Search PubMed⌕ Search

Biomedical subjects

S Tuhrim

Publications and source records attributed to S Tuhrim.

At least 37 records · Page 2Linked to original sources
PubMed1998

Diffusion-weighted MRI in acute subcortical infarction.

BACKGROUND AND PURPOSE: Conventional imaging lacks sensitivity and specificity for the detection of early subcortical cerebral infarction. The purposes of our study were (1) to determine the accuracy of diffusion-weighted (DW) MRI for early subcortical infarction and (2) to determine the efficacy of DW MRI for differentiating acute from nonacute subcortical infarctions when conventional MR demonstrates multiple infarctions. METHODS: Thirty-nine patients with clinically diagnosed acute subcortical infarction and 17 control subjects were imaged with both conventional and DW MRI from 7 hours to 4 days (mean, 2.0 days) after onset of symptoms. All images were read blinded to specific clinical findings. In all cases, the precise neuroanatomic locations of lesions were noted. These lesions were subsequently correlated by an experienced stroke neurologist to determine whether their locations correlated to the patients' symptoms. RESULTS: The accuracy of DW MRI for acute subcortical infarction was 94.6%. In 4 of 39 cases, the acute infarction was not detected on conventional MRI. In 24 of 39 cases, conventional MRI showed the acute lesion as well as multiple other subcortical lesions. In each of these 24 cases, the DW MRI showed a single lesion to be acute, and in all 24 cases, that lesion corresponded to the patients' acute symptoms. CONCLUSIONS: DW MRI has very high accuracy for acute subcortical infarction and can differentiate acute from nonacute lesions. These data have significant implications in guiding patient management and patient selection for clinical trials.

Acute Disease↗
PubMed1998

Diffusion-weighted MR of acute cerebral infarction: comparison of data processing methods.

BACKGROUND AND PURPOSE: Some investigators have proposed that either calculated diffusion trace images or apparent diffusion coefficient (ADC) maps, which require imaging with multiple diffusion sensitivities and/or postacquisition image processing, are essential for the accurate interpretation of diffusion-weighted images in acute stroke because of the possible pitfalls of regional diffusion anisotropy, magnetic susceptibility artifacts, and confounding T2 effects, all of which alter signal on diffusion-weighted MR images. The purpose of our study was to compare the sensitivity, specificity, and accuracy of simple, orthogonal-axis diffusion-weighted imaging for the diagnosis of early cerebral infarction with three other sets of postacquisition-processed images: isotropic diffusion-weighted, diffusion trace-weighted, and diffusion trace images. METHODS: Twenty-six consecutive adult patients with signs and symptoms consistent with a clinical diagnosis of early cortical and/or subcortical cerebral infarction and 17 control subjects were studied with multisection, single-shot, spin-echo echo-planar diffusion-weighted imaging at 1.5 T to generate a set of three orthogonal-axis diffusion-weighted images. Isotropic diffusion-weighted, diffusion trace-weighted, and diffusion trace (mean ADC) images were then generated off-line and all four sets of images were interpreted blindly by two neuroradiologists. RESULTS: The average sensitivity, specificity, and accuracy for the orthogonal-axis diffusion-weighted images were 98.1%, 97.1%, and 97.7%, respectively. The average sensitivity, specificity, and accuracy for isotropic diffusion-weighted images were 88.5%, 100%, and 93% respectively. The average sensitivity, specificity, and accuracy for diffusion trace-weighted images were 82.7%, 73.6%, and 79.1%, respectively. The average sensitivity, specificity, and accuracy for diffusion trace images were 50.0%, 85.3%, and 64.0%, respectively. CONCLUSION: Orthogonal-axis diffusion-weighted images have the highest sensitivity and accuracy and very high specificity for early cerebral infarction. Our data contradict the contention that quantitative diffusion maps, requiring imaging with multiple diffusion sensitivities and/or subsequent image processing, are necessary for clinical stroke imaging.

Acute Disease↗
PubMed1997

The Minorities Risk Factors and Stroke Study (MRFASS). Design, methods and baseline characteristics.

