Healing the Damaged Brain
Can it repair itself?
Our brain lives inside a closed vault. Solid bone, the skull, about a quarter of an inch thick. Our brain weighs a little more than 3 pounds, and as we know, incredibly complex processes take place there. So what happens if our brain inside that vault is injured?
When we break an arm, it heals and we go about our business. We cut ourselves, it heals and we go about our business.
But the brain, the master control center of our body’s universe - well, that’s another matter, so to speak. Can our brain repair itself after sustaining damage? If one area is injured, can the brain “remap” or “rewire” its connections to restore proper function? Is this what brain plasticity, or neuroplasticity—the brain’s ability to form new neural pathways—is all about?
Given the great number of brain-
injury scenarios, let’s look, for a minute, at the example of brain injury without skull damage, an injury that causes an area of bleeding to the brain.
In this case, says Wendy Pierce, MD, Assistant Professor in the Department of Physical Medicine and Rehabilitation at the University of Colorado School of Medicine and Attending Physician at Children’s Hospital in Colorado Springs, “there is decreased blood flow to the area of damage to the brain, causing reduced clearance of metabolic waste and toxins. In damaged areas there is cell death and continued inflammation and changes in the metabolism of the brain cells. In addition, there is swelling that occurs in the brain that can cause increased pressure.”
The brain cell has three parts, explains Dr. Pierce. “The cell body contains all the important factors to keep the brain cell alive. Dendrites receive information from other brain cells, while the axon is the wire that sends information out to other brain cells. There are also additional supportive cells in our brain that are activated after traumatic brain injury. These supportive cells attempt to prevent damage to the brain cells by releasing certain chemicals, but also contribute to scarring of the brain. The brain cannot regenerate entire brain cells that die, except in the area of the brain that is responsible for the sense of smell.”
“In high velocity accidents,” says Michael Nunley, Ph.D., Clinical Neuropsychologist working with Penrose Hospital’s inpatient and outpatient rehabilitation programs, “there can be stretching, in some cases tearing, of the axons – the tree root-looking connections between neurons. This is called diffuse axonal injury. These roots are covered by a myelin sheath to improve connections—much like the coverings on co-axial cable. When stretched or torn, the messages between cells are much less efficient. We know that myelin can often regenerate over time, likely accounting for a good deal of improvement, especially with attention and speed of processing. Axons themselves can regenerate, but we don’t know that they re-establish the same pre-injury connections.”
So the rewiring of the connections, aptly named given the role of the axon, seems to be an important part of the recovery process.
But what happens in the brain of, say, a young child, whose brain is still developing?
“Younger children, those especially under the age of 8,” says Dr. Pierce, “tend to have worse outcomes.” Overall, the effect of the impact causes more damage to the brain compared to adults.” Pierce says the problem with neuroplasticity in the developing brain is that the neural networks may not have been fully established. “They are able to try to rebuild after injury back to the prior immature form, but there is evidence that the injured developing brain does not mature like those without history of brain trauma.”
In children under two, says Dr. Pierce, the most serious traumatic brain injuries are the result of abuse. In toddlers, it’s falls, and in adolescence it’s motor vehicle collisions. “The more serious forms of traumatic brain injury, in my experience, occur due to prolonged lack of oxygen to the brain because it causes more global damage.”
In general, understanding to what extent the brain is able to repair itself is no easy feat. “It is currently unanswerable to state how a brain recovers from injury,” says Dr. Nunley, “and quite likely, recovery is due to a variety of processes in each patient case. There is one thought that with therapy and time, the brain region involved simply regains its abilities. Another thought is that neighboring regions of the brain begin to pick up the functions of the impaired region. Yet another is that an individual simply learns new ways to accomplish old tasks, and is likely employing very different parts of the brain than previously utilized.
“To date, there has been marginal support of all these hypotheses in research. However, the age is finally here where we can actually begin to look inside of a brain and its internal processes to make assumptions as to what is occurring. Functional MRI, spectroscopy scans, diffusion tensor imaging, etc., are all beginning to let us look at the brain’s processes under both typical and ‘injured’ conditions. In the future, this information very likely will allow us to ‘manipulate’ the internal curative processes of the brain to improve recovery. Neural plasticity then won’t be an abstract thought, but a clinically useful concept used in recovery from stroke, brain injury, tumors, etc.
“The area of traumatic brain injury research that most excites me,” says Dr. Pierce, “is current drug development trials on inflammatory effects in the injured brain. There have been promising findings with some of these medications in animal experiments, but these findings have not been reproduced in humans. These medications can represent potential treatments to improve recovery and could be available in the next 10-20 years.”
“We are finally developing the technology to understand both normal and abnormal processes at the cellular and molecular level,” says Dr. Nunley. “However, for the present time, recovery consists of rolling up our sleeves and asking patients to put in long hours and very hard work to make the recovery that we hope for them.”