Restoring blood flow to the brain quickly after a stroke is key to damage control as well as to optimal recovery. But restoring blood flow to brain tissue that is already dead can cause problems, like swelling and hemorrhage.
That makes the treatment of choice - an intravenous dose of a substance called tPA, which dissolves clots - a double-edged sword. The consensus in the medical community is that tPA is not a good idea once 4-1/2 hours have elapsed since a patient has suffered a stroke.
But the consensus is based on averages, derived from numerous studies. Clinicians have tended to treat that 4-1/2 hour time-point as analogous to a window slamming shut. Yet every stroke, and every patient who experiences one, is unique.
A new study published in the New England Journal of Medicine joins three earlier ones that show improved results when tPA administration is combined with the insertion of a device - a so-called stent retriever - that can mechanically break up clots in the brain.
Even more exciting, two of the four studies, including the new one, employed software called RAPID - designed and developed at Stanford at the instigation of Stanford neurologist Greg Albers, MD - that quickly interprets brain scans of patients and helps clinicians decide which patients will benefit from supplementing the standard intravenous tPA infusion with the stent retrieval procedure. In both of these two studies, substantial majorities of patients selected as good candidates for the combination had extremely high rates of solid recovery as measured three months after their stroke - the best results ever obtained in stroke studies.
Albers, who is also one of the co-authors of the new NEJM study, hopes to move stroke care away from the clock on the wall and instead focus on a biological clock - what the brain image shows to be going on inside this patient's brain, now - so that each patient's care can be individualized and optimized. It could turn out that for some patients, 4-1/2 hours after a stroke is already too late for aggressive clot-busting treatment, while for others the window remains wide open for 6, 7, 8 hours or longer.
Previously: Targeted stimulation of specific brain cells boosts stroke recovery in mice, Calling all pharmacologists: Stroke-recovery mechanism found, small molecule needed and Stanford neuroscientists uncover potential drug treatment for stroke