Diagnostic Impact of Intracranial Vessel Wall MRI in 205 Patients with Ischemic Stroke or TIA

BACKGROUND AND PURPOSE

Secondary prevention of ischemic stroke depends on determining the cause of the initial ischemic event, but standard investigations often fail to identify a cause or identify multiple potential causes. The purpose of this study was to characterize the impact of intracranial vessel wall MR imaging on the etiologic classification of ischemic stroke.

MATERIALS AND METHODS

This was a single-center, retrospective study of 205 consecutive patients who were referred for vessel wall MR imaging to clarify the etiology of an ischemic stroke or TIA. An expert panel classified stroke etiology before and after incorporating vessel wall MR imaging results using a modified Trial of Org 10172 in Acute Stroke Treatment system. We measured the proportion of patients with an altered etiologic classification after vessel wall MR imaging.

RESULTS

The median age was 56 years (interquartile range = 44-67 years), and 51% (106/205) of patients were men. Vessel wall MR imaging altered the etiologic classification in 55% (112/205) of patients. The proportion of patients classified as having intracranial arteriopathy not otherwise specified decreased from 31% to 4% (64/205 versus 9/205; P < .001) and the proportion classified as having intracranial atherosclerotic disease increased from 23% to 57% (48/205 versus 116/205; P < .001). Conventional work-up classification as intracranial arteriopathy not otherwise specified was an independent predictor of vessel wall MR imaging impact (OR = 8.9; 95% CI, 3.0-27.2). The time between symptom onset and vessel wall MR imaging was not a predictor of impact.

CONCLUSIONS

When vessel wall MR imaging is performed to clarify the etiology of a stroke or TIA, it frequently alters the etiologic classification. This is important because the etiologic classification is the basis for therapeutic decision-making.

Time for a Time Window Extension: Insights from Late Presenters in the ESCAPE Trial

BACKGROUND AND PURPOSE

The safety and efficacy of endovascular therapy for large-artery stroke in the extended time window is not yet well-established. We performed a subgroup analysis on subjects enrolled within an extended time window in the Endovascular Treatment for Small Core and Proximal Occlusion Ischemic Stroke (ESCAPE) trial.

MATERIALS AND METHODS

Fifty-nine of 315 subjects (33 in the intervention group and 26 in the control group) were randomized in the ESCAPE trial between 5.5 and 12 hours after last seen healthy (likely to have groin puncture administered 6 hours after that). Treatment effect sizes for all relevant outcomes (90-day mRS shift, mRS 0-2, mRS 0-1, and 24-hour NIHSS scores and intracerebral hemorrhage) were reported using unadjusted and adjusted analyses.

RESULTS

There was no evidence of treatment heterogeneity between subjects in the early and late windows. Treatment effect favoring intervention was seen across all clinical outcomes in the extended time window (absolute risk difference of 19.3% for mRS 0-2 at 90 days). There were more asymptomatic intracerebral hemorrhage events within the intervention arm (48.5% versus 11.5%, P = .004) but no difference in symptomatic intracerebral hemorrhage.

CONCLUSIONS

Patients with an extended time window could potentially benefit from endovascular treatment. Ongoing randomized controlled trials using imaging to identify late presenters with favorable brain physiology will help cement the paradigm of using time windows to select the population for acute imaging and imaging to select individual patients for therapy.

Acute ischemic stroke and abnormal blood hemoglobin concentration

OBJECTIVES

This study examines whether low or high blood hemoglobin concentration (HGB) is associated with stroke severity, worse clinical outcomes, and poorer prognosis after acute ischemic stroke (AIS).

METHODS

This retrospective cohort study included data from the Ontario Stroke Registry on consecutive patients with AIS who were admitted between July 2003 and March 2008. We excluded patients taking anticonvulsants or iron supplement; patients with cancer, renal failure, history of gastro-intestinal or genitourinary bleeding, and pregnancy. Patients were divided into groups as follows: low HGB, normal HGB, and high HGB. Outcome measures included the frequency of greater degree of disability at discharge (modified Rankin score: 3-6), 7-day, 30-day and 90-day mortality, and length of stay in the acute stroke care hospital.

