Three-year outcomes of repeated botulinum neurotoxin A injections to the lower extremities in young children with spastic cerebral palsy in GMFCS levels I to III.

Aim: To evaluate the effectiveness of repeated botulinum neurotoxin A (BoNT-A) injections on gross motor function over 3 years in ambulant children with spastic cerebral palsy (CP).

Method: A prospective observational cohort study of 124 participants was conducted comparing outcomes in children (aged 2-6 years) with spastic CP functioning in Gross Motor Function Classification System (GMFCS) levels I to III who did and did not receive BoNT-A. The primary outcome was the 66-item Gross Motor Function Measure (GMFM-66), assessed at baseline and annually over 3 years. Secondary outcomes included passive ankle dorsiflexion with knee extended (PADKE) and several measures of activity and participation.

Results: A total of 117 participants (94%), consisting of 61 cases and 56 comparisons, were assessed on the GMFM-66 at a follow-up of 1 year or longer, with 106 (85%) assessed at year 3. There were no significant differences in mean GMFM-66 scores adjusted for baseline differences between groups over time (β̂_group = 0.92, standard error [SE] = 0.81, 95% confidence interval [CI] = -0.66 to 2.50; p = 0.256). A difference in PADKE favouring the comparison group was observed (β̂_group = -4.17, SE = 1.58, 95% CI = -7.27 to -1.08; p = 0.009), approaching the 5° minimally important difference.

Interpretation: Repeated BoNT-A injections over 3 years were not associated with improvements in gross motor function or passive ankle dorsiflexion range in young children with spastic CP functioning in GMFCS levels I to III compared to a comparison group not receiving BoNT-A.