🔥 Achalasia Peroral Endoscopic Myotomy Simulator

Achalasia — Failure of a Neurally Controlled Valve

Achalasia is a primary esophageal motility disorder in which selective degeneration of inhibitory neurons in the myenteric plexus abolishes the two things a normal esophagus needs to deliver a bolus into the stomach: coordinated peristalsis in the body, and reflexive relaxation of the lower esophageal sphincter (LES) on swallowing.

• 1–3: Annual incidence (per 100,000 people/yr)
• 30–60: Peak diagnosis age (years, M ≈ F)
• >15 mmHg: Diagnostic IRP threshold (integrated relaxation pressure)
• >90%: Inhibitory neuron loss (in the myenteric plexus)

Loss of inhibitory innervation

Normal swallowing triggers a wave of peristalsis down the esophageal body and a reflex drop in LES pressure, mediated by inhibitory neurons in the myenteric (Auerbach's) plexus that release nitric oxide (NO) and vasoactive intestinal peptide (VIP). In achalasia, these inhibitory neurons are selectively destroyed — likely through an autoimmune process, possibly triggered by a latent viral infection (herpes simplex virus-1 has been implicated) in genetically susceptible individuals (HLA-DQ associations have been reported).

Excitatory cholinergic neurons are comparatively spared. The result is a functional paradox: an esophagus with unopposed cholinergic tone produces a hypertensive, non-relaxing LES immediately adjacent to a body that can no longer generate organized, propulsive peristalsis. Swallowed liquid and solids stall above the sphincter, the esophageal body progressively dilates, and patients develop dysphagia to both solids and liquids, regurgitation of undigested food, chest pain, and weight loss.

Idiopathic achalasia reflects selective, likely immune-mediated destruction of NO/VIP-producing inhibitory neurons while excitatory cholinergic neurons survive — producing a hypertensive, non-relaxing sphincter next to an aperistaltic esophageal body.

Chicago Classification subtypes (v4.0)

High-resolution manometry (HRM) subdivides achalasia into three manometric phenotypes that predict treatment response:

Type I (classic): minimal esophageal pressurization, absent contractility, the body behaves as a flaccid, dilated tube.

Type II: panesophageal pressurization on ≥30% of swallows — the whole esophageal body pressurizes as a single compartment against the closed LES. This is the best-prognosis subtype, responding well to any therapy (pneumatic dilation, Heller myotomy, or POEM).

Type III (spastic): premature or spastic distal esophageal contractions with a distal contractile integral (DCI) >450 mmHg·s·cm in ≥20% of swallows. This subtype responds poorly to pneumatic dilation and is technically hardest to treat surgically, because the spastic, hypercontractile segment can extend well up the esophageal body.

Diagnostic workup

High-resolution manometry is the diagnostic gold standard: an integrated relaxation pressure (IRP) above 15 mmHg together with absent or spastic peristalsis confirms achalasia and assigns the Chicago Classification subtype. Barium esophagram classically shows a smoothly tapered "bird-beak" narrowing at the GEJ with variable proximal dilation; a timed barium swallow (column height remaining at 1 and 5 minutes) is used to quantify emptying and to track treatment response over time. Upper endoscopy is mandatory in every suspected case to exclude pseudoachalasia — a similar manometric and radiographic picture caused by a GEJ or submucosal tumor infiltrating the myenteric plexus rather than a primary neurodegenerative process.

Chicago Classification subtypes and POEM implications

Submucosal Tunnel — A NOTES Approach to the LES

Peroral endoscopic myotomy, first described by Haruhiro Inoue in 2010, borrows from natural orifice transluminal endoscopic surgery (NOTES): the endoscope creates a working corridor within the esophageal wall itself, leaving the outer serosa and the mucosal lumen intact while giving full access to the circular muscle layer beneath.

• 2010: Technique introduced (Inoue et al., Endoscopy)
• 1.5–2: Mucosotomy incision (cm entry length)
• 10–13: Submucosal tunnel length (cm total dissection)
• 60–90: Typical procedure time (minutes)

Mucosotomy and entry point

An entry incision is created roughly 10–13 cm proximal to the gastroesophageal junction, most commonly on the anterior (~2 o'clock) or posterior (~5 o'clock) esophageal wall. A longitudinal or transverse mucosotomy of 1.5–2 cm is made with an electrosurgical knife, deliberately placed well away from the eventual myotomy site so the two incisions do not communicate and the tunnel roof provides a durable seal once closed.

