Electrical stimulation of the vagus nerve restores motility in an animal model of achalasia

Enteric neuropathy and the vagus nerve: Therapeutic implications

Enteric neuropathies are characterized by abnormalities of gut innervation, which includes the enteric nervous system, inducing severe gut dysmotility among other dysfunctions. Most of the gastrointestinal tract is innervated by the vagus nerve, the efferent branches of which have close interconnections with the enteric nervous system and whose afferents are distributed throughout the different layers of the digestive wall. The vagus nerve is a key element of the autonomic nervous system, involved in the stress response, at the interface of the microbiota-gut-brain axis, has anti-inflammatory and prokinetic properties, modulates intestinal permeability, and has a significant capacity of plasticity and regeneration. Targeting these properties of the vagus nerve, with vagus nerve stimulation (or non-stimulation/ pharmacological methods), could be of interest in the therapeutic management of enteric neuropathies.

Docking Proteins Upregulate IL-1β Expression in Lower Esophageal Sphincter Muscle in Esophageal Achalasia

Background/Objectives: Esophageal achalasia is an archetypal esophageal motility disorder characterized by abnormal peristalsis of the esophageal body and impaired lower esophageal sphincter (LES) relaxation. Methods: In this study, the mRNA expression of docking proteins 1 and 2 (DOK1 and DOK2, respectively) were analyzed and the mechanisms underlying achalasia onset were investigated. Results:DOK1 and DOK2 mRNA levels significantly increased in the LES of patients with achalasia. Moreover, significant correlations were observed between IL-1β and DOK1, IL-1β and DOK2, ATG16L1 and DOK1, and HSV1-miR-H1-3p and DOK2 expression levels. However, a correlation between ATG16L1 and DOK2 or between HSV-miR-H1-3p and DOK1 expression was not observed. In addition, a positive correlation was observed between patient age and DOK1 expression. Microarray analysis revealed a significant decrease in the expression of hsa-miR-377-3p and miR-376a-3p in the LES muscle of patients with achalasia. Conclusions: These miRNAs possessed sequences targeting DOK. The upregulation of DOK1 and DOK2 expression induces IL-1β expression in the LES of achalasia patients, which may contribute to the development of esophageal motility disorder.

Electroceuticals in the Gastrointestinal Tract

The field of electroceuticals has attracted considerable attention over the past few decades as a novel therapeutic modality. The gastrointestinal (GI) tract (GIT) holds significant potential as a target for electroceuticals as the intersection of neural, endocrine, and immune systems. We review recent developments in electrical stimulation of various portions of the GIT (including esophagus, stomach, and small and large intestine) and nerves projecting to the GIT and supportive organs. This has been tested with varying degrees of success for several dysmotility, inflammatory, hormonal, and neurologic disorders. We outline a vision for the future of GI electroceuticals, building on advances in mechanistic understanding of GI physiology coupled with novel ingestible technologies. The next wave of electroceutical therapies will be minimally invasive and more targeted than current approaches, making them an indispensable tool in the clinical armamentarium.

