The Bobblehead Effect of Repetitive Brain Trauma
Dr. Lee Goldstein explains how the axons, capillaries, and blood vessels in the brain are sheared when a "bobblehead" head on a rigid neck accelerates back and forth.
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So, the question is--what actually happens in the inciting injury? We call this the bobble head effect, but what does that mean, and how does that cause damage? So, if you think about a bobble head, the head is moving on top of a rigid neck, and the movement is relatively slow. The accelerations in the blast exposure are actually tremendous. It's far greater than we see in the NFL, and those accelerations are so fast and then are oscilating so quickly, that what it does to the inside of the skull and the brain is something akin to if you had a bowl of Jell-O. So if you take that bowl of Jell-O and now you rapidly turn it one way and then the other, you'll set up in the Jell-O shearing forces in the Jell-O. The one part of the Jell-O will slide over the other, and that will cause forces that are generated within the Jell-O. Now let's take this concotion and throw some vermicelli or some al dente spaghetti in there--and the spaghetti and vermicelli represent the long structures in the brain--the axons, and the capillaries, and the blood vessles. If you put that into this mix with the Jell-O and now you spin it quickly back and forth, you can actually shear the vermicelli and the spaghetti--if it's al dente-- you can shear it into smaller pieces, and that is what we think is happening to the vulnerable structures in the brain during this injury. It's the long structures, the axons, the capillaries, the small blood vessels that are sheared by these rapid movements that causes the damage. It also gives us some hope though that if that damage occurs-- the long term damage takes years to decades--that's when we want to intervene. That's where we think that our best hope is for treatments and diagnostics that can help people who've had these injuries to prevent the long term damage going forward.
Posted on BrainLine February 28, 2013.
Dr. Lee Goldstein is an associate professor of Psychiatry, Neurology, Ophthalmology, Pathology and Laboratory Medicine, and Biomedical Engineering at the Alzheimer's Disease Center at Boston University.
Produced by Brian King, Vicky Youcha, and Erica Queen, BrainLine.