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Andrew M Demchuk

Publications and source records attributed to Andrew M Demchuk.

At least 37 records · Page 2Linked to original sources
PubMed2005

A novel method to derive separate gray and white matter cerebral blood flow measures from MR imaging of acute ischemic stroke patients.

Perfusion-weighted imaging (PWI) measures can predict tissue outcome in acute ischemic stroke. Accuracy might be improved if differential tissue susceptibility to ischemia is considered. We present a novel voxel-by-voxel analysis to characterize cerebral blood flow (CBF) separately in gray (GM) and white matter (WM). Ten patients were scanned with inversion-recovery spin-echo EPI (IRSEPI), diffusion-weighted imaging (DWI), PWI<6 h from onset and fluid attenuated inversion-recovery (FLAIR) at 30 days. Image processing included coregistration to PWI, automatic segmentation of IRSEPI into GM, WM and CSF and semiautomatic segmentation of DWI/FLAIR to derive the acute and 30-day lesions. Five tissue compartments were defined: (1) 'Core' (abnormal acutely and at 30 days), (2) 'Growth' (or 'infarcted penumbra', abnormal only at 30 days), (3) 'Reversed' (abnormal acutely but normal at 30 days), (4) 'MTT-Delayed ' (tissue with delayed mean transit time but not part of the acute or 30-day lesion), and (5) 'Normal' brain. Cerebral blood flow in GM and WM of each compartment was obtained from quantitative maps. Gray matter and WM mean CBF in the growth region differed by 5.5 mL/100 g min (P=0.015). Mean CBF also differed significantly within normal and MTT-Delayed compartments. The difference in the reversed region approached statistical significance. In core, GM and WM CBF did not differ. The results suggest separate ischemic thresholds for GM and WM in stroke penumbra.

Aged↗
PubMed2005

MR perfusion and diffusion in acute ischemic stroke: human gray and white matter have different thresholds for infarction.

It is thought that gray and white matter (GM and WM) have different perfusion and diffusion thresholds for cerebral infarction in humans. We sought to determine these thresholds with voxel-by-voxel, tissue-specific analysis of co-registered acute and follow-up magnetic resonance (MR) perfusion- and diffusion-weighted imaging. Quantitative cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and apparent diffusion coefficient (ADC) maps were analyzed from nine acute stroke patients (imaging acquired within 6 h of onset). The average values of each measure were calculated for GM and WM in normally perfused tissue, the region of recovered tissue and in the final infarct. Perfusion and diffusion thresholds for infarction were determined on a patient-by-patient basis in GM and WM separately by selecting thresholds with equal sensitivities and specificities. Gray matter has higher thresholds for infarction than WM (P<0.009) for CBF (20.0 mL/100 g min in GM and 12.3 mL/100 g min in WM), CBV (2.4 mL/100 g in GM and 1.7 mL/100 g in WM), and ADC (786 x 10(-6) mm(2)/s in GM and 708 x 10(-6) mm(2)/s in WM). The MTT threshold for infarction in GM is lower (P=0.014) than for WM (6.8 secs in GM and 7.1 secs in WM). A single common threshold applied to both tissues overestimates tissue at risk in WM and underestimates tissue at risk in GM. This study suggests that tissue-specific analysis of perfusion and diffusion imaging is required to accurately predict tissue at risk of infarction in acute ischemic stroke.

Aged↗
PubMed2005

Bedside emergency transcranial Doppler diagnosis of severe carotid disease using orbital window examination.

