Klaus-Peter Juenemann

Clinical Significance of Sacral and Pudendal Nerve Anatomy

The neuroanatomy and neurophysiology of the external urethral closure mechanisms still are under debate because the motor fibers that emanate from the sacral plexus and pudendal nerve to supply this segment have not been traced, nor has their functional interrelationship been established. Therefore, we dissected 3 male human cadavers (aged 31 to 69 years) by tracing the entire sacral plexus, particularly the pudendal nerve, from the cauda equina throughout the branching of the nerves to their final destination. The dissection demonstrated that the extrinsic urethral sphincter, formed by the rhabdosphincter around the membranous urethra as well as the levator ani muscle and pelvic floor (especially the transversus perinei muscle), is innervated by somatic nerve fibers that emanate primarily from sacral roots S2 and S3. In 5 patients with neurogenic lower urinary tract dysfunction electrostimulation of the sacral root and pudendal nerve markedly increased intraurethral closure pressures. Stimulation of the pudendal nerve or its transversus perinei branch alone resulted in an increase in intraurethral closure pressure to 60 to 70 cm. water--an increase similar to that produced by stimulation of the sacral root without neurotomy. By means of neurotomy and/or neural blockade with lidocaine we were able to differentiate between the contributions of each muscular element to the external sphincteric mechanism. Almost 70 per cent of the closure pressure of the external urethral sphincter is induced by stimulation of the S3 ventral root, while the other 30 per cent derives from S2 and S4 neuronal impulses.

Mechanisms of venous occlusion during canine penile erection: an anatomic demonstration

Hemodynamic studies have clearly demonstrated that intracorporeal injection of papaverine causes an increase of venous outflow resistance, and we therefore undertook a study of the venous drainage of the canine penis to delineate the anatomic changes in the venular structure during papaverine-induced erection. In 11 dogs, the corpora cavernosa were examined by corrosion casting in six and serial trichrome staining and histologic sectioning in five. Low-power scanning electron microscopy of the corrosion casts demonstrated the existence of a venular plexus interposed between the tunica albuginea and the sinusoidal spaces. After papaverine injection, this subalbugineal venular plexus is compressed between the dilated sinusoids from below and the tunica albuginea from above, such that venous drainage is effectively impeded. Examination of two cadaveric human penile corrosion casts by low-power scanning electron microscopy revealed evidence of a similar subalbugineal venular plexus draining into the emissary veins along the shaft of the penis. Based on the above, a model for the anatomic basis of venous occlusion during penile erection is outlined. Along with arteriolar and sinusoidal smooth-muscle relaxation, this can account for the three basic hemodynamic changes necessary for erection: increased arterial inflow, increased intracorporeal pressure, and increased venous outflow resistance.

Hemodynamics of Papaverine- and Phentolamine-Induced Penile Erection

We investigated the hemodynamic changes induced in the canine corpora cavernosa by intracorporeal injection of papaverine or phentolamine. In six dogs studied, papaverine profoundly increased the resistance to venous outflow, whereas phentolamine (an alpha-adrenergic blocker) had little or no effect. In four other dogs, flow within the internal pudendal artery was measured with an ultrasonic flow probe placed directly on the artery. Papaverine increased arterial flow by 300 to 700 per cent over baseline levels, whereas the increase with phentolamine was only 50 to 100 per cent. We conclude that papaverine, by virtue of its direct smooth-muscle-relaxing properties, has a dual hemodynamic effect: it decreases the resistance to arterial inflow, thereby allowing large increases in the flow of blood into the penis during tumescence; and increases the resistance to venous outflow. Phentolamine only decreases the resistance to arterial inflow, more modestly than papaverine, and does not increase the resistance to venous outflow.

The Effect of Cigarette Smoking on Penile Erection

Clinical observations suggest that cigarette smoking impairs erectile function in patients with moderate arterial insufficiency. To evaluate the effects of smoking on the physiology of erection, we studied six healthy adult mongrel dogs in which bipolar cuff electrodes were implanted around the cavernous nerves. After threshold stimulation parameters for penile erection were established, cigarette smoke collected in a 60-ml. syringe was released slowly near the dogs mouth, to be inhaled by natural breathing. Stimulation of the cavernous nerve was repeated and blood samples for nicotine, cotinine and blood gases were obtained before and after each cigarette. The systolic and intracorporeal pressure, flow through the internal pudendal artery, and venous flow from the corpora cavernosa were recorded at baseline and with each electrostimulation after smoke inhalation. Five of the six dogs were unable to achieve full erection after inhalation of smoke from two to three cigarettes. Some decrease of flow through the internal pudendal artery occurred and the venous restriction ability was almost completely abolished by smoking. Further, when nicotine was injected intravenously into two additional dogs, the same phenomenon was observed. These findings support the idea that cigarette smoking may contribute to impotence in some patients.

