What is the primary mechanism by which fibrosis from radiation therapy leads to persistent dysphagia?

• A. Increased stool frequency
• B. Reduced mobility of swallowing muscles
• C. Enhanced gag reflex
• D. Increased mucus clearance

Answer: (B)

Radiation-induced fibrosis makes the tissues of the throat and esophagus stiff and less able to stretch. This early change narrows the range of motion and elasticity of swallowing muscles, especially the pharyngeal constrictors and the cricopharyngeal (upper esophageal) sphincter. With reduced mobility, the coordinated muscle contractions that propel the bolus downward are impaired, and the opening of the cricopharyngeal sphincter becomes less efficient. The result is slowed or incomplete bolus propulsion and residue, which drives persistent dysphagia after radiation therapy.

The other options don’t fit as the primary mechanism: stool frequency is unrelated to swallowing; a heightened gag reflex doesn’t account for chronic propulsion impairment; and increased mucus clearance would not cause lasting difficulty with swallowing.