RESULTS

Hemoglobin levels higher than the upper limit of normal are associated with a greater disability at discharge (OR = 1.49, 95% CI: 1.03-2.15, P = 0.0331), and higher 30-day mortality (HR = 1.98, 95% CI: 1.44-2.74, P < 0.0001) after adjustment for major potential confounders. The Kaplan-Meier curves indicate that abnormal HGB levels are associated with higher mortality after AIS (P < 0.0001). HGB levels below the lower limit of normal are associated with longer lengths of stay in the acute care hospital (OR = 1.11, 95% CI: 1.02-1.22, P = 0.017). Elevated HGB was associated with greater neurological deficit on admission (OR = 1.45, 95% CI: 1.06-1.95, P = 0.0195).

CONCLUSIONS

Our results suggest that an elevated HGB on the initial admission is associated with more severe strokes, greater disability at discharge, and higher 30-day mortality after AIS. A low HGB on admission is associated with longer stay in the acute care hospital.

A 5-item prediction rule to identify severe renal dysfunction in patients with acute stroke

BACKGROUND AND PURPOSE

Although patients with severe renal dysfunction who receive iodinated contrast are at high risk of CIN, contrast-enhanced CT scans are often obtained without prior knowledge of kidney function in patients with acute stroke. We aimed to develop a tool to identify patients with acute stroke at a high risk of CIN in the absence of a recent GFR.

MATERIALS AND METHODS

We used the RCSN (9872 patients) and OSA (2544 patients) for our derivation and validation cohort, respectively. A multivariable logistic regression model was performed to develop a predictive tool to identify severe renal dysfunction (defined as a GFR < 30 mL/min/1.73 m(2)).

RESULTS

The overall prevalence of severe renal dysfunction was 4.9% and 5.2% in the derivation and validation cohort, respectively. The prediction rule was designed as follows: (age in years) + (5 points for women) + (5 points for history of diabetes mellitus) + (15 points for preadmission insulin use) + (10 points for history of hypertension). The prevalence of severe renal dysfunction is negligible in patients with a total score of ≤70 (≤0.005%-0.7%) but increases with higher Renal Risk Scores (eg, scores 71-80: 2.1%-2.2%; scores 91-100: 6.6%-7.1%; scores 111-120: 15.9%-28.1%).

CONCLUSIONS

The Renal Risk Score is a validated tool that helps clinicians select which patients with stroke can safely proceed to contrast-enhanced brain imaging without waiting for laboratory evidence of good renal function.

Mapping white matter diffusion and cerebrovascular reactivity in carotid occlusive disease

OBJECTIVE

To characterize the relationship between cerebrovascular reactivity (CVR) and white matter (WM) diffusion in patients with internal carotid artery (ICA) occlusive disease.

METHODS

In this exploratory observational study, 41 patients with severe stenosis or occlusion of the extracranial ICA and 12 healthy control subjects underwent CVR mapping using the fMRI response to hypercapnia. Conventional anatomic and diffusion-weighted MRI sequences were used to calculate maps of the apparent diffusion coefficient (ADC) and to exclude areas of previous ischemic injury. In all subjects, ADC was compared between WM with positive and negative CVR. In 27 patients with unilateral ICA involvement, ADC and CVR were compared between ipsilateral and contralateral WM while covarying for relevant clinical risk factors.

RESULTS

In patients with bilateral disease and in the ipsilateral hemisphere of patients with unilateral disease, negative CVR was associated with increased WM ADC (p < 0.01 and p < 0.005, respectively). In patients with unilateral disease, the ipsilateral CVR deficit was correlated with the degree of hemispheric WM ADC elevation (p < 0.005). ADC elevation remained significant after correction for potential confounding risk factors.

