Our case report describes the use of EUS to guide intramuscular application of the botulinum toxin in patient with yet unclassified esophageal motility disorder.

The therapeutic potential for botulinum toxin in esophageal motility disorders has been first described in achalasia patients [7]. Its time-limited effect has been demonstrated in multiple studies [8,9,10]. This restricted its utilization for elderly and/or comorbid patients in whom no requirement for anesthesia and low incidence of undesirable effects outnumbers the transient effect [1, 9,10,11]. In achalasia, it is applied into the LES region, while in distal esophageal spasm and Jackhammer esophagus it is injected into the esophageal body. For all above mentioned indications, botulinum toxin is applied endoscopically into the muscularis propria layer.

Some significant landmarks in the area of botulinum toxin utilization in esophageal motility disorders could be highlighted based on our case. From the motility point of view, the possibility to apply botulinum toxin in a disorder with spastic component that is not yet classified according to the Chicago classification. Although one might argue that during the second visit of the patient the manometric finding was esophageal outflow obstruction, we considered the spasm in the mid esophagus more relevant for the symptoms, and therefore, a target for therapy. Significant symptom improvement further supports our approach. From the clinical point of view, there is the potential to expand the indications for the use of botulinum toxin not only in elderly comorbid patients, but also for younger subjects with yet unspecified motility defect. As it is shown by the natural course of the disease, this approach led to substantial symptom improvement until the motility disorder developed into achalasia.

Last but not least, our case points out the possibility of significantly more precise EUS navigation of botulinum toxin application rather than more common endoscopic navigation. Although the use of EUS is in the esophagus, it has been mostly indicated for sampling lymph nodes or metastases in neoplastic lesions [12]. EUS-guided tissue acquisition (TA) using fine needle aspiration (FNA) or fine needle biopsy (FNB) has been also widely used for subepithelial lesions (originating in the submucosa or muscularis propria) [13]. We took the advantage of the fact that the muscle layer was significantly thickened in our patient in the level of the spastic segment (similarly to thickened muscle at the level of the lower esophageal sphincter in patients with achalasia) [14]. Our approach might prevent complications (e. g. mediastinitis due to paraesophageal application) not only in unclassified motility disorders, but also patients with distal esophageal spasm or Jackhammer esophagus that are more commonly indicated for botulinum toxin application.

The relief of symptoms of our patient was considerable. Importantly, the effect was also confirmed by HRM with complete (although transient) elimination of the spastic segment that limits the possibility of the placebo effect.