Aflatoxin influences achalasia symptomatology

Achalasia is characterized by impaired swallowing due to lower esophageal sphincter (LES) dysfunction and an increased risk of esophageal carcinoma. Aflatoxin is a known carcinogen. Esophageal retention is relieved by per oral endoscopic myotomy (POEM), which lowers the esophageal cancer risk. The present study determined whether aflatoxin is involved in the pathogenesis of achalasia or esophageal cancer. A total of 75 patients with achalasia were prospectively enrolled from a tertiary center. Aflatoxin levels in their esophageal contents were measured using ELISA, and esophageal mucosal specimens were immunohistochemically evaluated for Ki67 and p53 expression prior to and 3 months after POEM. The effect of aflatoxin on esophageal contractility was assessed using murine specimens. Aflatoxin was detected in 67 patients before POEM and only 2 patients after POEM. The number of Ki67- and p53-immunopositive cells in the esophageal mucosa significantly decreased after POEM: [Ki67: 27.8% (95% confidence interval (CI), 25.98–29.70) vs. 20.7% (95% CI, 19.78–24.03), P=0.04 and p53: 2.14% (95% CI, 1.85–2.41) vs. 1.45% (95% CI, 1.22–1.68), P=0.03]. In vitro experiments revealed that 500 ng/ml aflatoxin significantly increased the amplitude (P<0.05) and frequency (P<0.05) of spontaneous LES contractions compared with the control group. These increases were blocked by co-treatment with atropine sulfate (P<0.05), but not with a nitric oxide synthase inhibitor (P>0.05). Aflatoxin was found in most patients with achalasia and was eliminated following POEM. Reduced Ki67 and p53 expression after POEM indicated a decreased risk of carcinogenesis. Aflatoxin accumulation increased LES contractility via cholinergic signaling. Therefore, aflatoxin may maintain achalasia symptoms and increase esophageal cancer risk.

Achalasia: treatment, current status and future advances

Achalasia was first described in the 17th century and its treatment continues to be challenging. Palliative treatment involves disruption of the lower esophageal sphincter, which can be accomplished mechanically (balloon dilation or surgical myotomy) or chemically (Botox). True surgical treatment originated some 100 years ago and remained largely unchanged until the advent of thoracoscopic and then laparoscopic myotomy beginning in the 1980s. Because these procedures provided relatively definitive treatment and were well tolerated by patients, minimal invasive surgery assumed a primary role in the treatment algorithms for achalasia. In 2008, an endoscopic (incision-less) myotomy approach, per-oral endoscopic myotomy, was described. This even less invasive approach has rapidly been adopted in the majority of high-volume achalasia centers. Newer interventions, such as stenting and cell transplant, are under active investigation.

Idiopathic (primary) achalasia: a review

Idiopathic achalasia is a primary esophageal motor disorder characterized by loss of esophageal peristalsis and insufficient lower esophageal sphincter relaxation in response to deglutition. Patients with achalasia commonly complain of dysphagia to solids and liquids, bland regurgitation often unresponsive to an adequate trial of proton pump inhibitor, and chest pain. Weight loss is present in many, but not all patients. Although the precise etiology is unknown, it is often thought to be either autoimmune, viral immune, or neurodegenerative. The diagnosis is based on history of the disease, barium esophagogram, and esophageal motility testing. Endoscopic assessment of the gastroesophageal junction and gastric cardia is necessary to rule out malignancy. Newer diagnostic modalities such as high resolution manometry help in predicting treatment response in achalasia based on esophageal pressure topography patterns identifying three phenotypes of achalasia (I-III) and outcome studies suggest better treatment response with types I and II compared to type III. Although achalasia cannot be permanently cured, excellent outcomes are achieved in over 90 % of patients. Current medical and surgical therapeutic options (pneumatic dilation, endoscopic and surgical myotomy, and pharmacologic agents) aim at reducing the LES pressure and facilitating esophageal emptying by gravity and hydrostatic pressure of retained food and liquids. Either graded pneumatic dilatation or laparoscopic surgical myotomy with a partial fundoplication are recommended as initial therapy guided by patient age, gender, preference, and local institutional expertise. The prognosis in achalasia patients is excellent. Most patients who are appropriately treated have a normal life expectancy but the disease does recur and the patient may need intermittent treatment.

