A 32-year-old woman has progressive dysphagia to both solids and liquids, regurgitation of undigested food, and a bird-beak oesophagram. Manometry shows absent distal oesophageal peristalsis and failure of lower oesophageal sphincter relaxation. The defect lies primarily in:

• A Destruction of inhibitory myenteric neurones releasing nitric oxide and VIP ✓
• B Loss of excitatory cholinergic vagal fibres to the circular muscle of the lower oesophagus
• C Hypertrophy of the crural diaphragmatic sling around the oesophageal hiatus
• D Loss of interstitial cells of Cajal confined to the upper oesophageal sphincter

Explanation

LES relaxation during swallowing depends on inhibitory postganglionic myenteric neurones releasing nitric oxide and VIP, which cause smooth muscle hyperpolarisation. In idiopathic achalasia these neurones are destroyed, so the sphincter fails to relax. Excitatory cholinergic function is comparatively preserved, explaining the retained high resting tone.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.