DOXORUBICIN CHEMOMYECTOMY AS A TREATMENT FOR CERVICAL DYSTONIA - HISTOLOGICAL ASSESSMENT AFTER DIRECT-INJECTION INTO THE STERNOCLEIDOMASTOID MUSCLE

The sternocleidomastoid muscle (SCM) is one of the major muscles invol ved in producing abnormal head position in cervical dystonia patients. This study tested whether doxorubicin chemomyectomy, direct injection of doxorubicin into the SCM to permanently remove muscle fibers, has the potential to be a nonsurgical, permanent treatment for cervical dy stonia. The right SCM of rabbits was injected with either 1 or 2 mg do xorubicin, Animals were sacrificed 1-2 months postinjection. The SCM w as prepared for histological examination of muscle fiber loss and fibe r type composition. In all cases, direct injection of doxorubicin resu lted in significant decreases in total muscle cross-sectional areas ra nging from 75% up to 98%. Individual myofiber cross-sectional areas we re smaller than normal after 2 mg doxorubicin treatment, but similar t o normal fiber size after 1 mg doxorubicin. There were increased numbe rs of myofibers that expressed slow and neonatal myosin heavy chain is oforms in these remaining muscle fibers compared to the untreated SCM on the contralateral side. Developmental myosin heavy chain (MHC) was also present in 53% of the remaining myofibers of the treated muscles. The fiber type composition of muscles contralateral to the doxorubici n injections was compared to the fiber type composition of SCM from no rmal, untreated controls; no difference was seen in the proportions of fast, slow, and neonatal MHC fiber types in these SCM muscles. In sum mary, the direct injection of doxorubicin into the SCM resulted in sig nificant muscle loss. This supports the use of doxorubicin chemomyecto my as a potential permanent, nonsurgical treatment for cervical dyston ia. (C) 1998 John Wiley & Sons, Inc. Muscle Nerve 21: 1457-1464, 1998.