BACKGROUND: Identifying internal carotid artery (ICA) stenosis in the acute stroke setting can provide clinically useful information. Transcranial Doppler (TCD) through the orbital window is an easy test to perform and to track and identify different vessels. Previous TCD studies have suggested that a reversed ophthalmic artery (OA) flow is a useful collateral pattern to predict ICA disease. The authors sought to evaluate the TCD orbital window for predicting cervical ICA (cICA) stenosis in the setting of acute stroke and TIA. METHOD: Power M-mode/TCD was performed in acute stroke and transient ischemic attack patients at 2 institutions. Each orbital window depth was detected on M-mode and evaluated for the direction of flow and resistance pattern. Gold standard for comparison was carotid evaluation using carotid duplex, computed tomography angiogram, or conventional angiography. The assessment of cICA disease was categorized by degree of stenosis or occlusion. RESULTS: A total of 216 transorbital exams were performed in 117 patients. Twenty-five cICA occlusions and 8 critical cICA stenoses (>or=95%) were identified by gold standard imaging. Reversed OA flow at 50 to 60 mm depth revealed high specificity (100%; confidence interval [CI], 97.6%-100.0%) and good sensitivity (75%; CI, 53.3%-90.2%) for identifying cICA occlusion or critical stenosis (>or=95%). Low pulsatility index (<1.2) and mean flow velocity (<15 cm/s) discriminated critical severe ICA stenosis or occlusion when OA flow was anterograde with good sensitivity (87.2%) and specificity (95.2%). CONCLUSION: The reversed OA sign at 50 to 60 mm depth is very specific for identifying cICA occlusion or critical stenosis. When OA flow is anterograde, a low mean flow velocity or pulsatility index is also useful to identify cICA critical stenosis or occlusion.

Carotid Artery, Internal↗
PubMed2005

Stroke prevention. MATCHing therapy to the patient with TIA.

The short-term risk of stroke after transient ischemic attack (TIA) is about 10% to 20% in the first 3 months, with much of the risk front-loaded in the first week. Unfortunately, little is known about the best therapies for hyperacute stroke prevention after TIA. A recent trial referred to by the acronym MATCH (for Management of Atherothrombosis With Clopidogrel in High-risk Patients With Recent Transient Ischemic Attack or Ischemic Stroke) provides hypothesis-generating data to suggest that double antiplatelet therapy in the short term may be appropriate. Here, the authors discuss treatment considerations, outlining the current knowledge and stressing the need for formal randomized trials to definitively establish the effectiveness of preventive therapies after minor stroke or TIA.

Aspirin↗
PubMed2004

Ultrasound-enhanced systemic thrombolysis for acute ischemic stroke.

BACKGROUND: Transcranial Doppler ultrasonography that is aimed at residual obstructive intracranial blood flow may help expose thrombi to tissue plasminogen activator (t-PA). Our objective was to determine whether ultrasonography can safely enhance the thrombolytic activity of t-PA. METHODS: We treated all patients who had acute ischemic stroke due to occlusion of the middle cerebral artery with intravenous t-PA within three hours after the onset of symptoms. The patients were randomly assigned to receive continuous 2-MHz transcranial Doppler ultrasonography (the target group) or placebo (the control group). The primary combined end point was complete recanalization as assessed by transcranial Doppler ultrasonography or dramatic clinical recovery. Secondary end points included recovery at 24 hours, a favorable outcome at three months, and death at three months. RESULTS: A total of 126 patients were randomly assigned to receive continuous ultrasonography (63 patients) or placebo (63 patients). Symptomatic intracerebral hemorrhage occurred in three patients in the target group and in three in the control group. Complete recanalization or dramatic clinical recovery within two hours after the administration of a t-PA bolus occurred in 31 patients in the target group (49 percent), as compared with 19 patients in the control group (30 percent; P=0.03). Twenty-four hours after treatment of the patients eligible for follow-up, 24 in the target group (44 percent) and 21 in the control group (40 percent) had dramatic clinical recovery (P=0.7). At three months, 22 of 53 patients in the target group who were eligible for follow-up analysis (42 percent) and 14 of 49 in the control group (29 percent) had favorable outcomes (as indicated by a score of 0 to 1 on the modified Rankin scale) (P=0.20). CONCLUSIONS: In patients with acute ischemic stroke, continuous transcranial Doppler augments t-PA-induced arterial recanalization, with a nonsignificant trend toward an increased rate of recovery from stroke, as compared with placebo.

Acute Disease↗
PubMed2004

Comparison of MRI and CT for detection of acute intracerebral hemorrhage.

