As physiotherapists, we are taught that brain plasticity is a tremendous opportunity for reorganization after a neurological injury. It is often presented as an ally, a driving force for learning and recovery.
But in clinical practice, this plasticity can become a trap. Because the brain doesn’t retain ‘the right movement’, it retains what works in the moment, what allows the patient to regain functionality, even if this solution deviates from the ideal motor pattern. This is what we call negative plasticity.
After a stroke, patients must face a multitude of impairments: spasticity, loss of strength, balance disorders, pain, deformities, cognitive disorders… In addition to this, there are environmental factors: nature of the ground, quality of shoes, technical aid (or lack thereof), distractions, fear of falling.
In this context, the patient does what they can: they adapt.
These adaptations are often effective in the short term. They allow walking, moving around, being a little more autonomous. These are compensations. And as long as they provide a concrete solution, they are reinforced, repeated, integrated. The brain adopts them.
Let’s take a common case: a hemiparetic patient with quadriceps spasticity. This spasticity prevents the muscle from relaxing properly during the swing phase of gait. Result: the knee doesn’t bend enough, and the foot risks catching on the ground.
Faced with this constraint, the patient finds a solution: they perform a circumduction movement (hip circumduction) to prevent their foot from dragging. And it works.
They don’t fall. They move forward. So they will do it again. And each repetition reinforces this strategy because it is functional.
The problem is that the brain ends up recording this movement as a norm. Even if, later on, we manage to reduce spasticity (through botulinum toxin, neurotomy, etc.), the patient may continue to circumduct even when they no longer need to.
Their motor pattern has changed. It has been learned. It will then be necessary to deconstruct what the body has put in place, and this requires much more work than if the compensation had been avoided upstream.
Plasticity does not distinguish between a good or bad strategy. It reinforces what allows functioning. From a neurological point of view, any effective adaptation is validated.
This is why our role in rehabilitation is to avoid as much as possible the need for the patient to compensate.
This means:
The more the patient evolves in a “normal” situation (without major constraints), the more likely they are to adopt a gait close to the expected standard.
On the contrary, if we let compensation set in, it quickly becomes a reflex, a motor habit, a new standard for the brain. And it’s this gait that will be reinforced by plasticity.
Brain plasticity can be a tremendous lever for learning. But it can also solidify a pattern that was intended to be temporary. This is why it is fundamental to intervene early, at the source, and to place the patient in conditions that do not push them to compensate.
Re-educating a bad pattern is always more difficult than avoiding it.
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