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Walter J Koroshetz

Publications and source records attributed to Walter J Koroshetz.

At least 19 recordsLinked to original sources
PubMed2007

Acute ischemic stroke: overview of recent therapeutic developments.

Stroke, a disorder encompassing all cerebrovascular accidents, is a public health problem of immense proportions across the globe. Therapeutic efforts are directed at three aspects: prevention, acute treatment, and rehabilitation. Preventative measures, which in many instances mirror those for cardiovascular disease, can achieve the greatest public health impact. Measures that enhance the recovery of neurologic function and reduce neurologic disability after stroke can also affect a large population of handicapped stroke survivors. In the past 10 years, the greatest changes have occurred in the field of acute stroke treatment. Ultra-early-stage therapies with the potential to dramatically reverse severe neurologic deficits, or halt their progression, have caused a restructuring of the emergency care of neurologic patients. The parallels with the evolution of emergency treatment of acute coronary syndromes after 1970 are striking. This review focuses on aspects of stroke therapy that are either just entering, or soon to enter, current practice.

Angioplasty, Balloon↗
PubMed2006

The real estate factor: quantifying the impact of infarct location on stroke severity.

BACKGROUND AND PURPOSE: The severity of the neurological deficit after ischemic stroke is moderately correlated with infarct volume. In the current study, we sought to quantify the impact of location on neurological deficit severity and to delineate this impact from that of volume. METHODS: We developed atlases consisting of location-weighted values indicating the relative importance in terms of neurological deficit severity for every voxel of the brain. These atlases were applied to 80 first-ever ischemic stroke patients to produce estimates of clinical deficit severity. Each patient had an MRI and National Institutes of Health Stroke Scale (NIHSS) examination just before or soon after hospital discharge. The correlation between the location-based deficit predictions and measured neurological deficit (NIHSS) scores were compared with the correlation obtained using volume alone to predict the neurological deficit. RESULTS: Volume-based estimates of neurological deficit severity were only moderately correlated with measured NIHSS scores (r=0.62). The combination of volume and location resulted in a significantly better correlation with clinical deficit severity (r=0.79, P=0.032). CONCLUSIONS: The atlas methodology is a feasible way of integrating infarct size and location to predict stroke severity. It can estimate stroke severity better than volume alone.

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PubMed2006

Transient ischemic attack: are there different types or classes? Risk of stroke and treatment options.

Recent advances in neuroimaging have revolutionized the evaluation of the clinical syndrome of transient ischemic attack (TIA). Diffusion-weighted imaging demonstrates microinfarctions (< 1 cm(3)) in approximately 50% of patients with TIA, establishing that not all clinically transient spells are transient at the tissue level. The clinical syndrome of TIA that is associated with ischemic brain injury is called "transient symptoms with infarction" (TSI). TSI appears to be a different subset because it harbors higher risk of imminent stroke than "TIA with no infarction." Armed with the evidence of ischemia as the cause of transient spell, clinicians can pursue the most appropriate therapy for stroke prevention by targeting the underlying etiology of brain ischemia.

Journal Article↗
PubMed2006

Unusual visual symptoms in a patient with bilateral vertebral artery dissection: a case report.

We present a previously unreported set of symptoms in a patient found to have bilateral vertebral dissections. Although visual symptoms are common in vertebral dissection, their pattern does not typically mimic those that commonly precede or accompany migraine headache. When they do occur, they usually take the form of diplopia or blurred vision. The patient we describe had visual symptoms that varied over three episodes of headache and included transient visual field loss and scintillations ("lightning bolts"), both common in migraine. However, our patient's new visual symptoms represented a change in pattern from those that had accompanied her previous migraines. This detailed history-taking prompted an evaluation for an etiology other than migraine and prevented a further delay in diagnosis and treatment.

Adult↗
PubMed2005

Conversion of ischemic brain tissue into infarction increases with age.