CONTEXT: Noncontrast computed tomography (CT) is the standard brain imaging study for the initial evaluation of patients with acute stroke symptoms. Multimodal magnetic resonance imaging (MRI) has been proposed as an alternative to CT in the emergency stroke setting. However, the accuracy of MRI relative to CT for the detection of hyperacute intracerebral hemorrhage has not been demonstrated. OBJECTIVE: To compare the accuracy of MRI and CT for detection of acute intracerebral hemorrhage in patients presenting with acute focal stroke symptoms. DESIGN, SETTING, AND PATIENTS: A prospective, multicenter study was performed at 2 stroke centers (UCLA Medical Center and Suburban Hospital, Bethesda, Md), between October 2000 and February 2003. Patients presenting with focal stroke symptoms within 6 hours of onset underwent brain MRI followed by noncontrast CT. MAIN OUTCOME MEASURES: Acute intracerebral hemorrhage and any intracerebral hemorrhage diagnosed on gradient recalled echo (GRE) MRI and CT scans by a consensus of 4 blinded readers. RESULTS: The study was stopped early, after 200 patients were enrolled, when it became apparent at the time of an unplanned interim analysis that MRI was detecting cases of hemorrhagic transformation not detected by CT. For the diagnosis of any hemorrhage, MRI was positive in 71 patients with CT positive in 29 (P<.001). For the diagnosis of acute hemorrhage, MRI and CT were equivalent (96% concordance). Acute hemorrhage was diagnosed in 25 patients on both MRI and CT. In 4 other patients, acute hemorrhage was present on MRI but not on the corresponding CT--each of these 4 cases was interpreted as hemorrhagic transformation of an ischemic infarct. In 3 patients, regions interpreted as acute hemorrhage on CT were interpreted as chronic hemorrhage on MRI. In 1 patient, subarachnoid hemorrhage was diagnosed on CT but not on MRI. In 49 patients, chronic hemorrhage, most often microbleeds, was visualized on MRI but not on CT. CONCLUSION: MRI may be as accurate as CT for the detection of acute hemorrhage in patients presenting with acute focal stroke symptoms and is more accurate than CT for the detection of chronic intracerebral hemorrhage.

Acute Disease↗
PubMed2004

ASPECTS on CTA source images versus unenhanced CT: added value in predicting final infarct extent and clinical outcome.

BACKGROUND AND PURPOSE: The Alberta Stroke Program Early CT Score (ASPECTS) is a grading system to assess ischemic changes on CT in acute ischemic stroke. CT angiography-source images (CTA-SI) predict final infarct volume. We examined whether the final infarct ASPECTS and clinical outcome were more related to acute CTA-SI ASPECTS than to the acute noncontrast CT (NCCT) ASPECTS. METHODS: ASPECTS was assigned by 2 raters on the acute NCCT, CTA-SI, and follow-up imaging. The mean baseline ASPECTS of acute NCCT and CTA-SI was compared with the follow-up ASPECTS. Rate ratios (RRs) were used to quantify the relationship between the dichotomized baseline ASPECTS (categorized as 0 to 7 versus 8 to 10) and favorable patient outcome. RESULTS: Thirty-nine patients were recruited. Proximal occlusion (internal carotid artery or middle cerebral artery) was seen in 62%, M2 occlusion in 18%, and no occlusion was seen in 20% of patients. The median time between symptom onset and imaging was 1.9 (1.2 to 2.5) hours. There was a significantly larger difference of 1.4 between the mean baseline NCCT and CTA-SI ASPECTS in patients who had more ischemic changes (follow-up ASPECTS=0 to 3) than a difference of 0.6 in patients who had near-to-normal CT scans (follow-up ASPECTS=8 to 10). The rate of favorable outcome for acute NCCT ASPECTS of 8 to 10 was 51.8% versus 25.0% for 0 to 7 (RR, 2.1, 95% CI: 0.7 to 5.9, P=0.12). For acute CTA-SI ASPECTS of 8 to 10, the rate of favorable outcome was 58.8% versus 31.8% for 0 to 7 (RR, 1.8, 95% CI: 0.9 to 3.8, P=0.09). CONCLUSIONS: CTA-SI ASPECTS provides added information in the prediction of final infarct size.

