Noninvasive assessment of intracranial perfusion in acute cerebral ischemia

New Regression Equation for 123I-IMP Non-invasive Cerebral Blood Flow Measurement Using the Graph Plot Method

PURPOSE

A graph plot (GP) method using 123I-N-isopropyl-p-iodoamphetamine (123I-IMP) has been proposed as a simple and non-invasive estimation of quantitative cerebral bloodflow (CBF). A regression equation for the GP method was estimated by the data of resting state. Therefore, the accuracy of CBF values in high flow range may be an underestimated possibility in this method.The aim of this study was to formulate a new regression equation for the GP method by the data of resting state and acetazolamide (ACZ) challenge, and to clarify the accuracy of it.

METHODS

The images of 26 consecutive patients who underwent both 123I-IMP chest radioisotope-angiography (RIA) and single photon emission computed tomography (SPECT) examinations were used to construct the new regression equation. Examinations of the resting state and ACZ challenge were performed in different days. All patients were analyzed by both the GP method and autoradiography (ARG) method which is the conventional examination with the one-point arterial blood sampling. A linear regression equation between the index of the input function was obtained by the GP method and CBF value of ARG. The linear regression equation based on the resting data was compared with the equation based on the resting and ACZ challenge (rest+stress) data.

RESULTS

Goodliner correlation was obtained between the index of the input function obtained by the GP method and CBF value of the ARG method in the rest+stress state (y=2.75x+15.1, r=0.78). In contrast, correlation results between the index of the input function obtained by the GP method and CBF value of the ARG method in the resting state was expressed as y=2.28x+18.4, r=0.54 rCBF values based on the resting data was 20% underestimated in the high flow range compared with values based on the rest+stress data.

CONCLUSION

The new linear regression equation for the GP method is useful for clinical study. Key words: non-invasive cerebral blood flow measurement method, graph plot (GP), autoradiography (ARG), 123I-N-isopropyl-p-iodoamphetamine (123I-IMP).

Imaging of cerebral ischemia: from acute stroke to chronic disorders

Cerebral ischemia manifests widely in patient symptoms. Along with the clinical examination, imaging serves as a powerful tool throughout the course of ischemia-from acute onset to evolution. A thorough understanding of imaging modalities, their strengths and their limitations, is essential for capitalizing on the benefit of this complementary source of information for understanding the mechanism of disease, making therapeutic decisions, and monitoring patient response over time.

Stroke in the young: The multiethnic prospective durban stroke data bank results

AIM

To determine the clinical syndromes, etiopathogenesis, and prognostic factors in a prospectively evaluated multiethnic young stroke population.

METHODS

Only first-ever patients with a World Heath Organization definition of stroke and anatomic brain imaging were included. A hierarchy of investigative modalities divided into three tiers was applied and a range of standardized scales scored in each patient. This allowed quantification of clinical deficit, etiopathogenesis, disability, and handicap. Standardized stroke scales included the Canadian Neurological Scale (CNS), the Oxfordshire Community Stroke Project (OCSP) clinical stroke scale, and TOAST (Trial of Org 10172 in Acute Stroke Study) etiological classification. Disability was measured with the Barthel Index and handicap with the Rankin Scale; cognitive impairment was separately evaluated according to predefined criteria. A prognostication measure was made in some patients with the Cerebral Perfusion Index (CPI).

RESULTS

A total of 236 patients was evaluated of whom 64 were excluded because of no lesion consistent with stroke on brain scanning leaving 172 for analysis. There were 87 women, 85 men, with a mean age of 43.8 years (range, 15 to 49 years). Despite many different predefined symptoms, 38 patients (22%) could not be classified. Hypertension (31%) and smoking (19%) were the most commonly encountered risk factors, with more recently determined risk factors such as infection (6%) and emotional stress (5%) relatively frequent. With respect to etiology, the TOAST category "other" was the most numerous group, numbering 93 of 172 (55%) with prothrombotic states in 25 (15%), vasculitis in 21 (12%), and dissection in 12 (7%) being the most frequent causes. Proportions of the remaining categories were small vessel disease (16%), cardioembolism (13%), large vessel disease (10%), and unknown (6%). X-square analysis for an association between the clinical OCSP and TOAST classifications was not significant. Severity of stroke was generally mild as judged by the CNS and Rankin scales. A high proportion of patients had cognitive impairment (54%). A cerebral perfusion index was possible in 31 patients, most of whom had a medium prognosis.

