22/01/2026
Botulinum neurotoxin A (BoNT-A) or "botox" is a neurotoxin that when injected into the muscle temporarily blocks nerve signals into the muscles, aka causes temporary muscle paralysis. It is commonly used to treat spasticity in children with cerebral palsy and results in partial paralysis and atrophy, which result in a temporary reduction in spasticity. (Yes this is also the same thing as many people inject into their faces for cosmetic purposes). BoNT-A reaches a maximum effect at
2 weeks and lasts approximately 3months, with a return of
spasticity after this time.
The goals of the use of botox have been for
"tone reduction, improved or preserved gross motor
function, pain reduction, and maintenance of passive range of motion to prevent or delay the development of
fixed contractures." We have been limited in our knowledge however of what the long term impact may be on causing temporary muscle paralysis.
Recently, concern was raised that repeated botox
injections may be associated with a persistent ⬇️ in muscle volume, weakness and long term atrophic changes. Animal studies have shown that repeated Botox injections lead to increased lipid (fat) accumulation, fibrosis in the muscle, loss of contractile material, changes in muscle fibre type distribution and that there has incomplete recovery at 6 months (Multani, 2019). This has resulted many to change clinical practice to wait 12 months between injections.
There has been an urgent need for long term controlled studies investigating the long term implications of these effects on function.
This 3-year prospective observational cohort study of children aged 2 to 6 years, with spastic CP and functioning at GMFCS levels I to III, did not identify greater improvement in gross motor function, goal attainment, functional mobility skills, recreational participation or ankle ROM.
Please take note that botox injections are normally followed by a period of intensive rehabiltation. So this lack of improvement in gross motor function is likely confounded by the finding that the children within the botox group received on average an additional 30 mins of physio per month.
It definitely gives us something to think about.