Aged↗
PubMed2004

Interobserver variation of ASPECTS in real time.

BACKGROUND: The Alberta Stroke Program Early CT Score (ASPECTS) has been used to quantify early ischemic changes on computed tomography (CT) brain scans of acute stroke patients. We sought to assess the reliability of the score when performed in real time as compared with an expert rating performed at a later time point. METHODS: Two hundred fourteen patients presenting with acute ischemic stroke or transient ischemic attack were prospectively recruited if they had a brain CT scan performed within 12 hours of symptom onset. Each scan was read for ASPECTS prospectively by the treating physician and later by 1 expert reader. A weighted kappa statistic was used to determine the interobserver agreement. RESULTS: The median baseline National Institutes of Health Stroke Scale score was 5 (range: 0 to 32) and the median time to CT scan was 152 minutes (range: 22 to 769). The interobserver agreement between ASPECTS performed in real time and expert ASPECTS was substantial (kappa(w)=0.69). The mean difference between real-time ASPECTS and expert ASPECTS was 0 (SD: 1.1). CONCLUSIONS: ASPECTS is a reliable clinical scale for rating early ischemic changes on CT when performed in real time.

Adult↗
PubMed2004

Mild neurological symptoms despite middle cerebral artery occlusion.

BACKGROUND AND PURPOSE: Only a small percentage of stroke patients are treated with thrombolytic therapy. We sought to determine whether vessel occlusion in mild strokes represented a new target population for interventional therapy. METHODS: We imaged 106 acute stroke patients with MRI. Patients were identified with evidence of middle cerebral artery (MCA) occlusion and mild or no stroke signs (National Institutes of Health Stroke Scale [NIHSS] 3, and MCA occlusion. RESULTS: We identified 5 patients with absent flow on MRA in the MCA and mild or no stroke signs (NIHSS <or=3). All 5 were functionally independent at 3 months. CONCLUSIONS: Caution should be exercised in considering thrombolytic therapy in these patients. Quantification of perfusion imaging is required to identify "at risk" mild stroke populations.

Acute Disease↗
PubMed2004

Prediction of hospital disposition after thrombolysis for acute ischemic stroke using the National Institutes of Health Stroke Scale.

BACKGROUND: Early determination of discharge destination after acute stroke may promote earlier rehabilitation and reduce costs by shortening the duration of hospitalization. OBJECTIVE: To determine whether the National Institutes of Health Stroke Scale (NIHSS) score predicts disposition in stroke patients treated with thrombolysis. DESIGN: Cohort study. SETTING: Academic and community hospitals from 3 countries. PATIENTS: Five hundred forty-six patients with acute ischemic stroke treated with recombinant tissue plasminogen activator (rt-PA). INTERVENTIONS: Medical records were reviewed for demographic information, vascular risk factors, location of stroke, initial NIHSS score, acute hospital disposition, and complications of symptomatic or asymptomatic intracerebral hemorrhage (ICH). MAIN OUTCOME MEASURE: Discharge destination to home, acute rehabilitation, or nursing facility. RESULTS: In multinomial regression analysis, increasing NIHSS score was a robust and independent predictor of discharge to rehabilitation or nursing facilities, roughly doubling for each 5-point increment. Patients who developed symptomatic ICH were never discharged to home, but asymptomatic ICH had no significant independent effect on disposition. CONCLUSIONS: Stroke severity as determined by the admission NIHSS score is the major independent predictor of disposition after hospitalization and treatment with rt-PA for acute stroke in a broad-based population. However, symptomatic ICH after rt-PA is a catastrophic event that may preclude discharge to home.

Acute Disease↗
PubMed2004

Can rt-PA be administered to the wrong patient? Two patients with somatoform disorder.