BACKGROUND AND PURPOSE: Brain regions normal on diffusion-weighted imaging (DWI) but abnormal on mean transit time (MTT) maps represent tissue at risk of infarction, yet the fate of these regions is quite variable. The imperfect correlation between tissue outcome and initial imaging parameters suggests that each patient's brain may have different susceptibility to ischemic stress. We hypothesize that age is a marker for tissue susceptibility to ischemia and thus plays a role in determining tissue outcome in human stroke. METHODS: Sixty patients with acute ischemic stroke and a region of DWI/MTT mismatch that was >20% of the DWI volume were included. All patients were scanned twice, within 12 hours of symptom onset and on day 5 or later. The percentage mismatch lost (PML) was calculated as percentage of initial DWI/MTT mismatch volume that was infarcted on the follow-up MRI. The statistical analysis explored relationships among the covariates age, Trial of Org 10172 in Acute Stroke Treatment (TOAST) subtypes, time-to-MRI, and initial DWI, MTT volume, mean arterial blood pressure and blood glucose level at admission, and previous history of hypertension and diabetes mellitus. RESULTS: Univariate comparisons showed that age (P=0.003), hypertension (P=0.009), and diabetes mellitus (P=0.0002) were significantly associated with PML. Regression analyses showed age to be a significant covariate (P=0.02). The regression model predicted a change in PML of approximately 0.65% per year. The adjusted proportion of variance (R2) in PML that could be explained by age alone was 14%. CONCLUSIONS: Age-dependent increase in conversion of ischemic tissue into infarction suggests that age is a biological marker for the variability in tissue outcome in acute human stroke.

Adult↗
PubMed2005

Poor outcomes in patients who do not receive intravenous tissue plasminogen activator because of mild or improving ischemic stroke.

BACKGROUND AND PURPOSE: Some patients with mild or improving ischemic stroke symptoms do not receive intravenous tissue plasminogen activator (tPA) because they look "too good to treat" (TGT); however, some have poor outcomes. METHODS: We retrospectively analyzed data from a prospective single-center study between 2002 and 2004. TGT patients were those arriving within 3 hours of symptom onset and not treated with intravenous tPA solely because of mild or improving symptoms. RESULTS: Of 128 patients presenting within 3 hours, 41 (34%) were not given tPA because of mild or improving stroke. Of the TGT patients, 11 of 41 (27%) died or were not discharged home because of neurological worsening (n=6) or persistent "mild" neurological deficit (n=5). No single variable at presentation was associated with death or lack of home discharge. There were 10 of 41 TGT patients (24%) who had > or =4-point improvement in National Institutes of Health Stroke Scale score before tPA decision; these patients were more likely to have subsequent neurological worsening (relative risk, 4.1, 95% CI, 1.1 to 15.4; P=0.05). CONCLUSIONS: A substantial minority of patients deemed too good for intravenous tPA were unable to be discharged home. A re-evaluation of the stroke severity criteria for tPA eligibility may be indicated.

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PubMed2005

Transcranial low-frequency ultrasound-mediated thrombolysis in brain ischemia: increased risk of hemorrhage with combined ultrasound and tissue plasminogen activator: results of a phase II clinical trial.

BACKGROUND: Clinical studies using ultrasound at diagnostic frequencies in transcranial Doppler devices provided encouraging results in enhancing thrombolysis with tissue plasminogen activator (tPA) in acute stroke. Low-frequency ultrasound does not require complex positioning procedures, penetrates through the skull better, and has been demonstrated to accelerate thrombolysis with tPA in animal experiments in wide cerebrovascular territories without hemorrhagic side effects. We therefore conducted the first multicenter clinical trial to investigate safety of tPA plus low-frequency ultrasound (300 kHz). METHODS: Acute stroke patients within a 6-hour time window were included (National Institutes of Health Stroke Scale scores >4). Magnetic resonance imaging (MRI) was used to document vascular occlusion and to rule out cerebral hemorrhage. Patients were allocated to combination therapy alternately; the first patient received tPA only, the second patient received tPA plus ultrasound, etc. Follow-up included serial MRI directly thereafter and 24 hours later to confirm recanalization and tissue imaging. Clinical recovery was measured after treatment and 3 months later. RESULTS: 26 patients (70.4+/-9.7 years) entered the trial (12 tPA, 14 tPA plus ultrasound). The study was prematurely stopped because 5 of 12 patients from the tPA only group but 13 of 14 patients treated with the tPA plus ultrasound showed signs of bleeding in MRI (P<0.01). Within 3 days of treatment, 5 symptomatic hemorrhages occurred within the tPA plus ultrasound group. At 3 months, neither morbidity nor treatment-related mortality or recanalization rates differed between both groups. CONCLUSIONS: This study demonstrated bioeffects from low-frequency ultrasound that caused an increased rate of cerebral hemorrhages in patients concomitantly treated with intravenous tPA.

