were used as parasympathetic nerve markers, and tyrosine hydroxylase (TH) was used as a marker of sympathetic nerves. In the region examined, nNOS-positive nerves (containing nNOS-positive fibers) were consistently predominant numerically. All fibers positive for these markers appeared to be thin, unmyelinated fibers. Accordingly, the pelvic plexus branches were classified into 5 types: triple-positive mixed nerves (nNOS+, VIP+, TH+, thick myelinated fibers + or -); double-positive mixed nerves (nNOS+, VIP-, TH+, thick myelinated fibers + or -); nerves in arterial walls (nNOS-, VIP+, TH+, thick myelinated fibers-); non-parasympathetic nerves (nNOS-, VIP-, TH+, thick myelinated fibers + or -); (although rare) pure sensory nerve candidates (nNOS-, VIP-, TH-, thick myelinated fibers+). Triple-positive nerves were 5-6 times more numerous in the paracolpium than in the periprostatic region. Usually, the parasympathetic nerve fibers did not occupy a specific site in a nerve, and were intermingled with sympathetic fibers. This morphology might be the result of an "incidentally" adopted nerve fiber route, rather than a target-specific pathway.

Continuous-wave infrared subsurface optical stimulation of the rat prostate cavernous nerves using a 1490-nm diode laser

OBJECTIVE

To optimize the infrared laser wavelength and optical nerve stimulation (ONS) parameters for both deep and rapid subsurface cavernous nerve (CN) stimulation in a rat model, in vivo.

MATERIALS AND METHODS

A 150-mW, 1490-nm diode laser providing an optical penetration depth (OPD) of 518 μm in water was operated in continuous-wave mode during stimulation of the CNs in 8 rats for 15 seconds irradiation time through a custom-built, single-mode fiber optic probe capable of producing a collimated, 1-mm diameter laser beam. Successful ONS was judged by an intracavernous pressure response in the rat penis. Subsurface ONS at 1490 nm was also compared with previous studies using 1455 nm and 1550 nm near-infrared diode laser wavelengths.

RESULTS

Subsurface ONS of the rat CN was successful through fascia layers with a thickness up to 380 μm using an incident laser power of ∼50 mW. Intracavernous pressure response times as short as 4.6 ± 0.2 seconds were recorded using higher laser powers below the nerve damage threshold.

CONCLUSION

The 1490-nm diode laser represents a compact, low cost, high power, and high quality infrared light source for use in ONS. This wavelength provides deeper penetration than 1455-nm diode laser and more rapid and efficient nerve stimulation than 1550-nm diode laser.

Bladder and urethral function in a mouse model of cavernous nerve injury

AIMS

To determine whether cavernous nerve injury (CNI) alters lower urinary tract function, we assessed bladder and urethral function over time in a mouse model of CNI.

METHODS

Twelve-week-old male C57BL/6 mice were divided into three groups: unoperated (UO; n = 6), sham-operated (SO; n = 18), and bilateral CNI (n = 30) group. At 1, 2, 4, 6, 8, 10 days bladder and urethral function were evaluated in these three groups using cystometry (CMG) and leak point pressure (LPP) recording under anesthesia.

RESULTS

There was no significant difference in maximum detrusor pressure between groups at all times. Compared with the UO group, bladder compliance, and capacity in the CNI group were significantly decreased at Days 1, 2, 4 (P < 0.05) and recovered gradually from Day 6 to Day 10. In the SO group, they were decreased at Day 1, however, recovered more rapidly than the CNI group. Non-voiding contractions (NVC) developed in the CNI group at all times. Intercontraction interval were significantly decreased in SO and CNI groups and recovered more rapidly in SO group. In the SO group NVC were observed only at Days 1 and 2. LPP in the CNI group was decreased significantly at Days 1 and 2 (P < 0.05) and rapidly recovered with time compared with the UO and SO groups.

CONCLUSION

In a mouse model of CNI, a transient decrease in bladder compliance, capacity, LPP and increased NVC was observed. These changes gradually recovered from Day 6 after CNI. Our findings suggest that CNI may affect bladder and urethral function, but alterations are reversible.