CONCLUSION

in this hospital-based consecutive series, most young stroke patients in our region were grouped into nonatherogenic (mostly prothrombotic states, infection asssociated and dissection) and noncardiac causes with a definite or probable cause found in 94%. The wide variety of stroke symptoms recorded in this study underscores the heterogeneity of stroke presentation and caution in the emergent evaluation of patients. Cognitive impairment in the majority of stroke patients in the acute and subacute stroke period has important implications for degree of clinical deficit especially as it applies to stroke scales and treatment trials.

Xenon-enhanced computed tomography cerebral blood flow measurements in acute cerebral ischemia: Review of 56 cases

OBJECTIVE

Ischemic stroke must be diagnosed promptly if patients are to be treated with thrombolytic therapy. The diagnosis of acute cerebral ischemia, however, is usually based on clinical and computed tomography (CT) scan findings. CT scans are often normal in the first few hours after stroke. The purpose of this study was to determine whether Xenon-enhanced CT (XeCT) cerebral blood flow (CBF) studies could increase the sensitivity of stroke detection in the acute stage.

METHODS

CBF studies performed within 8 hours of symptom onset were evaluated in 56 patients who presented with hemispheric stroke symptoms. Mean CBF in the symptomatic vascular territory was calculated and compared with the corresponding contralateral area. CBF values below 18 mL/100g/min on 2 adjacent regions of interest were considered ischemic lesions. CT scans and angiograms were compared with the XeCt findings. Neurological condition on admission and discharge was evaluated by using National Institutes of Health Stroke Scale (NIHSS) scores.

RESULTS

The mean NIHSS score on admission was 12+/-5. Early CT scans were abnormal in 28 (50%) patients. There were 9 (16%) patients who had normal XeCT scans because of spontaneous reperfusion of the ischemic area. XeCT studies showed an ischemic lesion in 47 (84%) patients. In these patients, the mean CBF in the affected vascular territory was 16+/-8 mL/100g/min compared with 35+/-13 mL/100g/min in the contralateral specular territory (P<0.001). There were no false positive or negative XeCT studies, and the location of the perfusion defect corresponded with the CT and/or angiographic findings in all cases. Eight patients died (14%), and the 48 survivors (86%) had a mean NIHSS score of 9+/-6 on discharge.

CONCLUSIONS

CBF measurements were correlated with the CT and angiographic results and greatly assisted in the diagnosis of acute ischemic stroke. XeCT studies used for estimating the location and extent of cerebral ischemia may be important in the triage of patients for acute stroke therapy.

Crossed cerebellar hypoperfusion in hyperacute ischemic stroke

OBJECTIVE

In chronic stage of cerebral hemispheric infarction, contralateral cerebellar blood flow and metabolism are depressed, which is known as crossed cerebellar diaschisis (CCD). The present study was performed to elucidate (1) whether the diaschisis occurs in hyperacute stage of ischemic stroke when computed tomography (CT) scans is not able to identify infarction, and (2) which site of lesion in the cerebrum is responsible for the depression in contralateral cerebellar blood flow.

METHODS

Single photon emission computed tomography was performed in 21 patients with middle cerebral artery (MCA) embolic infarction within 6 h of the onset (3.2+/-1.1 h, mean+/-S.D.). Regions of interest (ROIs) were symmetrically located in the cerebral hemispheres including cerebral cortex and subcortex, and in the cerebellar hemispheres.

