[Differential diagnosis of Alzheimer-type dementia and vascular dementia based on neuroimaging study]

A new method for differential diagnosis of Alzheimer-type dementia (AD) and vascular dementia (VD) based on neuroimaging studies was developed by Hayashi's quantification theory II. Fifty-five patients with AD and 36 patients with VD underwent both SPECT and MRI studies. Both images in each subject were scored according to the extent of hypoperfusion in areas including frontal and temporoparietal regions and the severity of deep white matter lesions and medial temporal lobe atrophy. The scores of AD and VD patients were significantly different, and this difference was considered to contribute most to the differential diagnosis of AD and VD. The weight of each score of SPECT and MRI items was computed, and the sum of the weights was calculated as a score for each subject to best distinguish AD from VD patients. This method was designed to simplify the calculation of the sample scores, and the sum of the weights was established so that a positive score (0 < or =) indicated the probability of AD, while a negative score (< 0) indicated the probability of VD. The correct diagnosis rate was 91% (50/55) for AD and 89% (32/36) for VD, for an overall discrimination of 90%. The present method seemed to be practically useful in the differential diagnosis of AD and VD.