CONCLUSIONS

CVR impairment is associated with ADC elevation in normal-appearing WM of patients with severe stenosis or occlusion of the extracranial ICA. This finding is consistent with the presence of early, low-grade ischemic injury.

Gender differences in carotid imaging and revascularization following stroke

BACKGROUND

Carotid endarterectomy is performed less often in women than in men, but it is unknown whether this reflects differences in screening rates, disease prevalence, or other factors.

METHODS

This was a cohort study of consecutive patients with acute stroke or TIA admitted to 11 Ontario stroke centers participating in the Registry of the Canadian Stroke Network between July 1, 2003, and September 30, 2007. We compared rates of carotid imaging, the severity of carotid stenosis, and rates of carotid endarterectomy or angioplasty within 6 months of the index event in women vs men.

RESULTS

We studied 6,389 patients (48% women) with ischemic stroke or TIA. Women were less likely than men to undergo carotid imaging (81% vs 86%, p < 0.0001); however, when the analysis was limited to patients without apparent contraindications to surgery, 92% received carotid imaging, with no difference between women and men. Women were less likely than men to have severe carotid stenosis (7.4% vs 11.5%, p < 0.0001). Women were half as likely as men to undergo carotid revascularization within 6 months of the index event (odds ratio 0.51, 95% confidence interval 0.37 to 0.70), but this gender difference was no longer significant in the subgroup with severe carotid stenosis (odds ratio 0.75, 95% confidence interval 0.49 to 1.15).

CONCLUSIONS

Although women with ischemic stroke or TIA are less likely than men to undergo carotid screening and revascularization, this difference is largely explained by potential contraindications to surgery and by sex differences in the severity of carotid disease.

Recombinant tissue plasminogen activator increases blood-brain barrier disruption in acute ischemic stroke: an MR imaging permeability study

BACKGROUND AND PURPOSE

Although thrombolytic therapy (recombinant tissue plasminogen activator [rtPA]) represents an important step forward in acute ischemic stroke (AIS) management, there is a clear need to identify high-risk patients. The purpose of this study was to investigate the role of quantitative permeability (KPS) MR imaging in patients with AIS treated with and without rtPA. We hypothesized that rtPA would increase KPS and that KPS MR imaging can be used to predict the risk of hemorrhagic transformation (HT).

MATERIALS AND METHODS

Thirty-six patients with AIS were examined within a mean of 3.6 hours of documented symptom onset. KPS MR imaging was performed as part of our AIS protocol. KPS coefficients in the stroke lesion were estimated for all patients, and the relationship between KPS and both HT and rtPA was investigated by using Student t tests. Receiver operating characteristic (ROC) curves were computed for predicting HT from KPS.

RESULTS

The occurrence rate of HT for patients who received rtPA and those who did not was 43% and 37%, respectively. Assessment of KPS in the lesion revealed significant differences between those who hemorrhaged and those who did not (P < .0001) as well as between rtPA-treated and untreated patients (P = .008). ROC analysis indicated a KPS threshold of 0.67 mL/100 g/min, with a sensitivity of 92% and a specificity of 78%.

CONCLUSIONS

The results of this study indicate that KPS is able to identify patients at higher risk of HT and may allow use of physiologic imaging rather than time from onset of symptoms to guide treatment decision.

Risk factors for posterior compared to anterior ischemic stroke: an observational study of the Registry of the Canadian Stroke Network

BACKGROUND

Traditional vascular risk factors appear to exert varying magnitudes of risk for different major vascular events. For example, hypercholesterolemia is a much stronger risk factor for myocardial infarction than ischemic stroke. Limited evidence also suggests that vascular risk factors may exert differing magnitudes of risk for ischemic stroke within different cerebral arterial territories. We sought to determine the association between traditional vascular risk factors and the location of ischemic stroke (posterior versus anterior).

METHODS

Consecutive patients with acute ischemic stroke who were admitted to 11 regional stroke centers within the Registry of the Canadian Stroke Network were included in the study sample. The Oxfordshire Community Stroke Project classification was used to distinguish posterior from anterior circulation ischemic stroke. Multivariable logistic regression was applied to determine the association between risk factors (age, gender, diabetes mellitus, hypercholesterolemia, hypertension, atrial fibrillation and smoking history) and posterior (compared to anterior) circulation ischemic stroke.

