TEMPORAL-LOBE MAGNETIC-RESONANCE-IMAGING CAN DIFFERENTIATE ALZHEIMERS-DISEASE FROM NORMAL AGING, DEPRESSION, VASCULAR DEMENTIA AND OTHER CAUSES OF COGNITIVE IMPAIRMENT

Background. Previous work suggests that temporal lobe magnetic resonan ce imaging (MRI) can distinguish those with dementia of the Alzheimer type (DAT) from healthy age-matched controls. However, its specificity with regard to conditions such as vascular dementia, depression and o ther disorders associated with cognitive impairment has not been deter mined. Methods. We studied 222 subjects using T1 weighted MRI with 5.1 mm coronal slices throughout the temporal lobe. Subjects included: he althy controls (N = 40); DSM-III-R major depression (N = 61); NINCDS/A DRDA DAT (N = 77) and OTHER (N = 44, comprising subjects with vascular dementia, Huntington's disease, schizophrenia, alcohol related cognit ive impairment and a group of 'memory complainers'). Hippocampus, amyg dala, entorhinal cortex, parahippocampal gyrus and cerebral cortex wer e rated visually on a 0-3 scale by two experienced neuroradiologists b lind to clinical diagnosis. Results. Ratings of temporal lobe atrophy provided good separation between those with AD and all other groups. F or example, anterior hippocampal atrophy had a sensitivity of 83% for detecting DAT, a specificity of 80% for controls, 87% for depressed su bjects and 89% for OTHER. Other regions were less sensitive, but more specific for the diagnosis of DAT. In particular parahippocampal gyrus and entorhinal cortex had high specificity (97% for depressed subject s and 98% for OTHER). Because of an age-related increase in atrophy, s ensitivity was highest for those over the age of 75, while specificity was highest for younger subjects. Significant correlations were obser ved between atrophy ratings of hippocampus, amygdala, entorhinal corte x and parahippocampal gyrus and CAMCOG memory score and length of hist ory. Conclusions. Temporal lobe MRI may have an important role in assi sting with the clinical diagnosis of DAT, particularly its differentia tion from depression and other disorders that may cause diagnostic dif ficulties in clinical practice.