Neurophysiological Testing to Assess Penile Sensory Nerve Damage After Radical Prostatectomy

Molecular characterization of human peripheral nerves using desorption electrospray ionization mass spectrometry imaging

Desorption electrospray ionization mass spectrometry imaging (DESI-MSI) is a molecular imaging method that can be used to elucidate the small-molecule composition of tissues and map their spatial information using two-dimensional ion images. This technique has been used to investigate the molecular profiles of variety of tissues, including within the central nervous system, specifically the brain and spinal cord. To our knowledge, this technique has yet to be applied to tissues of the peripheral nervous system (PNS). Data generated from such analyses are expected to advance the characterization of these structures. The study aimed to: (i) establish whether DESI-MSI can discriminate the molecular characteristics of peripheral nerves and distinguish them from surrounding tissues and (ii) assess whether different peripheral nerve subtypes are characterized by unique molecular profiles. Four different nerves for which are known to carry various nerve fiber types were harvested from a fresh cadaveric donor: mixed, motor and sensory (sciatic and femoral); cutaneous, sensory (sural); and autonomic (vagus). Tissue samples were harvested to include the nerve bundles in addition to surrounding connective tissue. Samples were flash-frozen, embedded in optimal cutting temperature compound in cross-section, and sectioned at 14 μm. Following DESI-MSI analysis, identical tissue sections were stained with hematoxylin and eosin. In this proof-of-concept study, a combination of multivariate and univariate statistical methods was used to evaluate molecular differences between the nerve and adjacent tissue and between nerve subtypes. The acquired mass spectral profiles of the peripheral nerve samples presented trends in ion abundances that seemed to be characteristic of nerve tissue and spatially corresponded to the associated histology of the tissue sections. Principal component analysis (PCA) supported the separation of the samples into distinct nerve and adjacent tissue classes. This classification was further supported by the K-means clustering analysis, which showed separation of the nerve and background ions. Differences in ion expression were confirmed using ANOVA which identified statistically significant differences in ion expression between the nerve subtypes. The PCA plot suggested some separation of the nerve subtypes into four classes which corresponded with the nerve types. This was supported by the K-means clustering. Some overlap in classes was noted in these two clustering analyses. This study provides emerging evidence that DESI-MSI is an effective tool for metabolomic profiling of peripheral nerves. Our results suggest that peripheral nerves have molecular profiles that are distinct from the surrounding connective tissues and that DESI-MSI may be able to discriminate between nerve subtypes. DESI-MSI of peripheral nerves may be a valuable technique that could be used to improve our understanding of peripheral nerve anatomy and physiology. The ability to utilize ambient mass spectrometry techniques in real time could also provide an unprecedented advantage for surgical decision making, including in nerve-sparing procedures in the future.

Assessment of changes in penile sensation by electrophysiological study after radical prostatectomy: A pilot study

Background:

To evaluate the changes in penile sensation by electrophysiological tests in patients who underwent radical prostatectomy (RP) and to demonstrate the role of dorsal penile nerve injury in postoperative erectile dysfunction.

Materials and methods:

Twenty-six volunteer patients who were eligible for RP were included in the study. Preoperative penile sensory electromyography and the International Index of Erectile Function-5 (IIEF-5) questionnaire were done for each patient. Erectile function assessment and electrophysiological evaluation of penile sensation were repeated at postoperative 3rd and 6th months.

Results:

Postoperative IIEF-5 scores and electromyography values were significantly lower than preoperative findings (p < 0.05). The IIEF-5 scores in the nerve sparing-RP (NS-RP) group were significantly higher than the non-nerve sparing-RP (NNS-RP) group in the postoperative period. Nerve conduction velocity values in the NS-RP group were also higher than the NNS-RP group at the postoperative 3rd and 6th months. However, these changes were not statistically significant (p > 0.05).

