Combining visual rating scales of medial temporal lobe atrophy and posterior atrophy to identify amnestic mild cognitive impairment from cognitively normal older adults: evidence based on two datasets

Background: Structural magnetic resonance imaging (MRI)-based visual rating scales are considered as the primary method for rapid and cost-effective evaluation of regional brain atrophy in patients with Alzheimer’s disease (AD) in routine clinical practice. Both medial temporal lobe atrophy (MTA) and posterior atrophy (PA) visual rating scales have been reported to be useful in AD diagnosis. However, very few existing studies have investigated the efficacy of combined MTA and PA for identification of amnestic mild cognitive impairment (aMCI) from cognitively normal elderly.Methods: This study included T1-weighted MRI images acquired inXuanwu Hospital of Capital Medical University, Beijing, China from two different cohorts. In the first cohort, we recruited 73 patients with aMCI and 48 group-matched cognitively normal controls for the training and validation. Visual assessments of MTA and PA, including left MTA, right MTA, mean MTA, left PA, right PA and mean PA, were carried out from each participant. Global gray matter (GM) volume and density was estimated using voxel-based morphometry analysis as the objective reference. Based on the receiver operating characteristic (ROC) analysis, we investigated the discriminative power of single visual rating scale and the combination of MTA and PA for successful classification between the two diagnostic groups, respectively, and then compared them to GM measures. The second cohort, consisted of 33 aMCI patients and 45 NCs, was used to verify the reliability of the discriminative power of visual assessments.Results: In the first cohort, visual rating scales of MTA and PA showed different potential to distinguish aMCI from controls. Moreover, the combination of MTA and PA exhibited the best discriminative power, with the AUC of 0.818 ± 0.041, which was similar to the diagnostic accuracy of GM volumetric measures (0.857 ± 0.034). The discriminative power was verified in the second cohort when combining MTA and PA visual rating scales, with the AUC of 0.824 ± 0.058.Conclusion: The combined visual rating scales of MTA and PA demonstrated practical diagnostic values for distinguishing aMCI patients from controls, suggesting its potential to serve as a convenient and reproducible method to assess the degree of atrophy in the clinical setting.