Achalasia: A mechanical and sensitivity disorder

Dear editor,

We read the original article written by Karyampudi et al. with great interest. ¹ The authors used a very robust methodology, reporting a high rate of severe esophagitis after per-oral endoscopic myotomy, although the patients seem to be oligosymptomatic of gastroesophageal reflux. Instead, they resemble the condition “silent gastroesophageal reflux disease,” in which patients suffer from severe reflux with few or no symptoms. The authors have hypothesized that mucosal denervation during submucosal tunneling and myotomy may result in esophageal hyposensitivity. However, esophageal hyposensibility may be due to the achalasia itself.

Chemical, physical, and thermal stimulus may induce the nociceptors of the esophagus. ² The nociceptive receptors on the esophageal nerves transmit to the central nervous system via either the spinal or vagal nerves. ²

Mechanical stimuli can cause heartburn and include esophageal distention and longitudinal contraction of esophageal smooth muscle. ² In achalasia patients, this mechanism is probably ineffective in inducing heartburn. The esophagus diameter is naturally enlarged and the refluxate probably does not cause a distention stimulus in the esophagus. Also, the longitudinal contraction does not happen due to the denervation of esophageal smooth muscle. In fact, some studies have shown achalasia patients have a lower mechanosensitivity to esophageal distention.^3,4

In addition, the same nervous degeneration that may be part of the underlying condition of impaired peristalsis in achalasia theoretically may be present in the autonomic or enteric nervous systems and could lead to impaired visceral sensation. ⁴ Rate et al. ⁵ reported diminished esophageal sensory responses to electrical stimulation in esophageal motility disorders.

Lastly, central desensitization due to chronic esophageal chemical irritation by food stasis might also contribute to the low esophageal sensibility to refluxate in achalasia patients.

The results of Karyampudi et al.’s study ¹ reinforces the idea that achalasia is not only a mechanical disturbance of esophagus, but also a sensitivity condition. The achalasia hyposensibility to the refluxate probably leads to silent gastroesophageal reflux disease after per-oral endoscopic myotomy.

In a recent published achalasia guideline, ⁶ it was said that gastroesophageal reflux occurs more frequently after per-oral endoscopic myotomy than after myotomy or pneumatic dilatation, but high grades of esophagitis are uncommon. However, as Karyampudi et al. ¹ showed, when esophagitis is set, it is usually severe, so we should never minimize this condition in the management of achalasia patients.