RESULTS

In total, 8,489 patients with acute ischemic stroke were included. On multivariable analysis, diabetes mellitus (OR = 1.14; 95% CI = 1.02-1.27) was associated with an increased odds of posterior circulation ischemic stroke, whereas age (OR = 0.86; 95% CI = 0.83-0.90), female sex (OR = 0.84; 95% CI = 0.76-0.93), atrial fibrillation (OR = 0.83; 95% CI = 0.74-0.94) and pulmonary edema (OR = 0.74; 95% CI = 0.62-0.88) were related to a reduced odds of posterior compared with anterior circulation ischemic stroke.

CONCLUSIONS

Some traditional vascular risk factors for ischemic stroke appear to exert different magnitudes of risk for posterior compared to anterior circulation ischemic stroke.

Gastrointestinal bleeding after acute ischemic stroke

OBJECTIVE

Recent studies report that major bleeding is associated with a significant increase in mortality after acute coronary syndrome. Major bleeding has also been reported to be common after ischemic stroke, most often gastrointestinal, but its association with clinical outcome is less certain. We sought to describe the incidence, risk factors, and association with clinical outcomes of gastrointestinal bleeding following acute ischemic stroke.

METHODS

Consecutive patients with acute ischemic stroke, who were admitted to 11 Ontario hospitals, were identified from the Registry of the Canadian Stroke Network (2003-2006). Stroke severity was measured using the Canadian Neurological Scale. Dependence was measured with the modified Rankin Scale (mRS), and categorized into strokes with no or mild-moderate dependency (mRS 0-3) and those with severe dependence or death (mRS 4-6). Multivariable logistic regression was used to determine the association between gastrointestinal bleeding and clinical outcome (death or severe dependence at hospital discharge and 6-month mortality), independent of comorbidities and in-hospital medical complications.

RESULTS

In total, 6,853 patients with acute ischemic stroke were included. One hundred (1.5%) patients experienced gastrointestinal hemorrhage during hospitalization, of which 36 (0.5%) required blood transfusion. On multivariable analyses, previous history of peptic ulcer disease, cancer, and stroke severity were independent predictors of gastrointestinal bleeding. Gastrointestinal hemorrhage was independently associated with death or severe dependence at discharge (OR 3.3; 95% CI 1.9-5.8) and mortality at 6 months (HR 1.5; 95% CI 1.1-2.0).

CONCLUSIONS

Gastrointestinal hemorrhage is relatively uncommon after acute ischemic stroke but is associated with increased odds of death and severe dependence.

Epidemiologic predictors of 30-day survival in cerebellar hemorrhage

BACKGROUND

Outcome after cerebellar hemorrhage is relatively poorly understood.

OBJECTIVES

To describe cerebellar hemorrhage and to establish if there were epidemiologic risk factors associated with early mortality.

METHODS

Computerized records were searched to identify intracerebral hemorrhage (ICD-9-CM code 431) from 1986 to 1996 at 2 hospitals. Charts were abstracted using a standardized protocol. The provincial vital statistics registry was used to confirm mortality data. A multivariable logistic regression model was developed to identify predictors of 30-day mortality.

RESULTS

Of 629 identified cases of intracerebral hemorrhage, 79 (12.5%) were cerebellar. The 30-day mortality was 41.7%. Approximately one third (31.7%) had an identifiable underlying cause. The odds of survival at 30 days was significantly reduced (odds ratio = 0.24; 95% confidence interval, 0.08 to 0.74) if the hemorrhage was caused by an identifiable underlying cause.

CONCLUSIONS

Cerebellar hemorrhage with an underlying cause is more likely to be fatal than idiopathic or hypertensive cerebellar hemorrhage.

