Achalasia and other motor disorders: loss of the inhibitory neurons
- Lesion
The valve at the lower oesophagus fails to open and the oesophagus stops squeezing, so food and fluid pile up above.
What it is
Achalasia is defined by a triad: the lower oesophageal sphincter fails to relax fully, its resting tone is high, and the body of the oesophagus loses peristalsis. Primary achalasia comes from degeneration of the inhibitory nitric oxide–releasing neurons of the myenteric plexus; secondary achalasia follows destruction of the plexus, classically by Trypanosoma cruzi in Chagas disease, which is endemic in Latin America. Other motor disorders cause intense or uncoordinated contractions without loss of the neurons.
Structure
- Gross: a dilated, sometimes tortuous oesophagus above a narrow gastro-oesophageal junction.
- Micro: few or no ganglion cells in the myenteric plexus, with lymphocytic inflammation of the plexus.
- Stasis causes squamous hyperplasia and inflammation of the mucosa above the sphincter.
- Chagas: chronic inflammation and neuronal loss in the plexus; amastigotes are rarely seen in late disease.
Step by step
- Inhibitory neurons of the myenteric plexus are lost (degeneration, autoimmunity or Trypanosoma cruzi).
- Without nitric oxide the lower sphincter cannot relax after swallowing.
- Loss of coordinated neurons also abolishes peristalsis in the oesophageal body.
- Food and fluid stay in the oesophagus, which slowly dilates.
- Stasis injures the mucosa and allows aspiration.
Oesophageal motor disorders compared
| Disorder | What the muscle does | Barium or manometry | Key cause |
|---|---|---|---|
| Achalasia | Sphincter does not relax; body does not contract | Dilated body, bird-beak taper | Loss of inhibitory neurons; Chagas |
| Diffuse oesophageal spasm | Repeated simultaneous contractions | Corkscrew oesophagus | Unknown |
| Hypercontractile (nutcracker) oesophagus | Very strong, uncoordinated contractions | Manometry needed; barium may be normal | Unknown |
| Scleroderma oesophagus | Weak contractions and an incompetent sphincter | Aperistaltic lower oesophagus with reflux | Fibrosis of smooth muscle |
Clinical notes
- Achalasia-like disease also follows diabetic autonomic neuropathy, infiltrative disease (amyloid, sarcoid, tumour) or damage to the vagal motor nucleus.
- Recurrent aspiration pneumonia can be the first sign.
Test yourself
Think of the answer, then tap the question to see it.
What is the triad of achalasia?
Incomplete relaxation of the lower oesophageal sphincter, increased sphincter tone and aperistalsis of the oesophageal body.
Which neurons are lost in primary achalasia?
The inhibitory, nitric oxide–producing neurons of the myenteric plexus that let the lower sphincter relax.
Which Latin American infection causes secondary achalasia and megacolon?
Chagas disease, caused by Trypanosoma cruzi, which destroys the myenteric plexus.
Elsewhere in DurgiPedia
Connections
Microorganisms1
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Achalasia (StatPearls (NCBI Bookshelf), 2025).
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Representative model, for educational purposes only.