Treatment of focal dystonia with botulinum toxin A

Local injections with Botulinum toxin A (BtxA) are safe and effective in th e 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 wr iter's cramp. In cervical dystonia, muscles for injection are selected by c linical presentation or in complex forms with EMG guidance. Several studies have shown that 500 units Dysport (R), are safe and effective in the treat ment of cervical dystonia. In blepharospasm, injections are performed in th e periorbital part of the orbicularis oculi muscle with good results for 12 -14 weeks. The most frequently employed starting dose is 120 units Dysport (R) per eye, divided in three periorbital injection sites. In case of levat or 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 inj ections in order to avoid side-effects. Dose recommendations for the variou s types of dystonia are given in the text. In up to 5% of patients with dystonia, the development of neutralising anti bodies is reported following repetitive injections with BtxA. Patients with antibodies had a shorter interval between injections, more "boosters", a h igher dose per 3-month interval, and a higher total dose injected. In case of neutralizing antibodies against the A toxin, the treatment with Botulinu m toxin B (Neurobloc (R)) is a possible alternative.