SEATTLE—The semiquantitative Visual Rating System (VRS) is as effective as validated volumetric methods and should be considered an option for measuring medial temporal atrophy for the diagnosis of prodromal and probable Alzheimer’s disease, according to data presented at the 61st Annual Meeting of the American Academy of Neurology.
Ranjan Duara, MD, Medical Director, Wien Center for Alzheimer’s Disease and Memory Disorders, Mount Sinai Medical Center, Miami Beach, and colleagues, compared the two neuroimaging assessment methods among English- and Spanish-speaking participants from the Florida Alzheimer’s Disease Research Center. Thirty-two subjects had no cognitive impairment (NCI), 45 were diagnosed with amnestic mild cognitive impairment (aMCI), and 30 had dementia. Automated volumetric measurement of the hippocampus was performed using a program known as Individual Brain Atlas and Statistical Parametric Mapping to assess the volume of the hippocampus. In the VRS analysis, a single 1.5-mm thick coronal slice, the level of mammillary bodies, was used to rate the severity of atrophy of the hippocampus, entorhinal cortex, and perirhinal cortex of each hemisphere. Exemplars of anatomical boundaries of these structures and levels of atrophy were provided by drop-down images from the VRS program, to enhance reliability and validity of the ratings.
“The area under the receiver operating curve for dementia versus noncognitive impairment for the left hemisphere was 0.80 for volumetry and 0.83 for VRS,” the researchers stated. Results for the right hemisphere were similar. Findings were also comparable for aMCI versus NCI in the left hemisphere. However, in the right hemisphere, the area under the curve was 0.73 for the VRS and 0.61 for volumetry.
“The correlations of right and left VRS measures with scores on an episodic memory test (r = 0.55 and r = 0.55, respectively) were slightly higher than with volumetric measures (r = 0.51 and r = 0.44, respectively),” Dr. Duara, who is also affiliated with the University of Miami Miller School of Medicine and the University of South Florida College of Medicine in Tampa, and colleagues commented.
“The use of a semiquantitative method—VRS—to measure medial temporal regions to distinguish aMCI and dementia from noncognitive impairment is at least as effective as validated volumetric methods,” Dr. Duara and colleagues stated. “Although the difference between the mean atrophy scores for aMCI and NCI was greater using VRS than volumetric analysis, the variance was much greater with VRS measures.
“The reason that VRS seems to do somewhat better than volumetric analysis in detecting prodromal Alzheimer’s disease (ie, distinguishing aMCI from NCI) is probably related to the fact that VRS focuses on a single slice where the pathology is most severe, and the atrophy measurement includes not only the hippocampus but also the entorhinal cortex, which is affected early in the disease course.
“With automated volumetric analyses, it is currently not possible to measure atrophy within subregions of the hippocampus (ie, the anterior one-third of the hippocampus) or in the entorhinal cortex, where atrophy occurs earliest and most severely in Alzheimer’s disease, so the effects get diluted by measuring the whole hippocampus,” Dr. Duara and coauthors concluded.
—Laura Sassano