Diffusion-weighted MRI in vascular dementia

Objective: To examine the ability of diffusion-weighted MRI (DWI) to detect ongoing cerebral ischemia in patients with vascular dementia (VaD). Backgr ound: VaD due to small-vessel disease results from the cumulative impact of recurrent cerebral ischemia. Cerebral ischemia may produce clinical manife stations, producing the "stepwise" decline characteristic of VaD. Conventio nal MRI can detect small regions of ischemic damage but cannot determine wh en injury developed. In contrast, DWI shows sensitivity in detecting ischem ia of recent onset. Design/Methods: Patients with VaD (n = 30) underwent DW I in addition to standard MRI sequences. Patients were divided into two gro ups according to the presence of new focal deficits or mental change within 10 days before MRI. In 10 patients of positive group, symptomatic neurolog ic decline occurred an average of 4.2 days before the imaging procedure. Re sults: Seven (70%) of 10 patients with a recent neurologic event showed 15 new regions of signal abnormality on DWI. The anatomic distribution of sign al change could account for the patients' new symptoms or signs in all but one patient. Similar signal abnormality was detected in 4 (20%) of 20 patie nts without a recent neurologic event. New foci of altered signal intensity were distinguishable from prior injuries only with DWI. No significant dif ference was found between patients with and without DWI abnormalities in ge nder, age, Mini-Mental State Examination score, Hachinski Ischemic Score, v ascular risk factors, or severity of increased signal on T-2-weighted MRI s cans. Conclusion: Small foci of abnormal signal on diffusion-weighted MRI ( DWI), presumably representing recent small infarcts, occur often in vascula r dementia (VaD) from small-vessel disease, even in patients without a rece nt "stepwise decline." The results suggest that DWI might be used to monito r VaD progression in future observational and interventional studies of thi s disorder.