Sectional neuroanatomy of the pelvic floor

This is the sixth in a series of articles on the spine. The first 5 reviewed the sectional anatomy of the cervical, thoracic, and lumbosacral spines. This paper will review both the male and female pelves. Procedures performed in the pelvis include electromyography of the anal sphincter, pudendal and sacral nerve stimulator implants, and botulinum toxin type A injections into the prostate, the bladder, the urethra, and the anus. Complications from these procedures are rare. Electromyography in this region is particularly uncomfortable. Botulinum toxin type A denervation may result in local effects such as incontinence or urinary retention or rarely remote effects such as limb weakness. Neurostimulators may get infected or may fail. This article provides anatomically accurate schematics of innervations of the pelvis that can be used to interpret magnetic resonance images of muscles and nerves in the pelvic floor region. Cross-sectional schematics of the male and female pelves were drawn as they appear on imaging projections. The relevant nerves were color coded. The muscles and the skin surfaces were labeled and assigned the color of the appropriate nerves. An organized comprehensive map of the motor innervation of both the male and female pelves allows the physician to increase the accuracy and efficacy of interventional procedures. This anatomic map could also assist the electromyographer in correlating the clinical and electrophysiologic findings on magnetic resonance images.