Of the study's 53 participants, 10 had experienced the most severe form of depolarizations. All died or had severe disabilities six months after their injury.
"Spreading depolarizations, which occur in up to 60 percent of patients who have experienced serious neurotrauma, are electrical failures of the brain's local networks," explains Hartings, the study's principal investigator. "When these networks fail, brain waves can no longer be generated, and they become dampened, or depressed, in amplitude."
Hartings likens each brain cell, or neuron, to a battery. When spreading depolarization occurs, the cell discharges its electricity completely. "The neuron, once alive with electrical activity, stops working and has to be resuscitated with glucose and oxygen," Hartings says. "You could also liken it to a battery in your car. If it drains, then the car doesn't work."
Because networks of the brain's cortex are connected in a continuum, a depolarization triggered by an injury will spread across the cortex like a tsunami on the ocean. The wave of short-circuiting cells travels almost imperceptibly, at a speed of 1 to 5 millimeters per minute.
Previous studies had suggested that depolarizations would last no longer than two or three minutes. But Hartings and his team have shown that, after trauma, they can be very long-lasting.
"We found that 25 percent of the cortical spreading depolarizations lasted longer than three minutes, with durations that ranged up to 16 minutes," Hartings says. "These are the types of depolarizations that are typically observed with a developing brain infarction, or stroke. It was a surprise to see them in trauma."
To measure depolarizations, researchers placed a linear strip of electrodes on the surface of the brain, near the injured area, during neurosurgery at UC Health University Hospital. Only patien
|Contact: Cindy Starr|
University of Cincinnati Academic Health Center