RESULTS

The side-to-side ratio of cerebellar blood flow ipsilateral to that contralateral to cerebral infarct was significantly increased compared with that in normal control (P<0.001), indicating that contralateral cerebellar blood flow was significantly depressed. In hyperacute stage, the ratio of cerebellar blood flow appeared to be associated with the ratio of cerebral blood flow in whole hemispheres (r=0.44, P<0.05), in anterior frontal lobe (r=0.44, P<0.05) and in anterior temporal lobe (r=0.58, P<0.01), but not in infarct areas (r=0.26, P=0.3). Stepwise regression analysis revealed that the ratios in cerebellar hemispheres were associated with those in anterior temporal lobe (multiple regression analysis, r=0.58, P<0.01).

CONCLUSIONS

Crossed cerebellar diaschisis occurs at hyperacute stage of stroke of the MCA infarction. It may be related to the hypoperfusion in the anterior frontal and anterior temporal lobes of the cerebrum where regional blood flow is decreased by ischemic infarction per se or by ipsilateral hemispheric depression from infarct area (diaschisis mechanism).

Timing of recanalization after tissue plasminogen activator therapy determined by transcranial doppler correlates with clinical recovery from ischemic stroke

BACKGROUND

The duration of cerebral blood flow impairment correlates with irreversibility of brain damage in animal models of cerebral ischemia. Our aim was to correlate clinical recovery from stroke with the timing of arterial recanalization after therapy with intravenous tissue plasminogen activator (tPA).

METHODS

Patients with symptoms of cerebral ischemia were treated with 0.9 mg/kg tPA IV within 3 hours after stroke onset (standard protocol) or with 0.6 mg/kg at 3 to 6 hours (an experimental institutional review board-approved protocol). National Institutes of Health Stroke Scale (NIHSS) scores were obtained before treatment, at the end of tPA infusion, and at 24 hours; Rankin Scores were obtained at long-term follow-up. Transcranial Doppler (TCD) was used to locate arterial occlusion before tPA and to monitor recanalization (Marc head frame, Spencer Technologies; Multigon 500M, DWL MultiDop-T). Recanalization on TCD was determined according to previously developed criteria.

RESULTS

Forty patients were studied (age 70+/-16 years, baseline NIHSS score 18.6+/-6.2). A tPA bolus was administered at 132+/-54 minutes from symptom onset. Recanalization on TCD was found at the mean time of 251+/-171 minutes after stroke onset: complete recanalization occurred in 12 (30%) patients and partial recanalization occurred in 16 (40%) patients (maximum observation time 360 minutes). Recanalization occurred within 60 minutes of tPA bolus in 75% of patients who recanalized. The timing of recanalization inversely correlated with early improvement in the NIHSS scores within the next hour (polynomial curve, third order r(2)=0.429, P<0.01) as well as at 24 hours. Complete recanalization was common in patients who had follow-up Rankin Scores if 0 to 1 (P=0.006). No patients had early complete recovery if an occlusion persisted for >300 minutes.

CONCLUSIONS

The timing of arterial recanalization after tPA therapy as determined with TCD correlates with clinical recovery from stroke and demonstrates a 300-minute window to achieve early complete recovery. These data parallel findings in animal models of cerebral ischemia and confirm the relevance of these models in the prediction of response to reperfusion therapy.

Transcranial Doppler ultrasonography: year 2000 update

In this update, the main clinical applications of transcranial Doppler ultrasonography are reassessed. A specific format for technology assessment, personal experience, and an extensive review of the literature form the basis of the evaluation. The document is approved by the American Society of Neuroimaging and the Neurosonology Research Group of the World Federation of Neurology.