BACKGROUND: Intravenous rt-PA (i.v. rt-PA) for acute stroke has raised many concerns, including its inadvertent use in patients presenting with acute stroke-like symptoms as the expression of their somatoform disorder. Diagnosis of the somatoform disorder is often delayed, and thrombolytics in these patients for their stroke-like presentation subjects them to risk for hemorrhage. METHODS: The presentation, neurological findings, and the therapeutic decision making was audited in 85 patients who received i.v. rt-PA for a diagnosis of acute stroke. All the surviving patients were re-examined neurologically at least three months after i.v. rt-PA. Baseline and follow-up brain CT scans were re-reviewed by a neuroradiologist who was blinded to clinical presentation and outcome. Patients whose clinical presentation, brain CT and neurological outcome did not fit into known or expected anatomical and clinical patterns of stroke underwent psychological assessment using the Minnesota Multiphasic Personality Inventory-2. RESULTS: In two patients three stroke-like presentations of somatoform disorder inadvertently were treated with i.v. rt-PA. This was primarily caused by abbreviated neurological examination and narrow differential diagnosis. INTERPRETATION: Patients with somatoform disorder may present with symptoms mimicking acute stroke. Under the time constraints of i.v. rt-PA use, a diagnosis of somatoform disorder can be missed, subjecting such patients to the potential complications of thrombolytics.

Acute Disease↗
PubMed2004

Ultrasound-enhanced thrombolysis for acute ischemic stroke: phase I. Findings of the CLOTBUST trial.

BACKGROUND: Tissue plasminogen activator (TPA) activity may be enhanced with ultrasound, potentially 2 MHz transcranial Doppler (TCD). The authors present Phase I data of the CLOTBUST (Combined Lysis of Thrombus in Brain ischemia using transcranial Ultrasound and Systemic TPA). SUBJECTS AND METHODS: Nonrandomized stroke patients with proximal arterial occlusion on a prebolus TCD receiving intravenous 0.9 mg/kg TPA within 3 hours after stroke onset were monitored with portable diagnostic TCD equipment and a standard headframe. Complete recanalization was defined as thrombolysis in brain ischemia (TIBI) flow grades 4-5. RESULTS: 55 patients (mean age 69 +/- 15 years, median baseline NIH Stroke Scale [NIHSS] 18, range 4-29, 90% with 3 9 points) were treated at 125 +/- 36 minutes from symptom onset. TCD monitoring began at 117 +/- 39 minutes. Complete recanalization on TCD within 2 hours after bolus was found in 20 patients (36%). Dramatic recovery (NIHSS score < or = 3) occurred in 20% at 2 hours and in 24% at 24 hours. Overall improvement by > or = 4 NIHSS points was found in 49% at 24 hours. Improvement was associated with recanalization during or shortly after TPA infusion (phi r2 = .5, P = .03); however, in 6/20 patients with complete recanalization (30%), no immediate clinical change was noticed within 2 hours. Overall symptomatic hemorrhage rate was 5.5%. CONCLUSIONS: Continuous TCD insonation for up to 2 hours at maximum intensities allowed by current bio-safety guidelines is safe. Dramatic recovery and complete recanalization shortly after TPA bolus are feasible goals for thrombolysis given with TCD monitoring.

Aged↗
PubMed2003

Improved detection of microbubble signals using power M-mode Doppler.

UNLABELLED: Background- Power motion-mode transcranial Doppler (TCD) (PMD) is a new, multigated technique that may simplify and enhance detection of embolus. We developed criteria for emboli detection using PMD. Then, we performed a blinded comparison of transcranial PMD with single-gate spectral TCD in TCD bubble study patients. METHODS: Patients with right-to-left shunt as detected with standard TCD were selected for this study. The international emboli criteria for spectral TCD were used. We defined novel PMD criteria for detecting emboli signature on PMD as follows: (1) signature at least 3 dB higher than the highest spontaneous PMD display of background blood flow; (2) embolic signature reflects motion in one direction at a minimum spatial extent of 7.5 mm and temporal extent of 30 ms; (3) embolus must traverse a prespecified depth. Each study was blindly assessed for microbubble signals (MBS) count on either modality. RESULTS: Thirty-six patients were included in the study. Mean age was 44.4 (SD 14.4), 50% were male, and median time from stroke onset to TCD bubble test was 12 days. Median MBS count in middle cerebral arteries (MCA) was 4 on both modalities. Spectral TCD MBS counts were highly correlated (rho=0.97) with PMD MBS counts in MCA and similarly in anterior cerebral arteries (ACA) (rho=0.79). When PMD microbubble counts in the ACA and MCA were summed, a clear 2-fold difference emerged between 2 modalities (P<0.001). CONCLUSIONS: When compared with spectral TCD, PMD detects more MBS with higher counts by identifying ACA as well as MCA emboli. Pitfalls of overcounting emboli with PMD can be avoided by following such criteria.

