Mohammed T. Abou-Saleh

VASCULAR DEMENTIA 253diagnosis of Binswanger’s disease (subcortical arterioscleroticencephalopathy; SAE) has become increasingly popular.It was initially thought that these CT findings were specific forBinswanger’s disease. However, similar CT findings can occasionallybe seen in normal people or even those with AD. Becauseof this, the term ‘‘leukoaraiosis’’ (Greek, for white matter of loosetexture) was used to describe the CT appearances 27 .Clinically there is a stepwise or progressive course, characterizedby pseudo-bulbar palsy, cognitive, behavioural and gaitdisturbances, with focal neurological deficits in approximately30%. The dementia tends to be subcortical in type. Many patientsare hypertensive and the pathological changes are thought to besecondary to chronic ischaemia in the deep end arteries.Although many patients are hypertensive, the final insult isprobably due to hypoperfusion. Indeed, Sulkara and Erkinjuntihave reported acute dementia after periods of hypotension andcardiac arrhythmia; CT showed leukoaraiosis 28 . Although hypertensionneeds to be treated, episodes of hypotension need to becarefully avoided, as vasodilatory reserve is impaired 29 .Inzitari et al. noted leukoaraiosis to be present in 100% ofpatients with multi-infarct dementia (MID) and 33% with ADcompared with 11% of the control population, although even inthis control population there was evidence of intellectual fall-off,but not severe enough to be labelled dementia 30 . A history ofstroke was four times more likely in those with leukoaraiosis thanin those without; most, however, die from cardiac causes 31 .Overall there appears to be considerable overlap betweenleukoaraiosis, subcortical atherosclerotic encephalopathy andmultiple lacunar states.In CADASIL, the MRI usually shows a combination ofleukoaraiosis and multiple lacunar infarction.Cerebral Amyloid AngiopathyAlthough cerebral amyloid angiopathy has been known about formany years, its role in the aetiology of dementia has attractedmuch attention 32 . Amyloid deposition in the small and mediumsizedarteries and arterioles may present with spontaneoushaemorrhage or thrombosis. More interestingly, there have nowbeen many reports of cerebral amyloid angiopathy (CAA)presenting as dementia without any preceding history of strokelikeepisodes. CAA is associated with areas of small subcorticalinfarction and histological changes similar to Binswanger’s SAE.Senile plaques in AD contain an amyloid core which appears tobe identical to CAA. Amyloid plaque cores are often foundimmediately adjacent to amyloid-laden capillaries. CAA is presentin more than 80% of cases of AD 33 .The association of AD with leukoaraiosis and cerebral amyloidangiopathy has renewed speculation that vascular risk factorsmay play a role in the pathogenesis of AD 34 .MANAGEMENTClinical AssessmentThe following criteria point towards a diagnosis of vasculardementia:1. Symptoms and signs of stepwise stroke-like episodes.2. Vascular risk factors.3. Evidence of vascular disease on CT and MRI.The validity of the different scoring systems is discussed elsewhere(q.v.). Factors suggesting that the dementia is not vascularinclude:1. Absence of the above.2. Early presence of extrapyramidal and autonomic features.3. Early hallucinations.4. Cerebellar signs.It should be noted that it is sometimes difficult in those whopresent with gait problems to distinguish leukoaraiosis/multiplelacunar strokes from normal pressure hydrocephalus andprogressive supranuclear palsy: it is important, then, to look forpoor upgaze, axial rigidity and perform CT or MRI scanning.There is no single illness making up vascular dementia. Theclinical management of any patient with vascular dementia shouldinclude a summary of the clinical presentation, the probablepathogenesis, risk factors and site of damage. This will allow arational approach to investigation and medical treatment tominimize the risk of further recurrence/progression. An attemptshould be made to decide whether the dementia is primarily athrombotic or an embolic process from the heart or great vessels,a hypertensive deep white matter disease, a hypoperfusion processor even one of the rarer causes of stroke.InvestigationInvestigation should include a routine vascular screen and thenfurther investigations, depending on the proposed pathophysiology.It is important to assess the routine vascular risk factors,especially as Meyer et al. have suggested that improved cognitionmay occur after the control of risk factors in MID 35 . A carefulassessment of the cardiovascular system is necessary, particularlypaying attention to blood pressure and possible sites of embolifrom the cerebral arteries (i.e. carotid stenosis) and heart,(especially valvular heart disease, atrial fibrillation or tumourand left ventricular thrombus) in those with cortical infarctions.The CT/MRI scan appearances in vascular dementia have alreadybeen discussed in some detail.All patients should have a full blood count (for polycythaemiaor thrombocythaemia), ESR (for arteritis), blood sugar, chestX-ray and ECG. I also check fasting lipids, as cholesterol is animportant risk factor for ischaemic heart disease and mostvascular patients die a cardiac death. Neurosyphilis remainstreatable. Evidence of arteritis and the antiphospholipid syndromeshould be looked for, both clinically and by checkingvarious blood tests, such as CRP, complement levels, antinuclearfactor, DNA binding, lupus anticoagulant and anticardiolipinantibodies. If the ESR is raised or the patient is over 50 it isimportant to consider the arteritides, such as granulomatousangiitis and temporal arteritis 17,36 .The diagnosis of granulomatous angiitis can be very difficultand may require both angiography and brain/meningeal biopsy. Itis often difficult to know how often one should pursue theseinvestigations, but a stuttering onset of recent vascular dementiawith a raised ESR and abnormal lymphocytic cerebrospinal fluid(CSF) should alert the physician. Unfortunately, in some cases theESR and CSF may be normal. A high index of suspicion is neededbecause with steroids and cyclophosphamide these patients can dovery well 17,20 . In spite of this, a raised ESR in stroke frequentlyremains unexplained.Ultrasound scanning of the carotid arteries to detect carotidstenosis or occlusion may be appropriate, although these usuallycause transitory ischaemic attacks or strokes, rather than adementia 37 .Echocardiography is important if a cardiac source of emboli isconsidered possible and should be performed in all patients withmore than one cortical infarct 18 .Skin biopsy, chromosome and DNA analysis may be helpful inthe diagnosis of CADASIL and MELAS. Measuring cerebral