The Pathogenesis and Management of Achalasia: Current Status and Future Directions

Achalasia is an esophageal motility disorder that is commonly misdiagnosed initially as gastroesophageal reflux disease. Patients with achalasia often complain of dysphagia with solids and liquids but may focus on regurgitation as the primary symptom, leading to initial misdiagnosis. Diagnostic tests for achalasia include esophageal motility testing, esophagogastroduodenoscopy and barium swallow. These tests play a complimentary role in establishing the diagnosis of suspected achalasia. High-resolution manometry has now identified three subtypes of achalasia, with therapeutic implications. Pneumatic dilation and surgical myotomy are the only definitive treatment options for patients with achalasia who can undergo surgery. Botulinum toxin injection into the lower esophageal sphincter should be reserved for those who cannot undergo definitive therapy. Close follow-up is paramount because many patients will have a recurrence of symptoms and require repeat treatment.

Esophageal motility disorders

The diagnosis of esophageal motility disorders has been greatly enhanced with the development of high-resolution esophageal manometry studies and the Chicago Classification. Both hypomotility disorders and hypercontractility disorders of the esophagus have new diagnostic criteria. For the foregut surgeon, new diagnostic criteria for esophageal motility disorders have implications for decision-making during fundoplication and may expand the role of surgical therapy for esophageal achalasia by clarifying diagnostic criteria.

Megaesophagus in a line of transgenic rats: a model of achalasia

Megaesophagus is defined as the abnormal enlargement or dilatation of the esophagus, characterized by a lack of normal contraction of the esophageal walls. This is called achalasia when associated with reduced or no relaxation of the lower esophageal sphincter (LES). To date, there are few naturally occurring models for this disease. A colony of transgenic (Pvrl3-Cre) rats presented with megaesophagus at 3 to 4 months of age; further breeding studies revealed a prevalence of 90% of transgene-positive animals having megaesophagus. Affected rats could be maintained on a total liquid diet long term and were shown to display the classic features of dilated esophagus, closed lower esophageal sphincter, and abnormal contractions on contrast radiography and fluoroscopy. Histologically, the findings of muscle degeneration, inflammation, and a reduced number of myenteric ganglia in the esophagus combined with ultrastructural lesions of muscle fiber disarray and mitochondrial changes in the striated muscle of these animals closely mimic that seen in the human condition. Muscle contractile studies looking at the response of the lower esophageal sphincter and fundus to electrical field stimulation, sodium nitroprusside, and L-nitro-L-arginine methyl ester also demonstrate the similarity between megaesophagus in the transgenic rats and patients with achalasia. No primary cause for megaesophagus was found, but the close parallel to the human form of the disease, as well as ease of care and manipulation of these rats, makes this a suitable model to better understand the etiology of achalasia as well as study new management and treatment options for this incurable condition.

On the origin of rhythmic contractile activity of the esophagus in early achalasia, a clinical case study

A patient with early achalasia presented spontaneous strong rhythmic non-propulsive contractions at ~7/min, independent of swallows. Our aim was to evaluate characteristics of the rhythmic contractions, provide data on the structure of pacemaker cells in the esophagus and discuss a potential role for interstitial cells of Cajal (ICC) in the origin of rhythmicity. We hypothesize that intramuscular ICC (ICC-IM) are the primary pacemaker cells. The frequency but not the amplitude of the rhythmic contractions was inhibited by the phosphodiesterase inhibitor drotaverine consistent with cAMP inhibiting pacemaker currents in ICC-IM. The frequency increased by wet swallows but not dry swallows, consistent with stretch causing increase in slow wave frequency in ICC-IM. New studies on archival material showed that ICC-IM were present throughout the human esophageal musculature and were not diminished in early achalasia. Although ICC-IM exhibited a low density, they were connected to PDGFRα-positive fibroblast-like cells with whom they formed a dense gap junction coupled network. Nitrergic innervation of ICC was strongly diminished in early achalasia because of the loss of nitrergic nerves. It therefore appears possibly that ICC-IM function as pacemaker cells in the esophagus and that the network of ICC and PDGFRα-positive cells allows for coupling and propagation of the pacemaker activity. Loss of nitrergic innervation to ICC in achalasia may render them more excitable such that its pacemaker activity is more easily expressed. Loss of propagation in achalasia may be due to loss of contraction-induced aboral nitrergic inhibition.