Dorsal vein complex preserving technique for intrafascial nerve-sparing laparoscopic radical prostatectomy

Objectives

To describe a novel dorsal vein complex preserving technique for intrafascial nerve-sparing laparoscopic radical prostatectomy and to evaluate its postoperative outcomes.

Methods

A total of 109 patients who underwent laparoscopic radical prostatectomy by a single surgeon were evaluated, including 44 patients with dorsal vein complex preserving technique for intrafascial nerve-sparing laparoscopic radical prostatectomy, 20 patients with conventional intrafascial nerve-sparing laparoscopic radical prostatectomy and 45 patients with non-nerve-sparing laparoscopic radical prostatectomy. Functional outcomes were evaluated using a self-administered questionnaire (Expanded Prostate Cancer Index Composite). Continence was defined as zero to one security pad per day. Oncological outcomes were evaluated based on positive surgical margin.

Results

In the dorsal vein complex preserving technique for intrafascial nerve-sparing laparoscopic radical prostatectomy group, the continence rate was 57%, 77% and 95% at 1, 3 and 12 months, respectively. The continence rate in the conventional intrafascial nerve-sparing laparoscopic radical prostatectomy group was 37%, 63% and 90%, and in the non-nerve-sparing laparoscopic radical prostatectomy group it was 23%, 57% and 82% at 1, 3, and 12 months, respectively. The dorsal vein complex preserving technique for intrafascial nerve-sparing laparoscopic radical prostatectomy group showed a significantly earlier recovery from incontinence compared with that in the conventional intrafascial nerve-sparing laparoscopic radical prostatectomy and non-nerve-sparing laparoscopic radical prostatectomy groups (log–rank test, P = 0.044 and P < 0.001). Similarly, the dorsal vein complex preserving technique for intrafascial nerve-sparing laparoscopic radical prostatectomy group tended to show a more early recovery in relation to urinary function of the Expanded Prostate Cancer Index Composite. Regarding sexual function, there were no significant differences between the dorsal vein complex preserving technique for intrafascial nerve-sparing laparoscopic radical prostatectomy and conventional intrafascial nerve-sparing laparoscopic radical prostatectomy groups. In pT2 patients, the positive surgical margin rate of the dorsal vein complex preserving technique for intrafascial nerve-sparing laparoscopic radical prostatectomy group (11%) was similar to that of the other two groups (conventional intrafascial nerve-sparing laparoscopic radical prostatectomy 7%; non-nerve-sparing laparoscopic radical prostatectomy 11%).

Conclusions

The dorsal vein complex preserving technique for intrafascial nerve-sparing laparoscopic radical prostatectomy technique provides early recovery from incontinence without adversely affecting the oncological outcome.

Subsurface near-infrared laser stimulation of the periprostatic cavernous nerves

Successful identification and preservation of the cavernous nerves (CN), which are responsible for sexual function and vulnerable to damage during prostate cancer surgery, will require subsurface detection of the CN's beneath a thin fascia layer. This study explores the feasibility of optical nerve stimulation (ONS) in the rat with a fascia layer placed over the CN. Two near-infrared diode lasers with wavelengths of 1455 and 1550 nm were operated in continuous-wave mode for stimulation of the CN in 8 rats, in vivo. Successful ONS was confirmed by an intracavernous pressure (ICP) response in the rat penis at 1455 nm through fascia with a thickness up to 110 μm and at 1550 nm through fascia with a thickness up to 450 μm. Higher incident laser power was required to produce an ICP response as fascia thickness was increased. Also, weaker and slower ICP responses were observed as fascia thickness was increased. Subsurface ONS of the rat CN at a depth of 450 μm using a 1550 nm laser is feasible as an intermediate step towards developing ONS as an intra-operative diagnostic tool for identification and preservation of the cavernous nerves during prostate cancer surgery.

Advances in imaging the neurovascular bundle

PURPOSE OF REVIEW

Much of the progress in improving potency outcomes after radical prostatectomy has been achieved due to a better visualization of the neurovascular bundle responsible for erectile function. We review the current literature evaluating the existing imaging modalities to image the neurovascular bundle around the prostate pre, intra, and postoperatively, thereby enabling development of surgical techniques for better preservation of nerve function.

