This post discusses how our brain fights back – its recovery attempts – after a stroke attack.
Non-linear trajectory of the brain’s recovery attempts
The brain’s recovery attempts follow a non-linear trajectory; the most gains occur in the first 3 months. Even within these three months, the most improvements happen during the first few weeks. After three months, the recovery tapers down towards the end of the sixth-month post-stroke.
However, there is good news; researchers have found the recovery attempts do not stop at the end of the sixth-month. It continues, although at a much slower pace, beyond the 12th month.
There is more good news: With appropriate training and other outside interventions, we can help the brain to speed up the process and achieve better recovery according to these researchers.
We need to consider the above non-linear trajectory as a general guideline according to some researchers.
Why should we consider the non-linear trajectory as a general guideline?
This is because they have found that some patients recover faster and better than others. The trajectory seems to depend on the initial level of impairment and where the stroke occurs.
Figure 1 illustrates this phenomenon more clearly; Christian Grefkes and Gereon Fink, the authors of the article, Recovery from stroke: current concepts and future perspectives, published on June 16, 2020, in the Neurological Research and Practice journal, describes the graph: Those with milder impairment on admission recovers much better than those with severe impairment on admission.
Researchers say that recovery is strongly associated with the development of new connections within the affected areas. This post examines what those are and when these occur.
What happens within the first three weeks post-stroke
The brain attempts to restore supply routes.
As soon as a stroke attack unleashes, the brain begins to strike back. Its alarm system activates the alternate collateral blood supply mechanisms to sustain oxygen and food supply to neurons and its supportive cells. Most of the time, this back-up mechanism cannot save all the cells.
Infarct area and the penumbra
Those who live inside the areas directly affected begin to die. This area is called the “infarct area” or the “ischemic core”. Meantime, its neighboring cells, become hyperactive, in spite of reduced supplies. This region is called the “penumbra”.
With time, if the brain becomes unable to sustain its blood supply above the critical threshold, the cells in the penumbra region also succumb adding to the infarct area; as a result, the infarct area becomes larger and larger. Figure 1 illustrates the scenario beautifully.
Attempts to restoring functions
The hyperactive cells in the penumbra begin to release growth molecules. They stimulate cells to begin “rewiring” and as a result, new dendrites and axons sprout by the second and third weeks. And new synapses too. The aim of these attempts is to establish new connections with still-alive neighbors to resume lost functions earlier carried out by their dead neighboring cells (Jillard et al. (2005). However, some researchers say these rewiring efforts sometimes hinder the task of initiating new meaningful connections too.
What happens between the third week and the 6th month post-stroke
Tissue repair (“rewiring”)
By the third week, the brain establishes its rebuilding project through neural repair- “rewiring”. It includes sprouting axons, generating new neurons, and glial cells too.
The neighboring cells who survived from the attack acquire some of the functions earlier carried out by their now-dead neighbors. The National Institute of Neurological Disorders and Stroke says the practice helps in this “rewiring” process. We can accelerate the process by initiating an intense rehab program within the first week according to the researchers.
However, these changes do not limit to the affected regions; the whole brain seems to make changes within its neural networks including in the non-affected half of the brain according to the researchers. And, these changes apply not only in recovering motor deficits but in language recovery too.