esophageal achalasia is a primary esophageal motility disorder characterized by lack of peristalsis and failure of the lower esophageal sphincter ( les ) to relax in response to swallowing . however , degeneration and loss of ganglion cells in the auerbach s nerve plexus have been reported and result in esophageal motor dysfunction . the diagnosis of achalasia is based on a careful clinical history and the results of barium esophagography , endoscopy , and esophageal manometry . dysphagia , regurgitation , chest pain , and weight loss are among the most recognized clinical features of the disease . achalasia is a rare disease , with an estimated annual incidence of one case per 100,000 people . by esophagogastroscopy , we identified esophageal dilation , atony , chaotic spasticity of the esophageal body , food or fluid retention , or resistance to the passage of the endoscope into the stomach . the main reason to perform endoscopy was to exclude the presence of other pathologies , such as cancer . patients with achalasia have an increased risk of developing stasis - related squamous cell cancer . botulinum toxin injection was developed in 1995 , and has been used for many patients in europe and the united states . botulinum toxin injection is the most common initial treatment for achalasia in the united states and is more efficacious than other treatments such as pneumatic dilation ( pd ) or laparoscopic heller myotomy ( lhm ) . according to one report of 896 patients with achalasia in the united states , botulinum toxin injection was the most frequently used as the first - choice endoscopic therapy in 41% . in japan , esophageal achalasia has been treated with oral drugs , endoscopic balloon dilation , per - oral endoscopic myotomy ( poem ) , and surgery . however , local injection of botulinum toxin for esophageal achalasia has not been approved as a treatment for medical insurance in japan . as a result , we have reported two cases of esophageal achalasia in japan , in which symptoms were improved by localized botulinum toxin injections . in this study , we conducted a pilot trial to evaluate the effectiveness of local injection of botulinum toxin for esophageal achalasia , and to assess its safety and adverse effects among japanese patients . between january 2008 and december 2014 , 10 patients were diagnosed with esophageal achalasia in saga medical school hospital , japan . patients were clinically assessed before treatment , including barium esophagography , esophagogastroscopy , and esophageal manometry . the definition of achalasia by barium esophagography is dilatation of the esophagus and/or liquid or food retention in the esophagus with the lower esophagus having the appearance of a   bird s beak. the maximum diameter of the thoracic esophagus was measured using barium esophagography , and achalasia was classified into grade i , diameter < 3.5  cm ; grade ii , diameter 3.56.0  cm ; and grade iii , diameter > 6.0  cm , in accordance with the descriptive rules . esophageal manometry analyzed each swallow for the morphology of the esophagogastric junction , the extent of esophagogastric junction relaxation , the contractile front velocity of peristalsis , vigor of the peristaltic contraction , and abnormality of intrabolus pressure . esophageal manometry was performed in all patients with four - channel manometry ( gmms-600 ; star medical , tokyo , japan ) . the manometric assembly was passed via an anesthetized nostril and positioned so that the most distal of the 4  cm interval side holes was 1  cm above the les . the les pressure was measured by the rapid pull - through method , with the subject in the standing position . baseline recordings of the lower esophageal sphincter pressure ( lesp ) were made for 5  min , after which primary peristalsis was assessed . the manometric protocol included 5  min to assess basal sphincter pressure and 5-ml water swallows . vigorous achalasia was defined by amplitude 37  mmhg , and classic achalasia as amplitude < 37  mmhg . eckardt score was the sum of the symptom scores for dysphagia , regurgitation , and chest pain ( with 0 indicating absence of symptoms , 1 occasional symptoms , 2 daily symptoms , and 3 symptoms at each meal ) , and weight loss ( with 0 indicating no weight loss , 1 loss of < 5  kg , 2 loss of 510  kg , and 3 indicating loss of > 10  kg ) . thus , the maximum score on the eckardt scale , indicating the most pronounced symptoms , was 12 . patients were considered to have reached clinical remission if the total symptom score was 3 . a total of 100  u botulinum toxin a ( botox ; allergan , irvine , ca ) was divided into eight aliquots ( 25  u per quadrant ) , with four injections every 90 degree at the esophagogastric junction and four injections every 90 degree 1  cm above