The current paper presents the consensus of the Diagnostic Criteria Working Group of the 9th International Congress on Vascular Dementia, held on October 16–18, 2015 in Ljubljana, Slovenia. The concept that late-life dementia can occur in the context of cerebrovascular disease has been known since the nineteenth century [
1,
2], and up until the 1960s, cerebral arteriosclerosis as well as widespread white matter lesions in patients with long-standing hypertension were seen as the main cause of dementia in older individuals [
1]. This view was challenged by Blessed et al. [
3] and others, who suggested that Alzheimer’s disease (AD) neuropathology is the landmark neuropathological feature in the majority of age-related dementia cases. This paradigm shift led to the development of the concept of multi-infarct dementia (e.g. dementia following multiple brain infracts), which subsequently was used to define vascular dementia (VaD) in several international classification systems such as the Diagnostic and Statistical Manual of Mental Disorders 4th edition (DSM-IV) and the International Classification of Diseases and Related Health Problems, 10th edition (ICD-10). However, subsequent studies suggested that the majority of VaD cases were caused by subcortical cerebrovascular changes, rather than by large cortical infarcts [
3]. As a result of these conflicting views, different sets of criteria for VaD were developed, including the National Institute of Neurological Disorders and Stroke – Association Internationale pour la Recherche et l’Enseignement en Neurosciences (NINDS-AIREN) [
4] and the State of California Alzheimer’s Disease Diagnostic and Treatment Centers criteria [
4], as well as criteria for specific subtypes such as subcortical VaD [
5]. Parallel to similar developments in the AD field, it was recognised that cerebrovascular disease frequently co-occurs with other pathological changes in the majority of patients over the age of 75 [
6], which is the age group when over 70 % of dementia cases occur [
7]. Simultaneously, there was controversy regarding the use of the term dementia, which became synonymous with the concept of AD dementia, requiring prominent memory deficits in addition to impairment in at least one other cognitive domain. Nevertheless, this pattern of cognitive decline is not necessarily applicable in patients with VaD [
8]. Furthermore, the need for inclusion of pre-dementia changes within a broader nosological concept similar to mild cognitive impairment due to AD was also acknowledged. Based on these considerations, the term ‘vascular cognitive impairment’ (VCI) was proposed [
9], which accounts for the heterogeneous nature (and degrees) of cognitive deficits related to prominent cerebrovascular pathologies. Vascular mild cognitive impairment [
6] or vascular cognitive impairment, no dementia [
7] were terms proposed to categorise the early clinical stages. However, despite VCI being clearly a step in the right direction, it has not been widely adopted and parallel classification systems are still being employed.
Validated clinical diagnostic criteria are important to identify suitable subjects for clinical trials in order to develop new drugs for VCI. Their relevance increases further if treatment strategies are to be developed that target specific pathogenic cerebrovascular mechanisms leading to VCI [
10]. Furthermore, lifestyle interventions and other non-pharmacological approaches can only be developed if the target populations are clearly defined [
8]. Current efforts towards a consensus on diagnostic criteria and guidelines to account for the heterogeneous nature of VCI, such as the recent International Society for Vascular Behavioural and Cognitive Disorders statement [
11], must be encouraged. However, despite considerable recent advances, there are significant gaps in our understanding of the neurobiological mechanisms underpinning the various dementia forms [
12]. Further research is therefore required before definitive criteria and guidelines can be formulated. Additionally, the success of such criteria will ultimately depend on a robust pathological and clinical validation and the support of the international research community.
The present paper summarises recent major developments in relation to the clinical diagnosis of VCI. We discuss how this entity is handled in the new DSM-V criteria, how our knowledge about the relevant neuro-pathological changes impacts on the concepts surrounding this diagnosis, and what role fluid and neuroimaging biomarkers play. Further, we briefly summarise the current knowledge about risk factors and how they should be addressed in the context of the clinical diagnostic process. Finally, rare genetic causes of VCI/VaD are discussed and recommendations are provided in relation to the most relevant next steps.