RECENT FINDINGS

Imaging modalities like multiphoton microscopy, optical coherence tomography, Coherent anti-Raman spectroscopy, exogenous fluoroscopy using prostate-specific membrane antigen, and so on have led to a better appreciation of the neurovascular bundle, thus encouraging novel techniques in nerve preservation during radical prostatectomy.

SUMMARY

In an age of heightened patient expectations and increasing life expectancy, better visualization of the neurovascular bundle around the prostate using novel imaging modalities may provide breakthroughs in improving potency outcomes after radical prostatectomy.

Classification of the distribution of cavernous nerve fibers around the prostate by intraoperative electrical stimulation during laparoscopic radical prostatectomy

We investigated the distribution of cavernous nerve (CN) fibers around the prostate by electrical nerve stimulation during laparoscopic radical prostatectomy to classify the distribution of the CN fibers. Electrical stimulation was performed on 30 consecutive patients with localized prostate cancer; middle of the neurovascular bundle (NVB, point A), base of the NVB (point B), the rectal wall 1 cm posterolateral to the NVB (point C) and the lateral aspect of the prostate (point D). We measured the intraurethral pressure at the midportion to detect the changes in intracavernosal pressure. The mean maximum changes were 10.5 ± 7.9, 11.6 ± 8.8, 9.6 ± 7.4 and 6.7 ± 7.0 cm H(2)O at points A, B, C and D, respectively. The patterns of CN fiber distribution were divided into four groups: type 1 (23%), the bundle corresponding to the NVB; type 2 (7%), the bundle from the rectal wall to the prostate; type 3 (27%), the plate including NVB and posterolateral to NVB; and type 4 (43%), the plate between the rectal wall posterolateral to the NVB and the lateral aspect of the prostate. Distribution of the CNs in a bundle-like formation was considered to account for 30%, whereas a plate-like formation accounted for 70%. Understanding these four patterns of CN fiber distribution should facilitate accurate CN-sparing radical prostatectomy.

The male rectourethralis and deep transverse perineal muscles and their relationship to adjacent structures examined with successive slices of celloidin-embedded pelvic viscera

BACKGROUND

The precise relationship of the structures dorsal to the membranous urethra, including the rectourethralis muscle, the rhabdosphincter, the deep transverse perineal muscle (DTPM), the perineal body, and Denonvillier's fascia, remains controversial.

OBJECTIVE

Our aim was to reexamine the detailed anatomy of the rectourethralis muscle and the deep transverse perineal muscle and their relationship with adjacent structures.

DESIGN, SETTING, AND PARTICIPANTS

The pelvic viscera, including bladder, prostate, and rectum, were obtained from 20 formalin-fixed adult male cadavers.

MEASUREMENTS

The pelvic viscera were embedded in celloidin and then cut into successive slices with an immersing-alcohol microtome. All slices were explored with anatomic microscopy.

RESULTS AND LIMITATIONS

The longitudinal muscle of the anterior rectal wall was divided into anterior and posterior bundles at the junction of the rectum and anal canal. The intermediate fibers of the anterior bundle ended at the perineal body. The lateral fibers of the anterior bundle terminated at the posterior connective tissue of the bulbus penis. The DTPM occupied the space between the rhabdosphincter, rectum, and the bilateral levator ani muscle. Denonvillier's fascia terminated at the junction of the prostate and rhabdosphincter. Numerous slender nerves coming from the neurovascular bundle perforated the DTPM.

CONCLUSIONS

The anterior bundle of the longitudinal muscle of the rectum inserts into the bulbus penis forming the rectourethralis muscle and ends at the perineal body forming the rectoperinealis muscle. The anterior bundle and DTPM together may contribute to the rectal angle of the anterior rectal wall, and they support the posterior border of the rhabdosphincter.