Cerebrovascular findings in Takayasu disease

The authors define the frequency, nature, and extent of cerebrovascular sequelae of Takayasu arteritis using functional imaging. Retrospective analysis of the cases derived from the Durban Stroke Data Bank (n = 1100) and Durban Metropolitan Vascular Surgery Database (n = 5300) consisted of evaluation by contemporary neuroimaging modalities including single positron emission computed tomography (SPECT), magnetic resonance imaging (MRI) diffusion scanning, and transcranial Doppler (TCD). Of all the patients identified with Takayasu disease (n = 142), 29 (20%) patients were identified with a primarily cerebrovascular presentation. The recent advent of modern functional imaging techniques allowed only the 10 most recent patients with a cerebrovascular presentation to be evaluated. Of these 10, 8 (80%) had normal neurologic deficit scores (Canadian neurologic score) and 9 (90%) were not disabled as determined by handicap scores (Rankin). The anatomic brain scans (9 MRI, 1 CT) were normal in 5 patients (50%). In 7 patients, transcranial Doppler sonography revealed increased velocities mainly in the anterior circulation with turbulence that was not circumscribed. Single positron emission computed tomography scanning revealed areas of hypoperfusion, mostly multiple, in all of the 7 cases investigated. The cerebral perfusion index was determined in 7 patients, with a good prognosis in 2 patients and a moderate prognosis in 5. Cerebral effects of Takayasu disease are best monitored by a combination of clinical and functional imaging such as TCD and SPECT scanning.

99m technetium-ethyl-cysteinate-dimer single-photon emission CT can predict fatal ischemic brain edema

BACKGROUND AND PURPOSE

We sought to study the prognostic value of early 99mtechnetium-ethyl-cysteinate-dimer single-photon emission CT (99mTc-ECD SPECT) for fatal ischemic brain edema in patients with middle cerebral artery (MCA) stroke compared with the prognostic value of CT and of clinical findings.

METHODS

We prospectively studied 108 patients clinically, with 99mTc-ECD SPECT, and with CT within 6 hours of symptom onset (Scandinavian Stroke Scale <40 points) appropriate to MCA ischemia. The follow-up consisted of Scandinavian Stroke Scale and CT on days 1 and 7, Barthel Index, and Modified Rankin Scale after 3 months. An activity deficit of the complete MCA territory on the SPECT scans and a parenchymal hypoattenuation of the complete MCA territory on CT scans were considered as predictors for a fatal MCA infarction due to mass effect and midbrain herniation.

RESULTS

In 11 of 108 patients (10%), the MCA infarction was the cause of death. The sensitivity of SPECT for fatal outcome was 82% in both visual and semiquantitative analyses, while specificity was 98% and 99%, respectively. The sensitivity and specificity of baseline CT were 36% and 100%, respectively; the sensitivity and specificity of clinical findings (Scandinavian Stroke Scale, depressed level of consciousness, gaze deviation) varied from 36% to 73% and from 45% to 88%, respectively. In a multivariate logistic regression model, only SPECT findings were found to be independent predictors of malignant MCA infarction/death.

CONCLUSIONS

We were able to identify patients with fatal MCA infarction with high accuracy by using 99mTc-ECD SPECT within 6 hours of stroke onset. This technique offers great potential to select stroke patients for specific therapies, eg, decompressive hemicraniectomy, soon after onset of symptoms.

Differentiation between transient ischemic attack and ischemic stroke within the first six hours after onset of symptoms by using 99mTc-ECD-SPECT

The aim of this study was to define the accuracy of 99mTc-ethyl cysteinate dimer-single photon emission computed tomography (99mTc-ECD-SPECT) in distinguishing transient ischemic attack from completed ischemic stroke at early stages after the onset of symptoms. In a prospective study we examined 82 patients within 6 hours after the onset of symptoms (neurologic deficit caused by middle cerebral artery ischemia) using both 99mTc-ECD-SPECT and computed tomography (CT). The follow-up was based on Scandinavian Stroke Scale (SSS) 24 hours and 5-7 days, as well as on CT 7 days, after the event. SPECT evaluation was performed both visually and using semiquantitative region-of-interest (ROI) analysis. According to visual SPECT analysis, on admission 59 of 82 patients had activity deficits in the symptomatic hemisphere. After 7 days, all these patients had neurologic symptoms (SSS 28 +/- 12 points), caused by a cerebral infarction as evidenced with CT. Twenty-three of 82 patients displayed no early activity deficit despite clinical symptoms. None of these patients had neurologic symptoms after 7 days (indicating transient ischemic attack or prolonged reversible ischemic neurologic deficit). In the semiquantitative SPECT analysis, all patients had abnormal count densities in the respective ROI (activity < 90% compared with the contralateral side). All patients with transient ischemia (n = 23) had count rate densities more than 70% of the respective contralateral ROI, whereas all patients with subsequent infarction (n = 59) had values < 70%. Use of 99mTc-ECD-SPECT allows transient ischemia to be distinguished from ischemic infarction using relative regional activity thresholds within the first 6 hours after onset of symptoms.

