Anatomy of the Pudendal Nerve at the Urogenital Diaphragm—A New Critical Site for Nerve Entrapment

Entrapment neuropathies of the pudendal nerve are uncommon and therefore often overlooked or misdiagnosed clinical entities. Detailed relationships of this nerve as it exits the pelvis through the urogenital diaphragm and enters the mobile part of the penis have not yet been delineated. It was the purpose of this work to investigate the relationships of the pudendal nerve in this complex anatomical region and to determine possible entrapment sites that are accessible for surgical decompression.

Detailed anatomic dissections were carried out in 10 formalin-preserved hemipelvices under X3.5 loupe magnification. The pudendal nerve was dissected from the entrance into Alcock's canal to the dorsum of the penis. The branching pattern of the nerve and its topographical relationship were recorded and photographs taken.

The dissections revealed that the pudendal nerve passes through a tight osteofibrotic canal just distal to the urogenital diaphragm at the entrance to the base of the penis. This canal is, in part, formed by the inferior ramus of the pubic bone, the suspensory ligament of the penis, and the ischiocavernous body. In two specimens, a fusiform pseudoneuromatous thickening was found.

The pudendal nerve is susceptible to compression at the passage from Alcock's canal to the dorsum of the penis. Individuals who are exposed to repetitive mechanical irritation in this region are especially endangered. Diabetic patients with peripheral neuropathy can suffer from additional compression neuropathy with decreased penile sensibility and will benefit from decompression of the pudendal nerve.