Electrodiagnosis of the anorectum: a review of techniques and clinical applications.

Electrodiagnostic tests may be valuable in the assessment of patients with anorectal dysfunction and are complementary to imaging and manometry. While the latter delineate morphological and functional sphincter changes, respectively, electrodiagnostic methods document, help to localize and assess the severity and mechanism of neural injury. These data are important for the treatment of patients and for estimating their prognoses. Among electrodiagnostic tests, concentric needle electromyography of the external anal sphincter is the most important. It demonstrates muscle denervation, quantitatively estimates muscle reinnervation, estimates the level of motor neuron excitability and assesses several kinesiological parameters. In addition, measurement of the bulbocavernosus reflex is often useful, while pudendal somatosensory evoked potentials are sometimes useful. Use of single tests of sacral nervous system by workers less familiar with theoretical principles of clinical neurophysiology is discouraged. In patients with suspected neurogenic bowel disorders, comprehensive electrodiagnostic approach, performed by clinical neurophysiologists experienced in application of these tests to the sacral nervous system, should complement data obtained by other methods and guide patient management.