African-Americans and probably Latinos are at increased risk of stroke compared with white, non-Latino Americans. This study seeks to determine if the known risk factors for stroke can account for this increased risk. In this case-control study controls (neighborhood volunteers) were group-matched to acute stroke cases by ethnicity in a ratio of approximately 2:1 for African-Americans and Latinos and 1:1 for whites. Extensive historical, clinical and laboratory data were collected on each subject. For each ethnic group cases were somewhat older and less well-educated than the volunteer controls. Patients in each ethnic group were similar with regard to time from stroke onset to hospital admission, stroke severity, length of stay, discharge disposition and mortality rate. With minor exceptions the distributions of stroke subtypes within each ethnic group appeared similar to those previously reported. Subject recruitment for this case-control study was completed in the manner and time frame planned. Analysis of risk factor information from this sample should provide valuable information regarding the relative risk associated with the major modifiable risk factors for stroke in the minority groups studied.

Adult↗
PubMed1997

Stroke mechanisms and clinical presentation in large subcortical infarctions.

Large subcortical infarctions may be due to cerebral embolism and cause cortical signs more frequently than small subcortical infarctions, which usually result from small-vessel disease and are not associated with cortical findings. We evaluated 51 consecutive patients with a subcortical infarct on CT that was 1.5 cm or larger for a potential carotid or cardiac source of embolism and determined how frequently aphasia, hemineglect, or gaze paresis occurred. A carotid or cardiac embolic source was identified in 63% of the total population with a carotid source occurring in 23% and a cardiac source occurring in 49%. More than one-half of the patients with hypertension or diabetes mellitus had an embolic source, whereas all patients without these risk factors had a possible carotid or cardiac source of embolism. Aphasia or hemineglect occurred in 39% of patients and gaze paresis occurred in 41%. Large subcortical strokes frequently result in a different clinical syndrome and from a different mechanism than small subcortical strokes.

Aged↗
PubMed1997

Intraventricular hemorrhage in adults: complications and treatment.

Intraventricular hemorrhage (IVH) frequently occurs in the setting of intracerebral and subarachnoid hemorrhage, and is an independent and significant contributor to morbidity and mortality in both conditions. Present therapy of IVH is directed at treating the associated complications of obstructive and communicating hydrocephalus. These therapies are often inadequate to treat the complications and do not remedy the underlying IVH. Intraventricular thrombolysis is a promising but unproven new therapy that directly addresses the IVH and may reduce the incidence of obstructive and communicating hydrocephalus.

Adult↗
PubMed1995

Validation and comparison of models predicting survival following intracerebral hemorrhage.

OBJECTIVE: To compare the performance of two previously reported logistic regression models using data independent from those data used to derive the models. DESIGN: Prospective. SETTING: Acute stroke unit of a tertiary care hospital. PATIENTS: One hundred twenty-nine patients with supratentorial intracerebral hemorrhage. MEASUREMENTS AND MAIN RESULTS: Model 1 contains the initial Glasgow Coma Scale score, hemorrhage size, and pulse pressure. The more complex model 2 includes, in addition to those three variables, the presence or absence of intraventricular hemorrhage and a term representing the interaction of intraventricular hemorrhage and Glasgow Coma Scale score. The areas under the receiver operating characteristic curves generated for each model were statistically indistinguishable. CONCLUSIONS: Model 1 predicts 30-day patient status as well as the more complex model 2. Model 1 provides a valid, easy-to-use means of categorizing supratentorial intracerebral hemorrhage patients in terms of their probability of survival.

Cerebral Hemorrhage↗
PubMed1994

High-specificity neurological localization using a connectionist model.

Most previous connectionist models for diagnosis have been developed using error backpropagation. While these systems function reasonably well, they have been limited by their need for a large database of test cases, to situations where a single disorder is present, and by the large number of connections required between fully-connected sets of processing units. Here we describe a recently developed connectionist model that overcomes these limitations. This approach can reuse existing causal knowledge bases, works well in situations where multiple disorders can occur simultaneously, and does not require fully-connected sets of processing units. We demonstrate that the accuracy of this model is comparable to that of more conventional AI programs using the same knowledge base in determining precisely the site of brain damage in a group of 50 stroke patients. These results support the conclusion that connectionist models can effectively use pre-existing causal knowledge bases from AI systems, and that they can function accurately when handling actual clinical problems.

Artificial Intelligence↗
PubMed1993

The recruitment of research participants: a review.

Social workers are involved in the recruitment of research participants in a variety of ways. Increased knowledge regarding recruitment issues will allow social workers to expand their role and improve their performance in this area. These individuals should be aware that there is a large body of literature addressing recruitment. This selective review of the literature prior to mid-1992 will focus on the Coronary Primary Prevention Trial, volunteer effects, recruitment sources, the recruitment process, impediments to recruitment, bias in recruitment, the amount of time required to recruit and the impact of recruitment and participation on individuals. This will be followed by a discussion of issues to be addressed in arriving at solutions to recruitment problems.