Pathogenesis of achalasia cardia

Achalasia cardia is one of the common causes of motor dysphagia. Though the disease was first described more than 300 years ago, exact pathogenesis of this condition still remains enigmatic. Pathophysiologically, achalasia cardia is caused by loss of inhibitory ganglion in the myenteric plexus of the esophagus. In the initial stage, degeneration of inhibitory nerves in the esophagus results in unopposed action of excitatory neurotransmitters such as acetylcholine, resulting in high amplitude non-peristaltic contractions (vigorous achalasia); progressive loss of cholinergic neurons over time results in dilation and low amplitude simultaneous contractions in the esophageal body (classic achalasia). Since the initial description, several studies have attempted to explore initiating agents that may cause the disease, such as viral infection, other environmental factors, autoimmunity, and genetic factors. Though Chagas disease, which mimics achalasia, is caused by an infective agent, available evidence suggests that infection may not be an independent cause of primary achalasia. A genetic basis for achalasia is supported by reports showing occurrence of disease in monozygotic twins, siblings and other first-degree relatives and occurrence in association with other genetic diseases such as Down’s syndrome and Parkinson’s disease. Polymorphisms in genes encoding for nitric oxide synthase, receptors for vasoactive intestinal peptide, interleukin 23 and the ALADIN gene have been reported. However, studies on larger numbers of patients and controls from different ethnic groups are needed before definite conclusions can be obtained. Currently, the disease is believed to be multi-factorial, with autoimmune mechanisms triggered by infection in a genetically predisposed individual leading to degeneration of inhibitory ganglia in the wall of the esophagus.

Pharyngeal dilation in cricopharyngeus muscle dysfunction and Zenker diverticulum

OBJECTIVES/HYPOTHESIS

Prolonged obstruction at the level of the lower esophageal sphincter is associated with a dilated, poorly contractile esophagus. The association between prolonged obstruction at the level of the upper esophageal sphincter (UES) and dilation and diminished contractility of the pharynx is uncertain. The purpose of this investigation was to evaluate the association between prolonged obstruction at the level of the UES and dilation and diminished contractility of the pharynx.

STUDY DESIGN

Case-control study.

METHODS

The fluoroscopic swallow studies of all persons with cricopharyngeus muscle dysfunction (CPD) diagnosed between January 1, 2006 and December 31, 2008 were retrospectively reviewed from a clinical database. Three categories of CPD were defined: nonobstructing cricopharyngeal bars (CPBs), obstructing CPBs, and Zenker diverticulum (ZD). The primary outcome measure was the pharyngeal constriction ratio (PCR), a surrogate measure of pharyngeal strength on fluoroscopy. Secondary outcome measures included pharyngeal area in the lateral fluoroscopic view and UES opening. The outcome measures were compared between groups and to a cohort of nondysphagic age- and gender-matched controls with the analysis of variance.

RESULTS

A total of 100 fluoroscopic swallow studies were evaluated. The mean age (+ or -standard deviation) of the cohort was 70 years (+ or -10 years). Thirty-six percent were female. The mean PCR progressively increased, indicating diminishing pharyngeal strength, from the normal (0.08), to the nonobstructing CPB (0.13), to the obstructing CPB (0.22), to the ZD group (0.28) (P < .001 with trend for linearity). There was a linear increase in pharyngeal area from the normal (8.75 cm(2)) to the nonobstructing CPB (10.00 cm(2)), to the obstructing CPB (10.46 cm(2)), to the ZD group (11.82 cm(2)) (P < .01 with trend for linearity).

CONCLUSIONS

The data suggest that there is an association between cricopharyngeus muscle dysfunction and progressive dilation and weakness of the pharynx. Laryngoscope, 2010.