Intergender differences in histological architecture of the fascia pelvis parietalis: a cadaveric study

The fascia pelvis parietalis (FPP) or endopelvic fascia is a well-known structure, but few studies described the detailed histological architecture, including the composite fiber directions. We hypothesized a gender-specific fiber architecture corresponding to the functional demand. For the first step to examine this hypothesis, we investigated specimens from 27 adult cadavers (10 males and 17 females) and 11 midterm fetuses (five males and six females) using immunohistochemistry and aldehyde-fuchsin staining. The adult female FPP was a solid, thick monolayered structure that was reinforced by abundant elastic fibers running across the striated muscle fibers, but it contained little or no smooth muscles (SM). In contrast, the male FPP was multilayered with abundant SM. In midterm fetuses, SM originated from the inferior part of the bladder and extended inferiorly along the gender-specific courses. Thus, we found a clear intergender difference in FPP architecture. However, the functional significance remained unknown because the basic architecture was common between nulliparous and multiparous women. Rather than for meeting the likely mechanical demands of pregnancy and vaginal delivery, the intergender difference of the FPP seemed to result from differences in the amount and migration course of bladder-derived SM as well as in hormonal background.

Resection of rectal cancer: a historical review

Local control of rectal cancer and patient survival have improved remarkably with advances in surgical techniques and adjuvant therapy. By applying advanced surgical principles, surgeons can now excise most rectal cancers completely, often preserving the anal sphincter and leaving the patient with relatively normal bowel and pelvic function. Historically, the earliest surgical approaches to rectal cancer were via the perineum. As surgical techniques and general anesthesia improved, other approaches such as a posterior approach were undertaken to improve access to the whole rectum. Consequently, abdominoperineal resection became the standard treatment until anterior resection was introduced for proximal rectal cancers. The most important surgical breakthrough in recent years has been the advent of total mesorectal excision (TME). The emphasis in rectal cancer surgery is on preservation of function, with dissection being done in appropriate anatomical planes. Thus, mobilization of the rectum has a long history, and is seen in modern procedures including TME and intersphincter resection. This article reviews the progression of the surgical management of rectal cancer with reference to historical perspectives. We discuss the major surgical considerations for mobilization of the rectum in several surgical procedures, from conventional operations to modern standardized TME.

Coexistence of adrenergic and cholinergic nerves in the inferior hypogastric plexus: anatomical and immunohistochemical study with 3D reconstruction in human male fetus

Classic anatomical methods have failed to determine the precise location, origin and nature of nerve fibres in the inferior hypogastric plexus (IHP). The purpose of this study was to identify the location and nature (adrenergic and/or cholinergic) of IHP nerve fibres and to provide a three-dimensional (3D) representation of pelvic nerves and their relationship to other anatomical structures. Serial transverse sections of the pelvic portion of two human male fetuses (16 and 17 weeks' gestation) were studied histologically and immunohistochemically, digitized and reconstructed three-dimensionally. 3D reconstruction allowed a 'computer-assisted dissection', identifying the precise location and distribution of the pelvic nerve elements. Proximal (supra-levator) and distal (infra-levator) communications between the pudendal nerve and IHP were observed. By determining the nature of the nerve fibres using immunostaining, we were able to demonstrate that the hypogastric nerves and pelvic splanchnic nerves, which are classically considered purely sympathetic and parasympathetic, respectively, contain both adrenergic and cholinergic nerve fibres. The pelvic autonomic nervous system is more complex than previously thought, as adrenergic and cholinergic fibres were found to co-exist in both 'sympathetic' and 'parasympathetic' nerves. This study is the first step to a 3D cartography of neurotransmitter distribution which could help in the selection of molecules to be used in the treatment of incontinence, erectile dysfunction and ejaculatory disorders.

A critical analysis of the current knowledge of surgical anatomy related to optimization of cancer control and preservation of continence and erection in candidates for radical prostatectomy

CONTEXT

Detailed knowledge of the anatomy of the prostate and adjacent tissues is mandatory during radical prostatectomy to ensure reliable oncologic and functional outcomes.

OBJECTIVE

To review critically and to summarize the available literature on surgical anatomy of the prostate and adjacent structures involved in cancer control, erectile function, and urinary continence.

EVIDENCE ACQUISITION

A search of the PubMed database was performed using the keywords radical prostatectomy, anatomy, neurovascular bundle, fascia, pelvis, and sphincter. Relevant articles and textbook chapters were reviewed, analyzed, and summarized.