Conclusions:

Patients who underwent RP have decreased penile sensation due to cavernous nerve damage and a possible dorsal penile nerve injury. The decrease of penile sensation may be associated with postoperative erectile dysfunction.

Use of a specific questionnaire and perineal electromyography to assess neuropathic pain after radical retropubic prostatectomy

Objective

Prostate cancer is the most frequent cancer in men and radical retropubic prostatectomy (RRP) is one of the first-line treatment. However, RRP has some side effects and can lead to chronic perineal pain. The objective of the study was to determine in patients suffering from perineal pain after RRP the possibility of a neurogenic damage by means of a specific questionnaire dedicated to track down neuropathic pain.

Methods

Forty patients were explored by a specific and validated questionnaire, the Neuropathic Pain Symptom Inventory (NPSI). Patients were divided into two groups: Group A with an NSPI score ≥4 was considered as suffering from neuropathic pain, and Group B was considered as a control group without neuropathic pain (NSPI score <4). All patients had a perineal electrophysiological testing to confirm the possibility of a neurogenic damage.

Results

Group A was composed by 13 men and Group B by 27 men, with mean age 72.45 years and mean duration of pain 2.7 years. In Group A, the most frequent symptoms were burning sensation, electrical shock and numbness. Location of the pain was global perineal area (8/13), anus (10/13), penis (5/13) and glans penis (2/13). Electromyography (EMG) findings confirmed the presence of denervation and neurogenic damages compared with controls (p < 0.001).

Conclusion

One third of the patients consulting for chronic pain following RRP had probably a neuropathic lesion leading to a chronic perineal pain as suggested by an NSPI score ≥ 4 and EMG alterations.

nNOS-positive minor-branches of the dorsal penile nerves is associated with erectile function in the bilateral cavernous injury model of rats

The changes in neuronal nitric oxide synthases (nNOS) in the dorsal penile nerves (DPNs) are consistent with cavernous nerve (CN) injury in rat models. However, the anatomical relationship and morphological changes between the minor branches of the DPNs and the CNs after injury have never been clearly explored. There were forty 12 week old male Sprague-Dawley rats receiving bilateral cavernous nerve injury (BCNI). Erectile function of intracavernous pressure and mean arterial pressure were measured. The histology and ultrastructure with H&E stain, Masson's trichrome stain and immunohistochemical stains were applied on the examination of CNs and DPNs. We demonstrated communicating nerve branches between the DPNs and the CNs in rats. The greatest damage and lowest erectile function were seen in the 14^th day and partially recovered in the 28^th day after BCNI. The nNOS positive DPN minor branches' number was significantly correlated with erectile function. The sub-analysis of the number of nNOS positive DPN minor branches also matched with the time course of the erectile function after BCNI. We suggest the regeneration of the DPNs minor branches would ameliorate the erectile function in BCNI rats.

Intravenous Infusion of Bone Marrow-Derived Mesenchymal Stem Cells Reduces Erectile Dysfunction Following Cavernous Nerve Injury in Rats

Introduction

Intravenous preload (delivered before cavernous nerve [CN] injury) of bone marrow–derived mesenchymal stem cells (MSCs) can prevent or decrease postoperative erectile dysfunction (J Sex Med 2015;12:1713–1721). In the present study, the potential therapeutic effects of intravenously administered MSCs on postoperative erectile dysfunction were evaluated in a rat model of CN injury.

Methods

Male Sprague-Dawley rats were randomized into 2 groups after electric CN injury. Intravenous infusion of bone marrow–derived MSCs (1.0 × 10⁶ cells in Dulbecco's modified Eagle's medium 1 mL) or vehicle (Dulbecco's modified Eagle's medium 1 mL) was performed 3 hours after electrocautery-induced CN injury.

Main Outcome Measures

To assess erectile function, we measured intracavernous pressure at 4 weeks after MSC or vehicle infusion. Histologic examinations were performed to investigate neuronal innervation and inhibition of smooth muscle atrophy. Green fluorescent protein–positive bone marrow–derived MSCs were used for cell tracking. To investigate mRNA expression levels of neurotrophins in the major pelvic ganglia (MPGs), quantitative real-time polymerase chain reaction was performed.

