Photo credit: http://www.huffingtonpost.com/2011/03/14/nhl-concussion-rules_n_835568.html
@jeffreyfdunn
Check out our paper. We paid $3200 USD for open access with
the publisher Liebert so I hope someone has a look!! Liebert has been great to work with. I hope they are able to reduce this cost, however, to make open access more accessible in future (small editorial comment).
Here is the online
reference number. 10.1089/neu.2014.3577
If that doesn’t work, search on the authors and/or title:
Urban, K. J., K. Barlow, B. G. Goodyear, J. J.
Jimenez and J. F. Dunn (2014) Functional Near-Infrared Spectroscopy Reveals
Reduced Inter-hemispheric Cortical Communication Following Pediatric
Concussion. J Neurotrauma (ahead of print. doi:10.1089/neu.2014.3577
PAPER SUMMARY:
If you are into concussions (for academic or personal reasons,
not because you like them..) you probably realize that there is no imaging
method in regular clinical use that can detect or monitor concussion reliably.
This has placed a major burden on all groups from the individual who has a head
injury, to those such as coaches, parents, family, first responders, the family
doctor, neurologists etc etc. Everyone wants to know—is the brain injured? When
can I return to activity?
There may be light
at the end of the tunnel. There are new imaging methods under active
investigation. They fall into groups, depending on the target of injury. For
instance, PET or magnetic resonance spectroscopy (MRS) may be useful for
detecting metabolic injury. MRI may be useful at detecting damage to large
fiber tracts through the brain using diffusion tensor imaging. The new kid on
the block, however, is based on light—near-infrared spectroscopy (NIRS).
Some background: the main oxygen carrying compound in blood
is hemoglobin. Hemoglobin absorbs light differently depending on whether it is
oxygenated or not. Oxy-hemoglobin has oxygen bound to it and deoxyhemoglobin
does not. Hemoglobin saturation (or blood saturation) is the percent of the
total hemoglobin in blood that is bound to oxygen. In arteries, this is about
98-100% at sealevel. In Calgary, where I live, it is more like 94-96% because Calgary
is at an altitude of 1000m, and so there is a bit less oxygen.
With NIRS, one shines light into the brain and measures the
changes in oxyhemoglobin and deoxyhemoglobin, based on measuring the difference
in absorption of the two compounds.
What does this tell us about brain? It turns out that when
brain activates, the increase in blood flow is more than is needed to supply
the extra oxygen. As a result, oxygen levels in the human brain actually
increase. This causes an increase in oxyhemoglobin and a decrease in
deoxyhemoglobin.
Thus, with NIRS, one can measure brain activation by
measuring changes in oxy- and deoxyhemoglobin. Not only that, you can do it in
a sport arena, a clinic, or an emergency department. The equipment is
relatively small—especially when compared with an MRI (which is one of the
medical gold standards for mapping brain activation).
What can activation tell us? NIRS can tell if the brain is
activating. That alone might be enough to identify some patients. We think a
more sensitive measurement would involve studying brain communication. Different
parts of the brain are in communication with other parts. When they are
communicating, there is a low frequency oscillation in function, and therefore
hemoglobin oxygenation. If we compare the frequencies between different
regions, say the left and right motor cortex, we get a measure of the level of
communication. If either region is damaged, or if the communicating networks in
between are damaged, then the communication will go down.
In a small pilot study of adolescents with long term
concussion symptoms, we used our NIRS system and showed just that! The level of
coherence (a measure of the similarity in frequencies) was down in the
concussion population. It would make sense that communication systems are
damaged after a concussive injury. After all, many people report functional
changes such as dizziness, or just not feeling right. These symptoms could be due
to impairments in brain function.
Thus, NIRS, based on light, may provide a new sensitive method
of monitoring brain injury.