the esophagogastric junction . after 1 week , we re - measured the shape of the esophagus using barium esophagography and lesp by esophageal manometry . after 1 week of follow - up of the local injection , the subjective symptoms for esophageal achalasia were assessed using a visual analog scale ( vas ; no symptom 0 , maximum symptoms 10 ) . patients were periodically followed up at our outpatient clinic . when symptoms of esophageal achalasia relapsed , local injection of botulinum toxin was repeated according to the patients request . the eckardt score , lesp and subjective symptom score data were analyzed using student s t test . the study was conducted after the protocol had been approved by the ethics review committee of saga medical school . there were five men and five women , with a mean age of 55 ( 3372 ) years . two cases had grade i achalasia ( diameter 4  cm ) and eight were grade ii ( diameter 46  cm ) . four cases had comorbidity of hypertension , diabetes mellitus , and chronic hepatitis c. cases that were treated effectively with botulinum toxin are shown in fig .  1 . the lower esophagus had a bird s beak appearance and barium did not pass through the esophagogastric junction for more than a few minutes ( fig . barium passage was improved in barium esophagography and passage of contrast agent was also improved in all cases . before botulinum toxin injection , esophageal manometry showed each swallow for the contractile abnormality of peristalsis and markedly elevated residual lesp . after botulinum toxin injection , esophageal manometry showed improvement of residual lesp , and abnormal peristaltic waves had disappeared . mean lesp was reduced from 46.9 ( 2871 ) mmhg before treatment to 29.1 ( 1263 ) mmhg after treatment ( 95% ci , 8.51527.095 , p  =  0.002 ) ( fig .  2 ) . mean eckardt score was reduced from 5.5 ( 29 ) before treatment to 1.6 ( 02 ) after treatment [ 95% confidence interval ( ci ) , 2.3025.498 , p<0.001 ] ( fig . mean score of subjective symptoms was reduced from 10 before treatment to 3.9 1 week after treatment ( 95% ci , 4.8307.370 , p<0.001 ) ( fig .  4 ) . during follow - up periods , five cases relapsed at 324 months after treatment ( table  2 ) . the mean score of subjective symptoms was 5.4 ( 47 ) in five recurrent cases and 2.4 ( 14 ) in nonrecurrent cases . the scores for recurrent cases were significantly higher than those of the nonrecurrent cases ( 95% ci , 1.3374.663 , p<0.001 ) . three cases relapsed at 3 , 6 and 24 months after treatment ( cases 3 , 5 and 9 ) and received additional botulinum toxin therapy at their request . treatment was effective until the end of observation . however , one case received pd therapy 6 months after initial treatment ( case 2 ) , and another received poem 3 months after initial treatment ( case 7 ) because of recurrence . the therapeutic effect in eight cases was conservatively sustained until december 2014 , with mean follow - up of 36 months . side effects of botulinum toxin injection were not experienced up to december 2014 in all cases . first , local injection of botulinum toxin was effective for japanese as well as western achalasia patients . second , botulinum toxin injection was safe compared with several other therapies for esophageal achalasia . third , a high score for subjective symptoms after treatment became an important indicator of recurrence . commercially available botulinum toxin is composed of botulinum toxin component ( botulinum neurotoxin and complexing proteins ) and excipients . botulinum neurotoxin consists of a heavy amino acid chain connected to a lighter amino acid chain by means of a single disulfide bridge . after injection into the target tissue , the botulinum toxin binds to glycoprotein structures on the cholinergic nerve terminals , and the light chain , a protease , is internalized and cleaves the soluble n - ethylmaleimide - sensitive fusion attachment protein receptor proteins , thereby disabling vesicles from anchoring to the membrane and releasing acetylcholine . this blockage of the cholinergic synapse forces the neurons to form new synapses ; a process known as sprouting the most commonly used and studied serotype is botulinum toxin a , and achalasia studies have used it exclusively . however , botulinum toxin b is also commercially available . in the united states , botulinum toxin injection was most frequently used as the first - choice endoscopic therapy in 41% of cases , followed by balloon dilation in 21% , savary dilation in 20% , maloney dilation in 10% , rigiflex in 4% , and other modalities in 4% . a previous study has reported that 1 month after botulinum toxin injection , 31 of 37 patients ( 83.7% ) showed significant improvement . botulinum toxin injection for esophageal achalasia is also useful in