Assessing cerebrovascular contribution to late dementia of the Alzheimer's type: the role of combined hemodynamic and structural MR analysis.

The critical question as to the respective role of Alzheimer's disease (AD) and cerebrovascular disease in dementia of the Alzheimer's type (DAT), the most common form of dementia, is still debated. But there has been considerable progress in understanding cerebral hemodynamics and the relationship between structural brain damage and cognitive decline, in routine neuro imaging techniques. These advances now allow the proposition of a novel MR classification of DAT including indicators of both cerebrovascular function and regional brain atrophy. MR indicators of windkessel function include the arterial pulsatility index, the intracranial blood stroke volume, the cerebral relative venous outflow rates and a relative index of craniospinal compliance. MR indicators of vascular conduct function include total arterial and superficial venous flow rates that are closely related to brain metabolism. Structural MR sequences allow the detection of structural markers of windkessel dysfunction and, beyond the non specific hippocampal atrophy, a more extensive AD-like MR pattern of atrophy. The first illustration of this MR classification in elderly patients that later progressed to dementia converges with recent neuropathological observations to suggest that the major enemy to combat in late-life dementia is not AD but cerebrovascular dysfunction.