Submucosal injection and tunnel dissection

A mixture of saline (often with indigo carmine or methylene blue dye, sometimes with dilute epinephrine) is injected into the submucosal space to raise a fluid cushion that separates the mucosa from the underlying muscularis propria. CO2, not room air, is used for insufflation throughout, because CO2 is rapidly absorbed and minimizes the risk of clinically significant capnoperitoneum or capnomediastinum should gas track through the wall.

The endoscope, working through its own created tunnel, dissects distally within the submucosal plane, staying strictly between the mucosa and the muscle. The tunnel is extended 2–3 cm past the gastroesophageal junction into the gastric submucosa, confirmed endoscopically by the blue-tinged mucosa, the palisade vessel landmark, and the characteristic funnel-shaped widening of the gastric cardia.

The submucosal tunnel is the defining innovation of POEM: it converts a full-thickness surgical myotomy into an endoluminal procedure, with the intact mucosal flap over the tunnel entry acting as the eventual seal once clipped closed.

Why the tunnel approach matters clinically

Because the myotomy is performed without any transmural incision or external scar, POEM avoids the abdominal wall trauma of laparoscopic Heller myotomy while achieving comparable access to the LES. Hospital stay after POEM is typically 1–2 days, compared with longer recovery historically associated with open or even laparoscopic surgical myotomy. The tunnel approach also allows a myotomy of variable, operator-chosen length — extended cranially as far as needed to cover a spastic segment — something not achievable through a fixed laparoscopic port-based dissection.

Selective Circular Myotomy

Inside the submucosal tunnel, the endoscopist divides only the circular muscle fibers of the esophageal wall — the layer principally responsible for the LES's resting tone — while preserving the outer longitudinal muscle wherever possible, extending the cut across the entire high-pressure zone and into the gastric cardia.

• 8–10: Standard myotomy length (cm total)
• 2–3: Gastric extension (cm across the cardia)
• 90–95: Clinical success at 2 yrs (% (Eckardt ≤3))
• Heller: Comparator procedure (laparoscopic myotomy)

Selective circular fiber division

Using a triangle-tip or hook knife, the endoscopist divides the circular muscle fibers bundle by bundle, beginning roughly 2–3 cm below the mucosotomy and working distally across the LES high-pressure zone into the gastric cardia. The longitudinal muscle layer, which lies outside the circular layer, is preserved wherever feasible — a "selective" myotomy that reduces the risk of full-thickness esophageal wall injury and helps maintain some structural integrity of the wall compared with a full-thickness cut.

Tailoring myotomy length to manometric phenotype

Type III (spastic) achalasia benefits from a longer, individualized myotomy extended proximally to cover the entire hypercontractile segment identified on preoperative high-resolution manometry — sometimes 15 cm or more. This flexibility is not readily available with the fixed ~6–8 cm myotomy of a laparoscopic Heller procedure, which is why POEM has become the preferred first-line option for Type III achalasia, with reported clinical success of roughly 85–98%, versus the comparatively poor response of Type III to pneumatic balloon dilation.

Comparative efficacy versus laparoscopic Heller myotomy

A multicenter European randomized trial (Werner et al., New England Journal of Medicine, 2019) found POEM non-inferior to laparoscopic Heller myotomy with Dor fundoplication for achalasia treatment success at two years, with clinical success rates in a broadly similar range for both procedures. The key divergence was reflux: objectively diagnosed esophagitis was more common after POEM, because Heller myotomy is almost always paired with an anti-reflux fundoplication, while POEM alone reconstructs no such valve.

The myotomy-length decision is the central intraoperative trade-off of POEM: a longer cut more reliably abolishes the LES's residual obstruction and treats spastic segments, but it also removes more of the sphincter's native antireflux barrier, raising downstream GERD risk.

Mucosal Closure — Sealing the Tunnel

Once the myotomy is complete, the endoscope is withdrawn from the submucosal tunnel back into the esophageal lumen, and the mucosotomy entry point is closed with endoscopic clips — re-establishing an intact mucosal barrier over the freshly divided muscle and separating the operated tissue plane from the swallowed food stream.