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PubMed2005

A pilot study of normobaric oxygen therapy in acute ischemic stroke.

BACKGROUND AND PURPOSE: Therapies that transiently prevent ischemic neuronal death can potentially extend therapeutic time windows for stroke thrombolysis. We conducted a pilot study to investigate the effects of high-flow oxygen in acute ischemic stroke. METHODS: We randomized patients with acute stroke (<12 hours) and perfusion-diffusion "mismatch" on magnetic resonance imaging (MRI) to high-flow oxygen therapy via facemask for 8 hours (n=9) or room air (controls, n=7). Stroke scale scores and MRI scans were obtained at baseline, 4 hours, 24 hours, 1 week, and 3 months. Clinical deficits and MR abnormalities were compared between groups. RESULTS: Stroke scale scores were similar at baseline, tended to improve at 4 hours (during therapy) and 1 week, and significantly improved at 24 hours in hyperoxia-treated patients. There was no significant difference at 3 months. Mean (+/-SD) relative diffusion MRI lesion volumes were significantly reduced in hyperoxia-treated patients at 4 hours (87.8+/-22% versus 149.1+/-41%; P=0.004) but not subsequent time points. The percentage of MRI voxels improving from baseline "ischemic" to 4-hour "non-ischemic" values tended to be higher in hyperoxia-treated patients. Cerebral blood volume and blood flow within ischemic regions improved with hyperoxia. These "during-therapy" benefits occurred without arterial recanalization. By 24 hours, MRI showed reperfusion and asymptomatic petechial hemorrhages in 50% of hyperoxia-treated patients versus 17% of controls (P=0.6). CONCLUSIONS: High-flow oxygen therapy is associated with a transient improvement of clinical deficits and MRI abnormalities in select patients with acute ischemic stroke. Further studies are warranted to investigate the safety and efficacy of hyperoxia as a stroke therapy.

Adult↗
PubMed2005

Training, competency, and credentialing standards for diagnostic cervicocerebral angiography, carotid stenting, and cerebrovascular intervention: a joint statement from the American Academy of Neurology, the American Association of Neurological Surgeons, the American Society of Interventional and Therapeutic Neuroradiology, the American Society of Neuroradiology, the Congress of Neurological Surgeons, the AANS/CNS Cerebrovascular Section, and the Society of Interventional Radiology.

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Angioplasty↗
PubMed2005

Transient ischemic attack with infarction: a unique syndrome?

It is debated whether transient symptoms associated with infarction (TSI) are best considered a minor ischemic stroke, a subtype of transient ischemic attack (TIA), or a separate ischemic brain syndrome. We studied clinical and imaging features to establish similarities and differences among ischemic stroke, TIA without infarction, and TSI. Eighty-seven consecutive patients with TIA and 74 patients with ischemic stroke were studied. All underwent diffusion-weighted imaging on admission. Symptom duration and infarct volume were determined in each group. Thirty-six patients (41.3%) with TIA had acute infarct(s). Although TIA-related infarcts were smaller than those associated with ischemic stroke (mean, 0.7 vs 27.3 ml; p < 0.001), there was no lesion size threshold that distinguished ischemic stroke from TSI. In contrast, the symptom duration probability density curve was not broad, but instead peaked early with only a few patients having symptoms for longer than 200 minutes. The probability density function for symptom duration was similar between TIA with or without infarction. The in-hospital recurrent ischemic stroke and TIA rate was 19.4% in patients with TSI and 1.3% in those with ischemic stroke. TIA with infarction appears to have unique features separate from TIA without infarction and ischemic stroke. We propose identifying TSI as a separate clinical syndrome with distinct prognostic features.

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PubMed2005

An evidence-based causative classification system for acute ischemic stroke.

