CT-CBF correlations of cognitive deficits in multi-infarct dementia

Nuclear medicine in cerebrovascular disease

Stroke and cerebrovascular diseases are major causes of mortality, morbidity, and disability. Nuclear Medicine, primarily via tomographic methods, has made significant contributions to the understanding of the hemodynamic and metabolic consequences of cerebrovascular diseases. In this review, the findings in acute, subacute, and chronic cerebrovascular diseases are described. Many of the pathophysiologic processes and consequences that follow stroke, including completed infarct core, adjacent penumbra, and diaschisis, have been investigated with Nuclear Medicine, and stroke outcome may be related to these phenomena. Additional topics included in this review are cerebrovascular reserve tests and multi-infarct dementia. Finally, Nuclear Medicine investigations of stroke recovery and cerebral plasticity appear to indicate that enhanced activity of preexisting networks, rather than substitution of function, represents the most important mechanism of improvement in chronic stroke rehabilitation.

Effect of cilostazol administration on cerebral hemodynamics and rehabilitation outcomes in poststroke patients

PRIMARY OBJECTIVE

Cilostazol is an antiplatelet agent that inhibits phosphodiesterase III in platelets and the vascular endothelium. We assessed the effects of cilostazol on human cerebral hemodynamics and rehabilitation outcomes.

RESEARCH DESIGN

Prospective, consecutive, observational trial with pretreatment and posttreatment evaluations.

EXPERIMENTAL INTERVENTIONS

Cilostazol (200 mg/day) administered for 8 weeks.

METHODS AND PROCEDURES

Cerebral blood flow at rest, cerebrovascular reserve capacity, and rehabilitation outcomes (Brunnstrom stage, Barthel index score, modified Rankin Scale score, and Mini-Mental State Examination score) were measured in 104 poststroke patients with an average age ± standard deviation of 60.8 ± 9.2 years.

MAIN OUTCOMES AND RESULTS

The cerebral blood flow increased by 23.8% on the affected side of the brain and by 16.9% on the nonaffected side. The cerebrovascular reserve capacity increased by 19.0% on the affected side of the brain and by 13.3% on the nonaffected side. Improvements were observed in the Brunnstrom stage, Barthel index score, modified Rankin Scale score, and Mini-Mental State Examination score.

CONCLUSIONS

Cilostazol appeared to have beneficial effects in poststroke patients with cerebral ischemia and might improve cerebral circulation and rehabilitation outcome.

The angiotensin II type 1 receptor antagonist olmesartan preserves cerebral blood flow and cerebrovascular reserve capacity, and accelerates rehabilitative outcomes in hypertensive patients with a history of stroke

We aimed to determine the effects of angiotensin II receptor blocker on cerebral hemodynamics and rehabilitative outcome. Sixteen hypertensive patients with a history of stroke received 10-20 mg olmesartan daily for eight weeks. Blood pressure decreased after treatment compared with the baseline, whereas cerebral blood flow (CBF) values of the affected and nonaffected sides increased. The results of the cerebrovascular reserve capacity were also statistically increased in the affected side. Improvements were observed in three rehabilitative outcome parameters. These findings suggest that olmesartan has beneficial effects in hypertensive patients with stroke and impaired CBF autoregulation, and might improve cerebral circulation and rehabilitative outcome.

Positron emission tomography in vascular dementia

BACKGROUND

Vascular dementia (VaD) is an ill-defined entity. It is not known how acute brain failure related to stroke becomes chronic leading to dementia.

PURPOSE

The present study investigates whether positron emission tomography (PET) can detect different metabolic patterns in VaD.

PATIENTS AND METHODS

Four groups of stroke patients were selected. The PET findings of 14 stroke patients with multiple large infarcts and dementia (MID) and 14 without dementia (MS) were compared. Sixteen stroke patients with lacunes, leukoaraiosis and dementia (LD) were assessed against nine without dementia (LS). The PET examination utilised the 15-O-steady-state technique in order to determine regional cerebral blood flow (rCBF), regional oxygen extraction rate (rOER) and regional cerebral metabolic rate for oxygen (rCMRO2) in different pre-established cortical, subcortical and cerebellar regions.