Results

The decrease of intracavernous pressure corrected for arterial pressure and area under the curve of intracavernous pressure in the bone marrow–derived MSC group was significantly lower than that in the vehicle group at 4 weeks after infusion (P < .05). Retrograde neuronal tracing indicated that the MSC group had a larger number of FluoroGold-positive neurons in the MPGs compared with the vehicle group. The ratio of smooth muscle to collagen in the MSC group was significantly higher than in the vehicle group. Green fluorescent protein–positive bone marrow–derived MSCs were detected in the MPGs and injured CNs using confocal microscopy, indicating homing of cells to the MPGs and injured CNs. Brain-derived neurotrophic factor and glial cell-derived neurotrophic factor expression levels in the MPGs were significantly higher in the MSC group than in the vehicle group (P < .01).

Conclusion

Intravenous infusion of bone marrow–derived MSCs after CN injury might have therapeutic efficacy in experimental erectile dysfunction.

Matsuda Y, Sasaki M, Kataoka-Sasaki Y, et al. Intravenous Infusion of Bone Marrow–Derived Mesenchymal Stem Cells Reduces Erectile Dysfunction Following Cavernous Nerve Injury in Rats. Sex Med 2018;6:49–57.

Stem-cell therapy for erectile dysfunction

Stem cell-based therapies have been recently investigated in the field of organic erectile dysfunctions, such as those associated with diabetes or the treatment of prostate cancer. The overall aim is to repair the repair the underlying penile cellular damage. Here, we review the rationale behind the use of stem cells injection in post-radical prostatectomy erectile dysfunction (pRP-ED).Radical prostatectomy for prostate cancer induces complex neurologic and vascular injuries that cause one of the most difficult-to-treat forms of erectile dysfunction. Evidence from animal models replicating pRP-ED suggests that intracavernous injection of autologous bone marrow mononuclear cells (BM-MNCs) may represent the first curative approach. Several clinical trials are ongoing and two of them have been completed with encouraging results.

A Novel Collaborative Protocol for Successful Management of Penile Pain Mediated by Radiculitis of Sacral Spinal Nerve Roots From Tarlov Cysts

INTRODUCTION

Since 14 years of age, the patient had experienced extreme penile pain within seconds of initial sexual arousal through masturbation. Penile pain was so severe that he rarely proceeded to orgasm or ejaculation. After 7 years of undergoing multiple unsuccessful treatments, he was concerned for his long-term mental health and for his future ability to have relationships.

AIM

To describe a novel collaboration among specialists in sexual medicine, neurophysiology, and spine surgery that led to successful management.

METHODS

Collaborating health care providers conferred with the referring physician, patient, and parents and included a review of all medical records.

MAIN OUTCOME MEASURE

Elimination of postpubertal intense penile pain during sexual arousal.

RESULTS

The patient presented to our sexual medicine facility at 21 years of age. The sexual medicine physician identifying the sexual health complaint noted a pelvic magnetic resonance imaging report of an incidental sacral Tarlov cyst. A subsequent sacral magnetic resonance image showed four sacral Tarlov cysts, with the largest measuring 18 mm. Neuro-genital testing result were abnormal. The neurophysiologist hypothesized the patient's pain at erection was produced by Tarlov cyst-induced neuropathic irritation of sensory fibers that course within the pelvic nerve. The spine surgeon directed a diagnostic injection of bupivacaine to the sacral nerve roots and subsequently morphine to the conus medullaris of the spinal cord. The bupivacaine produced general penile numbness; the morphine selectively decreased penile pain symptoms during sexual arousal without blocking penile skin sensation. The collaboration among specialties led to the conclusion that the Tarlov cysts were pathophysiologically mediating the penile pain symptoms during arousal. Long-term follow-up after surgical repair showed complete symptom elimination at 18 months after treatment.

