Anal Sphincter Electromyography and Sphincter Function Profiles Periprocedural Care

Updated: Aug 06, 2019
  • Author: Jasvinder Chawla, MD, MBA; Chief Editor: David C Spencer, MD  more...
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Periprocedural Care

Patient Education & Consent

Most clinical neurophysiology laboratories use a standard template for the procedure documenting the procedure and its explanation to the patient. The authors’ lab uses the following statement built into the template: “Prior to starting the procedure, the patient’s identity was verified and the nature of the procedure explained. The appropriate sites of the examination were confirmed directly with the patient, and a preprocedural pause was performed for final verification of all of the above.” A written informed consent is not a part of the standard practice at most institutions. A verbal consent as mentioned above with clear explanation to the patient about the risks involved is sufficient.

Pre-Procedure Planning

The presence of physiologic tone without volitional effort in the anal sphincter, in contrast to peripheral skeletal muscles, makes study of this muscle very challenging for an electromyographer. The subject at rest maintains sustained firing of isolated motor unit potentials at a low rate. This activity varies considerably with changes in subject position. The activity continues during sleep, although the discharge rate drops substantially compared with that during wakefulness. Sphincter activity ceases completely only during attempted defecation. The presence of physiologic tonic activity at rest makes detection of abnormal spontaneous potentials difficult in a partially denervated muscle. In contrast, the paretic sphincter may reveal abundant fibrillation potentials, positive sharp waves, and complex repetitive discharges, as in any denervated limb muscle.



See the list below:

  • The conventional concentric or monopolar needle is commonly used for routine clinical purposes.

  • Skin electrodes are the most commonly used method of recording information.

  • Anal plug electrodes may also be used.


Patient Preparation

Patients are asked to put on a surgical gown and lie on the examining table.


Patients are typically asked to lie in the lateral decubitus position. The patient may assume the knee-chest or modified lithotomy position, which allows the best examination in infants.


Monitoring & Follow-up

Detailed management of patients with sphincter-related abnormalities is beyond the scope of this article. Treatment is based upon the severity as well as the nature of the underlying disorder. One of the major aspects of treatment belongs to nonpharmacotherapy group. A combination approach involving volumetric rehabilitation, electroanal stimulation, kinesiotherapy, and biofeedback can be effective in patients without severe damage to the pelvic floor muscle. [24, 25, 26, 27]