Deep cerebral venous thrombosis: an illustrative case with reversible diencephalic dysfunction

BACKGROUND

Isolated thrombosis of the deep cerebral veins is rare and its diagnosis can be difficult. Mortality is often high and little is known about the long-term prognosis.

CASE REPORT

We report a 24-year-old woman with akinetic mutism and extensive bilateral thalamic lesions. CT and MRI allowed early diagnosis by demonstrating thrombosis within the internal cerebral veins, without the need for angiography. Heparin treatment was used safely despite the presence of thalamic and intraventricular hemorrhage. After five weeks, the patient recovered rapidly and remains well at 18 months. Serial MRI showed dramatic resolution of the imaging abnormalities.

CONCLUSIONS

The clinical features and characteristic neuroimaging appearance of deep cerebral venous thrombosis should be recognized by physicians caring for stroke patients. Deep cerebral venous thrombosis can produce extensive venous congestion and vasogenic edema without early infarction. Excellent clinical recovery is possible even after severe and prolonged neurological deficits.

Unrecognized persistence of beta-hydroxybutyrate in diabetic ketoacidosis

We quantitated serial serum beta-hydroxybutyrate (beta-OHB) levels using the Ketosite method in 9 children with IDDM who were treated for diabetic ketoacidosis (DKA) and compared them to urinary ketone measurements by dipstick. Persistent elevations of serum beta-OHB were seen in six patients when the urine became clear of ketones; five of these patients had a recurrence of ketonuria. We conclude that many patients recovering from ketoacidosis have continuing elevations of beta-OHB after the urine is free of ketones and this unrecognized abnormality is the likely cause of recurrence of the ketonuria. We recommend that fluid therapy be continued beyond clearance of ketonuria and suggest using the Ketosite method to document restoration of normal serum beta-OHB levels in patients recovering from DKA.

Stroke and pregnancy

BACKGROUND AND PURPOSE

We sought to characterize the subtypes of stroke associated with pregnancy and the puerperium, with emphasis on timing, etiology, risk factors, and outcome.

METHODS

We conducted a retrospective analysis of patients admitted to the Toronto Hospital between January 1, 1980, and June 30, 1997, with a diagnosis of stroke during pregnancy or within 6 weeks postpartum. Strokes were classified as ischemic (arterial or venous) or hemorrhagic (subarachnoid or intracerebral). All patients were investigated with at least a CT scan of the head, and most had MRI and/or cerebral angiography.

RESULTS

Of approximately 50 700 admissions for delivery, 34 patients with a diagnosis of stroke were identified (21 infarctions and 13 hemorrhages). Of patients with infarction, 13 were arterial and 8 were venous. Nine of 13 arterial events occurred in the third trimester or puerperium. Seven of 8 venous occlusions occurred postpartum. An etiologic diagnosis was made in 7 of 13 patients with arterial territory infarction, including cardiac emboli, coagulopathies, and carotid artery dissection. Of patients with hemorrhage, 7 were subarachnoid and 6 were intracerebral. The etiology was identified in 10 patients: 3 were due to ruptured aneurysms, 5 were associated with arteriovenous malformations, and 2 were associated with disseminated intravascular coagulation. All patients with infarction survived, but 3 patients with hemorrhage died.

CONCLUSIONS

The majority of strokes associated with pregnancy were arterial occlusions. Most presented during the third trimester and puerperium.

Rate of stroke recurrence in patients with primary intracerebral hemorrhage

BACKGROUND AND PURPOSE

Primary intracerebral hemorrhage (PICH) is a devastating illness with high early mortality. Hypertension is a major risk factor both for ischemic cerebrovascular disease and for intracranial hemorrhage. Survivors of PICH are at risk for both recurrent hemorrhage and ischemic cerebrovascular disease. We sought to determine the rate of recurrence of ICH or cerebral ischemia in a cohort of PICH patients at the Toronto Hospital, Toronto, Canada.

