Subcortical vascular dementia

Vascular dementia (VaD) incorporates different vascular mechanisms and changes in the brain, and has different causes and clinical manifestations. Current criteria for VaD select an aetiologically and clinically heterogeneous group and this definitional heterogeneity has affected clinical trial results. Focus on a more homogeneous group, such as that with subcortical (ischaemic) VaD, could be an alternative in clinical drug trials. This subtype incorporates two small vessel clinical entities - 'Binswanger's disease' and 'the lacunar state'. It comprises small vessel disease as the primary vascular aetiology, lacunar infarct(s) and ischaemic white matter lesions as the primary type of brain lesions, subcortical location as the primary location of lesions, and the subcortical clinical syndrome as the primary clinical manifestation. Subcortical VaD is expected to show a more predictable clinical picture, natural history, outcome and treatment responses.     

Subcortical ischaemic vascular dementia

Vascular dementia is the second most common type of dementia. The subcortical ischaemic form (SIVD) frequently causes cognitive impairment and dementia in elderly people. SIVD results from small-vessel disease, which produces either arteriolar occlusion and lacunes or widespread incomplete infarction of white matter due to critical stenosis of medullary arterioles and hypoperfusion (Binswanger's disease). Symptoms include motor and cognitive dysexecutive slowing, forgetfulness, dysarthria, mood changes, urinary symptoms, and short-stepped gait. These manifestations probably result from ischaemic interruption of parallel circuits from the prefrontal cortex to the basal ganglia and corresponding thalamocortical connections. Brain imaging (computed tomography and magnetic resonance imaging) is essential for correct diagnosis. The main risk factors are advanced age, hypertension, diabetes, smoking, hyperhomocysteinaemia, hyperfibrinogenaemia, and other conditions that can cause brain hypoperfusion such as obstructive sleep apnoea, congestive heart failure, cardiac arrhythmias, and orthostatic hypotension. Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL)and some forms of cerebral amyloid angiopathy have a genetic basis. Treatment is symptomatic and prevention requires control of treatable risk factors.     

Subcortical ischemic vascular dementia

Subcortical ischemic vascular dementia (SIVD) has been proposed as a subtype of vascular cognitive impairment. MRI often discloses "silent" hyperintensities in 20% to 40% of community-dwelling elderly. Efforts to relate MRI-measured lacunes and white matter changes to cognitive impairment have not been straightforward. The possibility that Alzheimer's disease pathology contributes to cognitive impairment increases with age. A rare disorder known as cerebral autosomal dominant arteriopathy with subcortical infarctions and leukoencephalopathy (CADASIL) provides an opportunity to study SIVD in the absence of Alzheimer's disease. Lacunes and deep white matter changes are associated with dysexecutive syndrome. Hypertension, the leading risk factor for sporadic SIVD, is treatable. High priority must be given to reducing vascular risk profiles.     

Subcortical ischemic vascular disease and dementia

Subcortical ischemic vascular disease and dementia (SIVD) incorporate small vessel disease as the chief vascular etiology, lacunar infarct and ischemic white-matter lesions (WMLs) as primary type of brain lesions, subcortical location as the primary location of lesions, and subcortical syndrome as the primary clinical manifestation. It incorporates two clinical entities: Binswanger's syndrome and the lacunar state. Patients with SIVD present with extensive white-matter lesions and multiple lacunae on neuroimaging. SIVD is expected to be a more homogenous subtype of vascular cognitive impairment and dementia. Recently modified NINDS-AIREN research criteria for SIVD have been proposed. Further empirical research is needed to refine the syndrome and stages and validate the brain imaging criteria, as well as to detail the natural history and outcomes of SIVD.     

Subcortical symptoms predominate in vascular dementia

Thirty-one patients with the clinical diagnosis of vascualar dementia were examined with regard to symptoms reflecting disturbances in various brain regions. Frontal, parietal, subcortical and non-regional symptom complexes were used to characterize each patient. Frontal (77%) and subcortical (68%) symptoms were the most common clinical patterns. Using an overall evaluation, subcortical symptomatology was the most prominent clinical picture (45%) Extrapyramidal symptoms, an important aspect of the subcortical symptom complex, were associated with histories of hypertension (p<0.05) and low levels of 5-hydroxyindoleacetic acid (p<0.05) in the spinal fluid. This study suggests that subcortical, and possibly also frontal, symptoms are typical and perhaps underestimated manifestations of vascular dementia and that they may reflect important pathogenetic pathways in this disorder.     

