Treatment of focal dystonia with botulinum toxin A

Local injections with Botulinum toxin A (BtxA) are safe and effective in the treatment of focal dystonia. In cervical dystonia and blepharospasm, BtxA injections have become the treatment of choice. However, good results have also been reported with oromandibular dystonia, spasmodic dysphonia and writer's cramp. In cervical dystonia, muscles for injection are selected by clinical presentation or in complex forms with EMG guidance. Several studies have shown that 500 units Dysport are safe and effective in the treatment of cervical dystonia. In blepharospasm, injections are performed in the periorbital part of the orbicularis oculi muscle with good results for 12-14 weeks. The most frequently employed starting dose is 120 units Dysport per eye, divided in three periorbital injection sites. In case of levator inhibition, the pretarsal part of the orbicularis oculi muscle should be injected in a lower dose. EMG guidance is not necessary. By contrast, BtxA treatment of spasmodic dysphonia and writer's cramp require EMG-guided injections in order to avoid side-effects. Dose recommendations for the various types of dystonia are given in the text. In up to 5% of patients with dystonia, the development of neutralising antibodies is reported following repetitive injections with BtxA. Patients with antibodies had a shorter interval between injections, more "boosters", a higher dose per 3-month interval, and a higher total dose injected. In case of neutralizing antibodies against the A toxin, the treatment with Botulinum toxin B (Neurobloc) is a possible alternative.