How Does the Brain Recover After Stroke?

People who have suffered traumatic brain injury or stroke often have serious, immediate deficits in motor, sensory, and cognitive function. Interestingly however, these functions often recover in the following weeks and months, without apparent reason. Until now, the repair mechanisms behind this spontaneous recovery have been a mystery. A recent study published in Brain demonstrates the ingenious ability of the central nervous system to repair itself after brain injury.

In anesthetised mice, Ueno and colleagues injured the region of the motor cortex that controls movement of the forelimb, in one hemisphere only. This resulted in the loss of forelimb function on one side, measured by behavioural tests that required the mice to walk across a ladder, up a staircase and through a cylinder. Similar to the spontaneous recovery seen in humans, the mice began to recover their motor function after two weeks, with improvement peaking after six weeks.

To try to understand and visualise the neural processes behind this recovery, the authors injected colored tracers into the injured motor cortex, the same cortical region in the opposite, uninjured hemisphere, and the corticospinal tract, which carries signals from the brain to the limbs to generate movement. This allowed the investigators to look at the changes in the brain and corticospinal tract associated with the loss of motor function and subsequent recovery.

Tracing showed that new fibres, originating in the uninjured motor cortex, began to grow and connect with neurons on the opposite, damaged side of the corticospinal tract. New fibres began to form 2 to 4 weeks after injury, with the new axons growing longer, sprouting “branches”, and finally connecting with the neurons involved in forelimb movement on the damaged side.

It was important to find out if this newly rewired pathway was responsible for the recovery in motor function seen in the mice. The authors stimulated the healthy motor cortex using a microstimulator, and recorded muscle activity in the forelimb on the opposite, injured side. When the healthy cortex was stimulated, the muscles on the injured side responded, demonstrating that this rewiring between the brain and spinal cord was indeed responsible for restoring motor function.

The authors also demonstrate the importance of one molecule, brain-derived neurotrophic factor (BDNF) in this rewiring process. BDNF is important for the growth of neurons throughout the brain, and in this experiment BDNF was necessary to induce sprouting and branching in the new pathways, a process essential for the recovery of function. When BDNF production was blocked, the animals did not recover their motor function.

This study demonstrates that the brain is extremely capable at repairing itself, and suggests exciting new possibilities for improving recovery after traumatic brain injury and stroke in humans. Developing treatments that enhance this rewiring, sprouting and branching process may improve the likelihood of recovery for people who have lost cognitive or motor function due to injury.


Ueno M, Hayano Y, Nakagawa H, & Yamashita T (2012). Intraspinal rewiring of the corticospinal tract requires target-derived brain-derived neurotrophic factor and compensates lost function after brain injury. Brain : a journal of neurology, 135 (Pt 4), 1253-67 PMID: 22436236

Image via Evgeny Korshenkov / Shutterstock.

  • Munwar ali



    on neurology.

  • mrs akison annable

    i had a brain injury in 3008 the right mtddle cerebal artery bled into hight basal ganglia, @ it effected my left stde, i have no use in my left arm, @ my keg is extremly tight, Iam ay the moment looking at treatment in stem cells, as i so much want my life back, if you could reccomend a good clinic, i would be more than grateful, i would be paying privatly,

    • Virginia

      I had a bleeding on the right side so left me with left side paralysis. It is not fun! but, I was a professional dancer and danced for 27 years. I can tell you that in my own experience I am stretching just like before and that helps a lot with spasticity. It hurts… But it is wort it. I am working with a personal trainer and I do find them to be more efficient than therapy. Just be aware that they may push you to much and also if the trainer has a yoga background or understand center, alignment and weight bearing. Those are very important things to do.
      Just keep on fighting!

  • Anonymous

    what is the cost of stem cell injection ?how many times it requires to give to cva patient ?

  • Hello doctor, I hope you don’t mind if I introduce myself with some of my history, I was hit by a car while I was riding my bicycle in Santa Barbara in October 2005 that resulted in traumatic brain injury (TBI).
    I was the new president of a company brand (TEVA) in the Deckers Group. I was in a coma for 2 months and two years after exiting the coma I found out that oxygen therapy – HBOT – can help brain injury, so I did 53 sessions in a hard chamber with 100% oxygen and then about 160 in a portable one I had rented breathing pure medical oxygen from a tank through a mask. But not with the outcome I was hoping for.

    My biggest disability is that since 2007 I’ve been trying to walk by myself but I’m currently still sitting on a wheelchair, this gives me big frustration and for this reason I don’t go back to work again, even if my logic and thinking/reasoning skills are still as good as they used to be.

    Very recently I’ve read about the Perispinal etanercept (or Enbrel) and I’m again very hopeful that by doing it, I will eliminate pain and spasticity; therefore I can walk by myself again and go back to work.

    I cannot believe that our government prefers to pay disabilities to the thousands of TBI victims like me, rather than help the FDA approval of Enbrel for what’s now considered an “off-label” use and that being a simple anti-inflammatory has proven to restart the natural neuroplasticity of the human brain.

    In short without the approval by the FDA of the “off-label” use of Enbrel none of my good doctors wants to take the risk to lose the medical license treating me and as a result I continue to receive my monthly disability and am forced to spend my days sitting on a wheelchair.

    I believe that by having the Enbrel reduce the inflammation in my brain the plasticity can return to operate to rewire my brain around the injury. I need to have something to say to my doctor to make him comfortable enough to treat me with Enbrel.

    Very much about myself and my history is in my blog here below that I invite you to look at.

    Thank you and best regards.

    Carlo Lingiardi PH.D.

India Bohanna, PhD

India Bohanna, PhD, earned her Bachelor of Science from Monash University and Doctor of Philosophy from University of Melbourne. She is currently a mental health research fellow.

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