RESULTS

Decreased coupled mean rCBF and rCMRO2 with comparable rOER values were observed in all cerebral regions except in the cerebellum of the MID compared to the MS group. In the LD group mean rCBF and rCMRO2 were decreased with increased rOER in all cerebral regions except in the cerebellum compared to the LS group.

CONCLUSIONS

The PET findings in demented patients with multiple large infarcts are in agreement with the concept of multi-infarct dementia. In demented patients with lacunes and leukoaraiosis, the PET pattern suggests a state of misery perfusion not only in the deep structures but also in the whole cerebral cortex. The present PET study argues that there are at least two possible mechanisms that can explain the occurrence of VaD in stroke patients.

Clinical implications of poststroke hypothalamo-pituitary adrenal axis dysfunction: A critical literature review

Persistent hypothalamo-pituitary adrenal axis dysregulation occurs in up to 40% of patients who have suffered a stroke. The degree of hypercortisolemia is partly determined by the size and site of the vascular lesion. Adrenocortical hyperactivity begins almost immediately after a cerebrovasacular infarct but is persistent in an important subgroup of patients. In the early poststroke period (1 day to 1 month) high corticosteroid levels correlate with the presence of an acute confusional state. In the medium term (1 month to 1 year) hypercortisolemia is associated with the development of a major depressive episode and also relates to functional outcome and survival. Neuroanatomical deficits (particularly in the frontal or medial temporal lobes), age of onset, cognitive impairment, and reduced functional status may act as maintaining factors in both the poststroke depression and the adrenocortical hyperactivity. Patients with persisting hypercortisolemia, with or without depression or cognitive impairment, have a worse prognosis with an increased mortality rate. The mechanism for this effect may involve induced hyperglycemia or direct glucocorticoid neurotoxicity, which impairs the brain's capacity for recovery. It is suggested that the cautions use of antiglucocorticoid strategies may be of value in the medical management of the neuropsychiatric complications that follow cerebrovascular accidents.

Vascular dementia: still a debatable entity?

Vascular dementia (VAD) is currently considered to be the second most common cause of dementia in Europe and the USA, second to dementia of the Alzheimer's type (DAT). However, in Asia and many developing countries the incidence of VAD exceeds that of DAT. The positive clinical diagnostic workup for VAD requires six steps: (1) clear-cut quantitative assessment of cognitive deficits utilizing standard neuropsychological tests to establish and quantify the dementia syndrome and rule out pseudo-dementia OF depression; (2) ascertaining the presence of risk factors for stroke; (3) identifying cerebral vascular lesions by neuroimaging (MRI, Iodine or Xenon contrasted CT, PET and SPECT); (4) exclusion of other causes of dementia; (5) differential diagnosis of possible, probable or definite VAD versus DAT and ascertaining when there are mixtures of the two; and (6) temporal identification of causality between onset and progression of the dementia with identified cerebral vascular lesions. There are eight subtypes of VAD: (1) multi-infarct dementias. These are due to large cerebral emboli, and are usually readily identifiable; (2) strategically placed infarctions causing dementia; (3) multiple subcortical lacunar lesions. Patients with these develop VAD at least five to twenty-five times more frequently than those in age-matched general population samples; (4) Binswanger's disease (arteriosclerotic subcortical leuko-encephalopathy). This form is rare. Neuroimaging confirms the diagnosis during life but the diagnosis can not be made by neuroimaging alone; (5) mixtures of two or more of above VAD subtypes; (6) hemorrhagic lesions causing dementia; (7) subcortical dementias due to cerebral autosomally dominant arteriolopathy with subcortical infarcts and leuko-encephalopathy (CADASIL), or to familial amyloid angiopathies and coagulopathies all of which present with multiple subcortical lacunar lesions similar to Binswanger's disease; (8) mixtures of DAT and VAD. The clinical significance of leukoaraiosis and its suspected relationships to VAD remains to be better established. The presence of ischemic infarctions, single or multiple large or multiple small (lacunar) by neuroimaging are necessary for the diagnosis of VAD, but identifying their presence, by neuroimaging alone, does not permit the diagnosis of dementia which can only be established by neuropsychological assessments. VAD is a clinical entity, identifiable in at least 30-70% of patients after strokes but mechanisms responsible for the cognitive impairments are complex. Some of these mechanisms are incompletely understood but provide subjects for important future research.

