The tomography dementia rating scale (TDR)—The rating scale of Alzheimer’s disease stages

Abstract

The purpose of this research is to develop a morphologically determined scale—the Tomography Dementia Rating scale (TDR) to diagnose AD stages, based on the measurement of the severity of voluminal atrophic changes of the temporal lobes of the brain detected among patients during CT and MRI at various stages of the disease. The research included 140 patients aged 28 - 79. Test Group comprised 81 patients aged 34 - 79 suffering from various AD stages. Control Group consisted of 59 patients aged 28 - 78 who had various types of brain lesions with manifestations of dementia and cognitive impairment but who did not suffer from AD. CT and MRI data obtained has made it possible to create a scale that allows determining the severity of atrophic changes in the temporal lobes at each stage of AD development: 1) Pre-clinical AD stage—TDR-0: temporal lobes atrophy with a 4% - 8% decrease in tissue mass (corresponds to 26 - 28 MMSE points); 2) Early AD Stage—mild dementia—TDR-1: temporal lobes atrophy with a 9% - 18% decrease in tissue mass (corresponds to CDR-1 and to 20 - 25 MMSE points); 3) Middle AD stage—moderate dementia—TDR-2: temporal lobes atrophy with a 19% - 32% decrease in tissue mass (corresponds to CDR-2 and to 12 - 19 MMSE points); 4) Late AD stage—heavy dementia—TDR-3: temporal lobes atrophy with a 33% - 62% decrease in tissue mass (corresponds to CDR-3 and to 7 - 11 MMSE points). Thereby, the developed Tomography Dementia Rating scale (TDR) complements the Clinical Dementia Rating scale (CDR) and allows a correct and objective determination of AD stages as well as an easy differentiation of existing lesions with neurodegenerative changes characteristic for other diseases accompanied by dementia and cognitive impairment.