The clinical diagnosis of vascular dementia: A comparison among four classification systems and a proposal for a new paradigm.
To aid in the prospective study of Binswanger's disease, a poorly understood form of vascular dementia, a standardised criteria for its antemortem diagnosis was proposed. These criteria include dementia, bilateral radiological abnormalities on computed tomography (CT) or magnetic resonance imaging (MRI), and at least two of the following three clinical findings: A) a vascular risk factor or evidence of systemic vascular disease; B) evidence of focal cerebrovascular disease; and C) evidence of "subcortical" cerebral dysfunction. These criteria were validated in two ways. First, by retrospectively applying them to a series of 30 demented patients with various pathological diagnoses. Second, by prospectively applying them to a series of 184 patients with clinically typical Alzheimer's disease. The sensitivity and specificity of the criteria appear adequate for use in clinical research. Rush Presbyterian-St Lukes Medical Center, Chicago, Illinois, United States Rush Alzheimer's Disease Center D A Bennett R S Wilson D W Gilley J H Fox Department of Neurology D A Bennett J H Fox Department of Psychology and Social Sciences R S Wilson Correspondence to: Dr Bennett, Rush Alzheimer's Disease Center, 710 S Paulina Street, 8 North JRB, Chicago, Illinois 60612-3864, United States. Received I I October 1989 and in revised form 5 March 1990. Accepted 14 March 1990 Vascular disease is consistently reported as the second leading cause of dementia.'2 Nonetheless, neither its prevalence nor defining clinical, radiological or histopathological features are settled.34 Much of the controversy stems from the heterogeneity of the vascular dementias.34 Therefore, recent reviews of vascular dementia stress the need to dinstinguish between the various vascular dementias and to develop specific clinical, radiological and pathological criteria for each type."' Binswanger's disease (BD), a forrn of vascular dementia, was for years considered a relatively rare disorder diagnosed only Ltt necropsy.' The sensitivity of magnetic resonance imaging (MRI) to subcortical white matter pathology, however, has rekindled interest in the disorder and raised the possibility of its antemortem diagnosis. Unfortunately, the typical radiological lesions ofBD are routinely seen in both elderly demented and non-demented patients.67 Furthermore, not all of the lesions visualised by MRI have a vascular basis."2 In fact, about 30% of patients with clinically typical Alzheimer's disease (AD) have similar lesions.'3 For physicians evaluating demented patients, the controversy surrounding the radiological abnormalities poses the clinical dilemma of how to diagnose demented patients who have white matter lesions (WMLs) on computed tomography (CT) or MRI. Clearly, many of these patients do not have BD. Resolution of this dilemma requires standardised criteria for the clinical diagnosis of Binswanger's disease. The purpose of this paper is to propose such criteria. Although there is undoubtedly a prodromal phase of BD when dementia is not evident, Binswanger considered this illness a dementing disorder and a recent review by Babikian and Ropper concluded that the illness is "characterized clinically by disorders of memory, mood, and cognition".6 Therefore, we propose that the diagnosis be reserved for patients who are demented. The identical restriction is placed on the diagnosis of AD. For research purposes, the presence of dementia should be confirmed by neuropsychological testing. Radiological criteria for BD are complicated by the fact that several types of lesions are identifiable on MRI. Periventricular caps and rims are nearly ubiquitous findings on MRI. Pathologically, they represent areas of subependymal gliosis, and probably do not have a vascular aetiology. Subcortical WMLs may be either small infarcts, focal areas of demyelination, or dilated perivascular spaces."'" It is difficult to distinguish between these lesions. However, a recent MRI-pathological study found that the majority of MRI lesions corresponding to dilated perivascular spaces were round or linear, isointense relative to cerebrospinal fluid, and less than 2 x 2 mm." Therefore, the radiological criteria for the diagnosis of BD requires bilateral leukoaraiosis on CT, or bilateral, multiple or diffuse, subcortical high signal T2 weighted Table I Criteria for the clinical diagnosis ofpossible Binswanger's Disease 1 Dementia must be established by clinical examination and confirmed by neuropsychological tests. 2 One finding from two of the following three groups must be present: A) the presence of a vascular risk factor or evidence of systemic vascular disease (for example, hypertension, diabetes, a history of myocardial infarction, cardiac arrhythmia, or congestive heart failure); B) evidence of focal cerebrovascular disease (for example, a history of stroke, or demonstration of a focal pyramidal or sensory sign); C) evidence of "subcortical" cerebral dysfunction (for example, a Parkinsonian, magnetic, or "senile" gait, Parkinsonian or gegenhalten rigidity, or a history of incontinence secondary to a spastic bladder). 3 The radiological criteria requires bilateral leukoaraiosis on computed tomography (CT), or bilateral and, multiple or diffuse, subcortical high signal T2 weighted lesions greater than 2 x 2 mm on magnetic resonance (MR) scan. The proposed criteria lose their validity in the presence of: 1 multiple or bilateral cortical lesions on CT or MR; or 2 severe dementia (for example, MMS < 10) 961 group.bmj.com on June 18, 2017 Published by http://jnnp.bmj.com/ Downloaded from