Muscle activity changes in spasmodic torticollis after botulinum toxin treatment

Area of Science:

• Neurology
• Physiology
• Biomedical Engineering

Background:

• Spasmodic torticollis (ST) is a movement disorder characterized by involuntary neck muscle contractions.
• Understanding the underlying muscle activation patterns is crucial for effective treatment strategies.

Purpose of the Study:

• To investigate changes in electromyographic (EMG) activity in neck muscles before and after botulinum toxin injections in patients with ST.
• To explore the relationship between botulinum toxin treatment, muscle activation, and head deviation in ST.

Main Methods:

• Surface electromyography (EMG) was used to record muscle activity in sternocleidomastoid, trapezius, and splenius capitis muscles bilaterally in 28 ST patients.
• EMG data was collected before and after botulinum toxin injections.
• Clinical benefit was assessed using Tsui's score.

Main Results:

• Objective benefit was observed in 78% of patients.
• Botulinum toxin injections led to decreased EMG activity in 65% of injected muscles and 68% of non-injected muscles.
• Interestingly, EMG activity increased in over half of muscles that initially showed no activity, suggesting a central motor control adaptation.

Conclusions:

• Treatment-induced changes in EMG activity occurred without significant alteration in the primary direction of head deviation.
• These findings support the hypothesis that spasmodic torticollis involves abnormal central motor programming leading to non-specific neck muscle activation.