DES is an uncommon disorder characterized by impairment of ganglionic inhibition in the distal esophagus [2, 9]. DES is now considered a major disorder of peristalsis based upon the updated Chicago classification. DES is characterized by a normal median IRP, ≥20% premature contractions (contraction occurring within a phase when esophageal contractile activity is normally inhibited), and with a DCI >450 mmHg.s.cm. Normal peristalsis may also be present. It is important to note that DES is intermittent, and so the typical manometric findings may not be seen with all test swallows. Although most patients with DES usually have normal relaxation of the LES, approximately 30% may have high resting pressure or incomplete relaxation. The prevalence of DES is low and accounts for only 2% of patients evaluated for dysphagia by HRE manometry [9].

Hypercontractile or Jackhammer esophagus is characterized by at least two swallows with DCI >8000 mmHg.s.cm (Fig. 7.2). Hypercontractility may involve, or even only be localized to, the LES [1]. Jackhammer esophagus is likely due to an excess of cholinergic drive causing asynchronous contraction of the circular and longitudinal muscle layers of the esophagus [10]. Jackhammer esophagus is a rare disorder that is present in 4.1% of patients referred for manometric evaluation in a tertiary center [9].

Despite differences in pathophysiology, these disorders share many similarities, including their clinical manifestations. Patients with SEDs may present with one or all of the following symptoms: dysphagia (for solids or both solids and liquids), non-cardiac chest pain, regurgitation, and refractory gastroesophageal reflux disease (GERD) symptoms. Dysphagia is the predominant symptom and occurs because of impairment of bolus transit through the esophagus. Chest pain is another frequent symptom and is often severe in nature.

Identification of SEDs is based on the contractile patterns observed during HRE manometry with esophageal pressure topography (EPT). Other diagnostic tests are required to rule out structural abnormalities or other causes of dysphagia.

Upper endoscopy is required during the initial evaluation of SEDs to exclude mechanical causes of dysphagia such as malignancy, stenosis, peptic strictures, or eosinophilic esophagitis. Endoscopic findings of esophageal dilation and/or resistance to passage of endoscope at the GEJ may suggest a motility disorder. However, none of these endoscopic findings is specific.

In patients with DES severe, non-peristaltic contractions may result in the classic corkscrew appearance of the esophagus. In patients with hypercontractile esophagus barium swallow usually shows normal sequential peristalsis [11].

There is a potential overlap of symptoms in DES and GERD. Therefore, 24-h pH monitoring should be considered in patients with chest pain, regurgitation, and/or heartburn [2].

HRE manometry with EPT is the gold standard for diagnosis of esophageal motility disorders. HRE manometry with EPT is superior to conventional manometry, as EGJ relaxation is more reliably seen with HRE manometry in comparison to conventional manometry. EGJ relaxation is essential for distinguishing DES from spastic achalasia [2]. Furthermore, the use of IRP, the DCI, and the distal latency (DL) measurements in HRE manometry are more accurate than the metrics used in conventional manometry [1, 2]. Identification of these spastic disorders is based on the esophageal contractile pattern and IRP observed in HRE manometry with EPT (Table 7.1).

Cross-sectional imaging can detect esophageal muscle thickening in patients with SEDs. CT scan revealed marked esophageal wall thickening at the lower esophagus in 21% of patients with DES (p < 0.01), which corresponded to non-propulsive contractions detected on barium study [12]. A CT scan is not routinely indicated in patients with spastic disorders unless there is a suspicion of extrinsic esophageal compression. Alternatively, endoscopic ultrasonography (EUS) can quantify esophageal thickening and reveal mediastinal, infiltrative/malignant extramural, or intramural abnormalities that may mimic achalasia (pseudoachalasia). A retrospective study of 62 patients with esophageal motility disorders evaluated the clinical utility of a radial endoscopic ultrasound examination [3]. EUS identified 15% clinically relevant findings that altered patients’ management and explained the etiology of the esophageal outflow obstruction. These included aortic compression, intramural mass, leiomyoma, congenital muscular ring, and sarcoidosis. There were no pathological EUS findings in patients with DES or hypercontractility [3].

Although multiple medical, endoscopic, and surgical therapeutic modalities have been used to treat SEDs, the treatment success rates have been less than ideal. In order to meet the treatment objective of alleviating patients’ symptoms, we believe the anatomic and physiologic goal is to reduce the vigorous abnormal esophageal contraction and to alleviate the EGJ obstruction.

Medical therapies include calcium channel blockers, nitrates, or tricyclic antidepressants. One small, randomized, crossover study compared the effect of nifedipine (10 mg three times daily) versus placebo for 4 weeks in 20 patients with primary esophageal disorders (hypertensive LES n = 10, DES n = 4, spastic achalasia n = 3, nutcracker n = 2, and achalasia n = 1). Patients who received nifedipine had significantly higher rates of relief of chest pain (p < 0.01) and dysphagia (p < 0.05) within 1–6 weeks of treatment [13].

