Clinical and neuropsychological features in autopsy-defined vascular dementia

Studies reporting that ischemic vascular dementia (IVD), compared to Alzheimer's disease (AD), is associated with relatively greater impairment of executive function and relatively preserved episodic memory raise the question of whether there is a distinctive neuropsychological profile of impairment associated with IVD and whether this might be useful in clinical diagnosis. However, prior reports are almost all based on clinically diagnosed cases, raising obvious issues of possible circularity and leaving unanswered questions of validity. Here we report on clinical and neuropsychological findings in 18 prospectively studied cases that had substantial pathology-defined cerebrovascular disease (CVD) at autopsy. Nine cases had minimal AD pathology, while the remainder had moderate or severe degrees of AD pathology. Cognitive status at last evaluation ranged from mild cognitive impairment to moderate dementia. Clinical features were quite variable; only 40% of cases with high CVD levels had elevated Hachinski Ischemia Scale scores and neither abrupt onset nor stepwise progression was found in most high CVD cases, even when AD changes were essentially absent. The presence of dementia was predictably related to the level of neurofibrillary pathology, but was not related to the severity of CVD. Neuropsychologists expert in the evaluation of dementia used a priori criteria to diagnose neuropsychological protocols (blind to all other data) from cases with pathology-informed diagnoses of AD, IVD, and mixed dementia. Sensitivity and specificity were both high for AD, sensitivity for detecting pure IVD was poor, and values were intermediate for detecting IVD irrespective of AD levels. A illustrative case example is included. We conclude that the profile of cognitive impairment in IVD is highly variable, but that in clinical settings neuropsychological readings may contribute to the differential diagnosis of dementia.