Real-time dynamics of nitric oxide shifts within the esophageal wall

BACKGROUND

Currently, indirect evidence suggests that the neurotransmitter nitric oxide (NO) plays a crucial role in the genesis of aboral propagation of esophageal peristalses during swallowing. However, direct evidence in this regard currently is lacking. This study aimed to assess the feasibility of using NO-selective microprobes to detect real-time NO changes within the esophageal wall of North American opossums (Didelphis virginiana) during normal progressive esophageal peristalsis and induced esophageal dysmotility.

METHODS

Six adult opossums of both sexes (mean weight, 2.28 +/- 0.41 kg) were included in the study. All had normal esophageal motility, as documented by water-perfused esophageal manometry. A calibrated carbon fiber NO-selective microelectrode (ISNOP30, ISNOP100) was placed within the smooth muscle portion of the esophageal wall, and changes in NO levels were measured as redox current in pico-amperes (pA) with the Apollo-4000 NO meter. The dynamics of NO in response to reflexive deglutition were assessed during both normal propagative peristalsis and abnormal esophageal contractions induced by intravenous (i.v.) administration of the neural NO synthase inhibitor L-nitro L-arginine methyl ester (L-NAME) and banding of the gastroesophageal junction (GEJ) for 4-weeks.

RESULTS

During normal propagative esophageal peristalsis, a mean change of 2,158.85 +/- 715.93 pA was measured by the NO meter. Intravenous administration of L-NAME and chronic banding of the GEJ induced achalasia-like esophageal contractions. A significantly smaller change in levels of NO was detected within the esophageal wall during dysfunctional motility (331.94 +/- 188.17 pA; p < 0.001) than during normal propagative peristalsis (579 +/- 385 pA; p < 0.001).

CONCLUSION

The results of this study indicate that carbon fiber NO-selective microprobes can successfully measure changes in the concentration of NO, an important inhibitory neurotransmitter, within the esophageal wall and that these preliminary data support the involvement of this crucial neurotransmitter in programming normal propagation of peristaltic waves within the esophagus.

Return of esophageal function after treatment for achalasia as determined by impedance-manometry

BACKGROUND

Treatment for achalasia is aimed at the lower esophageal sphincter (LES), although little is known about the effect, if any, of these treatments on esophageal body function (peristalsis and clearance). We sought to measure the effect of various treatments using combined manometry (peristalsis) with Multichannel Intraluminal Impedance (MII) (esophageal clearance).

METHODS

We enrolled 56 patients with Achalasia referred to the University of Washington Swallowing Center between January 2003 and January 2006. Each was grouped according to prior treatment: 38 were untreated (untreated achalasia), 10 had undergone botox injection or balloon dilation (endoscopic treatment), and 16 a laparoscopic Heller myotomy. The preoperative studies for 8 of the myotomy patients were included in the untreated achalasia group. Each patient completed a dysphagia severity questionnaire (scale 0-10). Peristalsis was analyzed by manometry and esophageal clearance of liquid and viscous material by MII.

RESULTS

Mean dysphagia severity scores were significantly better in patients after Heller Myotomy than in either of the other groups (2.0 vs. 5.3 in the endoscopic group and 6.5 in untreated achalasia, p < 0.05). Peristaltic contractions were observed in 63% of patients in the Heller myotomy group, compared with 40% in the endoscopic group and 8% in untreated achalasia (p < 0.05 for both treatment groups vs. untreated achalasia). Liquid clearance rates were significantly better in both treatment groups: 28% in Heller myotomy and 16% in endoscopic treatment compared to only 5% in untreated achalasia (p < 0.05). Similarly, viscous clearance rates were 19% in Heller myotomy and 11% in endoscopic treatment, vs. 2% in untreated achalasia (p < 0.05). In the subset of patients who underwent manometry/MII both pre- and postoperatively, peristalsis was observed more frequently postoperatively than in preop studies (63% of patients exhibiting peristalsis vs. 12%), as was complete clearance of liquid (35% of swallows vs. 14%) and viscous boluses (22% of swallows vs. 14%). These differences were not significant, however. In the patients who had a myotomy the return of peristalsis correlates with effective esophageal clearance (liquid bolus: r = 0.46, p = 0.09 and viscous bolus: r = 0.63, p < 0.05). There is no correlation between peristalsis and bolus clearance in the endoscopic treatment group.

