Morphological Changes in Extraocular Muscle of Rabbit Eye Produced by Subtenon's Botulinum A Toxin Chemodenervation

PURPOSE: Currently, when injecting botulinum a toxin into the extraocular muscle, EMG (Electromyography) is used for accurate location. In this study, we examined the effects of subtenon botulinum toxin injection without EMG guidance by quantifying the morphological changes of the extraocular muscle fibers in rabbits. METHODS: Using 10 New Zealand white rabbits, 10 units of botulinum a toxin in 0.1 ml of normal saline was injected into the subtenon space of the superior rectus muscles, 5 mm from the muscle insertion in right eyes. As a control, 0.1 ml of normal saline was injected into the subtenon space of the superior rectus muscles in left eyes. At 3 weeks after injections, the bilateral superior rectus muscles of each rabbit were carefully dissected from the globe. Cross-sections of 5 micrometer thickness were obtained at the site, 5 mm from the insertion of each superior rectus muscle. Sections were stained with Masson's trichrome and observed by light microscopy. Using Image-Pro Plus software, the diameter of the orbital layer myofibers was measured and statistical analysis was done using the Kruskal-Wallis test. RESULTS: The average diameter of the orbital layer fiber cells after botulinum toxin injection was 11.5+/-2.26 micrometer at 3 weeks, whereas that of the control was 14.4+/-3.77 micrometer. The difference was statistically significant (p<0.01). CONCLUSIONS: The diameter of myofibers in the orbital layer was reduced after subtenon botulinum a toxin injection. Further studies on the duration of botulium toxin in subtenon space and the change in the size of myofibers depending on the dosage of botulinum toxin will be necessary.

Effect of Botulinum Toxin Type a Chemodenervation in Esotropia

PURPOSE: To investigate the efficacy of botulinum toxin type A chemodenervation in various types of esotropia(ET). METHODS: Enrolled eleven esotropic patients treated with botulinum toxin type A and examined the amount of esotropic correction and success rate of less than 10 PD (prism diopter) of postinjection deviation at 5 months after injection. RESULTS: Among the eleven esotropic patients, there were 7 cases of infantile ET, 2 cases of partially accommodative ET and 2 cases of basic ET. The mean preinjection deviation was 30.5 +/- 7.3 PD. The amount of correction was 17.7 +/- 4.3 PD and correction rate of deviation was 57.5%. In 6 of 11 cases, the postinjection deviation was within 10 PD and therefore success rate was 54.5%. In 5 patients (45.5%), their ET was undercorrected. In patients with under 20 PD of preinjection deviation, success rate was 75% (3/4) and those with over 20PD, the rate was 42.9% (3/7). In partially accommodative ET, 2 (100%) of 2 cases were aligned within 10PD. CONCLUSIONS: In comitant ET, botulinum toxin chemodenervation shows high undercorrection rate. The effects of botulinum toxin type A chemodenervation were better for relatively small angle and in partially accommodative ET than nonaccommodative one. But further study with more cases is needed.

Botulinum Toxin A Chemodenervation in Strabismus

PURPOSE: We investigated the therapeutic effect of botulinum toxin chemodenervation for the treatment of Korean strabismus patients. METHODS: From February 1996 to November 2001, 52 patients with various strabismus were treated with botulinum toxin chemodenervation and followed up for more than 6 months. There were 15 acute paralytic strabismus, 14 chronic paralytic strabismus (more than 6 months), 13 sensory strabismus, 5 consecutive strabismus, 3 residual strabismus and 2 comitant strabismus. We reviewed the final angle of deviation and complications. RESULTS: There were 29 men and 23 women with the mean age of 38.8+/-12.1 years. The mean follow up period was 8.08+/-2.27 months. The mean deviation before and after chemodenervation were 32.6+/-16.0 PD and 12.9+/-16.0 PD and improving rate of the strabismus angle was 60.4%. The final deviation of 36 patients (69.2%) were within 10 PD. Hypertropia occurred in 10 patients (19.2%), ptosis in 9 patients (17.3%), and subconjuntival hemorrhage in 2 patients (3.8%). CONCLUSION: Botulinum toxin chemodenervation is thought to have good therapeutic effects in acute paralytic strabismus as well as in chronic paralytic strabismus and other strabismus. The complications were relatively temporary and insignificant, so it is thought to be a safe method of strabismus treatment.

The Complications of Botulinum Toxin Type A Chemodenervation in Strabismus

We studied the safety and complication associated with treatment with botulinum A toxin chemodenervation. 70 eyes was entrolled and treated with botulinum A toxin chemodenervation. They were examed at 1 day, 1 week, 2 weeks, 1 month, 3 months and 6 months after the injection. Ptosis developed in 19 of 70 eyes(27.1%), but all of them recovered fully at 6 months after injection. A vertical deviation was noted in 19 eyes(27.1%), but all except one recovered fully at 6 months. Ptosis and vertical deviation developed more frequently in the group with the medial rectus muscle injection than with lateral rectus muscle injection. Subconjunctival he.morrhage and headache were also noted in 1 eye, respectively, but they disappeared at 4 weeks after the injection. Aggrevation of diplopia after injection was noted in 1 eye, which disappeared at 3 weeks after injection. Botulinum A toxin chemodenervation can be considered to be a safe method for the treatment of strabismus without the long-lasting serious complications.

The Effect of Botulinum Toxin Chemodenervation in Chronic Paralytic Strabismus

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.

Effects and Side Effects of Chemodenervation According to Neurolytic Agents

OBJECTIVE: To compare the effects and side effects of chemodenervation according to the neurolytic agents, injection techniques and treatment indications. METHOD: One hundred and seventy three cases of chmodenervation were reviewed. They were classified into three groups(phenol, b otulinum toxin, mixed) according to the neurolytic agents and into three groups(nerve trunk block, motor point block, both) according to the injection technique and nine gruoups(cervical dystonia, elbow flexor spasticity, wrist and hand spasticity, hip adductor spasticity, stiff knee gait, ankle plantar flexor spasticity, sustained ankle clonus, rear foot varus, toe clawing) according to the treatment indications. The rate of suboptimal results and side effects was descriptively measured. RESULTS: 1) The suboptimal results were observed in 19% of phenol blocks and 17% of Botulinum toxin injections. But the side effects were more frequently observed in phenol blocks(25%) than Botulinum toxin injections(2%). 2) In terms of phenol injection techniques, a nerve trunk injection was more successful(88%) than a motor point injection(69%). In case of simultaneous injections into the nerve trunk and motor point, the effects were very promising(100%). But the side effects were more frequently observed in the nerve trunk injections(26%) than the motor point injections(12%). 3) In terms of treatment indications, suboptimal results were observed in 44% of stiff knee gaits, 38% of cervical dystonias and 27% of toe clawing cases. Side effects were observed in 33% of toe clawing cases, 25% of sustained ankle clonus cases and 21% of elbow flexor spasticity cases. CONCLUSION: The suboptimal results were slightly higher in botolinum toxin injections than in phenol blocks. The side effects were more frequently observed in phenol blocks than in botulinum toxin injections.