Mixed dementia--the most common cause of dementia.

The existence of vascular dementia (VaD) was first identified by Marie, who described the etat lacunaire, and by Binswanger, who identified white matter lesions. The role of cortical lesions, while clear to clinicians, was highlighted only later by the pathological studies of Tomlinson and the clinical demonstrations of Hachinski et al., who have defined multi-infarct dementia. Lately, the emphasis shifted to pathogenic mechanisms with the identification of a multitude of processes, including lipohyalinosis, cardiac dysfunction, and genetic causes, to name only a few. Epidemiologic studies have demonstrated the high frequency of VaD, as well as the fact that vascular factors can contribute to Alzheimer's disease (AD). All these considerations converge to the realization that VaD is an extremely important clinical entity and that its prevention and treatment are within reach. In fact, there are more data on how to prevent strokes (and presumably VaD) than AD. Moreover, many factors that were identified as contributing to cerebrovascular disease in general and VaD in particular are frequently suspected as predisposing to AD as well. This surprising finding highlights the importance of mixed vascular-degenerative dementia as a disorder that has to be properly defined and has important implications on prevention and treatment.