New research suggests magnetic resonance imaging (MRI) may allow physicians to predict if an individual with mild cognitive impairment will progress to Alzheimer’s disease.
Although normal age-related memory loss does not lead to mild cognitive impairment (MCI), MCI is an intermediate form of memory loss affecting up to 16 percent of the population. MCI can advance to dementia and Alzheimer’s disease (AD).
Individuals with mild cognitive impairment develop AD at a rate of 15 to 20 percent per year, which is significantly higher than the one to two percent rate for the general population.
Some people with MCI remain stable while others gradually decline and some quickly deteriorate.
“Being able to better predict which individuals with mild cognitive impairment are at greatest risk for developing Alzheimer’s would provide critical information if disease-modifying therapies become available,” said the study’s lead author, Linda K. McEvoy, Ph.D.
Researchers studied 203 healthy adults, 317 individuals with MCI and 164 patients with advanced Alzheimer’s, reviewing baseline MRI exams and one-year follow-up MRI’s. The average age of the study participants was 75.
Using MRI, the researchers measured the thickness of the cerebral cortex — the outermost layer of the cerebral hemispheres of the brain which plays a key role in memory, attention, thought and language — and observed the pattern of thinning to compute a risk score.
One of the characteristics of Alzheimer’s disease is a loss of brain cells, called atrophy, in specific areas of the cortex.
“MRI is very sensitive to brain atrophy,” McEvoy said. “There’s a pattern of cortical thinning associated with AD that indicates the patient is more likely to progress to Alzheimer’s disease.”
Using the baseline MRI, the researchers calculated that the patients with MCI had a one-year risk of conversion to AD ranging from three to 40 percent.
“Compared to estimating a patient’s risk of conversion based on a clinical diagnosis only, MRI provides substantially more informative, patient-specific risk estimates,” McEvoy said. “The baseline MRI helped identify which patients were at very low risk of progressing to Alzheimer’s and those whose risk was doubled.”
By combining results of the baseline MRI and the MRI exam performed one year later, the researchers were able to calculate a rate of change in brain atrophy that was even more informative. The MCI patients’ risk of disease progression based on the serial MR exams ranged from 3 to 69 percent.
“Rapid thinning of the cortex is reflective of a degenerative disorder,” Dr. McEvoy explained.
Although no treatments currently exist that slow or prevent the neurodegeneration associated with AD, McEvoy said patients at high risk of progressing to AD might want to enroll in clinical trials of disease-modifying therapies.
She said the information would also help ensure patients receive optimal care and allow families more time for planning.