OPTIMIZATION OF BOTULINUM TREATMENT FOR CERVICAL AND AXIAL DYSTONIAS - EXPERIENCE WITH A JAPANESE TYPE-A TOXIN

Twenty two patients with cervical and axial dystonias were treated wit h Japanese type A botulinum toxin. Injections were given repeatedly at intervals of 28-30 days to carefully chosen muscles with increased ac tivities, with a maximum dose per session of 300 units. The maximum im provements in subjective and objective ratings were obtained only afte r repeated injections. No antitoxin antibodies were detected; nor did any muscle fail to respond to the toxin. During the treatment, previou sly ''silent'' muscles were activated to reproduce the original abnorm al posture, as if driven by a central motor programme. This resistance to treatment was overcome by injecting the toxin into newly activated muscles. Repeated injections are thus required to override central me chanisms in dystonias or to maximise drug delivery to large muscles. A ntibody development may be controlled by the use of a less immunogenic toxin.