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Electromyography
Electromyography (EMG) of the anal sphincter has been in use for over 70 years. There are now
four variations of the technique in use:
- Monopolar wire electrode
EMG
- Concentric needle EMG
- Single fiber EMG
- Anal plug EMG
The
anal plug EMG is perhaps the most acceptable, as it is the least
invasive. All the techniques give information about the innervation
and function of the pelvic floor muscles. They are more sensitive
to paradoxical puborectalis contraction than defecography, in
that a clear deviation of the anorectal angle from normal is not
always seen, whereas an EMG will show continuing muscle activity
during straining in such patients. Anal sphincter EMG is widely
used in biofeedback training in the therapy of functional outlet
obstruction (Bleijenberg
and Kuijpers, 1987), but this is outside the area of this
review.
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