Botulinum toxin type A versus anticholinergics for cervical dystonia

Area of Science:

• Neurology
• Movement Disorders
• Pharmacology

Background:

• Cervical dystonia is a common, disabling focal dystonia causing involuntary head posturing and pain.
• Botulinum toxin type A (BtA) is a current first-line therapy, previously preceded by anticholinergics.
• This review updates evidence on BtA versus anticholinergic efficacy and safety in cervical dystonia.

Purpose of the Study:

• To compare the efficacy, safety, and tolerability of botulinum toxin type A (BtA) against anticholinergic drugs.
• To evaluate treatment outcomes for adults diagnosed with cervical dystonia.

Main Methods:

• Searched multiple databases (CENTRAL, MEDLINE, Embase) and reference lists up to July 2020.
• Included one double-blind, randomized controlled trial (RCT) comparing BtA (Dysport) with trihexyphenidyl.
• Assessed risk of bias and extracted data; planned meta-analysis if sufficient data were available.

Main Results:

• One RCT (66 BtA-naive participants) found BtA reduced cervical dystonia severity more than trihexyphenidyl (2.5 points on TWSTRS).
• Adverse events were reported more frequently with trihexyphenidyl (76 events) than BtA (31 events).
• BtA showed a decreased risk of dry mouth and memory problems; other side effects were inconclusive.

Conclusions:

• Evidence suggests BtA may be more effective, better tolerated, and safer than trihexyphenidyl for cervical dystonia.
• The certainty of this evidence is very low, necessitating cautious interpretation.
• Further research is needed on BtA dose-response, formulations, injection guidance, and treatment duration.