Visceral analgesic agents such as tricyclic antidepressants have also been proposed as therapy for these disorders. A low dose of clomipramine (25 mg daily for 4 weeks) was shown to be effective in a small case-control study of nine patients with DES compared with 26 healthy volunteers. Patients with DES received initial isosorbide dinitrate (15 mg daily) for 1 month, followed by clomipramine (25 mg daily) for an additional month. Patients with DES had greater improvement of chest pain (n = 88%, p < 0.05), but only 40% of those patients had slight manometric improvement after treatment [14].

Endoscopic therapies include botulinum toxin injection and esophageal dilation. Botulinum toxin reduces smooth muscle tone in the gastrointestinal tract by blocking the release of acetylcholine in the excitatory motor neurons. Botulinum toxin injection results unlimited degeneration of the nerve endings. However, after a few months nerves regenerate, which leads to the loss of toxin effect [15]. A recent retrospective study evaluated the effect of botulinum toxin injection in 45 patients with SEDs (Type III achalasia n = 22, Jackhammer esophagus n = 8, DES n = 7, EGJOO n = 5, nutcracker n = 1, unclassified n = 2) [16]. After Botulinum toxin injection, 71% had significant improvement of symptoms at 2 months, and 57% remained in remission for more than 6 months. The clinical response rates were apparently worse (although not significantly, p = 0.13) in patients with normal EGJ relaxation (Jackhammer esophagus, DES, nutcracker esophagus, and type III achalasia with IRP <15 mmHg; 10/22, 45%) compared to those patients with abnormal EGJ relaxation (achalasia with IRP >15 mmHg, EGJOO; 14/20, 70%).

Pneumatic balloon dilation has been proposed for treating SEDs. In a study of 61 patients with DES, pneumatic balloon dilation was performed in 20 patients who were refractory to medical therapy. Seventy percent of those patients had significant improvement of dysphagia [17]. However, Pandolfino et al. [18] observed that pneumatic balloon dilation was ineffective in patients with spastic achalasia compared with other types of achalasia. A total of 1000 HRE manometry studies were reviewed, and 213 with impaired EGJ relaxation were identified. Ninety-nine patients were newly diagnosed with achalasia (21 Type I, 49 Type II, and 29 Type III). All patients underwent therapeutic interventions including botulinum toxin injection, pneumatic balloon dilation, or Heller myotomy. Patients with Type III achalasia had the worst response to therapy, despite having a significant number of therapeutic interventions during a mean follow-up of 20 months (success rate was 22% with botulinum toxin injection, 0% with pneumatic balloon dilation, and 0% with Heller myotomy) [18].

Heller myotomy is an established treatment for achalasia; however, a lower response rate has been observed in patients with spastic achalasia [2, 18, 19]. In SEDs, the disease process involves the proximal esophageal body in addition to the LES. Hence, a longer surgical myotomy is likely needed to target the proximal esophageal body [2]. Patti and colleagues compared the outcomes in patients with DES and nutcracker esophagus treated by surgical myotomy with the outcomes in those treated medically. Thirty patients with nutcracker and DES were treated with dilation and/or medication (a calcium channel blocker), and ten patients underwent a thoracoscopic myotomy. A higher response rate was seen in the surgical myotomy group compared to the medical group (80% vs. 26%, p = 0.001) [20].

POEM is an effective procedure that has been performed to treat achalasia with clinical success rates of 82–100% [21]. Data suggest that a long surgical myotomy may be effective in treating patients with SEDs [22–26]. Surgical myotomy of the upper thoracic esophagus is technically challenging via transabdominal approach [20]. However, during POEM, the endoscopist is able to access the entire length of the esophagus, which renders POEM an attractive, minimally invasive therapeutic modality for the treatment of SEDs. POEM facilitates myotomy of the LES as well as the esophageal body, where hypertensive contractions occur. There have been multiple case reports and case series demonstrating excellent clinical efficacy of POEM for various SEDs including Jackhammer esophagus, DES, spastic achalasia, and Nutcracker esophagus (Table 7.2) [22–31]. A retrospective trial comparing 49 patients who underwent POEM for spastic achalasia (Type III achalasia) with 26 patients who underwent laparoscopic Heller myotomy (LHM) showed a higher rate of clinical success in the POEM group (98% vs. 80.8%, p = 0.01). Furthermore, procedure duration was significantly shorter in the POEM group (102 min vs. 264 min, p < 0.01) despite longer myotomy (16 cm vs. 8 cm, p < 0.01). The rate of adverse events was also significantly lower in the POEM group (6% vs. 27%, p < 0.01) [27].

