Analyzing MRI studies of the brain with software developed at the Martinos Center for Biomedical Imaging at Massachusetts General Hospital (MGH) may allow diagnosis of Alzheimer's disease and of mild cognitive impairment, a lesser form of dementia that precedes the development of Alzheimer's by several years.
In their report that will appear in the journal Brain and has been released online, the MGH/Martinos team show how their software program can accurately differentiate patients with mild cognitive impairment or Alzheimer's disease from normal elderly individuals based on anatomic differences in brain structures known to be affected by the disease.
"Traditionally Alzheimer's has been diagnosed based on a combination of factors – such as a neurologic exam, detailed medical history and written tests of cognitive functioning – with neuroimaging used primarily to rule out other diseases such as stroke or a brain tumor," says Rahul Desikan MD, PhD, of the Martinos Center and Boston University School of Medicine, lead author of the Brain paper. "Our findings show the feasibility and importance of using automated, MRI-based neuroanatomic measures as a diagnostic marker for Alzheimer's disease."
The researchers note that mild cognitive impairment occurs in about 20 percent of elderly individuals – as many as 40 percent of those over 85 – 80 percent of whom develop Alzheimer's within five or six years. Since drugs that may slow the progression of Alzheimer's are in development, the ability to treat patients in the earliest stages of the disease may significantly delay progression to dementia. To investigate whether MR imaging can produce diagnostic markers for mild cognitive impairment and Alzheimer's disease, the research team used FreeSurfer – an openly available imaging software package developed at the Martinos Center and the University of California at San Diego – to examine a number of neuroanatomic regions across a range of normal individuals and patients with mild cognitive impairment and Alzheimer's disease.
In the first phase of the study, the investigators examined MR images of 97 elderly individuals, some who had been determined to have mild cognitive impairment and others who were cognitively normal. Analyzing those images identified three regions of the brain where structural differences distinguished the normal controls from participants with mild cognitive impairment with an accuracy of 91 percent. Earlier pathological and imaging studies have found evidence of early Alzheimer's disease in these three areas – the hippocampus, entorhinal cortex and the supramarginal gyrus.