Not paralysis, but dystonia causes stridor in multiple system atrophy

Area of Science:

• Neurology
• Otolaryngology
• Clinical Electrophysiology

Background:

• Multiple system atrophy (MSA) can present with laryngeal and pharyngeal symptoms, including stridor and dysphagia.
• The precise pathophysiology of these symptoms in MSA is not fully understood.
• Electromyography (EMG) is a valuable tool for assessing neuromuscular function.

Purpose of the Study:

• To investigate the neuromuscular mechanisms underlying stridor and dysphagia in patients with multiple system atrophy.
• To determine if vocal cord and cricopharyngeal muscle dysfunction contribute to these symptoms.
• To evaluate the therapeutic potential of botulinum toxin in managing these MSA-related symptoms.

Main Methods:

• Electromyography (EMG) was conducted on 10 patients diagnosed with multiple system atrophy (MSA) who exhibited laryngeal or pharyngeal symptoms.
• EMG recordings focused on vocal cord muscles during quiet breathing and cricopharyngeal muscle activity during swallowing.
• Botulinum toxin was injected into the adductor muscles of patients experiencing subjective improvement.

Main Results:

• Persistent tonic activity was observed in both abductor and adductor vocal cord muscles in patients with stridor during quiet breathing.
• Patients with dysphagia demonstrated persistent EMG activity in the cricopharyngeal muscle throughout the swallowing process.
• Botulinum toxin injection into the adductor muscles led to subjective symptom improvement and a reduction in tonic EMG activity.

Conclusions:

• The findings suggest that vocal cord dystonia is a primary cause of stridor in multiple system atrophy.
• Dysphagia in MSA may be associated with abnormal cricopharyngeal muscle activity during swallowing.
• Botulinum toxin represents a potential treatment option for stridor associated with vocal cord dystonia in MSA.