L. M. P. Ramos

Prevalence of cerebral white matter lesions in elderly people: a population based magnetic resonance imaging study. The Rotterdam Scan Study

OBJECTIVE White matter lesions are often seen on MR scans of elderly non-demented and demented people. They are attributed to degenerative changes of small vessels and are implicated in the pathogenesis of cognitive decline and dementia. There is evidence that especially periventricular white matter lesions are related to cognitive decline, whereas subcortical white matter lesions may be related to late onset depression. The frequency distribution of subcortical and periventricular white matter lesions according to age and sex reported. METHODS A total of 1077 subjects aged between 60–90 years were randomly sampled from the general population. All subjects underwent 1.5T MR scanning; white matter lesions were rated separately for the subcortical region and the periventricular region. RESULTS Of all subjects 8% were completely free of subcortical white matter lesions, 20% had no periventricular white matter lesions, and 5% had no white matter lesions in either of these locations. The proportion with white matter lesions increased with age, similarly for men and women. Women tended to have more subcortical white matter lesions than men (total volume 1.45 ml v 1.29 ml; p=0.33), mainly caused by marked differences in the frontal white matter lesion volume (0.89 ml v 0.70 ml; p=0.08). Periventricular white matter lesions were also more frequent among women than men (mean grade 2.5 v 2.3; p=0.07). Also severe degrees of subcortical white matter lesions were more common in women than in men (OR 1.1; 95% confidence interval (95% CI) 0.8–1.5) and periventricular white matter lesions (OR 1.2; 95% CI 0.9–1.7), albeit that none of these findings were statistically significant. CONCLUSIONS The prevalence and the degree of cerebral white matter lesions increased with age. Women tended to have a higher degree of white matter lesions than men. This may underlie the finding of a higher incidence of dementia in women than in men, particularly at later age.

Impact of microembolism and hemodynamic changes in the brain during carotid endarterectomy.

Background and Purpose Monitoring of carotid endarterectomy with electroencephalography and transcranial Doppler ultrasonography provides instantaneous information about hemodynamic changes and embolic signals. However, a relation between these findings and intraoperative infarcts has not yet been demonstrated. Methods In this study we compared preoperative and postoperative computed tomographic scans (58 patients) or magnetic resonance imaging (40 patients) of the brain, assessed by two independent observers, to detect intraoperative infarcts, and we related any such new lesions to the findings of intraoperative monitoring. Results In the computed tomography series one intraoperative infarct occurred, with corresponding clinical deficits. In the magnetic resonance group four patients developed new lesions that occurred intraoperatively, all of which were clinically silent. There was a significant relation between the number of embolic signals during the surgical dissection of the carotid artery and the occurrence of intraoperative infarcts (P<.005). Three of the four infarcts were of the lacunar type; the fourth patient had a border-zone infarct, associated not only with many embolic signals but also with low flow during cross-clamping. There were no demonstrable ultrasound side effects on brain tissue. Conclusions Embolic signals detected by transcranial Doppler monitoring in the dissection phase of carotid endarterectomy show a significant relation to new ischemic lesions and therefore are potentially harmful. The phenomenon should alert the vascular surgeon.

Reproducibility of Measurements of Cerebral Infarct Volume on CT Scans

Background and Purpose — Infarct volume is increasingly used as an outcome measure in clinical trials of therapies for acute ischemic stroke. We tested which of 5 different methods to measure infarct size or volume on CT scans has the highest reproducibility. Methods — Infarct volume and total intracranial volume were measured with Leica Q500 MCP image analysis software, or with a caliper, on 38 CT scans of patients who participated in the Tirilazad Efficacy Stroke Study II (TESS II). The scans were performed 8 days (±2 days) after the onset of symptoms. The 5 methods tested were based on (1) semiautomated pixel thresholding, (2) manual tracing of the perimeter, (3) a stereological counting grid, (4) measurement of the 3 largest diameters, and (5) the single largest diameter. The measurements were performed independently by 2 observers; the first observer performed all measurements twice. Results — The single largest diameter did not correlate well with infarct volume. Of the other methods, manual tracing of the perimeter of the infarct had the lowest intraobserver and interobserver variability: coefficients of variation were 8.6% and 14.1%, respectively. For total intracranial volume, manual tracing also provided the highest reproducibility: intraobserver and interobserver coefficients of variation were 3.3% and 4.9%, respectively. Conclusions — Manual tracing of the perimeter is the most reproducible method for measuring the volumes of the infarct and the total intracranial space in multicenter trials of therapies for acute ischemic stroke.