EVIDENCE SYNTHESIS

Anatomy of the prostate and the adjacent tissues varies substantially. The fascia surrounding the prostate is multilayered, sometimes either fused with the prostate capsule or clearly separated from the capsule as a reflection of interindividual variations. The neurovascular bundle (NVB) is situated between the fascial layers covering the prostate. The NVB is composed of numerous nerve fibers superimposed on a scaffold of veins, arteries, and variable amounts of adipose tissue surrounding almost the entire lateral and posterior surfaces of the prostate. The NVB is also in close, cage-like contact to the seminal vesicles. The external urethral sphincter is a complex structure in close anatomic and functional relationship to the pelvic floor, and its fragile innervation is in close association to the prostate apex. Finally, the shape and size of the prostate can significantly modify the anatomy of the NVB, the urethral sphincter, the dorsal vascular complex, and the pubovesical/puboprostatic ligaments.

CONCLUSIONS

The surgical anatomy of the prostate and adjacent tissues involved in radical prostatectomy is complex. Precise knowledge of all relevant anatomic structures facilitates surgical orientation and dissection during radical prostatectomy and ideally translates into both superior rates of cancer control and improved functional outcomes postoperatively.

Electrical field and temperature model of nonthermal irreversible electroporation in heterogeneous tissues

Nonthermal irreversible electroporation (NTIRE) is a new minimally invasive surgical technique that is part of the emerging field of molecular surgery, which holds the potential to treat diseases with unprecedented accuracy. NTIRE utilizes electrical pulses delivered to a targeted area, producing irreversible damage to the cell membrane. Because NTIRE does not cause thermal damage, the integrity of all other molecules, collagen, and elastin in the targeted area is preserved. Previous theoretical studies have only examined NTIRE in homogeneous tissues; however, biological structures are complex collections of diverse tissues. In order to develop electroporation as a precise treatment in clinical applications, realistic models are necessary. Therefore, the purpose of this study was to refine electroporation as a treatment by examining the effect of NTIRE in heterogeneous tissues of the prostate and breast. This study uses a two-dimensional finite element solution of the Laplace and bioheat equations to examine the effects of heterogeneities on electric field and temperature distribution. Three different heterogeneous structures were taken into account: nerves, blood vessels, and ducts. The results of this study demonstrate that heterogeneities significantly impact both the temperature and electrical field distribution in surrounding tissues, indicating that heterogeneities should not be neglected. The results were promising. While the surrounding tissue experienced a high electrical field, the axon of the nerve, the interior of the blood vessel, and the ducts experienced no electrical field. This indicates that blood vessels, nerves, and lactiferous ducts adjacent to a tumor treated with electroporation will survive, while the cancerous lesion is ablated. This study clearly demonstrates the importance of considering heterogeneity in NTIRE applications.

Anatomical description of the periprostatic nerves in the male rhesus monkey (Macaca mulatta)

OBJECTIVES

Recent publications have revealed a variable course of the periprostatic nerves in humans. It is unclear to what extent nerves outside the dorsolateral region of the prostate are involved in the physiology of erectile function. As functional studies in humans are limited by ethical aspects investigations in animal models could provide further insight. The intention of this study was to give a detailed description of the topographical anatomy of autonomic nerves along the seminal vesicles and the prostate in male rhesus monkeys (Macaca mulatta) to investigate its suitability as an animal model for future physiological studies.

METHODS

Wholemount serial sections of pelvic organ blocks of ten male rhesus monkeys were investigated. Autonomic nerves were stained with an antibody against S100.

RESULTS

Autonomic nerves were dispersed along the dorsolateral to the ventrolateral aspect of the capsule of the prostate within a layer of connective tissue. There was no accumulation of vessels and nerves in the dorsolateral position of the prostate. The prostate is located dorsally to the urethra and does not encircle it. No adjacent nerves were found in the cranial two-thirds of the seminal vesicles.

CONCLUSIONS

The male rhesus monkey is limited suitable as an animal model for studies on the periprostatic nerves provided the following differences to humans are considered: the special topography of the prostate, the nerve course along the seminal vesicles and the missing nerve accumulation dorsolaterally to the prostate.