The era of postautopsy confirmation of Alzheimer's disease may be coming to an end. MR imaging could spot signs of brain deterioration predictive of cognitive decline months, even years, before the onset of dementia, according to recent studies performed in Canada, Europe, and the U.S.
Clinical studies have found significant links between mild cognitive impairment and AD. Patients with MCI do not always progress to Alzheimer's disease, however. Many go on to develop different types of dementia, while others remain cognitively healthy.
Albeit promising, breakthroughs in early AD diagnosis using sophisticated nuclear medicine techniques have not been echoed by more conventional and readily available imaging modalities. MRI may help turn this trend around, according to lead investigator Dr. Robert Bartha, an associate professor of radiology and nuclear medicine at the University of Western Ontario.
Bartha and colleagues at UWO's Robarts Research Institute reviewed data from 500 individuals with and without cognitive impairment and AD enrolled in the Alzheimer's Disease Neuroimaging Initiative. The ADNI project, sponsored by the National Institutes of Health, aims to build the largest online registry of MRI and PET data to identify MCI and AD biomarkers. It comprises more than 50 sites across Canada and the U.S.
Study subjects underwent MR scans at baseline and six months. MRI data were reconstructed with software developed by Cedara Software (Merge Healthcare, Milwaukee). The investigators found a significant correlation between the increase in the size of brain ventricles and the development of MCI before the diagnosis of AD. They also found that the ventricles continue to increase after AD's onset, and that AD patients with a genetic marker for the condition showed the fastest ventricle volume growth.
They published their findings online in the July 11 issue of Brain.
"These findings mean that, in the future, by using MRI to measure changes in brain ventricle size, we may be able to provide earlier and more definitive diagnosis," Bartha said. "As new treatments for Alzheimer's are developed, the measurement of brain ventricle changes can also be used to quickly determine the effectiveness of treatment."
Another study by researchers at the Vrije Universiteit Medical Centre in Amsterdam and University College London validated these findings.
From 2004 to 2006, principal investigator and radiologist Dr. Jasper D. Sluimer and colleagues prospectively enrolled 65 AD patients, 45 MCI patients, 27 patients suspected with cognitive decline, and 10 healthy controls who underwent 1T MR scanning at baseline and again at an average interval of 1.8 years. The researchers measured baseline brain volume and whole-brain atrophy rates.
They found that the whole-brain atrophy rate was strongly associated with cognitive decline in demented patients and with an increased risk of progression to dementia in nondemented subjects. The researchers published their findings in the August issue of Radiology (2008;248:590-598).
"Since individuals with a higher whole-brain atrophy rate had greater risks of progression to dementia, repeat MR imaging may be helpful in the diagnostic workup of patients suspected of having dementia," the researchers said.
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