Predisposing factors to pattern change in cervical dystonia.

Area of Science:

• Neurology
• Movement Disorders
• Pharmacology

Background:

• Cervical dystonia (CD) is a neurological movement disorder characterized by involuntary neck muscle contractions.
• Botulinum toxin (BoNT) injections are a primary treatment for CD, but disease patterns can evolve over time.
• Understanding factors influencing CD pattern changes is crucial for optimizing treatment strategies.

Purpose of the Study:

• To investigate the temporal dynamics of phenotype changes in cervical dystonia patients undergoing BoNT treatment.
• To identify specific CD phenotypes and patient factors that predispose individuals to pattern alterations.
• To determine the relationship between disease severity and the likelihood of phenotype switching.

Main Methods:

• A cohort of 100 idiopathic cervical dystonia patients was divided into groups based on whether their phenotype changed during BoNT treatment.
• Clinical and demographic variables, BoNT treatment duration, and Tsui scores (total and subscores) were collected before treatment (T0) and at follow-up (T1).
• Kaplan-Meier curves and Cox regression analysis assessed the risk of pattern change, while multivariate linear regressions examined correlations between Tsui severity and pattern alteration.

Main Results:

• Out of 100 patients, 37 experienced a phenotype switch, predominantly within the first five years of BoNT therapy.
• Laterocollis and rotatocollis at T0 were significant predictors of phenotype change (HR=3.5, P=0.01 and HR=1.5, P=0.03, respectively).
• Higher Tsui subscores for neck tilt (OR=6, P=0.002) and lower overall Tsui total scores (OR=0.8, P=0.03) were associated with a higher likelihood of pattern change.

Conclusions:

• Laterocollis and rotatocollis are the cervical dystonia phenotypes most susceptible to change following BoNT treatment.
• CD presentations involving neck tilt and those with lower overall severity are more likely to exhibit phenotype switching.
• Variations in muscle activation patterns and the mechanism of action of BoNT may contribute to observed phenotype modifications.