ALS dysphagia pathophysiology: differential botulinum toxin response

This study looked at the effect of botulinum toxin type A (BoTox-A) in patients with amyotrophic lateral sclerosis (ALS) with dysphagia due to isolated upper motor neuron (UMN) involvement or combined UMN/lower motor neuron (LMN) impairment associated with oral phase or oropharyngeal muscles involvement. Establishing whether different pathophysiologic mechanisms underlie different responses to BoTox-A treatment may have important implications for patient management.

We screened 35 patients with sporadic ALS with dysphagia and included in the study 20 out of 35 with upper esophageal sphincter (UES) hyperactivity. We divided these 20 patients into 2 groups, based on the presence or absence of LMN impairment. Irrespective of the groups, we treated all 20 patients with BoTox-A injected into the UES. The study outcome was dysphagia severity scored using the Penetration/Aspiration Scale (PAS), measured before and 2, 4, and 20 weeks after injection.

Significant mean PAS reduction was noted at weeks 2 and 4. The botulinum-dependent PAS reduction was entirely associated with the variability shown by the group of patients with no sign of LMN impairment (group 2) and was not observed in group 1.

The significant improvement observed in patients with isolated UES dysfunction suggests that a different pathophysiology of ALS dysphagia predisposes patients to a different response to treatment with BoTox-A. This treatment may represent an alternative treatment to percutaneous endoscopic gastrostomy (PEG) or prolong PEG-free time.

This study provides Class III evidence that botulinum is more effective at 2 and 4 weeks in improving dysphagia in patients with ALS with UES hyperactivity without LMN involvement (vs those with LMN involvement).