CONCLUSION

This case provides evidence that (i) Tarlov cysts can cause sacral spinal nerve root radiculitis through sensory pelvic nerve and (ii) there are management benefits from collaboration among sexual medicine, neurophysiology, and spine surgery subspecialties. Goldstein I, Komisaruk BR, Rubin RS, et al. A Novel Collaborative Protocol for Successful Management of Penile Pain Mediated by Radiculitis of Sacral Spinal Nerve Roots From Tarlov Cysts. Sex Med 2017;5:e203-e211.

Measurement of electrochemical conductance of penile skin using Sudoscan®: A new tool to assess neurogenic impotence

OBJECTIVES

To investigate the value of electrochemical skin conductance (ESC) measurement at penile level using Sudoscan^® for the diagnosis of neurogenic impotence in diabetics.

METHODS

The following neurophysiological parameters were assessed in 25 male diabetics who complained of impotence and 25 age-matched normal male subjects without erectile dysfunction (age range: 29-70 years): ESC, sympathetic skin responses (SSR), warm detection thresholds (WDT), and cold detection thresholds (CDT) for the penis and the feet, vibration detection thresholds (VDT) for the penis, and sensory nerve conduction study of the dorsal nerve of the penis (DNP) with sensory nerve action potential (SNAP) recording.

RESULTS

Diabetic patients with impotence differed from controls with regard to most neurophysiological results at both penile and foot levels. Among penile innervation variables in the group of impotent diabetics, penile ESC was found to be the most frequently abnormal (80% of patients), followed by penile WDT, CDT, and DNP-SNAP amplitude (52% of patients), and then penile SSR amplitude and VDT (44% of patients). Various combinations of abnormalities were observed: penile ESC was the only abnormal test in 2 patients, while all tests were abnormal in 2 patients and remained normal in only one patient.

CONCLUSION

Erectile dysfunction is common in diabetic men, but the diagnosis of a neurogenic origin is challenging. This study showed that ESC measurement using Sudoscan^® is feasible and more sensitive than SSR recordings to show penile sympathetic innervation impairment. This new test should be further studied to better define its diagnostic accuracy and clinical correlates.

[Sexual consequences after treatment of prostate cancer: Inquiry among members of the Association Nationale des Malades du Cancer de la Prostate]

INTRODUCTION

Complications of prostate cancer treatments are responsible of a lower quality of life. We evaluated the prevalence and the perceptions of sexual consequences of prostate cancer treatments.

MATERIALS AND METHODS

A retrospective self-administered questionnaire was sent to all the members of the Association Nationale des Malades du Cancer de la Prostate (ANAMACAP). All the answers were analyzed.

RESULTS

226 questionnaires were analyzed, the average age was 67.3 years old, the average follow-up was 58.1 months. 110 patients had surgery only, 29 had hormone therapy plus radiotherapy, 28 had radiation therapy only and 49 had combined treatments. After the treatment of the prostate cancer, an erectile dysfunction was reported by 75.2% of the patients; an orgasmic dysfunction by 69%; a climacturia by 21%; a reduced penile length by 70% of them and a less sensitive glans by 59%. They were responsible of a lower quality of life for 75% to 90% of the patients depending on the symptom. A PDE5-inhibitor treatment was effective for only 25.6% of them when taken daily and for 39% on demand.

CONCLUSION

Functional consequences of prostate cancer treatments are common, diverse and directly involved in the sexual life. It is necessary to improve therapeutical education and onco-sexology with the help of patients' associations, to build a new balance in the couples.

LEVEL OF EVIDENCE

3.

