The Effect of Botulinum Toxin Chemodenervation in Chronic Paralytic Strabismus

ABSTRACT

Botulinum toxin chemodenervation is widely used for the treatment of acute paralytic strabismus. We reviewed the effect of botulinum toxin chemodenervation for the treatment of chronic paralytic strabismus. Between 1996 and 1998, 13 patients with chronic paralytic strabismus were treated with botulinum toxin chemodenervation. The palsy of extraocular muscle persisted for at least 6 months. Each patient received an injection of 1.25 to 5 units of botulinum toxin[Botox]to the antagonist muscle of the paralytic muscle and two patients received injections two times. The follow-up was more than 6 months [mean 7.62 months].2 patients were treated with surgery of horizontal muscles and 3 patients were treated with muscle transposition surgery before injection. The mean preinjection deviation was 36.7PD and the mean strabismus angle after injection was 19.2PD and improving rate of the strabisbismus angle was 47.6%. The final deviations of 6 patients were within 10PD[46.2%]and 4 of 7 patients with final deviation above 10PD were treated with surgery later. Ptosis occurred in 4 patients[30.8%]and hypertropia occurred in 4 patients[30.8%]. In addition to the prevention of muscle contracture with botulinum toxin injection, it is likely that the therapeutic effect of botulinum toxin is produced by permanent alteration in the muscle and influence on the peripheral and central nervous system. Therefore botulinum toxin chemodenervation can be considered as a primary therapy or a subsequent therapy of surgery for chronic paralytic strabismus and further study is needed.