Researchers believe they can see revealing brain shrinkage years before a person develops memory loss or other symptoms of Alzheimer’s disease. The new finding may ultimately let physicians detect the disease and treat patients earlier with the goal of keeping them functional longer.
Massachusetts General Hospital and the University of Pennsylvania researchers used magnetic resonance imaging (MRI) scans to measure how thick the brain’s outer layer is in 159 people who did not suffer from memory loss. Earlier studies have linked Alzheimer’s disease with distinctive shrinkage in nine regions of the brain’s gray matter, or cerebral cortex. This is what physicians call the “Alzheimer’s signature.”
According to researchers, the brain shrinks as it loses nerve cells – more commonly known as neurons. They aren’t entirely sure what causes this. One theory is that the cells die after they become choked by excess amounts of two kinds of protein — beta amyloid and tau. “The neurons degenerating over time are really what we think causes the shrinkage,” said researcher Brad Dickerson, M.D., an associate professor of neurology at Harvard Medical School and director of the frontotemporal disorders unit at Massachusetts General Hospital. “And that shrinkage in their size is something you can measure with an MRI scan.”
Alzheimer’s is the sixth leading cause of death in the United States, according to the Alzheimer’s Association. The number of deaths has increased in recent years, and there is no cure. In the new study, researchers focused on how thick the edges of the brain are. “We’re looking at the parts of the cortex that are particularly vulnerable to Alzheimer’s disease, parts that are important for memory, problem-solving skills and higher-language functions,” Dickerson said.
The 15 percent of participants – who averaged 76 years old –who had the thinnest brain areas performed poorly on the tests: About one in five of them were experiencing cognitive decline, as well as increases in signs of abnormal spinal fluid, a possible sign of developing Alzheimer’s disease. “That suggests they may be developing symptoms,” according to Dickerson.
Susan Resnick, PhD, who works at the National Institute of Aging, wrote: “The ability to identify people who are not showing memory problems and other symptoms but may be at a higher risk for cognitive decline is a very important step toward developing new ways for doctors to detect Alzheimer’s disease.”
Dr. Simon Ridley, from the charity Alzheimer’s Research UK, said, “The ability to predict who will develop Alzheimer’s disease is a key target for dementia research, as it would allow new treatments to be tried early, when they are more likely to be effective. These findings add weight to existing evidence that Alzheimer’s begins long before symptoms appear, although it’s important to note that the study did not assess who went on to develop the disease. This research provides a potential new avenue to follow, but we need to see larger and longer-term studies before we can know whether this type of brain scan could accurately predict Alzheimer’s.”
Writing in Time, Alice Park notes that “Alzheimer’s disease has always been difficult to diagnose — the only way to identify it definitively is by autopsying the brain after death — but scientists may now have an easier way to spot the degenerative brain disease long before that, even before symptoms appear, using brain scans. By studying people’s brain scans over time, they were able to see that these nine brain regions appear to be thinner in people who eventually go on to develop Alzheimer’s — but that it takes many years for this structural difference to show up as symptoms of memory loss or cognitive problems. Using this brain-size signature as a yardstick, the researchers decided to confirm the correlation by testing the patients’ cognitive abilities three years after a baseline brain scan. Indeed, they found that 21 percent of participants, who had the thinnest Alzheimer’s-related brain regions but showed no signs of memory problems or other cognitive deficits at the start of the study did show signs of cognitive decline three years later, compared with none of the subjects who did not have the same brain thinning and seven percent who showed moderately thinner brain areas.”