While the MRI features of the different causes of dementia overlap considerably, researchers from the U.K. suggest that visual inspection of the scans is both simple and fast. It may aid in the differentiation between diseases when used in conjunction with clinical information and other imaging techniques.
Valerie M. Anderson and colleagues from University College of London identified 62 subjects with pathologically confirmed dementia who had had MR scans. Anderson reported the results at the 9th International Conference on Alzheimer's Disease and Related Disorders in Philadelphia on Sunday.
Subjects included 25 with Alzheimer's disease, 17 frontotemporal dementia, eight prion disease, five vascular dementia, two vascular/AD, three corticobasal degeneration, three progressive supranuclear palsy, and one multiple system atrophy, as well as 22 control subjects.
Three neuroradiologists blinded to clinical details independently examined the MR images of each subject. They visually rated regional atrophy and made a diagnosis based on imaging.
The agreement of radiological and pathological diagnoses was 57%. The readers distinguished 85% of dementia cases from controls. Of the pathological AD and FTD cases, 65% and 59%, respectively, were correctly identified.
MRI features that were specific for FTD (all pathologies) were anterior-posterior atrophy gradient (99%) and left-right asymmetrical atrophy (94%). High sensitivities for FTD were recorded for atrophy of the parahippocampal gyrus (92%), anterior temporal lobe (92%), and lateral temporal gyri/fusiform gyrus (90%), while specificity averaged 59%.
Hippocampal atrophy was sensitive for AD (91%) but was often observed in other diseases (specificity 34%). Intrarater agreement was 64%.
The researchers concluded that visual assessment of hippocampal atrophy is a relatively sensitive but nonspecific marker of AD. Conversely, anterior-posterior gradient of atrophy and left-right asymmetrical atrophy are relatively specific but insensitive markers of FTD.
