An electrophysiological approach to the diagnosis of neurogenic dysphagia; implications for botulinum toxin treatment

Abstract

Objectives: Botulinum toxin (BTX) injection into the cricopharyngeal (CP) muscle has been proposed for the treatment of neurogenic dysphagia due to CP hyperactivity. We aimed to find out whether an electrophysiological method exploring oro-pharyngeal swallowing could guide treatment and discriminate responders from non-responders, based on the association of CP dysfunction with other electrophysiological abnormalities of swallowing.

Methods: We examined patients with different neurologic disorders: Parkinson¡¦s Disease, progressive supranuclear palsy, multiple system atrophy-Parkinson variant, multiple system atrophy- Cerebellar variant, stroke, multiple sclerosis, and ataxia-telangiectasia. All patients presented with clinical dysphagia, and with complete absence of CP muscle inhibition. Each patient underwent clinical and electrophysiological investigations before and after treatment with BTX into the CP muscle of one side (15 units of BOTOX, Allergan®). Clinical and electrophysiological procedures were performed in a blind manner by two different investigators. The following electrophysiological measures were analysed : 1) duration of EMG activity of suprahyoid/submental muscles (SHEMG-D); 2) duration of laryngeal-pharyngeal mechanogram (LPM-D); 3) duration of the inhibition of the CP muscle EMG activity (CPEMG-ID); and 4) interval between onset of EMG activity of suprahyoid/submental muscles and onset of laryngeal-pharyngeal mechanogram (I-SHEMG-LPM).

Results: Two months after treatment, 50 % of patients showed significant improvement. The graphical analysis of the distribution of SHEMG-D and I-SHEMG-LPM at baseline highlighted values for which BTX had no effect (warning values).

Conclusions: Our electrophysiological method can recognize swallowing abnormalities which may affect the outcome of the therapeutic approach to dysphagia with BTX treatment.