Article

Intramuscular botulinum toxin-A (BoNT-A) injections reduce spasticity by
blocking neurotransmission at the motor endplate (MEP). The goal of this study
was to assess the reduction in spasticity achieved by injecting BoNT-A at
different sites of the gracilis muscle. METHOD: Thirty-four gracilis muscles, in
27 children (10 females and 17 males, mean age of 8.6y [SD 2.5y]) with spastic
cerebral palsy (unilateral and bilateral, Gross Motor Function Classification
System [GMFCS] levels I-IV), were randomly assigned to one of two groups. In one
group BoNT-A was injected proximally (at a site 25% of the distance from the
pubic tubercle and the medial epicondyle) and in the other it was injected at the
MEP zones (half of the dose was administered at 30% of this distance and half at
60%). Spasticity was assessed before and after BoNT-A injection using
simultaneous measurements of surface electromyography (sEMG) and angular velocity
during passive muscle stretch applied at different velocities. The primary
outcome measure included the velocity-dependent change in average root mean
square electromyography (RMS-EMG). Secondary outcome was assessed with the
Modified Ashworth Scale (MAS) and Modified Tardieu Scale (MTS). RESULTS:
Spasticity decreased more in MEP-targeted muscles than in proximally injected
muscles, as demonstrated by a larger reduction in average RMS-EMG values
(p=0.04), though this difference was not found with the MAS or MTS.
INTERPRETATION: The results suggest that BoNT-A injection of the gracilis at
sites with a high concentration of MEPs is effective at reducing spasticity.
These preliminary findings should be confirmed by larger studies. In the case of
long muscles, such as the gracilis, the injection site is important.
CI - (c) 2015 Mac Keith Press.

Langue : ANGLAIS