Adult↗
PubMed2003

Improving the predictive accuracy of recanalization on stroke outcome in patients treated with tissue plasminogen activator.

BACKGROUND AND PURPOSE: Although early recanalization is a powerful predictor of stroke outcome after thrombolysis, some stroke patients remain disabled despite tissue plasminogen activator (tPA)-induced recanalization. Therefore, we sought to investigate whether the predictive accuracy of early recanalization on stroke outcome is improved when combined with clinical and radiological information. METHODS: We evaluated 177 patients with nonlacunar strokes in the middle cerebral artery (MCA) treated with intravenous tPA who were followed up during 3 months. Transcranial Doppler monitoring of recanalization was conducted during the first hours after tPA administration. The relative contribution of clinical, transcranial Doppler, and radiological information on stroke outcome was evaluated. We used logistic regression to derive a predictive model for good outcome (modified Rankin Scale score < or =2) after thrombolysis. RESULTS: Median National Institutes of Health Stroke Scale (NIHSS) score before tPA was 16. At 3 months, 87 patients (49.2%) became functionally independent (modified Rankin Scale score < or =2). In a logistic regression model, degree of recanalization within 300 minutes (P<0.001), proximal MCA occlusion (P<0.001), baseline NIHSS score (P=0.0013), systolic blood pressure (P=0.0116), and early ischemic changes on CT (P=0.0253) independently predicted outcome at 3 months. A 5-item score was developed on the basis of the factors significantly associated with stroke outcome in the logistic regression (total score range, 0 to 7). The likelihood of good outcome at 3 months was 0.82 (95% CI, 0.72 to 0.92) in patients who scored 0 to 2, 0.51 (95% CI, 0.36 to 0.66) in those who scored 3 to 4, and 0.15 (95% CI, 0.05 to 0.25) in those who scored 5 to 7 points. CONCLUSIONS: The combination of clinical, radiological, and hemodynamic information predicts with a high accuracy long-term stroke outcome during or shortly after intravenous tPA administration.

Academic Medical Centers↗
PubMed2003

Reliability of assessing percentage of diffusion-perfusion mismatch.

BACKGROUND AND PURPOSE: Emergent neurovascular imaging holds promise in identifying new and optimum target populations for thrombolysis in stroke. Recent research has focused on patients with diffusion-weighted MRI (DWI)-perfusion-weighted MRI (PWI) mismatch as a marker of tissue at risk of infarction and a means to select the most suitable candidates for thrombolysis. The present study sought to estimate the reliability of assessing the percentage of DWI-PWI mismatch. METHODS: Thirteen patients with acute strokes had DWI and PWI within 7 hours of symptom onset. Six raters independently created relative mean transit time (rMTT) maps and then compared them with DWI images to assess the percentage of mismatch (PWI>DWI) in 10% increments. The MR scans were reassessed by 4 raters, tracing around the lesions to calculate the volume percentage of mismatch. RESULTS: Visual assessment had an interrater reliability of 0.68 (95% CI, 0.52 to 1.0; SEM=21.6%) and an intrarater reliability of 0.80 (95% CI, 0.47 to 1.0; SEM=16.9%). Hand-drawn assessment had an interrater reliability of 0.66 (95% CI, 0.45 to 1.0; SEM=26.2%) and an intrarater reliability of 0.94 (95% CI, 0.81 to 1.0; SEM=10.9%). CONCLUSIONS: Results from the present study suggest that quantifying mismatch by the human eye is reproducible but not reliable among observers. This raises doubts about using mismatch for clinical decision making and clinical trial enrollment.

Acute Disease↗