Cortical processing to anorectal stimuli after rectal resection with and without radiotherapy

Area of Science:

• Neurogastroenterology
• Surgical Oncology
• Radiation Oncology

Background:

• Bowel dysfunction is a frequent complication following rectal cancer surgery, particularly when neoadjuvant radiotherapy is administered.
• The specific role of sensory pathway dysfunction in the brain-gut axis in the pathogenesis of these issues remains unclear.

Purpose of the Study:

• To investigate and characterize the sensory pathways of the brain-gut axis in patients who underwent rectal cancer resection, with or without prior radiotherapy.
• To compare these sensory pathways with those of healthy volunteers.

Main Methods:

• Sensory evaluation was conducted using rectal distensions and recording of sensory evoked potentials (SEPs) during rapid balloon distensions of the neorectum and anal canal.
• Participants included patients who had undergone resection (with n=8 and without n=12 radiotherapy) and 20 healthy volunteers.
• Analysis involved comparing neorectal SEP latencies and amplitudes, alongside spectral band analysis of SEPs as a measure of neuronal processing.

Main Results:

• Neorectal sensation thresholds were significantly elevated in both patient groups compared to controls (p < 0.008).
• No significant differences were observed in neorectal SEP latencies or amplitudes between patient groups and controls.
• Spectral analysis revealed significant differences in neorectal SEPs across all frequency bands among all groups (p < 0.01).
• Anal SEP analysis showed significant differences only in delta, theta, and gamma bands between the radiotherapy subgroup and healthy volunteers (p < 0.02).

Conclusions:

• Rectal cancer surgery results in altered cortical processing of neorectal sensations.
• The addition of radiotherapy modifies the central sensory processing patterns for both neorectal and anal sensations.
• These alterations in sensory processing may contribute to the functional outcomes experienced by patients.