CONCLUSIONS

With treatment Achalasia patients exhibit some restoration in peristalsis as well as improved bolus clearance. After Heller Myotomy, the return of peristalsis correlates with esophageal clearance, which may partly explain its superior relief of dysphagia.

Idiopathic (primary) achalasia

Idiopathic achalasia is a primary esophageal motor disorder characterized by esophageal aperistalsis and abnormal lower esophageal sphincter (LES) relaxation in response to deglutition. It is a rare disease with an annual incidence of approximately 1/100,000 and a prevalence rate of 1/10,000. The disease can occur at any age, with a similar rate in men and women, but is usually diagnosed between 25 and 60 years. It is characterized predominantly by dysphagia to solids and liquids, bland regurgitation, and chest pain. Weight loss (usually between 5 to 10 kg) is present in most but not in all patients. Heartburn occurs in 27%-42% of achalasia patients. Etiology is unknown. Some familial cases have been reported, but the rarity of familial occurrence does not support the hypothesis that genetic inheritance is a significant etiologic factor. Association of achalasia with viral infections and auto-antibodies against myenteric plexus has been reported, but the causal relationship remains unclear. The diagnosis is based on history of the disease, radiography (barium esophagogram), and esophageal motility testing (esophageal manometry). Endoscopic examination is important to rule out malignancy as the cause of achalasia. Treatment is strictly palliative. Current medical and surgical therapeutic options (pneumatic dilation, surgical myotomy, and pharmacologic agents) aimed at reducing the LES pressure and facilitating esophageal emptying by gravity and hydrostatic pressure of retained food and liquids. Although it cannot be permanently cured, excellent palliation is available in over 90% of patients.

Esophageal motility disorders after gastric banding

The long-term effects of gastric banding on esophageal function are not well described. This report describes a 28-year-old woman who developed signs and symptoms of abnormal esophageal motility and lower esophageal sphincter hypotension after gastric banding for morbid obesity. The current literature addressing the effects of gastric banding on esophageal function in light of this case report is discussed.

A model for gastric banding in the treatment of morbid obesity: the effect of chronic partial gastric outlet obstruction on esophageal physiology

OBJECTIVE

This work establishes an animal model for nonadjustable gastric banding and characterizes the effect of gastric banding on esophageal physiology.

SUMMARY BACKGROUND DATA

Obstruction at the esophagogastric junction (EGJ) results in esophageal dilation and aperistalsis. Although laparoscopic gastric banding as a primary treatment of morbid obesity has been widely accepted, the effects of this therapy on esophageal function remain unknown.

METHODS

Twenty-five opossums were randomly divided into sham (n = 5), EGJ band (n = 5), and gastric band (n = 15) groups. Gastric and EGJ bands were surgically placed, and esophageal manometry was performed prebanding, at 2-week intervals during the banding period (up to 14 weeks), and 2 and 4 weeks after band removal.

RESULTS

Manometric measures were equivalent prior to banding in all groups. There were no changes in LES or esophageal pressures during the study period in the sham group. During banding, there was a 36% decrease in baseline mean resting lower esophageal sphincter pressure in the gastric band group (P = 0.003). Mean distal esophageal peristaltic pressure decreased from baseline by 36% in gastric band animals (P < 0.001). The incidence of esophageal motility disorder during the study period for sham, EGJ band, and gastric band groups, was 2.9%, 42.1%, and 31.3%, respectively (P = 0.001, P = 0.381, pairwise comparisons of gastric band vs. sham and gastric band versus EGJ groups, respectively). Immediately prior to band removal, the probability of an abnormal peristaltic sequence with each swallow was 1%, 38%, and 16% for sham, EGJ, and gastric band groups, respectively (P < 0.005, pairwise comparisons of band groups with sham).