POEM may have additional benefits even in the setting of prior therapies such as balloon dilation, botulinum toxin injection, or surgical myotomy. Surgical re-do myotomy is known to be difficult due to fibrosis and scaring [32]. A retrospective analysis of 40 POEM procedures, including treatment-naïve patients (n = 28) and patients with previous endoscopic intervention (2 with nutcracker and 1 with DES; 10 with previous botulinum toxin injection and 2 with previous pneumatic balloon dilation) (n = 12), demonstrated no significant difference in the mean procedure duration (131 ± 41 min vs. 134 ± 43 min, p = 0.8) or the incidence of intraoperative complications (3% vs. 17%, p = 0.2) between the two groups [33].

During standard POEM procedures, a submucosal tunnel is initially created prior to performance of endoscopic myotomy of the LES and esophageal body. Performance of POEM occurs in four consecutive steps: (1) mucosal incision, (2) formation of submucosal tunnel, (3) myotomy, and (4) closure of mucosal incision. The myotomy is started 2–5 cm distal to the mucosal incision and continued to the end of the submucosal tunnel (2–3 cm distal to the GEJ). The length of the esophageal myotomy in patients with achalasia types I and II is typically 6–8 cm but varies based on patient symptoms (such as amount of chest pain), manometry results, and even operator preference [21]. However, the length of myotomy in SEDs should be based on the proximal extent of hypertensive contractions seen on HRE manometry and has been reported to be 14–16 cm on average [34]. Patients with spastic achalasia and DES are believed to have a higher response rate than those with Jackhammer esophagus (96.3, 100, and 70%, respectively) [34]. The reason is not well known, but it may be due to extreme hypercontractility of the esophageal body in jackhammer patients [34]. Therefore, concomitant bilateral (anterior and posterior) myotomy in patients with Jackhammer esophagus may be considered as possible alternative for such patients, although this approach remains to be studied. Insufficient myotomy or remnant of esophageal body contraction may lead to residual symptoms in those patients [26].

Patients with Jackhammer esophagus may or may not have EGJ outflow obstruction, and some patients with DES do not have this abnormal manometric finding [2]. It is arguable whether patients without outflow obstruction will require myotomy of the LES. Myotomy of the esophageal body induces aperistalsis, and this may result in dysphagia in patients who do not undergo LES myotomy. The inclusion of the LES seems warranted by the potential after effects of myotomy, even in the setting of normal LES pressure, since preserving the LES pressure may result in postoperative dysphagia caused by induced aperistalsis [25]. After POEM, there are several esophageal motility changes such as a decrease in the LES resting pressure, as well a dramatic decrease in LES relaxation pressure [4, 35, 36].

A recent retrospective study by Ren et al. [37] reported the therapeutic effect of POEM on the proximal esophagus in all types of achalasia. Thirty-two patients with achalasia (Type I n = 6, Type II n = 17, Type III n = 9) who underwent POEM and follow-up high-resolution esophageal manometry were included in the analysis. The LES resting pressure and IRP were significantly decreased post POEM (38.12 ± 13.48 mmHg vs. 14.53 ± 4.92 mmHg, P < 0.001 and 31.28 ± 10.03 mmHg vs. 8.80 ± 4.22 mmHg, P < 0.001). POEM also resulted in a significant reduction in the contractile integral (CI) in both the distal esophageal segments with myotomy (DM) and the proximal segments with no myotomy (PNM) (CI-DM: 43.95 mmHg.s.cm vs. 3.79 mmHg.s.cm, p < 0.001, and CI-PNM, 1337.73 mmHg.s.cm vs. 480.85 mmHg.s.cm, p < 0.001). The upper esophageal sphincter relaxing pressure (UES) was also reduced after POEM (12.74 ± 7.14 mmHg vs. 5.79 ± 6.11 mmHg, p < 0.001). Nevertheless, the UES resting pressure and relaxation duration were unchanged [37]. After POEM, there was a positive linear correlation of CI changes between the distal esophageal body segment with myotomy and the proximal esophageal body without myotomy (correlation coefficient = 0.901, p < 0.001). The changes in the UES relaxing pressure were positively correlated with CI of the distal segment of esophageal body with myotomy and the proximal segment of esophageal body without myotomy (CI-DM: correlation coefficient = 0.705, p < 0.001, and CI-PNM: correlation coefficient = 0.755, p < 0.001). In type II achalasia, the positive correlation of changes of CI was significant between the distal esophageal body with myotomy and the proximal esophageal body without myotomy (correlation coefficient = 0.917, p = 0.001). These findings suggested that myotomy of the distal esophagus could influence contraction of the proximal esophagus and UES relaxation pressure [37]. Ren et al. [38] hypothesized that simultaneous contraction or pressurization of esophageal body would provide a “viscous resistance” to food bolus during swallow. Therefore, myotomy of the distal esophagus was found to significantly inhibit the pressurization of the whole esophageal body and lead to less “viscous resistance” [37, 38].