Anatomical Study of the Human Pudendal Nerve and its Application in Clinical Practice

Background: The pudendal nerve block is widely used in patients undergoing gyaenecologic, obstetric and penile surgery. But in some cases, the pudendal nerve block may fail and be ineffective. This may be due to failure of localization of the pudendal nerve or anatomical variations in its origin, course or branching pattern.  Aim of the work was to study the anatomical variations of the pudendal nerve and the accurate localization of the pudendal nerve in relation to surface landmarks such as the ischial spine. Materials and Methods: This study was carried out on thirteen dissected human Egyptian pelves, gluteal regions and perineums (11 males and 2 females). Results: According to our examinations, the roots and trunks of the pudendal nerve could be grouped into four types: In Type I, the pudendal nerve arose from s3&4  in the form of one trunk (19.2%). This trunk divided into inferior rectal nerve, perineal nerve and dorsal nerve of the penis. In Type II, the pudendal nerve arose from s2,3&4 in the form of two trunks (34.6%). The medial trunk continued as the inferior rectal nerve, while the lateral trunk divided into perineal nerve and dorsal nerve of penis. In Type III, the pudendal nerve arose from s2&3  in the form of two trunks (15.5%). The lateral trunk got connected with the sciatic nerve, while the medial trunk divided into the perineal nerve and dorsal nerve of the penis. The inferior rectal nerve arose directly from the 3rd sacral nerve. In Type 1V, the pudendal nerve arose from s2&3 in the form of one trunk (30.8%). The origin of the inferior rectal nerve was variable. In 50%, it arose as a branch from the pudendal nerve after passing through the greater sciatic foramen. In 34.6%, the inferior rectal nerve was the continuation of the medial trunk of the pudendal nerve. In 15.4%, it arose directly from S3 and never joined the pudendal nerve. The dorsal nerve of the penis divided into two branches (medial and lateral) in 81.8% and three branches (medial, lateral and ventral) in18.2%. The medial branches of both sides communicated with each other to form a plexus behind the corona glandis to supply the glans. The ischial spine was an essential bony landmark for localization of the pudendal nerve. In the gluteal region, the point of the tip of the ischial spine represented the junction between the upper 2/3 and the lower 1/3 of a line extending between the posterior superior iliac spine and the ischial tuberosity. The point of crossing of the pudendal nerve to the sacrospinous ligament lay 1±0.5 cm medial to the point of the tip of the ischial spine. The surface line of the pudendal nerve divided equally the line extending between the base of the coccyx and the ischial tuberosity.