What is the role of botulinum toxin in the treatment of dystonia?
Botulinum toxin, one of the most lethal biologic toxins, is produced by the bacteria Clostridium botulinum .
It acts at the neuromuscular junction, where it binds to the presynaptic cholinergic terminal and inhibits the release of acetylcholine. This functional denervation causes weakness and atrophy.
After 3 to 4 months, sprouting and regrowth of the nerve terminals occur. Botulinum toxin has been found to be effective in 95% of patients with blepharospasm, 90% of patients with spasmodic dysphonia, 85% of patients with cervical dystonia, and a majority of patients with oromandibular and hand dystonia.
Patients with generalized dystonia displaying prominent disability in a single region may benefit from application of botulinum toxin to the involved area. The complications of botulinum toxin treatment are limited to local weakness; different consequences depend on the area.
For example, patients with blepharospasm may have ptosis, whereas dysphagia is a potential complication of treatment for cervical dystonia.
Most complications, however, resolve spontaneously after 2 to 4 weeks.
A small percentage (3% to 5% in some series) of patients develop antibodies directed against botulinum toxin.
