The role of MRI in dementia

Neuroimaging techniques aimed at studying structural changes of the brain m ay provide useful information for the diagnosis and the clinical management of patients with dementia. Magnetic resonance imaging (MRI) may show abnor malities amenable to surgical treatment in a significant percentage of pati ents with cognitive impairment. MRI may also assist the differential diagno sis in dementia associated with metabolic or inflammatory diseases. MRI has the potential to detect focal signal abnormalities which may assist the clinical differentiation between Alzheimer's disease (AD) and vascular dementia (VaD). Severe temporal atrophy, hyperintensities involving the hi ppocampal or insular cortex, and gyral hyperntense bands are more frequentl y noted in AD. Basal ganglionic/thalamic hyperintense foci, thromboembolic infarctions, confluent white matter and irregular periventricular hyperinte nsities are more common in VaD. The high sensitivity of MRI in detecting T2 hyperintense lesions and the lo w specificity of white matter lesions have resulted in a poor correlation b etween MRI findings and both neuropathological and clinical manifestations. In particular, MRI has disclosed a series of white matter focal changes in the elderly population, which are not necessarily associated with cognitiv e dysfunction. The recent advent of a new MRI method sensitive to the microstructural chan ges of white matter, the so-called diffusion tensor imaging, may be helpful in correlating clinical manifestations with white matter abnormalities.