• TTS clips: Closure method (through-the-scope hemoclips)
• 4–8: Clips typically placed (per closure)
• Endoscopic: Alternative closure (suturing device)
• <1: Reported delayed leak rate (% of cases)

Clip closure technique

After the endoscope exits the tunnel, the mucosotomy is closed with a row of through-the-scope hemostatic clips placed side by side from the distal to the proximal edge of the incision, grasping healthy mucosal edges on either side and drawing them together. This restores the mucosal barrier over the myotomy site, which now lies sealed within the submucosal space, and prevents saliva, food, and gastric contents from tracking into the freshly dissected tunnel.

Closure alternatives and safety surveillance

Some centers use an endoscopic suturing device for a more secure closure, particularly in obese patients or when clip apposition of the mucosal edges is difficult. A water-soluble contrast esophagram is frequently obtained the following morning to confirm there is no leak and that free flow of contrast into the stomach has been restored before oral intake resumes. Overall, POEM carries a low adverse event profile: intraprocedural mucosal injury or bleeding, capnoperitoneum requiring needle decompression, and delayed leak are the most frequently reported complications, together occurring in well under 5% of cases and usually managed conservatively.

Recovery and hospital course

Patients are typically kept nil-by-mouth overnight, started on a liquid diet after a confirmatory contrast study shows no leak, and progressed to a soft then regular diet over 1–2 weeks. Most patients are discharged within 1–2 days of the procedure — a substantially shorter recovery than has historically been associated with open, and even laparoscopic, surgical myotomy, and one of the practical advantages that has driven POEM's rapid adoption since 2010.

LES Pressure, Symptom Relief, and the Reflux Trade-off

POEM reliably converts a hypertensive, non-relaxing LES into a low-pressure, freely opening sphincter, translating into durable symptomatic remission for the large majority of patients. That relief comes with a predictable cost: because no anti-reflux valve is constructed, gastroesophageal reflux is more common after POEM than after a fundoplication-paired surgical myotomy.

• 90–95: Clinical success at 2 yrs (% (Eckardt ≤3))
• ~85: Clinical success at 5 yrs (% durable response)
• 20–40: Post-POEM GERD (any measure) (% of patients)
• ~65–70: LES pressure reduction (% from baseline)

Measuring success — the Eckardt score

The Eckardt score sums four symptom domains — dysphagia, regurgitation, retrosternal chest pain, and weight loss — each graded 0 to 3, for a total ranging from 0 to 12. Clinical success is defined as a post-treatment score of 3 or less. Most POEM patients fall from a symptomatic baseline of roughly 6–9 to 0–2 within weeks of the procedure, and durable remission is maintained in approximately 85–90% of patients at five years of follow-up, figures comparable to those reported for laparoscopic Heller myotomy in randomized comparisons.

The reflux trade-off

Because POEM does not reconstruct an anti-reflux valve — unlike Heller myotomy, which is almost always combined with a partial (Dor or Toupet) fundoplication — disrupting the LES's mechanical barrier increases pathologic esophageal acid exposure. Reported post-POEM reflux esophagitis on surveillance endoscopy ranges from roughly 20% to over 40%, depending on the definition used and the length of follow-up, and ambulatory pH-monitoring studies often report even higher rates of abnormal acid exposure than endoscopy alone — figures generally higher than the ~15–20% reflux esophagitis reported after Heller myotomy with fundoplication. Most cases are managed successfully with long-term proton pump inhibitor therapy, and periodic post-procedure pH testing or surveillance endoscopy is recommended in current guidelines.

In head-to-head comparisons, POEM and laparoscopic Heller myotomy achieve broadly similar rates of symptom control, but POEM's lack of a fundoplication step means a meaningfully higher rate of objectively diagnosed reflux esophagitis — making the myotomy-length-versus-reflux-risk trade-off a central decision both intraoperatively and in long-term follow-up care.

Positioning POEM within achalasia management

Contemporary achalasia treatment options include pneumatic balloon dilation, laparoscopic Heller myotomy with fundoplication, and POEM. Large comparative and randomized trials show broadly similar symptomatic success between Heller myotomy and POEM. POEM offers particular advantages for Type III/spastic achalasia, where a customizable, extendable myotomy length is decisive; for patients with a prior failed Heller myotomy or pneumatic dilation, where POEM is technically more feasible as a redo procedure; and for patients prioritizing a less invasive recovery. The principal ongoing consideration is the higher relative burden of post-procedural GERD, which requires long-term medical management and surveillance that Heller-with-fundoplication patients need less often.