METHODS

A retrospective search of computerized hospital records from 1986 to 1996 for patients with a discharge diagnosis of intracerebral hemorrhage (International Classification of Diseases, Ninth Revision-Clinical Modification [ICD-9-CM] code 431) was conducted to identify the index cases. Charts were abstracted for demographic and clinical characteristics. CT scans, MR scans, or radiologist reports were reviewed. To determine recurrence, the database was linked to the Ontario Provincial Government Vital Statistics Registry and to the Canadian Institute for Health Information database of hospital discharge abstracts. Logistic regression analysis was used to identify predictive factors for mortality after PICH. A Cox proportional hazards model was fitted to identify predictive factors for recurrent ICH or stroke.

RESULTS

A total of 746 charts were identified by computer search. After abstraction, 423 index patients with PICH were identified. Of these, 27.4% died in the first 30 days of their admission. Predictors of death were age, intraventricular rupture of hemorrhage, and trilobar hemorrhage. The recurrence rate for PICH was 2.4% (95% CI 1.4% to 3. 9%) per year, whereas the recurrence rate for ischemic cerebrovascular disease was 3.0% (95% CI 1.8% to 4.7%) per year. The only significant predictor of readmission for ICH was lobar location of the index hemorrhage, with a hazard ratio of 3.8 (95% CI 1.2 to 12.0).

CONCLUSIONS

PICH has a high 30-day mortality rate. Survival from the initial insult portends a moderate risk of recurrence of 2. 4% per year for PICH and 3.0% per year for ischemic cerebrovascular disease. Patients with PICH are at risk for both ischemic stroke or TIA and recurrent hemorrhage; thus, PICH may be a marker for ischemic stroke. Patients with lobar hemorrhage have a 3.8-fold increased risk of recurrent ICH.

Preventive health care, 1999 update: 2. Echocardiography for the detection of a cardiac source of embolus in patients with stroke. Canadian Task Force on Preventive Health Care

OBJECTIVE

To develop guidelines for the use of echocardiography in the investigation of patients with stroke.

OPTIONS

(1) Routine transthoracic echocardiography (TTE); (2) routine transesophageal echocardiography (TEE); (3) routine TTE followed by TEE if the TTE findings are noncontributory; (4) selective TTE or TEE in patients with cardiac disease who would not otherwise receive anticoagulant therapy.

OUTCOMES

This article reviews the available evidence on the yield of TTE and TEE in detecting cardiac sources of cerebral emboli in patients with stroke, the effectiveness of treatment for cardiac sources of emboli and the effectiveness of screening echocardiography for secondary stroke prevention.

EVIDENCE

MEDLINE was searched for relevant articles published from January 1966 to April 1998; also reviewed were additional articles identified from the bibliographies and citations obtained from experts.

BENEFITS, HARMS AND COSTS

Echocardiography can detect intracardiac masses (thrombus, vegetation or tumour) in about 4% (with TTE) to 11% (with TEE) of stroke patients. The yield is lower among patients without clinical evidence of cardiac disease by history, physical examination, electrocardiography or chest radiography (less than 2%) than among patients with clinical evidence of cardiac disease (less than 19%). The risks of echocardiography to patients are small. TTE has virtually no risks, and TEE is associated with cardiac, pulmonary and bleeding complications in 0.18%. Patients with an identified intracardiac thrombus are at increased risk for embolic events (absolute risk uncertain, range 0%-38%), and this appears to be reduced with anticoagulant therapy (absolute risk reduction uncertain). Anticoagulant therapy carries a risk of major hemorrhage of 1% to 3% per year. The overall effectiveness of echocardiography in the prevention of recurrent stroke is unknown.

VALUES

The strength of evidence was evaluated using the methods of the Canadian Task Force on Preventive Health Care.

