Effects of Botulinum Neurotoxin on Muscle Mass and Volume in Individuals with Spastic Cerebral Palsy: A Systematic Review and Meta-analysis.

Objective: To comprehensively survey the impact of botulinum neurotoxin (BoNT) on muscle volume or mass in treating lower limb spasticity in individuals with spastic cerebral palsy (CP).

Methods: We searched PubMed, Embase, Web of Science, and the Cochrane Library up to May 15, 2024. We focused on changes in the volume or mass of the gastrocnemius, triceps surae, or entire distal lower limb muscles at various follow-up periods. Meta-regression analysis was conducted to assess the moderating effects of age and gross motor function classification system (GMFCS) level.

Results: Our analysis included 11 cohort studies. A significant decrease in gastrocnemius muscle volume or mass was observed 2 to 3 months post-BoNT treatment (SMD -0.496, 95% CI [-0.810, -0.181]) but not at earlier (SMD -0.134, [-0.397, 0.129]) or later (SMD -0.223, [-1.199, 0.752]) periods. The triceps surae and entire distal lower limb muscles showed no changes. Older patients (P = 0.026) and those with GMFCS I-II levels (P = 0.0191) had more pronounced decreases.

Conclusions: The present study showed a decrease in muscle volume or mass of the BoNT-injected gastrocnemius after a short follow-up period but not in the triceps surae or the distal lower limb in individuals with spastic CP.