Computed tomography and cerebral blood flow correlations of mental changes in chronic subdural hematoma

To elucidate the pathophysiology of mental disturbances associated with chronic subdural hematoma, we performed quantitative and three-dimensional measurements of cerebral blood flow (CBF) on xenon-enhanced computed tomographic scans in 12 patients who had chronic subdural hematomas and manifested mental disturbances. In 2 patients who had no headache or hemiparesis, minimal mass effect, and severe multiple infarctions on computed tomographic scan, mentation did not improve after surgery. The CBF reduction was severe, and it further deteriorated after surgery. On the other hand, mentation improved to a varied extent in the other 10 patients, who had headache and/or hemiparesis and minimal, moderate, or severe mass effect and minimal or moderate multiple infarctions on computed tomographic scan. The CBF reduction was diffuse on both sides, but was more marked in the thalamus and putamen than it was in the cortex and subcortex. It was restored after surgery, but insufficiently. The restoration rate was statistically significant only in the thalamus, on both sides (with and without hematoma) (P less than 0.05). Dementia scores and CBF values after surgery were correlated on the side with the hematoma in the frontal cortex and thalamus (P less than 0.01) and in the hemisphere and temporoparietal cortex (P less than 0.05). There was no correlation on the side with the hematoma in the occipital cortex, putamen, and frontal and temporoparieto-occipital subcortices or on the side without the hematoma. The thalamus undergoes displacement and distortion by the hematoma, which in turn leads to changes in consciousness. Postoperative residual mental deficits consist primarily of dementia related to preexisting multiple infarctions.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of thalamus and white matter in cognitive outcome after head injury

Local CBF (LCBF) and local partition coefficients (L lambda) were measured by xenon-enhanced computed tomography among 15 patients with remote cerebral trauma resulting from severe head injury. Results were compared with similar measures among age-matched normal volunteers (N = 20). The patients were divided into two groups according to different outcomes based on serial cognitive testing: Group I (N = 10) improved but Group D (N = 5) deteriorated throughout a mean interval of 10 years of follow-up. Initial LCBF measurements were performed at mean intervals of 6.8 years after injury. Cortical LCBF values were decreased in frontal (p less than 0.01) and temporal (p less than 0.05) regions among both groups, but only in Group D were flow values decreased in putamen and thalamus (p less than 0.05). L lambda values were reduced in frontotemporal cortex among both groups but in the thalamus only among Group D (p less than 0.05). Mean white matter flow values were normal in Group I but were reduced in Group D (p less than 0.05). Mean partition coefficients for white matter were reduced in both groups (p less than 0.01) but were lower in Group D (p less than 0.05). Reduced perfusion of frontotemporal gray matter is consonant with neuropathological reports following severe brain trauma of neuronal atrophy, gliosis, and infarction affecting these regions. Group comparisons between patients who cognitively improved versus those that deteriorated demonstrate an association between reductions of CBF in putamen, thalamus and subcortical white matter and impaired cognition after severe head injury.

