Architectural Changes of the Gastrocnemius Muscle after Botulinum Toxin Type A Injection in Children with Cerebral Palsy

PURPOSE: This study used ultrasonography (US) to investigate the architectural changes in gastrocnemius muscles (GCM) after botulinum toxin injection (BoNT-A) in children with cerebral palsy (CP). MATERIALS AND METHODS: Thirteen children with CP who received a BoNT-A injection into their GCM to treat equinus were recruited (9 males and 4 females). Architectural changes in both the medial and lateral heads of the GCM from a total of 20 legs were assessed using B-mode, real-time US. Muscle thickness (MT), fascicle length (FL), and fascicle angle (FA) were measured over the middle of the muscle belly in both a resting and neutral ankle position. Measures at 1 and 3 months after the injection were compared with baseline data taken before the injection. RESULTS: The mean age of the subjects was 5.8 (±1.6) years. Spasticity was significantly reduced when measured by both the modified Tardieu scale and the modified Ashworth scale at 1 and 3 months after injection (p<0.05). The MT and FA of both the medial and lateral heads of the GCM were significantly reduced for both neutral and resting ankle positions at 1 and 3 months after the injection. The FL of both the medial and lateral heads of the GCM were significantly increased in a resting position (p<0.05), but not in a neutral position. CONCLUSION: Our results demonstrated muscle architectural changes induced by BoNT-A injection. The functional significances of these changes were discussed.