Diabetic penile neuropathy.

In vitro studies strongly suggest the presence of autonomic neuropathy in impotent patients with diabetes mellitus. Morphologic studies reveal structural damage to the penile autonomic nerves. Biochemical, histochemical, and immunohistochemical evidence suggests a general depletion of the adrenergic, cholinergic, and NANC neurotransmitter systems that control penile erection. These in vitro studies on human tissue are, however, not performed with appropriate control tissue from potent patients with diabetes mellitus. For this reason, it is important to study diabetic penile neuropathy by developing animal models. The investigative work by Crowe and Fani in streptozocin-induced diabetes mellitus is encouraging, but more research efforts should be directed toward this objective. Clinical testing is needed to assess the functionality of the autonomic corporal nerves objectively. At present, the patient's erectile response to an intracavernosal injection of vasoactive agents is being studied. If there is an isolated autonomic neuropathy, as commonly exists in young patients with spinal cord injury, the erectile response to the intracavernosal injection is immediate and complete. This intracavernosal injection test for autonomic neuropathy records hemodynamic and not neurophysiologic responses. In patients with an accompanying hemodynamic impairment, such as cavernosal artery insufficiency or corporal veno-occlusive dysfunction, as commonly exists in patients with diabetes mellitus, the hemodynamic erectile response to the intracavernosal injection is impaired, and the presence or absence of autonomic neuropathy is subsequently masked.