Clinical Trials as Topic↗
PubMed1993

Frontiers in the treatment of ischemic stroke.

Advances in the understanding of the pathophysiology of ischemic neuronal death have led to the development of new approaches to treating acute stroke. Concurrently technologic advances have permitted application of older approaches in a more sophisticated manner. These advances herald an era in which rapid, precise evaluation and treatment of the patient with acute stroke may dramatically alter prognosis. This article reviews some of these advances.

Brain Ischemia↗
PubMed1992

Features on initial computed tomography scan of infarcts with a cardiac source of embolism in the NINDS Stroke Data Bank.

BACKGROUND AND PURPOSE: The lack of valid criteria for the clinical diagnosis of cardiogenic embolism is a major problem in both patient care and research. The aim of this study was to identify features on the initial computed tomogram of the brain that discriminate between patient groups with and without a cardiac source of embolism. To gain insight into the neuroradiological features relevant to the diagnosis of cardiac embolic stroke, we studied the initial computed tomogram of the 1,267 patients with ischemic stroke and such a scan in the National Institute of Neurological Disorders and Stroke (NINDS) Stroke Data Bank. METHODS: We analyzed the initial computed tomographic data from 1,267 patients with ischemic stroke in the NINDS Stroke Data Bank. Based solely on the presence of cardiac sources of embolism, we defined groups with high (n = 244), medium (n = 165), and low (n = 858) risk for cardiogenic embolism and compared the features on the initial computed tomogram among these three groups. RESULTS: Patients in the high-risk group were significantly more likely (p < 0.001) to have infarcts involving one half lobe or larger or infarcts involving both superficial and deep structures than patients in the medium- or low-risk groups. In contrast, deep small infarcts had a negative association (p = 0.004) with the presence of a cardiac source of embolism. There was no significant trend across risk groups in the percent with hemorrhagic infarction, regardless of whether patients with anticoagulant use at the time of the stroke were excluded. CONCLUSION: Although some features of the initial computed tomogram had highly significant associations with the presence of a cardiac source of embolism, the predictive value of these features for an embolic source was low.

Cerebral Infarction↗
PubMed1992

Mechanisms in lacunar infarction.

BACKGROUND AND PURPOSE: Lacunes are thought to occur in patients with hypertension or diabetes mellitus as a result of small-vessel disease. This study evaluated the importance of other stroke mechanisms in a population of patients with lacunar infarction. METHODS: We evaluated 108 consecutive patients with a lacune in the lenticulostriate distribution for other stroke risk factors such as carotid and cardiac disease. RESULTS: Hypertension was present in 68% of the patients and diabetes mellitus in 37%; both occurred in 28% and neither occurred in 23%. Noninvasive carotid studies identified atherosclerotic plaque as a possible embolic source in 23%. By previously established criteria, 18% were at high risk for cardioembolism. Of those with hypertension or diabetes mellitus, 36% were at risk for a carotid or cardiac embolus. Of those without hypertension or diabetes mellitus, 32% had a possible carotid or cardiac etiology. CONCLUSIONS: The high incidence of carotid and cardiac disease in those with and without hypertension or diabetes mellitus suggests the importance of other stroke mechanisms in this population. Patients with lacunar infarction should therefore be evaluated for other causes of stroke that may be treatable.

Aged↗
PubMed1992

Infarcts with a cardiac source of embolism in the NINDS Stroke Data Bank: neurologic examination.

To gain insight into neurologic signs relevant to the diagnosis of cardiogenic embolism, we analyzed data from 1,290 patients with cerebral infarcts in the NINDS Stroke Data Bank. Based solely on the presence of potential cardiac sources of embolism, we divided patients into groups of high (N = 250), medium (N = 167), and low (N = 873) risk of a cardiogenic mechanism for their stroke. Diminished level of consciousness was highly associated with the presence of a cardiac source of embolism. Of the four primarily cortical deficits assessed, three (visual field abnormalities, neglect, and aphasia) showed a highly significant graded relationship to the cardiac risk groups. For the fourth cortical deficit (other nonlanguage cognitive functions), this relationship did not attain statistical significance. Conversely, hemiparesis without sensory or cortical deficits had a strong inverse association to the presence of a cardiac source of embolism. This inverse association was weaker for sensorimotor strokes and nonexistent for pure sensory strokes. Although some neurologic findings had highly significant associations with the presence of a cardiac source of embolism, their predictive value for an embolic source was low.

