Botulinum toxin type A injections in the psoas muscle of children with cerebral palsy: muscle atrophy after motor end plate-targeted injections.
Drug shots shrank a hip muscle in kids with CP, but behavior studies show we can also train motor skills without drugs.
01Research in Context
What this study did
Doctors gave botulinum toxin shots to the psoas muscle in kids with cerebral palsy.
They aimed the needle right at the motor end plate zone in one group and farther away in another.
MRI scans later checked how much the muscle shrank.
What they found
Shots that hit the motor end plate made the muscle 20 % smaller.
Shots placed farther away did not shrink the muscle.
The atrophy lasted the whole study period.
How this fits with other research
Annable et al. (1979) used food rewards and spoon prompts to stop tongue thrust in one child with CP.
That study got better mouth control with pure behavior tricks—no drugs needed.
Shakya et al. (2024) are now testing a head-trunk brace for posture; again, no medicine.
Together the papers show two paths: change the muscle with drugs or train the child with practice and rewards.
Why it matters
You can’t give BoNT-A shots, but you can write goals that match what the drug is trying to fix—looser hips for stepping, straighter trunk for sitting.
Pair your ABA sessions with PT or OT so the child moves right when the muscle is relaxed.
Track active range and step length; if the family chooses shots, you have data to show if therapy keeps the gain alive.
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02At a glance
03Original abstract
UNLABELLED: MEP targeting during BoNT-A injections has been demonstrated to improve outcome. Two injection techniques of the psoas muscle - proximal MEP targeting versus a widely used more distal injection technique - are compared using muscle volume assessment by digital MRI segmentation as outcome measure. METHOD: 7 spastic diplegic children received injections in both psoas muscles: two different injection techniques randomly in 5 patients, in 2 patients bilateral MEP targeting. MRI images of the psoas were taken before, after 2 months and in 3 patients after 6 months. RESULTS: Average post injection volume (in relation to pre-injection volume) for the MEP targeted muscles (9) is 79.5% versus 107.8% in the 5 distal injected psoas muscles (p=0.0033). In all 5 asymmetric injected patients the MEP targeted psoas had a larger volume reduction than the more distal injected psoas muscle. This atrophy remains even 6 months after the injection. This is the first study were a longitudinal follow-up by MRI demonstrates muscle atrophy after BoNT-A in children with CP. Injections in the MEP zone of the muscle, which is the more proximal part of the psoas muscle, cause atrophy in contrary to more distal injections were this atrophy is not observed.
Research in developmental disabilities, 2013 · doi:10.1016/j.ridd.2012.11.016