Achalasia is best described as which physiological failure?

• A. Esophageal cancer
• B. Rapid relaxation of LES
• C. Failure of the lower esophageal sphincter to relax due to lack of innervation
• D. Obstruction at the pyloric sphincter

Answer: (C)

Achalasia is driven by loss of inhibitory innervation to the distal esophagus and lower esophageal sphincter. The neurons that normally cause the LES to relax (primarily nitric oxide– and VIP-mediated pathways) are lost, so the LES remains in a tonic, nonrelaxing state and does not open properly when a swallow occurs. This creates a functional blockage at the gastroesophageal junction and disrupts esophageal peristalsis, leading to dysphagia and regurgitation. The description “failure of the lower esophageal sphincter to relax due to lack of innervation” captures this neural mechanism precisely.

By contrast, a cancerous esophageal obstruction would be a mechanical narrowing, pyloric sphincter obstruction affects the stomach outlet, and rapid LES relaxation would not produce the characteristic pattern of achalasia.