Subcortical dementia. Review of an emerging concept

Subcortical dementia is a clinical syndrome characterized by slowness of mental processing, forgetfulness, impaired cognition, apathy, and depression. First recognized in progressive supranuclear palsy and Huntington's disease, the concept has been extended to account for the intellectual impairment of Parkinson's disease, Wilson's disease, spinocerebellar degenerations, idiopathic basal ganglia calcification, the lacunar state, and the dementia syndrome of depression. Disorders manifesting subcortical dementia have pathologic changes that involve primarily the thalamus, basal ganglia, and related brain-stem nuclei with relative sparing of the cerebral cortex. Recent studies of neuropsychologic deficits following focal subcortical lesions also support a role for these structures in arousal, attention, mood, motivation, language, memory, abstraction, and visuospatial skills. The clinical characteristics of subcortical dementia differ from those of dementia of Alzheimer's type where prominent cerebral cortical involvement produces aphasia, amnesia, agnosia, and apraxia.     

Prevention of vascular dementia

Stroke is an important public health problem worldwide. Those at high risk of stroke may be at high risk of cognitive impairment and dementia after stroke. Modifiable cardiovascular risk factors in midlife including hypertension, alcohol use, cigarette smoking, and certain dietary factors may be important targets for prevention of vascular causes of cognitive impairment. These same types of factors may also be associated with Alzheimer disease. Better control of cardiovascular disease risk factors might lead to delay or prevention of vascular dementia and Alzheimer disease.     

Rivastigmine in vascular dementia

Vascular dementia (VaD), like Alzheimer's disease (AD), is associated with cholinergic deficits. Rivastigmine provides sustained, brain-selective inhibition of acetylcholinesterase and butyrylcholinesterase. Preliminary data suggest that rivastigmine may provide significant benefits in patients with AD and cerebrovascular disease (mixed dementia), and in patients with VaD. Open-label rivastigmine treatment has been associated with improved cognitive and functional abilities, behavioral symptoms, and reduced caregiver stress in a small pilot study in these patients. Larger, prospective, double-blind studies of rivastigmine in patients with VaD are under way. These studies will confirm whether rivastigmine is an efficacious treatment option for a range of patients for whom, until now, there have been few symptomatic therapies.     

Drugs and vascular dementia

Between 20 and 35% of all dementias are vascular in origin, their etiology is due to cerebrovascular disease and the risk factors are known (e.g. hypertension, diabetes, smoking, or hyperlipidemia). Primary and secondary preventions are the basis of therapeutics. Symptomatic treatment is emerging, notably in the field of cognitive disorders. In that respect, monoamine oxidase inhibitors, and more recently acetylcholinesterase inhibitors, are in the process of being recognized as first-line treatments of established vascular dementia.     

Neuroprotection in vascular dementia

Vascular dementia (VaD) is the second most common form of dementia after Alzheimer's disease (AD), and one of the major causes of mental and physical disability in developed countries. As such, the identification and implementation of strategies which prevent the development of the condition or enable improvements in patients with VaD are healthcare objectives of the first order. VaD is now regarded as a combined group of clinical-pathological entities rather than one disease, that is, multiple pathogenic mechanisms and lesion types underlie a cognitive impairment of vascular origin. The clinical diagnosis of VaD is complex and difficult because of the heterogeneous nature of its clinical presentation and progression and the low sensitivity of existing clinical criteria. Moreover, there is growing evidence of the epidemiological significance of mixed forms of dementia, and that ischemic processes may precipitate and exacerbate cognitive impairment in AD. Numerous compounds have been proposed as potentially useful in the treatment of patients with VaD, comprising vasodilatative, antithrombotic, hemorrheological, nootropic, antiserotoninergic and, most recently, antiglutamatergic and cholinergic approaches. In spite of some initially favorable reports based on the use of memantine, donepezil and galantamine, there is as yet no conclusive evidence of a definitive treatment for VaD. Unsatisfactory results from VaD drug trials may be attributed in part to the diversity of the patients included (underlying pathogenic mechanisms, number, type, and location of vascular lesions), and to methodological limitations in the design of the trials (outcome measures, end-points, size, follow-up period). The treatment of modifiable vascular risk factors - hypertension, diabetes mellitus, hypercholesterolemia and heart disease - is an important strategy for the reduction of the risk of dementia, and is likely to slow the progress of cognitive decline.