CONCLUSIONS

Nonadjustable gastric banding results in impaired esophageal body motility, a reduction in esophageal peristaltic pressure, and a reduction in resting lower esophageal sphincter pressure. These findings suggest that gastric banding causes esophageal outlet obstruction and subsequent decompensation of peristaltic function as well as a compromise of the native antireflux mechanism.

Achalasia: physiology and etiopathogenesis

Achalasia is a disorder of esophageal motility that has been well documented for over 300 years. Despite this, the initiating factor or factors and the underlying mechanisms leading to the characteristic features of achalasia, the absence of distal esophageal peristalsis and abnormal lower esophageal sphincter relaxation, are still not well understood. Recent work has shed light on changes in neurotransmission and cell signaling in the lower esophagus and lower esophageal sphincter that lead to achalasia. A number of recent reviews have thoroughly discussed diagnostic and therapeutic modalities and the reader is referred to these for in-depth review of these topics. The focus of this review will be on our current understanding of the physiology of esophageal peristalsis and lower esophageal sphincter function as it relates to achalasia and on available evidence for etiology and proposed pathophysiologic mechanisms.

Does vagal nerve stimulation affect body composition and metabolism? Experimental study of a new potential technique in bariatric surgery

BACKGROUND

It has been shown that vagal nerve stimulation (VNS) can affect body mass. The aim of this study was to evaluate effect of VNS on body mass, body composition, metabolic rate, and plasma leptin and IGF-I levels.

METHODS

Eight female pigs were included in the study. Under general anesthesia, a bipolar electrode was implanted on the anterior vagal nerve by laparoscopy. Group A was treated by VNS, and group B was the control. After 4 weeks, stimulation was discontinued in group A and started in group B. The following parameters were evaluated: body mass, body composition, metabolic rate, plasma leptin and IGF-1 levels and intramuscular fat content (IMF).

RESULTS

VNS attenuated body weight gain (2.28 +/- 3.47 kg vs 14.04 +/- 6.75 kg; P = .0112, for stimulation and nonstimulation periods, respectively), backfat gain (0.04 +/- 0.26 mm vs 2.31 +/- 1.12 mm) and IMF gain (-3.76 +/- 6.06 mg/g MS vs 7.24 +/- 12.90 mg/g MS; P = .0281). VNS resulted in lower backfat depth/loin muscle area ratio (0.33 +/- 0.017 vs 0.38 +/- 0.35; P = .0476). Lower plasma IGF-I concentration was found after VNS (-3.67 +/- -11.55 ng/mL vs 9.86 +/- 10.74 ng/mL; P = .0312). No significant changes in other parameters were observed.

CONCLUSIONS

VNS affects body weight mainly at the expense of body fat resources; however, metabolic rate is not affected.

Etiology and pathogenesis of achalasia: the current understanding

Idiopathic achalasia is an inflammatory disease of unknown etiology characterized by esophageal aperistalsis and failure of LES relaxation due to loss of inhibitory nitrinergic neurons in the esophageal myenteric plexus. Proposed causes of achalasia include gastroesophageal junction obstruction, neuronal degeneration, viral infection, genetic inheritance, and autoimmune disease. Current evidence suggests that the initial insult to the esophagus, perhaps a viral infection or some other environmental factor, results in myenteric plexus inflammation. The inflammation then leads to an autoimmune response in a susceptible population who may be genetically predisposed. Subsequently, chronic inflammation leads to destruction of the inhibitory myenteric ganglion cells resulting in the clinical syndrome of idiopathic achalasia. Further studies are needed to better understand the etiology and pathogenesis of achalasia-such an understanding will be important in developing safe, effective, and possibly curative therapy for achalasia.