Cerebral blood flow and event-related potential in patients with multiple cerebral infarcts

Cerebral blood flow and P300, a long-latency, positive component of the scalp-recorded, event-related potential (ERP), were measured in 26 patients with multiple cerebral infarcts (mean age, 65.0 years). Compared with age-matched normal subjects, patients with multiple cerebral infarcts had significantly lower cortical blood flow values and had prolongation of the P300 latency. There was a significant correlation between the P300 latency and the mean cortical blood flow values in patients with multiple cerebral infarcts. These results suggest that, in patients with multiple cerebral infarcts, the cognitive impairment associated with change of the ERP may be related to reduction of cortical blood flow.

Cerebral hypoperfusion correlates with mild and parenchymal loss with severe multi-infarct dementia

Relative contributions of two potential pathogenetic factors for cognitive impairments among patients with multi-infarct dementia (MID) are reported. Cognitive test scores were correlated with measures of cerebral hypoperfusion and loss of brain parenchyma. Local cerebral blood flow values were determined utilizing stable xenon contrasted computed tomography and volumes for brain parenchyma were estimated from ratios of volumes of infarcted brain plus cerebrospinal fluid/total intracranial volume measured on the same CT slices among two groups of patients, one with mild and the other with severe MID. A total of 26 demented patients with multiple cerebral infarcts were divided into 2 index groups, one with mild and the other with severe MID (mild MID, CCSE greater than or equal to 15, n = 16; severe MID, CCSE less than 15, n = 10). Results were compared with similar measures among age-matched neurologically normal volunteers (n = 14). Ratios for volumes of lost brain parenchyma were significantly higher among severe MID patients than among age-matched normal volunteers, whereas estimates of brain loss among patients with mild MID did not differ from elderly normal volunteers. In patients with mild MID, LCBF values for cortical gray matter were decreased compared with age-matched normal volunteers. Results suggest that chronic cerebral hypoperfusion is an important determinant for mild dementia among patients in the early stages of MID, but volumes of lost cerebral parenchyma due to cerebral infarctions is an important determinant for advanced stages of MID.

Periventricular lucencies on computed tomography in multiple cerebral infarcts: correlation with cerebral blood flow measurements

Forty-nine patients with multiple cerebral infarcts with a mean age of 70.2 years were studied to elucidate the effect of periventricular lucencies (PVLs) on cerebral blood flow (CBF). Patients with multiple cerebral infarcts showed significantly lower mean cortical blood flow (F1) values compared to 15 age-matched normal subjects (p less than .01). The mean F1 values were most significantly decreased in severe group of PVLs and moderately decreased in moderate and mild groups (p less than .05 between severe and mild groups); however, no significant differences in mean F1 values were found between severe and moderate groups. Demented patients showed significantly lower F1 values compared to nondemented patients (p less than .001) and normal subjects (p less than .001). There was no significant difference in the degree of PVL between demented and nondemented groups. As well, the mean F1 values were not significantly correlated with either the number of infarcts or ventricular dilatation. These results suggest that PVLs on CT (especially in severe cases of PVLs) may have some role in the reduction of cortical blood flow in patients with multiple cerebral infarcts.

Vascular dementia. A clinicopathological study

We have reviewed the clinical and pathological records of 40 aged patients who showed only vascular lesions on histological examination. They were followed up for 3.5 +/- 6.3 years before death, and in 28 cases the diagnosis of dementia was done during life. Demographic data, vascular and systemic illnesses, psychiatric neurological and neuropsychological disturbances, and pathological findings were compared between demented and non-demented patients. The number of strokes, several neurological and almost all neuropsychological disturbances, the volume of macroscopic cerebral infarct, especially in frontal, occipital and basal regions, the lacunar state and the white matter lesions, were significantly greater in demented patients. However most of them had less than 100 ml3 of brain infarct. The relative influence of each type of cerebral vascular lesion upon the dementia syndrome was determined by means of multivariate analysis. The volume of macroscopic cerebral infarct, the white matter lesion and the lacunar state showed quite similar contributions to mental deterioration.