The Role of Vasoactive Intestinal Polypeptide as a Neurotransmitter in Canine Penile Erection: A Combined in Vivo and Immunohistochemical Study

Vasoactive intestinal polypeptide (VIP), a 28-amino-acid polypeptide found in the human gut and genitourinary tract, primarily affects vasodilation and smooth-muscle relaxation. These effects have led to speculation that this neuropeptide may be a neurotransmitter in certain bodily functions, such as penile erection. We therefore designed an in vivo animal model to elucidate the influence of VIP and VIP antibody on the different stages of penile erection. We also performed immunohistochemical studies of the penile tissue to obtain further information about the distribution of VIP in the corpora cavernosa. Intracavernous injection of VIP induced penile erection. Its effect on arterial inflow was minor, but it caused active venous outflow restriction and was important in maintaining erection. VIP antibody blocked venous outflow restriction during neurostimulation-induced erection. VIP was found in the cavernous tissue (in the area between the smooth-muscle cells and the sinusoidal spaces) in close proximity to the arteries. We conclude that VIP is a neurotransmitter in the erectile tissue of the penis, and that its effects are similar to those from electrostimulation of the cavernous nerve. VIP increases arterial flow, decreases venous flow, and induces sinusoidal relaxation.

Priapism induced by chlorpromazine and trazodone: mechanism of action.

To investigate the mechanism of drug-induced priapism, we gave the antipsychotic agent chlorpromazine and the antidepressant trazodone to 14 dogs by intravenous and intracorporeal injection. Bilateral intracorporeal pressure, blood flow within the internal pudendal artery, and systemic blood pressure were monitored. Venous outflow restriction was evaluated by continuous saline infusion of the corpus cavernosum with the infrarenal aorta clamped. When delivered by intracorporeal injection, both drugs induced erection in a manner similar to that of intracorporeal injection of papaverine. Internal pudendal arterial flow increased slightly at the beginning of tumescence, and excellent venous restriction occurred. Intravenous injection, however, could neither induce an erection nor facilitate an erection after sub-threshold neurostimulation. We believe that the alpha-adrenergic antagonist properties of chlorpromazine and trazodone probably cause priapism by local action.

Chronic Papaverine Treatment: The Effect of Repeated Injections on the Simian Erectile Response and Penile Tissue

To investigate the effect of chronic papaverine treatment, seven monkeys underwent repeated intracavernous injections for one year. One monkey died after 56 injections; the others received a total of 100 each. The strength and duration of erection were recorded after each injection, and the erectile tissue was examined histologically at the end of the study. Over the long term, papaverine maintains its erection-inducing capability, but it does cause pathologic changes in the erectile tissue: minimal to marked fibrosis at the injection site and hypertrophy of smooth muscle in the non-injected area of the corpus.

Blood Gas Analysis in Drug-Induced Penile Erection

To elucidate the hemodynamic changes during erection, we measured corporeal blood gases in 6 monkeys before, during, and after erection induced by either papaverine or phentolamine or a combination of the two. Papaverine alone caused a strong erection (maximal tumescence and rigidity) by means of a rapid, large increase in pO2 and pCO2 with a pH drop to the acidic range. Phentolamine alone caused delayed tumescence with less rigidity; the intracorporeal pO2 level increased, but pCO2 and pH values did not change significantly. The combination of both drugs offered no advantage over papaverine alone. We conclude that papaverine is a potent erection-inducing drug that acts in a bimodal manner, namely, it increases the arterial inflow and, at the same time, decreases the venous outflow. Phentolamine affects the arterial component of erectile function only.

Lymph-node metastases in intermediate-risk squamous cell carcinoma of the penis

To evaluate the metastatic risk of pT1 G2 squamous cell carcinoma (SCC) of the penis.

Penile Carcinoma (pT1 G2): Surveillance or Inguinal Lymph Node Dissection?

Background: Due to the low incidence of squamous cell penile cancer and lack of well-designed studies, controversies persist over the therapeutic approach in patients with pT1 G2 carcinoma. Patients and Methods: Between 1992 and 2003, 16 patients with T1 squamous penile cancer were treated in our institution either by surveillance or by inguinal lymph node dissection (ILND). Results: A total of 8 primary lesions were classified as pT1 G2 carcinoma with 4 tumors developing early or delayed inguinal metastatic disease. Conclusions: The natural behavior of pT1 G2 squamous penile carcinoma and its metastatic potential has been underestimated in recent literature. Since morbidity after early ILND has markedly decreased and its superiority over delayed ILND has been shown, we advocate the early modified inguinal lymph node dissection until strong prognostic factors for positive inguinal lymph nodes have been validated.