After brain injury, can a drug stem the damage?
Could freestyle skier Sarah Burke, who died Jan. 19, nine days after a devastating crash, have been helped by an experimental drug? A new study offers a glimmer of hope for future victims of traumatic brain injury.
In the hours after she has sustained a blow to the head, the victim of a traumatic injury experiences a slow down of blood flow to the brain--arguably when she needs it most. That mismatch between a brain’s response and its needs in the wake of injury has set many a neuroscientist thinking: Can a way be found to keep the flow of oxygenated blood pumping normally? And if it can, could that reduce the damage done by a blow that affects the brain?
A new study conducted on rats offers preliminary answers to both of those questions, as well as a crucial third question: How soon after brain injury should such a drug be administered to have its best effects?
In rats who were subjected to a high-speed blow to the head, a still-investigational drug called clazosentan, when administered two hours after an injury and again at 24 hours post-injury, maintained blood flow to the hippocampus, a key brain region involved in memory, and resulted in better post-injury maze-running, a new study has found. The study, still unpublished, is to be presented at the American Academy of Neurology‘s yearly meeting in April.
Clazosentan blocks the receptors in the brain that start the restriction in blood flow. It wasn’t found to be effective in improving blood flow or cognitive behavior when it was given to rats 12 hours after injury, and its benefits were weak when given only at two hours after injury. So it may be a drug that can help only if it’s administered very soon after the brain is hurt and again, in a hospital, a day later.
This experimental drug has had a mixed record of success in reducing the damage done in human patients by aneurysmal subarachnoid hemorrhage, a brain bleed caused by a ruptured vein or artery. A study presented earlier this month at the American Stroke Assn.'s annual conference found that in human subjects who suffered such a stroke, clazosentan reduced the risk of post-stroke vasospasm--a common and deadly complication--but that it did not lower the likelihood of death or major disability following an aneurysm’s rupture.
With brain injury becoming a research priority for the military and organized sports, researchers are busily trying to find some kind of rescue drug to protect the brain in cases of injury or stroke--with limited results so far. One agent being tried is progesterone, a feminine hormone, which might reduce the spasms of electrical activity that are set off by trauma.