Cervical Dystonia: From Pathophysiology to Pharmacotherapy

Background: Dystonia is a chronic disorder characterised by an aberration in the control of movement. Sustained co-contraction of opposing agonist and antagonist muscles can cause repetitive and twisting movements, or abnormal postures. Cervical dystonia (CD), often referred to as spasmodic torticollis, is a type of focal dystonia involving the muscles of the neck and sometimes the shoulders. Methods: This systematic review collates the available evidence regarding the safety and efficacy of a range of treatments for CD, focusing on their effectiveness as shown by double-blinded, randomised controlled trials. Results: Our review suggests that botulinum toxin type A (BTA), botulinum toxin type B (BTB) and trihexyphenidyl are safe and efficacious treatments for CD. Evidence shows that botulinum toxin therapies are more reliable for symptomatic relief and have fewer adverse effects than trihexyphenidyl. When comparing BTA to BTB, both are found to have similar clinical benefits, with BTA possibly having a longer duration of action and a marginally better side effect profile. BTB is also safe and probably just as efficacious a treatment in those patients who are unresponsive or have become resistant to BTA. Discussion: The current evidence shows that the pharmacological management of CD relies on BTA and BTB, two agents with established efficacy and tolerability profiles.