Initial and follow-up screening for aneurysms in families with familial subarachnoid hemorrhage

Background and Objective: In families with two or more relatives with subarachnoid hemorrhage (SAH), other first-degree relatives have an increased risk of SAH. We studied the presence of unruptured intracranial aneurysms in 125 members of 23 families with familial SAH, defined as two or more affected first-degree relatives, in a cross-sectional design. Methods: MR angiography was performed in 116 relatives; CT angiography was performed in the remaining 9 relatives because they had been treated for intracranial aneurysms in the past. Results: Overall, we found 16 aneurysms in 10 of 125 relatives (8%; 95% CI, 4 to 14%). Of the nine patients with previous surgery for ruptured or unruptured intracranial aneurysms, three had new aneurysms. Two factors were associated with a significantly higher risk of intracranial aneurysms: 1) a history of treatment for ruptured or unruptured intracranial aneurysms (relative risk 5.5; 95% CI, 1.7 to 17.8) and 2) having three or more affected relatives (relative risk 3.3; 95% CI, 1.0 to 10.6). Siblings tended to have a higher risk of intracranial aneurysms than did children of SAH patients, although the difference was not significant. Conclusions: Because the yield is high, screening is recommended in first-degree members of families with familial SAH. Repeated screening should be considered in relatives who have been treated for familial intracranial aneurysms.

Perimesencephalic Hemorrhage Exclusion of Vertebrobasilar Aneurysms With CT Angiography

BACKGROUND AND PURPOSE It is important to recognize a perimesencephalic pattern of hemorrhage in patients with subarachnoid hemorrhage (SAH), because in 95% of these patients the cause is nonaneurysmal and the prognosis is excellent. The purpose of this study was to investigate whether CT angiography can accurately exclude vertebrobasilar aneurysms in patients with perimesencephalic patterns of hemorrhage and therefore replace digital subtraction angiography (DSA) in this setting. METHODS In 40 patients with posterior fossa SAH as shown on unenhanced CT, 2 radiologists independently evaluated unenhanced CT for distinguishing between perimesencephalic and nonperimesencephalic pattern of hemorrhage and assessed CT angiography for detection of aneurysms. All patients subsequently underwent DSA or autopsy. RESULTS Observers agreed in 38 of 40 patients (95%) in differentiating perimesencephalic and nonperimesencephalic patterns of hemorrhage on unenhanced CT. On the CT angiograms, both observers detected a vertebrobasilar aneurysm in 16 patients and no aneurysm in 24 patients. These findings were confirmed by DSA or autopsy. No patients with a perimesencephalic pattern of hemorrhage were found to have an aneurysm on either CT angiography or DSA. CONCLUSIONS Good recognition of a perimesencephalic pattern of hemorrhage is possible on unenhanced CT, and CT angiography accurately excludes and detects vertebrobasilar aneurysms. DSA can be withheld in patients with a perimesencephalic pattern of hemorrhage and negative CT angiography.

Carotid angiography in patients with lacunar infarction. A prospective study.

We prospectively studied the results of carotid angiography in 45 patients with transient or nondisabling neurologic deficits caused by lacunar infarction in the internal capsule or corona radiata and demonstrated by computed tomography. An ipsilateral stenosis at the bifurcation of the internal carotid artery was found in 14 patients (31%, 95% confidence limits 18-47%), seven of whom also had stenosis of the contralateral internal carotid artery. In previous studies an average of 65% of patients with transient hemispheric deficit had internal carotid artery stenosis or occlusion. Hypertension and hypertensive retinal vasculopathy assessed by fundus photographs were found in most patients, but not significantly more often in the patients without internal carotid artery stenosis. Our findings support the notion that small vessel disease rather than emboli from the carotid bifurcation is the most common cause of lacunar infarction.

