Reducing flow through the neck veins that drain blood from the head tops up the fluids that surround the brain, allowing for more cushioning, according to Joseph Fisher, a University of Toronto anesthesiologist and one of the study's authors.
compares a helmet to the sheet metal that encases a car: Upon impact, it can't stop the contents of the vehicle from jostling around.
"Helmets basically prevent trauma to the skull, but don't protect impact to the brain," he
The fluid around the brain does that.
It can act like a seatbelt, or an airbag, but it needs to be topped up in order to be most effective.
Most of the time it's not topped up, and there's a little extra space that allows the brain to slosh around.
But Dr. Fisher
colleagues determined the amount of pressure - about the equivalent of a shirt collar half-an-inch too small - it takes to stop the sloshing.
They conducted trials in rats, and compared the damage to the brains of rodents in collars to those without after a controlled injury.
"There was a dramatic reduction, one that's never been seen before to my knowledge, in the markers of brain injury," Dr. Fisher
If they work, the collars could prove an affordable and effective tool for brain-injury prevention.
colleagues hope to begin human trials as soon as possible.