Evaluation of young men with organic erectile dysfunction

Erectile dysfunction (ED) in men under the age of 40 was once thought to be entirely psychogenic. Over the last few decades, advances in our understanding of erectile physiology and improvements in diagnostic testing have restructured our understanding of ED and its etiologies. Although psychogenic ED is more prevalent in the younger population, at least 15%-20% of these men have an organic etiology. Organic ED has been shown to be a predictor of increased future morbidity and mortality. As such, a thorough work-up should be employed for any man with complaints of sexual dysfunction. Oftentimes a treatment plan can be formulated after a focused history, physical exam and basic lab-work are conducted. However, in certain complex cases, more testing can be employed. The major organic etiologies can be subdivided into vascular, neurologic, and endocrine. Specific testing should be directed by clinical clues noted during the preliminary evaluation. These tests vary in degree of invasiveness, precision, and at times may not affect treatment. Results should be integrated into the overall clinical picture to assist in diagnosis and help guide therapy.

Comprehensive evaluation of embarrassment and pain associated with invasive urodynamics

AIMS

To evaluate pain and embarrassment associated with invasive urodynamics and to determine underlying factors.

METHODS

One hundred seventy one consecutive patients referred to our department for invasive urodynamics were evaluated using visual numeric rating scales for sensations of apprehension, pain, and embarrassment during several steps of the procedure (scores ranging from 0 [no symptom] to 10 [worst imaginable symptom]). We also investigated the influence of sex, age, information provided before urodynamics, and medical indication on these sensations. The Spearman correlation, non-parametric test, and logistic regression analysis were performed to determine explicative factors for the most painful sensations.

RESULTS

The mean age was 61.0 (standard deviation ± 15 years). The mean (95% confidence interval [CI]) apprehension level was 2.9/10 (2.4; 3.4). The mean (95% CI) pain levels at installation on urodynamic table, transurethral catheter insertion (cystometry), and catheter repositioning (urethral pressure profilometry) were 0.3/10 (0.1; 0.5), 1.9/10 (1.6; 2.3), and 1.3/10 (1.0; 1.7), respectively. At catheter insertion, 25% of patients reported a pain level ≥ 4/10. The mean embarrassment level due to urination in front of the doctor was 1.9/10 (1.4; 2.3). Painful sensations reported during the different steps were strongly correlated with each other and with levels of apprehension and embarrassment. Age <54 years (lower quartile) and apprehension level were the only factors associated with painful sensation.

CONCLUSIONS

Our study confirms that invasive urodynamics is a well-tolerated procedure. However, some patients experience high levels of pain and embarrassment throughout the procedure. Younger age and apprehension were the most influential factors.

Standard operating procedures for neurophysiologic assessment of male sexual dysfunction

INTRODUCTION

Can neurophysiological testing in male patients with sexual dysfunction benefit the decision-making process? The answer remains unclear.

AIM

To provide standard operating procedures for the neurophysiologic assessment of male sexual dysfunction.

METHODS

Medical literature was reviewed and combined with expert opinion of the authors.

RESULTS

Bulbocavernosus reflex latency time, pudendal somatosensory evoked potentials, and sympathetic skin responses have been considered as potential candidates for the diagnosis and assessment of erectile dysfunction (ED). Currently, there is no consensus on a standardized methodology for these neurophysiological investigations in the overall assessment of ED. These procedures are unable to assess the integrity of the efferent parasympathetic proerectile penile innervation; accordingly, none of these assessment procedures is recommended for ED patients. Corpus cavernosum electromyography (CC-EMG) can detect abnormalities in cavernous smooth muscle although these alterations can be attributed both to damage to autonomic penile innervation and to degenerative processes of the cavernous smooth muscle. CC-EMG is still considered experimental. Evidence does not support that men with premature ejaculation (PE) are consistently characterized by penile hypersensitivity; accordingly, penile threshold determination is not recommended to in the diagnosis of PE. Neurophysiological investigation of other components of the penile sensory pathways in PE patients has not provided any definitive contribution to the diagnosis.

CONCLUSION

No neurophysiological assessment procedures yield additional information that consistently aids in the assessment of PE and ED.