japanese patients , as reported in western countries . however , some studies have reported that most patients who are treated with botulinum toxin injection experience relapse , usually 612 months after the first treatment , and often require repeated treatment . a meta - analysis of nine studies indicated that the percentage of patients with symptomatic improvement after one session of botulinum toxin injection was 78.7% at 1 month , 70% at 3 months , 53.3% at 6 months , and 40.6% at > 12 months follow - up . however , at least a second botulinum toxin injection was required in 46.6% of patients . therefore , botulinum toxin injection is considered to be effective in the short term , but has a risk of relapse . our study was a small pilot study and the therapeutic effect was conservatively sustained in eight cases and good progress was achieved . the mean follow - up was 2 years , but we need to extend the surveillance periods and increase the number of patients . botulinum toxin injection into the les is an established therapy for achalasia and has few side effects . reported side effects of botulinum toxin injection include mild chest pain and mild heartburn , which is easily controlled by antacid therapy . rare systemic side effects such as diffuse neuromuscular jitters and autonomic side effects such as dry mouth and eye accommodation difficulties have been reported , especially with high doses of botulinum toxin b. in the present study , there were no serious side effects . one study has shown that there was no significant difference in remission rates between pd and botulinum toxin at 4 weeks of intervention . however , pd appeared to be more effective after long - term follow - up of > 6 months . according to five studies that compared botulinum toxin injection with pd , the remission rate was 65.8% for pd compared with 36% for botulinum toxin injection , and the time to relapse after the first intervention was shorter for patients who received botulinum toxin compared with pd . some perforations can be managed nonoperatively , but free perforation requires urgent laparotomy or thoracotomy . poem is a new endoscopic procedure to treat achalasia , and is a modification of pasricha s submucosal endoscopic esophageal myotomy . in poem , visible complete transmural openings into the mediastinum and peritoneal cavity are created in the majority of patients . therefore , poem potentially carries the risk of mediastinitis , peritonitis and damage to surrounding organs . the following complications were reported for poem : perforation ( 4% ) , mucosal injury ( 4% ) , bleeding requiring intervention ( 1% ) , and mediastinal hematoma ( 1% ) . esophageal perforation is the most common major complication for lhm , with an incidence of 04.6% . in another study , lhm had complications such as gastrointestinal perforation ( 1.5% ) , pneumothorax ( 1.9% ) , and pulmonary complications ( 1.3% ) . the difference in safety between botulinum toxin injection and other invasive treatment options such as pd or lhm is arguably the reason why botulinum toxin is the most commonly used initial therapy for achalasia in the united states . the outcome of botulinum toxin injection was comparable to the outcome of several other therapies for esophageal achalasia , while injection therapy was safer than other therapies . in our study , the subjective symptoms score in five recurrent cases was significantly higher than in the nonrecurrent cases . however , there was no difference in eckardt score and lesp between the recurrent and nonrecurrent cases . patients with high subjective symptom scores are likely to experience recurrence within a short time . . the limitations of our study were its small number of participants and single center analysis . in addition , there is no universal gold standard technique for injecting botulinum toxin into the les . a previous study has reported that relapse of symptoms was evident in 19% of patients who received two injections of 100  u compared with 47% and 43% in the single 50  u and 200  u groups , respectively . further studies are required to validate botulinum toxin injection for achalasia and establish an adequate method of injection . in conclusion , botulinum toxin injection for achalasia was safe and effective , with few complications in japanese patients . therefore , botulinum toxin could be one of the less invasive treatment modalities for esophageal achalasia in japan . guarantor of the article : daisuke yamaguchi , md . specific author contributions : principal investigator , subject recruitment , subject evaluation , data collection and manuscript preparation : daisuke yamaguchi ; manuscript preparation and statistical analysis : nanae tsuruoka , yasuhisa sakata , ryo shimoda , kazuma fujimoto , ryuichi iwakiri .