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Anal sphincter responses after perianal electrical stimulation.
Journal of Neurology, Neurosurgery, and Psychiatry
|September 1, 1982
Summary
Researchers identified three distinct electrical responses in the external anal sphincter during perianal stimulation. Two rapid responses, likely not spinal reflexes, were unaffected by epidural anesthesia, unlike the slower classical anal reflex.
Area of Science:
- Neuroscience
- Physiology
- Clinical Electrophysiology
Background:
- The external anal sphincter's reflex activity is crucial for continence.
- Understanding the neurophysiological basis of anal reflexes aids in diagnosing and managing related disorders.
Purpose of the Study:
- To characterize the electrophysiological responses of the external anal sphincter to perianal electrical stimulation.
- To differentiate between spinal and non-spinal reflex pathways involved in external anal sphincter activation.
Main Methods:
- Perianal electrical stimulation was applied to healthy subjects.
- Electromyography (EMG) recordings were obtained from the external anal sphincter.
- Latencies, thresholds, and response characteristics were analyzed, including the effect of epidural anesthesia.
Main Results:
- Three distinct EMG responses with latencies of 2-8 ms, 13-18 ms, and 30-60 ms were identified.
- The first two responses exhibited short, constant latencies, higher thresholds, and were unaffected by epidural anesthesia.
- The third response, representing the classical anal reflex, had longer latency, decreased with stimulation intensity, and was abolished by epidural anesthesia.
Conclusions:
- The two short-latency responses are likely not spinal reflexes, possibly involving antidromal impulse propagation.
- The classical anal reflex is a spinal reflex, distinct from the faster, non-spinal responses.
- These findings contribute to a better understanding of the neural control of the external anal sphincter.