Onabotulinum Toxin A (Botox) in the Treatment of Pharyngo-esophageal Dysphagia

Swallowing is a neurologically coordinated physiologic event that requires sequential and overlapping movements of various craniofacial, pharyngo-esophageal and laryngeal muscles. In the process of swallowing, ingested bolus and oral secretions are shifted from the mouth into the esophagus. Neurological disorders adversely affecting any portion of this coordinated sequence may lead to oropharyngeal or Pharyngo-esophageal dysphagia. During swallowing, the upper esophageal sphincter (UES) transiently relaxes and larynx is subsequently pulled in the antero-cephalad direction by contractions of the suprahyoid muscles; this traction results in active opening of the UES.

In the resting state, the function of this sphincter is to keep the upper esophagus closed during inspiration and between swallows. It relaxes only during deglutition in coordination with the other muscles of the tongue, larynx, anterior cervical muscles and allows the ingested bolus to pass into the esophagus from the hypopharynx. In the resting state, this closed UES prevents the reflux of gastric and esophageal contents into the hypopharynx. Dysfunction of the cricopharyngeal relaxation can cause dysphagia and is called cricopharyngeal dysfunction (CPD). It may lead to weight loss, aspiration pneumonia, airway obstruction, need to use nasogastric tube for feeding or change to liquid based diet. Treatment of dysphagia due to CPD by injecting botulinum toxin in the cricopharyngeus described by Schneider et al. in 1994. More than 100 cases have been described after that, however there are no randomized controlled trials. A meta-analysis from Cochrane has also concluded that there is no sufficient evidence to conclude regarding the efficacy and safety of Botulinum toxin injection in cricopharyngeal dysfunction.

Problem statement Neurological disorders including stroke, multiple sclerosis, movement disorders including parkinsonism, dystonia etc. can cause dysphagia. In some of these cases there is a relative hyper-tonicity of the cricopharyngeus muscle. There is a relatively newer entity of this form of pure dysphagia due to dystonia which has been described by Samal et al. Increased tone of the cricopharyngeus due to spasticity or dystonia leads to failure of adequate relaxation of the upper esophageal sphincter leading to CPD. When the pharyngeal contraction is adequate, due to pre bolus resistance, the ingested bolus may stay as a residue in the hypopharynx leading to dysphagia or choking sensation or pushed into the upper airway leading to aspiration. In such cases, so far no medical treatment exists which can promote relaxation of the cricopharyngeus and lead to better swallowing function. Two modalities of management have been described in case series and reports, one of is surgical myotomy of the cricopharyngeus and the other is a relatively easy and lesser invasive procedure of injecting botulinum toxin in the horizontal part of the cricopharyngeus muscle. However, since there are no randomized controlled trials, no definite recommendations regarding the efficacy and safety of the procedure can be made.

So this RCT is necessary to fill this void in knowledge

Inclusion criteria

• Patients attending neurology OPD with swallowing dysfunction due to central nervous system dysfunction
• At least 14 years of age of all sexes
• mRS (modified Rankin scale) of ≤3 at time of study enrolment
• In case of post stroke dysphagia, at least 6 months have passed following stroke
• Willing to undergo swallowing assessment clinically and with video fluoroscopy, flexible upper GI endoscopy and esophageal manometry before and after the injection
• Above investigations show impaired cricopharyngeal relaxation, adequate pharyngeal strength and anterocephalad laryngeal movement
• Ready to provide consent for Botulinum neurotoxin injection.
• Willing to adhere to protocol and comply with follow up visits
• No major neurologic or systemic medical condition that reduces life expectancy to less than 1 year based on clinical prediction scores

Exclusion criteria

• Diagnosed cases of neuromuscular disorders of the peripheral nervous system and ALS
• mRS at time of enrolment >3
• Patients with expected life expectancy less than 1 year due to primary disease or co morbidity based on clinical prediction scores
• Known allergy to botulinum neurotoxin or its preservatives/excipients
• Received botulinum toxin for any indication in the last 12 weeks
• Those with known antibodies against Botulinum neurotoxin A
• Those who underwent myotomy of the cricopharyngeus muscle
• Those who had undergone procedures like denervation of the cervical musculature
• Dysphagia of other causes not fulfilling inclusion criteria
• Women of childbearing potential who are not using adequate contraception or who are pregnant and lactating
• Not willing to provide consent