Sidelined: Sports Concussions
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Dr. Pratik Mukherjee, a radiologist specializing in brain imaging, sits in front of an MRI scanner at the UCSF China Basin campus in San Francisco.
Studying the damage caused by a concussion at its source, inside the brain, is no easy feat. As Dr. Geoffrey Manley, Chief of Neurosurgery at San Francisco General Hospital told me, "What we’re dealing with is one of the most complicated injuries in the most complicated organ in the body. The brain has millions of cells that use many, many neurotransmitters to be able to talk to different regions of the brain, so it’s very complicated."
It's also an injury that afflicts two million people in the U.S. each year, according to the Centers for Disease Control.
Today, new brain imaging tools are revealing how concussions, which result from a blow to the head that causes the brain to move inside the skull cavity, are more serious than previously thought, producing actual damage to the brain's intricate network of wires that connect key regions of mental activity.
"The white matter of the brain is essentially the wiring of the brain," said Dr. Pratik Mukherjee, a professor of radiology at the U.C. San Francisco Medical Center. "Brain cells have a transmission unit called the axon, which is a long cable, essentially, that runs for a long distance throughout the brain. And bundles of these axons are called white matter fibers. And they are by analogy the fiber optic cables that produce long-range connection in the brain," he added.
Diffusion Tensor Imaging, a new, advanced form of Magnetic Resonance Imaging, measures the rate of water movement along the brain's bundle of white matter fibers. Additionally, scientists can also measure changes in the rate of water flow, which would occur in the event of damage to the white matter following, for example, a moderate to severe brain concussion. (Degenerative brain diseases like Alzheimer's Disease can also change the movement of water along white matter fibers). Even more impressively, the direction of this water movement can be tracked, thereby allowing scientists to create 3-D maps which show the connections the fibers make between key brain regions. The different colors in these brain visualizations refer to the different directions the white mater fibers are oriented in the brain, such as up-down and left-right.
A slide taken from a D.T.I.-rendered visualization of the brain. The arrow points to a region in the frontal lobe that is vulnerable to damage from concussions. Image courtesy Dr. Alexander Leemans.
Although D.T.I. is not currently in widespread clinical use, it is nonetheless proving to be a promising research tool to better understand the structural damage that concussions can cause.
"The evidence is that the concussions, especially the ones causing rotational injury to the head, cause microscopic damage to these white matter fibers. And that causes a disconnection of brain regions that should be in communication. And that we believe is the cause of the altered thinking, the altered memory, the altered attention that many concussion patients suffer from," said Dr. Mukherjee.
This damage is not even visible with Computed Tomography, an x-ray scanning procedure, which has been routinely administered for decades to brain injured patients.
"A C.T. scan is actually very good for the early phases of trauma," said Dr. Manley. "It tells us whether or not there’s a skull fracture, it tells us whether or not there’s bleeding in the brain. However, we’ve learned over the years that an M.R.I. scan is far more sensitive for looking at abnormalities of soft tissue, and the soft tissue that we’re talking about is the brain. So in fact, an M.R.I. scan gives you a much better picture of the brain than a C.T. scan does," he added.
Dr. Geoffrey Manley looks at M.R.I brain scans with his colleague, Dr. Alisa Gean, at San Francisco General Hospital.
Advanced MRI machines that are powered with magnets twice as strong as those employed in conventional MRI machines can now reveal small areas of bleeding, or "micro-bleeds", in the brain after concussions.
During our filming for this story, Dr. Mukherjee shared with me two sets of scans, one of which was generated with a conventional C.T. scanner, while the other was generated with advanced M.R.I. technology. Both sets of scans were performed on the same concussion-injured patient. Dr. Mukherjee pointed out a black dot on the M.R.I. scans in the left frontal lobe of the patient's brain.
"This black dot is a micro-bleed, which indicates that there has been damage to the white matter in this location," he said. "This indicates tearing at the level of the brain cells, as well as bleeding in the adjacent blood vessels," he added.
Damage to the frontal lobe can cause impairments in attention and focus, which Dr. Mukherjee said can be confirmed with timed tests of mental activity given to patients who have suffered concussions.
Joe Redmond, center, suffered a concussion from a helmet-to-helmet hit while playing on Marin Catholic High School's football team. He lost consciousness after the hit and experienced headaches, confusion and a loss of memory afterwards.
The new imaging tools are highlighting other regions of the brain that are also vulnerable to damage with concussions. For example, patients who have suffered moderate to severe concussions often complain of memory impairments. Dr. Mukherjee's research is showing that the hippocampus – a structure long known to play a critical role in memory formation and learning – can actually shrink following concussions.
"It can help explain why some concussion patients have long-term problems with memory, with attention and with other problems with mood and thought," said Dr. Mukherjee.
But most concussion patients don't suffer any perceptible long-term damage from concussions. In fact, about half the people who suffer concussions recover from their injury in seven to ten days. Nonetheless, they may experience the sluggishness, headaches and mental 'fogginess' that often result from concussions.
In this group of individuals, the neurological effects of the concussion injury may be due more to neurochemical changes than actual structural damage to the brain's white matter.
Eric Freitag, a neuropscyhologist based in Walnut Creek, helps roughly 60 to 70 mostly adolescent athletes each year get back on track following their concussion injuries. I asked him to explain to me how a concussion can disrupt the neurochemical activity of brain cells.
"At the moment of impact of a concussion, all cells in the brain fire. And the brain is asking for more energy, but also in that moment of impact, you have a dramatic decrease in brain blood flow," Freitag said. The energy the brain uses is in the form of glucose which is carried in the blood flowing into the brain.
"So when the brain is asking for more energy, your body can’t provide it. And it’s this metabolic mismatch that causes the symptoms of a concussion. It causes the confusion, it can cause the loss of consciousness, and also other neurological symptoms that can occur for minutes, hours, days, weeks and sometimes months," he added.
Both Dr. Mukherjee and Dr. Manley stress that additional work must be done before the widespread adoption of advanced M.R.I imaging techniques in clinical settings like an emergency room. Nonetheless, they hope that the technological advances in brain imaging will help clinicians more nimbly diagnose and more effectively treat this complex and all-too common injury.
"In the future, a patient will come in, we will have an M.R.I, we will have a blood test where we can go back and we can say, ‘this is the diagnosis that you carry, this is my specific treatment for you.’ But the only way that we’re going to get there is with the same kind of focus, comprehensive and well-funded effort that’s been applied to cancer and heart disease," he said.
A special thanks to Dr. Alexander Leemans for the kind use of his 3D tractography brain imagery and animations.