While many patients know the warning signs of stroke, far fewer are aware of the risk that silent or “mini-strokes” pose to their health. The effects of these so-called mini-strokes were examined in a new study published in the Journal of Neuroscience. Mini-strokes can cause progressive damage and lead to dementia. Mini-strokes may also cause permanent neurological damage and increase the patient’s risk for a full-blown stroke.
Rodents were used to examine the impact of small strokes. Strokes were induced by injecting cholesterol crystals into the mice. The mice that had mini-strokes were put through a series of tasks, including recalling objects and audio cue responses. The mice who suffered strokes were found to be more likely to fail these tasks.
Maiken Nedergaard, MD, professor of neurosurgery at the University of Rochester Medical Center and lead author of the study, says that the prevalence of mini-strokes is “an epidemic,” estimating that around 50% of individuals over the age of 60 will experience at least one mini-stroke during their lifetime. These mini-strokes are frequently not diagnosed or detected by a doctor because a patient does not immediately present with stroke signs.
Mini-strokes often are detected after a patient has had several of them, well after the damage has been done. Dr. Nedergaard said, “Often you don’t have symptoms. That’s the scary thing about them; you don’t know they’re occurring. If you are elderly and something doesn’t work quite right, you think, I should take a nap. You don’t go to the hospital unless you have big stroke.”
In many cases, the patient visits their doctor complaining of chronic migraines and the MRI ordered to rule out brain tumors shows several little dots where mini-strokes have caused damage to the brain. Larry Goldstein, MD, director of the Stroke Center at Duke University and a spokesperson for the American Heart Association says, “When you have a stroke, there’s an area of the brain that dies rapidly almost at the epicenter of the injury, but there are neurons around it that die slowly.”
The study authors say mini-strokes are similar to ischemic strokes, provoked by a loss of blood supply in an area of the brain, depriving that area of oxygen. Dr. Nedergaard said, “A big stroke is caused by a clot in the artery. We assume that’s the same that happens in the mini-stroke, but it’s not clear. What we do know is they cause this very delayed loss of cells in the brain.”