Use of botulinum toxin type A in the treatment of cervical dystonia

Botulinum toxin is the most neurotoxic substance known, with a specific act ion at cholinergic synapses. Acting as a zinc endopeptidase, botulinum toxi n cleaves specific proteins involved in vesicle fusion, thereby preventing release of acetylcholine. The therapeutic effect of the toxin taken up pres ynaptically at the neuromuscular junction is to weaken muscle. Botulinum to xin type A (BTX-A) has been shown to be safe and effective in the treatment of cervical dystonia (CD; also known as spasmodic torticollis). In patient s with CD, injections of botulinum toxin dampen or eliminate involuntary mu scle activity and improve control of neck movement, pain, and range of moti on. To successfully use botulinum toxin as a therapeutic modality, targetin g the dystonic muscles, injecting a sufficient quantity of toxin and minimi zing diffusion into uninvolved muscle collectively provide the best outcome with the fewest adverse reactions. EMG guidance may allow more precise inj ections. To maintain responsiveness to the toxin over repeated injections, using the lowest dose at the longest dosing interval has been suggested.