Simple visual analysis of brain perfusion on HMPAO SPECT predicts early outcome in acute stroke

BACKGROUND AND PURPOSE

Single-photon emission computed tomography (SPECT) is used in patients with acute stroke but as yet is of controversial value. We investigated an association of brain perfusion changes in stroke patients with stroke severity, volume of brain damage, and recovery.

METHODS

Consecutive patients with hemispheric stroke were studied prospectively with serial neurological examinations using the Canadian Neurological Scale (CNS), CT. and 99mTc-hexamethylpropyleneamine oxime (HMPAO) SPECT. Visual SPECT patterns of brain perfusion (normal, high, mixed, low, and absent) were correlated with the severity of stroke, lesion volume, and short-term outcome.

RESULTS

SPECT studies were performed in a total of 458 consecutive acute stroke patients within 2 weeks after the onset (mean time, 5 days; range, 1 to 12 days). SPECT perfusion patterns correlated with stroke severity (CNS score) during the first 2 weeks (P < .001). Focal absence of brain perfusion on SPECT was associated with the largest volume of brain damage: 104 +/- 84 mL (P < .0001). SPECT perfusion patterns predicted the shortterm outcome: 97% of patients with normal and increased HMPAO uptake made good recovery, 52% of those with decreased perfusion had moderate stroke, and 62% of patients with absent patterns fared badly. In a multiple logistic regression model, admission CNS scores had the strongest predictive value (P = .0001). SPECT had its own prognostic value independent of clinical judgment (P = .03). SPECT statistically improved predictive power of the CNS score (+1% receiver operating characteristic curve area, [X2]2 = 20, P < .001) because of distinction between focal decrease or absence of brain perfusion in patients studied within the first 72 hours of stroke.

CONCLUSIONS

Visual brain perfusion patterns correlate with the extent, severity, and short-term outcome of hemispheric stroke. HMPAO SPECT may improve the prognostic value of clinical examination if performed during the first 72 hours of stroke.

Clinical significance of increased uptake of HMPAO on brain SPECT scans in acute stroke

Single-photon emission computed tomography (SPECT) with 99mtechnetium-hexamethylpropylamineoxime (HMPAO) noninvasively shows brain perfusion in patients after acute stroke. However, the clinical significance of the increased HMPAO uptake remains unclear. In this study, consecutive patients with hemispheric hemorrhagic and ischemic stroke admitted to the hospital were evaluated prospectively. The increased uptake of HMPAO was determined by visual analysis of SPECT images. The pathogenic mechanism of ischemic stroke was determined using the clinical and computed tomography (CT) criteria including the Toronto Embolic Scale. Of the 500 consecutive patients with acute hemispheric stroke, SPECT was performed in 458 at a mean time 5 +/- 7 days after the onset of symptoms. A strong association was found between SPECT perfusion patterns and pathogenic subtypes of stroke (p < 0.0001). Thus, in 95% of patients with intracerebral hemorrhage the focal absence of perfusion was found, and 26% of lacunar infarctions presented with a normal SPECT appearance. The mean volume of lacunar lesions that did not produce significant abnormalities on SPECT was 2.5 +/- 1.2 ml. Increased HMPAO uptake was associated with a cardioembolic mechanism of stroke: High and mixed perfusion patterns were present subacutely in 29% of patients with cardioembolic stroke, compared to 15% of patients with other types of ischemic stroke (p < or = 0.0006). The increased uptake of HMPAO on SPECT as determined by visual analysis is associated with a cardioembolic mechanism of cerebral ischemia, which could be explained by glutathione-mediated trapping of the tracer during reperfusion and later in newly developed granulation tissue. HMPAO-SPECT may help in early management decisions since it indicates stroke pathogenesis and evolution.