Botulinum toxin in movement disorders.

Botulinum toxin has gained immense popularity since its introduction for therapeutic use. It is used in a variety of movement disorders like hemi-facial spasm, focal dystonias like blepharospasm, cervical dystonia, oromandibular dystonia, limb dystonias. It is also being used in patients with tremors, tics and for a variety of indications in Parkinson's disease as well. There are eight subtypes of toxins available, but type A and B are the ones used in movement disorder clinics. The toxin mainly acts by inhibiting the release of acetylcholine at the neuromuscular junction and causing weakness. Type B toxin has more effect over the autonomic nervous system and hence is preferred for hyper-secretory disorders. The use of electromyography and ultrasound further improve the accuracy of the procedure. It is a relatively safe therapeutic option with its effect lasting for around three months. It has very few side effects. The key is to start with the lowest possible dose and then gradually increase the dose depending upon the patient's response. Selecting the right muscles for injection is of utmost importance and is guided by the knowledge of anatomy of the muscles.