Drug treatments of dementia

Present drug treatments for the more common types of dementia are largely palliative or symptomatic, but the promise of drugs to prevent the development of dementia does not seem unrealistic. Neuropharmacological strategies that aim to improve behavioural or cognitive symptoms in dementia are subdivided into drugs that modify central cholinergic, serotonergic, dopaminergic, GABAnergic, and peptidergic transmission. There are no clear clinical guidelines for the management of demented patients who are also hypertensive. The early identification of patients with incipient dementia, the detection of slight but theoretically important beneficial effects, the optimum method of drug administration, more soundly based treatment of behavioural symptoms, and the evaluation of drug combinations are all identified as areas requiring further research.

Randomized clinical trial of daily aspirin therapy in multi-infarct dementia. A pilot study

Seventy multi-infarct dementia patients were randomized into an aspirin-treated group and an untreated control group for an exploratory investigation to determine any effects of 325 mg aspirin daily on cognitive performance. The control group did not receive placebo but evaluations were carried out in a blinded manner. The index group (N = 37, mean age 67.1 years) received 325 mg of aspirin by mouth once daily while the control group (N = 33, mean age 67.6 years) was followed and treated in a similar manner except that they received no aspirin. Both groups had comparable risk factors for stroke, which were treated similarly, as well as comparable initial cerebral blood flow values, as measured by the 133xenon inhalation method, and initial scores on Cognitive Capacity Screening Examination testing. Patients were evaluated at intervals of one year. Significant improvements were demonstrated for cerebral perfusion values (P less than .0001) and cognitive performance scores (P less than .0001) among aspirin-treated patients compared to untreated controls at each of three annual follow-up evaluations. Both men and women benefited from aspirin therapy and their quality of life and independence appeared to be improved, which was not apparent in the control group. Daily aspirin appears to improve or stabilize declines in cerebral perfusion and cognition among patients with multi-infarct dementia.

Aetiological considerations and risk factors for multi-infarct dementia

One hundred and seventy five multi-infarct dementia (MID) patients were evaluated for risk factors for stroke as well as for the types of cerebrovascular lesions that were present. The incidence of associated risk factors for stroke were as follows: hypertension (66%), heart disease (47%), cigarette smoking (37%), diabetes mellitus (20%), moderate alcohol consumption (19%) and hyperlipidaemia (21%). The most frequently occurring type of lesions were multiple lacunar infarctions of the brain (43%). These were combined with other types of stroke in an additional 21%. Atherosclerotic occlusive disease of the carotid and vertebrobasilar arteries occurred alone in 18% and was associated with other types of stroke in another 25%. Embolic cerebral infarctions were present alone in 8% and were combined with other types of stroke in 15%. MID was more frequent in men (62%) than women (p less than 0.002). Mean bihemispheric gray matter cerebral blood flow (CBF) values showed a fluctuating course and when results were pooled and compared between different types of MID, extracranial occlusive disease and/or multiple lacunar infarctions resulted in lowest CBF values. The location of cerebral infarctions was more importantly related to cognitive impairments than was the total volume of infarcted brain. Mortality rates among 125 MID patients followed for 31 months has been 5%. Correct clinical classification of the types of cerebrovascular lesions was confirmed in three necropsied cases.

Amine accumulation in Parkinson's disease and other disorders

Amine accumulation in the axons of degenerating, amine-containing neurones is a natural component of neurone death in many species, including man. While it is becoming increasingly clear that this phenomenon may have functional significance in animal models of Parkinson's Disease, its potential importance in the clinical syndrome has been pretermitted. There are several reasons for this. Failure to sample tissue which contains accumulated amines, the masking of accumulation by adjacent depleted tissues and the degradation of accumulated amines in post-mortem tissues from Parkinsonian brains could account for the low incidence of detection of accumulation in this disorder. Increased levels of amines have been detected in the brains of patients with other conditions including cerebral infarction, Alzheimer's Disease and Huntington's Chorea. These increases have been attributed previously to enhanced aminergic activity, rather than a stage in the degenerative process, as our hypothesis suggests. In addition to the potential importance of amine accumulation in the pathophysiology of various clinical syndromes, a more thorough investigation of this phenomenon in animal models would seem essential since they are used routinely to both describe the basic principles of dopamine function and to evaluate therapeutic possibilities in Parkinson's Disease.