RECOMMENDATIONS

There is fair evidence to recommend echocardiography in patients with stroke and clinical evidence of cardiac disease by history, physical examination, electrocardiography or chest radiography (grade B recommendation). There is insufficient evidence to recommend for or against TEE in patients with normal results of TTE (grade C recommendation). There is insufficient evidence to recommend for or against routine echocardiography in patients (including young patients) without clinical cardiac disease (grade C recommendation). Routine echocardiography is not recommended for patients with clinical cardiac disease who have independent indications for or contraindications to anticoagulant therapy (grade D recommendation). There is fair evidence to recommend anticoagulant therapy in patients with stroke and intracardiac thrombus (grade B recommendation). There is insufficient (no) evidence to recommend for or against any specific therapy for patent foramen ovale (grade C recommendation).

VALIDATION

The findings of this analysis were reviewed through an iterative process by the members of the Canadian Task Force on Preventive Health Care.

Low-dose and high-dose acetylsalicylic acid for patients undergoing carotid endarterectomy: a randomised controlled trial. ASA and Carotid Endarterectomy (ACE) Trial Collaborators

BACKGROUND

Endarterectomy benefits certain patients with carotid stenosis, but benefits are lessened by perioperative surgical risk. Acetylsalicylic acid lowers the risk of stroke in patients who have experienced transient ischaemic attack and stroke. We investigated appropriate doses and the role of acetylsalicylic acid in patients undergoing carotid endarterectomy.

METHODS

In a randomised, double-blind, controlled trial, 2849 patients scheduled for endarterectomy were randomly assigned 81 mg (n=709), 325 mg (n=708), 650 mg (n=715), or 1300 mg (n=717) acetylsalicylic acid daily, started before surgery and continued for 3 months. We recorded occurrences of stroke, myocardial infarction, and death. We compared patients on the two higher doses of acetylsalicylic acid with patients on the two lower doses.

FINDINGS

Surgery was cancelled in 45 patients, none were lost to follow-up by 30 days, and two were lost by 3 months. The combined rate of stroke, myocardial infarction, and death was lower in the low-dose groups than in the high-dose groups at 30 days (5.4 vs 7.0%, p=0.07) and at 3 months (6.2 vs 8.4%, p=0.03). In an efficacy analysis, which excluded patients taking 650 mg or more acetylsalicylic acid before randomisation, and patients randomised within 1 day of surgery, combined rates were 3.7% and 8.2%, respectively, at 30 days (p=0.002) and 4.2% and 10.0% at 3 months (p=0.0002).

INTERPRETATION

The risk of stroke, myocardial infarction, and death within 30 days and 3 months of endarterectomy is lower for patients taking 81 mg or 325 mg acetylsalicylic acid daily than for those taking 650 mg or 1300 mg.

Atherosclerotic carotid artery disease in patients with retinal ischemic syndromes

The extracranial carotid systems of 105 patients with retinal ischemia were examined using B-mode ultrasonography with integrated pulsed Doppler. Sixty-four patients had amaurosis fugax (AF), 17 central retinal artery occlusions (CRAO), and 21 branch retinal artery occlusions (BRAO). The prevalence of carotid stenosis (greater than or equal to 60%) ipsilateral to the symptomatic eye was low (16%). Eighty-six percent of AF patients had either no plaque causing less than a 60% stenosis. A significant proportion of subjects with normal duplex scans had alternative explanations for their retinal ischemia (eg, migraine, cardiac embolus). Patients with Hollenhorst plaques were more likely to have stenotic or ulcerated plaque (p = 0.04). The degree of carotid stenosis correlated significantly with the number of vascular risk factors identified in individual patients (p = 0.02). The presence of risk factors was more common in CRAO and BRAO patients compared with the AF group. Combined ultrasound-Doppler investigations of the carotid bifurcation are valuable noninvasive tools for the screening of patients with retinal ischemia.

Resolving metabolic abnormalities in a case of pure alexia

We report resolving metabolic abnormalities corresponding to clinical improvement in a patient with pure alexia secondary to acute cerebral infarction. Local cerebral glucose metabolism (lCMRgl) was measured with positron emission tomography (PET) using 18F-fluorodeoxyglucose (18F-FDG) close to ictus and 4 1/2 months later. Serial CTs and a subsequent MRI demonstrated small, unchanging left-hemispheric lesions involving the area of the lateral geniculate body and the splenium of the corpus callosum. PET demonstrated the evolution of the metabolic abnormality resulting from intrahemispheric (lateral geniculate) and interhemispheric (splenium) disconnection in the absence of occipital lobe infarction. This case illustrates that cerebral disconnection can result in the syndrome of pure alexia. The factors accounting for focal hypometabolism in the absence of cerebral infarction are discussed.