Cerebral Infarction↗
PubMed1992

Aortic plaque in patients with brain ischemia: diagnosis by transesophageal echocardiography.

We evaluated 183 patients with brain ischemia for an embolic source, using transesophageal echocardiography with extensive imaging of the thoracic aorta. There were mobile, frond-like projections of aortic plaque in seven (4%) patients. The plaque originated on a wide base on the posterior aspect of the ascending aorta at its junction with the transverse arch in six patients, and on the aortic root in one. The acute event was a cerebral infarction in five patients, and a transient ischemic attack in two. This type of aortic plaque could be a previously underdiagnosed source of cerebral embolism that is now easily visualized by transesophageal echocardiography.

Aorta, Thoracic↗
PubMed1991

Intracerebral hemorrhage: external validation and extension of a model for prediction of 30-day survival.

We report validation of a previously reported logistic regression model for predicting 30-day survival after supratentorial intracerebral hemorrhage using independent, prospectively collected data. The original model, using initial Glasgow Coma Scale score, hemorrhage size, and pulse pressure, accounted for mortality or survival at 30 days in 92% of patients in the Pilot Stroke Data Bank with a sensitivity of 0.84 and a specificity of 0.96. For external validation, the model was used to predict 30-day status for each patient in the Main Phase Stroke Data Bank for whom complete risk factor information was available. Overall, 90% of patients' outcomes were correctly predicted with a sensitivity of 0.85 and a specificity of 0.92. Two factors not collected in the Pilot Stroke Data Bank, hyperglycemia and intraventricular hemorrhage extension, were assessed to determine if they provided additional predictive information on 30-day mortality. Intraventricular hemorrhage extension contributed significant predictive information in a logistic regression, whereas hyperglycemia did not. The resulting four-factor model with an interaction term (intraventricular hemorrhage extension and Glasgow Coma Scale score) correctly classified the survival status of 94% of patients at 30 days. A more general outcome, death or failure to achieve a "good" Activities of Daily Living Score by one year, was analyzed with respect to the same four factors. The resulting model correctly classified 95% of the patients in the cohort.

Blood Glucose↗
PubMed1991

The design and automated testing of an expert system for the differential diagnosis of acute stroke.

Stroke is the third leading cause of death in the United States and a major source of morbidity. [1] Recent studies have shown a potential use for thrombolytic agents in the treatment of ischemic stroke (IS) but these agents are contraindicated in intracerebral hemorrhage (ICH). A computed tomographic scan is used to distinguish between these two stroke types prior to the use of thrombolytic agents, but may not be readily obtainable. Decision making aids such as algorithms developed at Guy's Hospital and Strong Memorial Hospital have been designed in an attempt to make this distinction on clinical grounds. We have constructed computerized medical decision-making (CMD) systems based upon these algorithms and compared their performance to a system we developed with the use of National Stroke Data Bank data. Relevant medical data for each of 337 patient cases in the Mount Sinai Hospital Stroke Data Bank were presented to each of the CMD systems. In consideration of the clinical task of using thrombolytic agents, we attempted to maximize the positive predictive value (PPV) for ischemic stroke. The CMD systems based upon the Guy's Hospital and Mount Sinai algorithms produced PPV's of 95% and 94% with sensitivities of 77% and 78% respectively compared to a PPV of 93% and sensitivity of 56% with the Strong Memorial CMD system. The Mount Sinai CMD system was judged more efficacious than the Guy's Hospital system in that it required less clinical information that could be more easily obtained to arrive at similar results.

Acute Disease↗
PubMed1990

Infarcts with a cardiac source of embolism in the NINCDS Stroke Data Bank: historical features.

To gain insight into the historical features relevant to the diagnosis of cardiac embolic strokes, we studied the 1,290 patients with cerebral infarcts in the NINCDS Stroke Data Bank. Based solely on the presence of cardiac sources of embolism, we divided the patients into groups of high (n = 250), medium (n = 166), and low (n = 874) risk of a cardiogenic mechanism for their stroke. There was a highly significant graded relationship between increasing risk of a cardiac source and a history, or presence of, systemic embolism, abrupt onset, and diminished level of consciousness at onset. These clinical features may be useful for assessing the likelihood of a cardiac embolic mechanism in patients with cerebral infarcts.

Cerebral Infarction↗