Prognostic value of perfusion- and diffusion-weighted MR imaging in first 3 days of stroke

Abstract. The aim of this study was to evaluate the differences in cerebral perfusion seen on mean transit time (MTT) and cerebral blood volume (CBV) maps and to assess the subsequent prognostic value of the MTT–DWI (diffusion-weighted MRI) and CBV–DWI mismatch in the first three days of stroke on lesion enlargement and clinical outcome. In 38 patients, imaged 1–46 h after onset of symptoms, lesion volumes on proton-density (PD)-weighted MRI, DWI and PWI (both MTT and CBV maps) were compared with lesion volumes on follow-up PD-weighted scans, and to clinical outcome (National Institutes of Health Stroke Scale, Barthel index, and Rankin scale). The MTT-CBV, MTT–DWI and CBV–DWI mismatches were compared with change in lesion volume between initial and follow-up PD-weighted scans. Lesion volume on both DWI and PWI correlated significantly with clinical outcome parameters (p < 0.001) with strongest correlation for lesion volume on CBV. Perfusion–diffusion mismatches were found for both CBV and MTT and correlated significantly with lesion enlargement on PD-weighted imaging with strongest correlation for the CBV–DWI mismatch. The CBV–DWI mismatch has the highest accuracy in predicting lesion size on follow-up imaging and in predicting clinical outcome. Lesion volume measurements on CBV maps have a higher specificity than on PD-weighted, MTT or DWI images in predicting clinical follow-up imaging and in predicting clinical outcome.

Altered flow territories after extracranial-intracranial bypass surgery.

OBJECTIVE: To prevent stroke after carotid sacrifice and to augment cerebral perfusion in patients with internal carotid artery (ICA) occlusion, high-flow extracranial-intracranial (EC-IC) bypass operations are performed. Although the function and efficacy of the bypass is monitored during surgery, the postoperative flow through the bypass is significantly lower than the flow in the contralateral ICA. Thus far, it is unknown whether decreased bypass flow is caused by a low tissue perfusion or by a relatively small flow territory. METHODS: Seven patients, four with an atherosclerotic ICA occlusion and three with a giant aneurysm of the ICA, were investigated; each underwent a high-flow EC-IC bypass and permanent occlusion of the ICA. Cerebral blood flow was measured with arterial spin labeling perfusion magnetic resonance imaging. Separate flow territory mapping of the EC-IC bypass, contralateral ICA, and posterior circulation was performed with selective arterial spin labeling magnetic resonance imaging. RESULTS: No significant difference was found in cerebral blood flow between the hemisphere ipsilateral to the EC-IC bypass (70.9 ± 11.3 ml/min/100 g tissue), contralateral to the EC-IC bypass (71.9 ± 14.3 ml/min/100 g tissue), and comparable findings in 50 healthy control participants (69.1 ± 17.5 ml/min/100 g tissue). Paired analysis of the individual flow territories demonstrated a 15% volume reduction (P = 0.018) in flow territory of the EC-IC bypass compared with the contralateral side. CONCLUSION: In the present study, we demonstrate the feasibility of selective arterial spin labeling magnetic resonance imaging for clinical follow-up of patients after high-flow EC/IC bypass surgery, providing both information on flow territories and the level of regional cerebral blood flow.

Blood supply of the posterior cerebral artery by the carotid system on angiograms

Background and Purpose Occipital lobe infarcts are traditionally attributed to vertebrobasilar disease. However, anatomical studies indicate that in some people the supply of the posterior cerebral artery is via the carotid system. We investigated how often such a developmental variant in the cerebral blood supply was present during life. Methods We retrospectively studied 212 conventional four-vessel cerebral angiograms. Eighteen subjects were excluded beforehand, because of vascular abnormalities causing important hemodynamic changes. We determined whether a fetal variant was present, and in other cases whether there was a functioning posterior communicating artery. Results In 11 % of hemispheres the posterior cerebral artery was exclusively supplied by the internal carotid artery; in a further 46 % of hemispheres the internal carotid artery might contribute, via a patent posterior communicating artery. In 75 % of subjects the internal carotid artery contributed in at least one hemisphere to the blood flow of the posterior cerebral artery. Conclusions The implication of our findings is that an occipital lobe infarct can be caused by ipsilateral carotid disease in a proportion of cases between 10 and 60 %. This implies that carotid endarterectomy might be beneficial in some patients with severe carotid stenosis and infarction in the territory of the posterior cerebral artery.

Ischaemic stroke in the basal ganglia and internal capsule in childhood

Ischaemic stroke in childhood is rare. In particular, there have only been a few reports of lacunar infarcts in children. In this study, four children with true lacunar infarcts and four with larger subcortical infarcts are described. We compare the clinical features and the possible pathogenesis of ischaemic strokes in the basal ganglia and internal capsule in childhood with those in adults, and discuss diagnostic and therapeutic management.