[Clinical and instrumental diagnosis of Alzheimer's and multi-infarct dementia]

We investigated the possible correlation between functional and anatomical imaging techniques and clinical exams in patients with Alzheimer's and vascular dementia. We examined 24 patients affected with dementia, 16 of them with Alzheimer's disease. 7 with multiinfarct and 1 with mixed dementia. All patients were submitted to clinical, morphological (MRI, CT) and functional (SPECT, cerebral flowmetry) studies. The severity of hypoperfusion revealed by SPECT was highly correlated with cognitive impairment in Alzheimer's dementia patients. The abnormal perfusion was mostly bilateral, in the temporal-parietal region, and involved the frontal regions only in the most severe cases. CT and especially MRI showed aspecific cortical and subcortical atrophy, most evident in the medial temporal region. In the patients with multiinfarct dementia, the hypoperfused cortical regions revealed by SPECT were sometimes related to vascular lesions proved at MRI and CT. In the patients with multiinfarct dementia, MRI showed more or less apparent white matter lesions referrable to ischemic insult, besides cortical and subcortical atrophy. MRI allows a differential diagnosis between these two cerebral pathologic conditions of aging. Cerebral flowmetry by Xenon 133 inhalation showed reduced cerebral blood flow in both dementia types. In Alzheimer patients, regional flow was reduced especially in the posterior parietal regions. In multiinfarct dementia patients, flow was more diffusely reduced and asymmetrical. Brain function imaging appears to yield useful information for the differential diagnosis in the most common dementia syndromes. Since the neuropathologic data from brain biopsy are rarely available, clinical and instrumental findings must be integrated for diagnostic and pathogenetic insights of the diseases causing cognitive impairment.