Cognitive performance correlates with cerebrovascular impairments in multi-infarct dementia

Cerebral blood flow (CBF) was measured by the 133Xe inhalation method in patients with multi-infarct dementia (MID, N = 26), Alzheimer's dementia (AD, N = 19), and among age-matched, neurologically normal, healthy volunteers (N = 26). Cognitive performance was assessed in all subjects using the Cognitive Capacity Screening Examination (CCSE). Cerebral vasomotor responses were calculated from differences in values of mean hemispheric gray matter blood flow (Delta CBF) measured during inhalation of 100% oxygen (hyperoxia) compared with CBF measured while breathing room air. Significant correlations were found between CCSE performance and vasomotor responsiveness in patients with MID (P less than .01), but not in patients with AD or in neurologically normal volunteers. Loss of vasomotor responsiveness is an indicator of cerebrovascular disease with rigidity and/or loss of reactivity of cerebral vessels, which impairs cerebrovascular responses to situational demands and predisposes to cerebral ischemia. Loss of cerebral vasomotor responsiveness among MID patients, which is a biologic marker of cerebrovascular disease, provides confirmatory evidence of the vascular etiology of MID and assists in separating MID from AD patients.

Prospective analysis of long term control of mild hypertension on cerebral blood flow

A group of 12 otherwise normal elderly volunteers (mean age = 69.8 years), were detected to have mild hypertension. Cerebral blood flow (CBF) values were measured using 133Xe inhalation method prior to initiating medical treatment and repeated at 6, 12, 24 and 36 months after BP was adequately controlled and restored to normal (below 150/90). Results indicate that CBF values increased markedly during follow-up intervals at 6, 12 and 24 months but not at 36 months. Hypertension is known to be a risk factor for stroke and 4 of the 12 subjects subsequently developed symptoms of cerebrovascular disease (stroke, multi-infarct dementia or transient ischemic attacks) despite control of hypertension. Analyses separating asymptomatic and symptomatic groups indicated that the eight asymptomatic patients continued to maintain increased CBF levels throughout the entire three year interval, whereas the 4 symptomatic patients developed declines in CBF which began, and progressively decreased below the initial pretreatment values, during the second and third years.

Cerebral atrophy and hypoperfusion improve during treatment of Wernicke-Korsakoff syndrome

Nineteen patients with sudden onset of impaired recent memory, cerebellar ataxia, peripheral neuropathy, and other signs of Wernicke-Korsakoff syndrome (WKS) were treated and examined prospectively for 3 months. Serial studies included histories, neurological examinations, cognitive capacity screening examinations (CCSE), computed tomography (CT) scans, and measurements of regional CBF. Patients were detoxified and withdrawn from sedatives before CBF measurements were examined. Treatment included alcohol withdrawal, nutritious diet, and 300 mg thiamine daily. Before treatment CCSE scores and blood flow values of both white and gray matter were reduced, particularly within both temporoparietal regions. After treatment of compliant patients (n = 10), white and gray matter blood flow increased concurrently with improved CCSE scores. Abnormal eye signs, ataxia, peripheral neuropathy, and performance of activities of daily living also improved. Cerebral atrophy and ventricular enlargement measured by CT decreased. Early recognition and treatment of WKS in compliant patients permit rapid reversals of cognitive and neurological impairments associated with increased blood flow of gray and white matter and improvements of brain atrophy measured by CT scanning.