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

Overview

Dysphagia in patients with stroke, multiple sclerosis, parkinsonism or dystonia can occur due to relative hypertonia of the cricopharyngeus muscle. In the resting state, muscle is contracted and relaxes only during deglutition. Treatment of dysphagia by injecting botulinum toxin in the cricopharyngeus was 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. So this study is necessary to fill this void in knowledge

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