External anal sphincter contraction during cough: not a simple spinal reflex

Area of Science:

• Neuroscience
• Physiology
• Urology

Background:

• The external anal sphincter (EAS) contracts during voluntary coughing.
• The neural pathways mediating this EAS contraction are not fully understood.

Purpose of the Study:

• To determine if the EAS contraction during voluntary coughing is a simple spinal reflex.
• To investigate the timing of EAS activity relative to respiratory muscle activation during coughing.

Main Methods:

• Electromyographic (EMG) recordings of EAS and external intercostal (EIC) muscles in 15 continent women.
• Simultaneous recording of abdominal pressure.
• Analysis of latencies between muscle activations and pressure changes during voluntary cough.

Main Results:

• EAS EMG activity consistently preceded the increase in abdominal pressure.
• In a subset of participants, EAS EMG activity also preceded EIC EMG activity.
• The latency of EAS activation before EIC activation suggests a non-spinal reflex pathway.

Conclusions:

• The EAS contraction during coughing is not a simple spinal reflex.
• The observed timing indicates a more complex reflex involving higher central nervous system integration.
• This provides new insights into the neural control of pelvic floor muscles during forceful expiratory maneuvers.