Regional cerebral blood flow in stroke: hemispheric effects of cognitive activity

Regional cerebral blood flow (rCBF) was measured with the xenon-133 inhalation technique in 15 patients with unilateral cerebral infarction and 12 matched controls. Measurements were performed during a standard resting baseline condition and during the performance of standardized verbal analogies and spatial line orientation tasks. Resting and activated CBF were lower in patients than in controls, and there were differences in the hemispheric pattern of activated CBF. Control subjects replicated earlier findings of asymmetric increase in CBF for the cognitive tasks, whereas patients showed abnormalities in lateralized CBF changes consistent with side of infarction. These findings underscore the utility of cognitive challenges in the study of rCBF in stroke. This can lead to an experimental paradigm in clinical studies of the relation between behavioral deficits and regional brain dysfunction and may also improve the utility of CBF measurements in clinical settings.

Recovery of vision after ischemic lesions: positron emission tomography

We used [18F]fluoro-2-deoxyglucose positron emission tomography (PET) to study serial changes in the local cerebral metabolic rate of glucose in 5 patients with ischemic lesions of the posterior afferent visual system causing homonymous visual field defects. All 5 patients had striking impairment of glucose metabolism in the striate cortex shortly after ictus. In 2 patients, visual field defects abated, and repeat PET scans showed reduced size of the metabolic lesion and improvement of striate metabolism. Three patients did not recover vision, and repeat PET scans did not show improvement. Patients who recovered vision had ischemic lesions outside the occipital lobe, while those who did not experience improvement had primary damage to the occipital lobe itself.

Regional brain function in schizophrenia. I. A positron emission tomography study

Local cerebral glucose metabolism was determined with 18-F-fluorodeoxyglucose using positron emission tomography in a sample of 12 unmedicated schizophrenics and 12 matched normal controls. The data were analyzed for absolute metabolic rates and region/whole-brain ratios using the cortical-subcortical, antero-posterior, and laterality dimensions. Lobar areas within cortical regions were also compared. Across groups, subcortical metabolism was higher than cortical metabolism. Patients had lower metabolism, cortically and subcortically, and a steeper subcortical to cortical gradient. Patients with higher scores on the Brief Psychiatric Rating Scale had higher absolute metabolism and higher left relative to right hemispheric metabolism than did patients with lesser severity. The results did not show "hypofrontality" in schizophrenia. These findings provide some support for cerebral dysfunction in schizophrenia and indicate the need for further examination of the cortical-subcortical dimension.

Early mortality following stroke: a prospective review

Analysis of early deaths after stroke is important, since some deaths may be preventable. Previous studies have relied on retrospective and often incomplete clinical data, for comparison with pathological findings. The present study is based on 1073 consecutive stroke patients admitted to an intensive care stroke unit from a well-defined population. There were 212 deaths within the first 30 days, yielding a mortality rate of 20%. Clinical, radiological, and laboratory data were collected prospectively according to a standardized protocol. Autopsies were performed on 90 of the 212 patients, and CT scanning on a further 27. Early mortality after stroke exhibits a bimodal distribution. One peak occurs during the first week, and a second during the second and third weeks. The majority of deaths in the first week are due to transtentorial herniation. Of these, deaths due to hemorrhage usually occur within the first three days, whilst deaths due to infarction peak between the third and sixth day post ictus. After the first week, deaths due to relative immobility (pneumonia, pulmonary embolism and sepsis) predominate, peaking towards the end of the second week. Cardiac deaths occur throughout the first month, and unfortunately account for many deaths in patients with small functional deficits.