Regular, evidence-based assignment of patients to etiologic stroke categories is essential to enable valid comparison among studies. We designed an algorithm (SSS-TOAST) that incorporated recent advances in stroke imaging and epidemiology to identify the most probable TOAST category in the presence of evidence for multiple mechanisms. Based on the weight of evidence, each TOAST subtype was subdivided into 3 subcategories as "evident", "probable", or "possible". Classification into the subcategories was determined via predefined specific clinical and imaging criteria. These criteria included published risks of ischemic stroke from various mechanisms and published reports of the strength of associations between clinical and imaging features and particular stroke mechanisms. Two neurologists independently assessed 50 consecutively admitted patients with acute ischemic stroke through reviews of abstracted data from medical records. The number of patients classified as "undetermined-unclassified" per the original TOAST system decreased from 38-40% to 4% using the SSS-TOAST system. The kappa value for inter-examiner reliability was 0.78 and 0.90 for the original TOAST and SSS-TOAST respectively. The SSS-TOAST system successfully classifies patients with acute ischemic stroke into determined etiologic categories without sacrificing reliability. The SSS-TOAST is a dynamic algorithm that can accommodate modifications as new epidemiological data accumulate and diagnostic techniques advance.

Adult↗
PubMed2005

Magnetic resonance imaging: implication in acute ischemic stroke management.

Multimodality magnetic resonance imaging (MRI) techniques, including diffusion-weighted imaging (DWI), perfusion-weighted imaging (PWI), fluid-attenuated inversion recovery (FLAIR), T2 susceptibility imaging, and magnetic resonance angiography (MRA), quickly provide accurate information about ischemic penumbra (DWI/PWI mismatch), tissue perfusion, and vascular localization in acute stroke setting. These techniques help physicians to select the proper candidates for thrombolysis and/or neuroprotective treatment to salvage tissue at risk (mismatch) and monitor acute stroke patients after treatment. Recent and ongoing trials demonstrate the benefit of treating acute stroke patients depending on tissue at risk of infarction rather than timing of onset. These techniques will extend timing to salvage ischemic brain tissue beyond the 3-hour window. MRI is a powerful tool for managing acute stroke patients and helps elucidate the pathophysiology of cerebral ischemia in a given patient.

Acute Disease↗
PubMed2005

Applying instance-based techniques to prediction of final outcome in acute stroke.

OBJECTIVE: Acute cerebral stroke is a frequent cause of death and the major cause of adult neurological disability in the western world. Thrombolysis is the only established treatment of ischemic stroke; however, its use carries a substantial risk of symptomatic intracerebral hemorrhage. A clinical tool to guide the use of thrombolysis would be very valuable. One of the major goals of such a tool would be the identification of potentially salvageable tissue. This requires an accurate prediction of the extent of infarction if untreated. In this study, we investigate the applicability of highly flexible instance-based (IB) methods for such predictions. METHODS AND MATERIALS: Based on information obtained from magnetic resonance imaging of 14 patients with acute stroke, we explored three different implementations of the IB method: k-NN, Gaussian weighted, and constant radius search classification. Receiver operating characteristics analysis, in particular area under the curve (AUC), was used as performance measure. RESULTS: We found no significant difference (P = 0.48) in performance for the optimal k-NN (k = 164, AUC = 0.814 +/- 0.001) and Gaussian weight (sigma = 0.17, AUC = 0.813 +/- 0.001) implementations, while they were both significantly better (P < 1 x 10(-6) for both) than the constant radius implementation (R = 0.28, AUC = 0.809 +/- 0.001). Qualitative analyses of the distribution of instances in the feature space indicated that non-infarcted instances tends to cluster together while infarcted instances are more dispersed, and that there may not exist a stringent boundary separating infarcted from non-infarcted instances. CONCLUSIONS: This study shows that IB methods can be used, and may be advantageous, for predicting final infarct in patients with acute stroke, but further work must be done to make them clinically applicable.

Adult↗
PubMed2005

Neuroimaging of ischemia and infarction.

