Neuroanatomy and clinical significance of the external urethral sphincter

Although the topographic muscular architecture of the pelvic floor is essentially understood, its nerve supply and functional anatomy remain controversial. We therefore dissected 3 male human cadavers by tracing the entire sacral plexus and the pudendal nerve from the cada equina down to their final destination. Our anatomic dissection demonstrated that the voluntary external urethral sphincter mechanism is augmented by two separate muscular components: the levator ani and the transversus perinei muscle. Urodynamic findings with sacral neurostimulation support our anatomic description.