Variation in course of cavernous nerve with special reference to details of topographic relationships near prostatic apex: histologic study using male cadavers.

OBJECTIVES: To study interindividual variation in the cavernous nerve course near the rhabdosphincter and the apex of the prostate as a basis for refining nerve-sparing radical prostatectomy. The varying anatomy of the cavernous nerve might account for the disparate potency rates after nerve-sparing radical prostatectomy.
METHODS: We examined serial histologic sections from 20 male pelves (7 frontal, 8 sagittal, and 5 axial sections) and performed 5 fresh cadaver dissections.
RESULTS: In the fresh dissections, the macroscopically identified neurovascular bundle consistently showed an almost straight proximal-to-distal course along the urethra. However, on histologic analysis, the types of the nerve course were classified as frontal (2 of 7 specimens), sagittal (3 of 8), and axial (2 of 5). In the frontal and sagittal courses, the nerves passed through the connective tissue of a narrow potential space between the rhabdosphincter and the levator ani. In the specimens showing an axial course, the nerves were spatially distinct from the prostate, coursing ventromedially in the pararectal space. Thus, the nerves could display a long, tortuous course, passing through the rectourethral muscle at its thickest portion. In addition, a nerve component supplying the area of the rhabdosphincter seemed to accompany the cavernous nerve.
CONCLUSIONS: The neurovascular bundle, previously defined in terms of surgery, is likely to differ from the actual course of the cavernous nerve when this is axial, passing through the pararectal space and rectourethral muscle. To avoid cavernous nerve injury, the rectourethral muscle must be managed carefully in both the retropubic and the perineal approaches.