Morphometric Definition of Alzheimer's Disease Stages by Means of The Tomography Dementia Rating Scale (TDR)

Abstract

Background: The research is dedicated to developing an objective method for determining dementia severity in patients with different AD stages. The method is based on morphometric analysis of specific atrophic changes in temporal lobes detected during cerebral CT and MRI and it allows differentiating these particular changes from those common for other cerebral neurodegenerative diseases. Materials and Methods: 1105 patients aged 28 years to 81 years (mean age 75) were examined: 786 men (71.13%), 319 women (28.61%), 93 had different AD stages-test group, 1012 had another neurodegenerative diseasescontrol group. Results: The scale of dementia stages during AD, Tomography Dementia Rating Scale (TDR), was developed, allowing to determine dementia severity with objective, morphometrically grounded data of atrophic changes in temporal lobes obtained during CT and MRI: 1. Preclinical AD stage-TDR-0: results from atrophic changes in temporal lobes with 4% to 8% tissue mass decrease and cognitive functions decline equal to 26 to 28 MMSE points. 2. Early AD stage-TDR-1: mild dementia resulting from atrophic changes in temporal lobes with 9% to 18% tissue mass decrease, corresponds to CDR-1, is accompanied by cognitive functions decline equal to 20 to 25 MMSE points. 3. Middle AD stage-TDR-2: moderate dementia resulting from atrophic changes in temporal lobes with 19% to 32% tissue mass decrease, corresponds to CDR-2, cognitive functions decline is equal to 12 to 19 MMSE points. 4. Late AD stage-TDR-3: severe dementia resulting from atrophic changes in temporal lobes with 33% to 62% tissue mass decrease, corresponds to CDR-3, cognitive functions decline is equal to MMSE 7 to 11 points. 5. Control group patients did not have any similar changes. Conclusion: The proposed objective, morphometrically validated TDR scale allows to identify preclinical and clinical AD stages; it is easy to use and is complementary to the clinical dementia rating scale. Besides, this scale makes it possible to differentiate AD from other neurodegenerative diseases.