What is anal sphincter electromyography (EMG)?

Updated: Aug 06, 2019
  • Author: Jasvinder Chawla, MD, MBA; Chief Editor: David C Spencer, MD  more...
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Anal sphincter electromyography may be clinically useful in the evaluation of patients with urinary, bowel, and sexual dysfunction. It should be considered for all patients with a history and clinical examination suggestive of a central or peripheral sacral neuropathic lesion. The external anal sphincter (EAS), innervated by the pudendal nerve, is the best muscle for detection of neuropathic lesions in lower sacral myotomes. [1, 2] Its circular superficial location and muscle bulk allows for easier access and less painful needle insertion in order to diagnose particularly proximal sacral nervous system disorders. [1, 3]

Surface recordings from the sphincter have shown increased activity with body actions and decreased activity in sleep. Although surface EMG has been studied, needle EMG is clearly superior. [4] This article describes the clinical utility, commonly used technique, and role of EMG in various neurological disorders associated with anal sphincter abnormalities.

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