Since the introduction of thrombolytic therapy as the foundation of acute stroke treatment, neuroimaging has rapidly advanced to empower therapeutic decision making. Diffusion-weighted imaging is the most sensitive and accurate method for stroke detection, and, allied with perfusion-weighted imaging, provides information on the functional status of the ischemic brain. It can also help to identify a response to thrombolytic and neuroprotective therapies. Additionally, multimodal magnetic resonance imaging, including magnetic resonance angiography, offers information on stroke mechanism and pathophysiology that can guide long-term medical management. Multimodal computed tomography is a comprehensive, cost-effective, and safe stroke imaging modality that can be easily implemented in the emergency ward and that offers fast and reliable information with respect to the arterial and functional status of the ischemic brain. Accessibility, contraindications, cost, speed, and individual patient-determined features influence which is the best imaging modality to guide acute stroke management.

Animals↗
PubMed2005

Arterial occlusion revealed by CT angiography predicts NIH stroke score and acute outcomes after IV tPA treatment.

BACKGROUND AND PURPOSE: The relationship between location of occlusion and clinical outcome is poorly understood in patients receiving intravenous tissue-type plasminogen activator (IV tPA). We postulated that acute stroke patients receiving IV tPA with patent vasculature or occult arterial occlusion by CT angiography (CTA) would have better outcomes and decreased hemorrhagic risk. METHODS: We identified 47 patients from our prospective stroke database who underwent CTA before treatment with IV tPA. Site of occlusion was categorized as M1 segment of the middle cerebral artery, M2 segment, multiple (either carotid, basilar, or both middle and anterior cerebral arteries), or absent (no occlusion proximal to M3). The effect of site of occlusion on National Institutes of Health Stroke Scale (NIHSS), early improvement (> or = 4-point improvement in NIHSS at 24 hours after treatment), intracranial hemorrhages, and modified Rankin scale (mRS) at 7 days was tested in a multivariate analysis. RESULTS: The location of occlusion correlated with initial NIHSS for multiple, M1, M2 and absent occlusions (median NIHSS scores were 18, 18, 15, 10, respectively) (P < .02, rank sum). Following adjustment for initial NIHSS, age, and time to treatment, the absence of occlusion remained associated with early improvement (OR 5.0, 95% CI 1.1-23.3; P = .04) and independence at day 7 (mRS < or = 2) (OR 6.8, 95% CI 1.3-34.6; P = .02). Overall prevalence of symptomatic hemorrhages was 6.4%. Patients without occlusion had no hemorrhages (0% versus 23.3%; P < .04). CONCLUSION: Among patients treated with tPA, those with patent vasculature or occult distal occlusion on CTA before treatment have lower NIHSS, better chances of early improvement and early independence with fewer hemorrhages.

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PubMed2005

Hypoattenuation on CT angiographic source images predicts risk of intracerebral hemorrhage and outcome after intra-arterial reperfusion therapy.

BACKGROUND AND PURPOSE: Symptomatic hemorrhagic transformation (HT) is a significant complication of intravenous and catheter-based reperfusion. We hypothesized that the degree of vascular insufficiency, reflected as hypoattenuation on initial CT angiography (CTA) axial source images, is predictive of HT risk in stroke patients receiving intra-arterial reperfusion therapy. METHODS: We examined initial CTA source images and follow-up CT scans in 32 consecutive patients. Regions of interest were semiautomatically segmented and reviewed. Mean intensity was determined in the region of maximal hypoattenuation and in normal contralateral tissue, and the arithmetic difference (deltaHU) calculated. Receiver operator characteristic (ROC) curves and cross-validation were used to identify threshold deltaHU values. RESULTS: Thirteen patients had HT on follow-up CT (seven with parenchymal hematoma, six with hemorrhagic infarction). Patients with and those without HT did not differ in age, blood glucose level, lesion volume, or time to treatment or recanalization, though the former had a greater mean deltaHU (9.0 vs 6.3, P = .006). The ROC threshold at deltaHU > or = 8.1 was 69% sensitive and 90% specific for patients who developed HT (odds ratio = 19.1; 95% confidence interval: 2.9, 125; P = .002) and was predictive of poor clinical outcome (modified Rankin scale score > 2, P = .03). Neither HT in general nor parenchymal hematoma subtype was associated with poor outcome. CONCLUSION: The degree of hypoattenuation on initial CTA source images is a risk factor for HT and poor clinical outcome after intra-arterial reperfusion therapy. Prospective validation of this relationship in large populations may permit feasible real-time risk stratification.

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