Response to botulinum neurotoxin injections in large-angle infantile esotropia: a post hoc analysis

PURPOSE To determine the anticipated reduction of baseline angle of esotropia and identify predictors of change following botulinum neurotoxin (BNT) injections in large-angle infantile esotropia. METHODS This was a prospective, longitudinal study of children <10 years of age diagnosed with infantile esotropia of >30(Delta) and given either 1, 2, or 3 BNT injections. Post-injection change from baseline deviation was recorded, and predictors of reduction were analyzed. For this study, children were further divided into subgroups based on initial deviation of <= 60(Delta) (group 1) and >60(Delta) (group 2). The outcomes of subsequent surgeries in failed cases were analyzed. RESULTS A total of 117 children were included, 55 in group 1 and 62 in group 2. Mean age was 30.3 +/- 18.8 months. Mean baseline deviation was 62.5(Delta) +/- 13.1(Delta): 51.4(Delta) +/- 8.4(Delta) in group 1 and 73(Delta) +/- 7.5(Delta) in group 2. The mean number of injections was 2.2 +/- 0.7. Success was achieved in 25.6% of patients (33.4% in group 1; 16.2% in group 2). The mean percentage reduction of deviation after BNT injection was 55.2% +/- 26%, larger in group 1 than in group 2 (61.3% vs 51.1% [P = 0.001]). Five children reverted to baseline deviation. In multivariate analysis, adjusting for number of injections, younger age and larger baseline deviation were significant independent predictors of a larger absolute amount of reduction (P = 0.02, and 0.002, resp.). Thirty-two children had subsequent surgery; 22 were followed for a minimum of 6 months, and 20 were aligned within 10(Delta) of orthotropia. CONCLUSIONS In large-angle esotropia there was a reduction of approximately 50% of baseline deviation, with greater relative reduction for smaller baseline deviations; the absolute change in angle was greater in younger children. Alignment after subsequent surgery appeared to remain stable and surgery required less recession than would have been needed for the original angle of esotropia.