Maxim Hammer - Academia.edu (original) (raw)

Papers by Maxim Hammer

Research paper thumbnail of Three-Dimensional Representations of Objects in Dorsal Cortex are Dissociable from Those in Ventral Cortex

Cerebral cortex (New York, N.Y. : 1991), Jan 18, 2015

An established conceptualization of visual cortical function is one in which ventral regions medi... more An established conceptualization of visual cortical function is one in which ventral regions mediate object perception while dorsal regions support spatial information processing and visually guided action. This division has been contested by evidence showing that dorsal regions are also engaged in the representation of object shape, even when actions are not required. The critical question is whether these dorsal, object-based representations are dissociable from ventral representations, and whether they play a functional role in object recognition. We examined the neural and behavioral profile of patients with impairments in object recognition following ventral cortex damage. In a functional magnetic resonanace imaging experiment, the blood oxygen level-dependent response in the ventral, but not dorsal, cortex of the patients evinced less sensitivity to object 3D structure compared with that of healthy controls. Consistently, in psychophysics experiments, the patients exhibited si...

Research paper thumbnail of Abstract 3730: Length Of Hospitalization And Discharge Disposition Among Acute Ischemic Stroke Patients With Moderate To Severe Stroke by Treatment

Research paper thumbnail of Abstract 2627: Outcomes After Endovascular Treatment For Anterior Circulation Stroke Presenting Beyond 8 Hours Of Time Last Seen Well Do Not Differ In Wake-up Strokes Vs. Witnessed Onset Beyond 8 Hours

Research paper thumbnail of Intra-arterial Thrombolysis Initiated Greater than 24 Hours after Stroke Onset

Research paper thumbnail of Safety and Efficacy of Transplanting Immortalized Neural Stem Cells in Stroke Patients

Current Clinical Neurology, 2008

Research paper thumbnail of Aspirin Response Test Role in Platelet Transfusion Following Intracerebral Hemorrhage*

Clinical Neurology and Neurosurgery, 2015

Spontaneous intracerebral hemorrhage (ICH) results in high morbidity and mortality. A target for ... more Spontaneous intracerebral hemorrhage (ICH) results in high morbidity and mortality. A target for therapy might be hematoma expansion, which occurs in a significant proportion of patients, and can be exacerbated by antiplatelet medications, such as aspirin. It is not clear whether platelet transfusion neutralizes aspirin. The Aspirin Response Test (ART) is commonly ordered in this patient population, but it is not clear whether the results of this test can help select patients for transfusion of platelets. The aim of our study is to investigate whether a selected group of ICH patients, those with reduced platelet activity ("aspirin responders"), will benefit from platelet transfusion. This retrospective study included 63 patients who were taking aspirin but no other antithrombotic medication prior to the ICH. For each patient, we measured hematoma size by head CT on admission and compared with follow-up head CT 1 day later. In the general cohort, 41% of transfused patients and 29% of non-transfused patients had a hematoma expansion. In the "aspirin responders" group, 46% of transfused patients and 22% of non-transfused patients had an expansion. Our data suggest that platelet transfusion following an ICH in "aspirin responders" does not reduce hematoma expansion rates in those patients. A larger prospective study is needed.

Research paper thumbnail of Predictors of Outcome in Patients Presenting with Acute Ischemic Stroke and Mild Stroke Scale Scores

Journal of Stroke and Cerebrovascular Diseases, 2015

Although National Institutes of Health Stroke Scale (NIHSS) is a known predictor of outcome in ac... more Although National Institutes of Health Stroke Scale (NIHSS) is a known predictor of outcome in acute ischemic stroke, there are other factors like age, ambulatory status, and ability to swallow that may be predictors of outcome but are not assessed by the traditional NIHSS. The aim of this retrospective review was to identify predictors of outcome in mild ischemic stroke. Discharge outcomes from patients who presented to our large academic stroke center with acute ischemic stroke from 2005 to 2013 were retrospectively reviewed. Of 7189 patients reviewed, 2597 had initial NIHSS less than 5. Outcome measures were modified Rankin Scale (MRS) score 0-1 and discharge to home. In all, 65% of patients with NIHSS 0-4 were discharged directly home independent of treatment. Of those patients discharged to home, 74% were able to ambulate independently and 98% passed their dysphagia screen. Of patients not discharged directly home, 66% were unable to ambulate independently and 21% did not pass their dysphagia screen. Multivariate logistic regression analysis revealed a significant effect of dysphagia screen (P = .001), ability to ambulate independently (P = .002), age (P = .016), and NIHSS (P = .005) on discharge to home but not MRS of 0-1 (P = .564). In patients with mild stroke scale scores defined as NIHSS 0-4, several factors including age, NIHSS, ambulatory status, and ability to swallow may be independent predictors of functional outcome and discharge home. These data support the development of a modified grading system for assessing functional outcome in mild stroke that considers these factors.

Research paper thumbnail of Hypothermia for acute ischemic stroke: not just another neuroprotectant

The neurologist, 2003

Based on empirical experience, hypothermia has long been known to be a potent putative neuroprote... more Based on empirical experience, hypothermia has long been known to be a potent putative neuroprotectant. Recent insights into the mechanisms of central ischemia and reperfusion suggest reasons why hypothermia may be an ideal modality for extending the time window for thrombolytic stroke therapy. Hypothermia protects brain tissue from the effects of ischemia in multiple ways. It retards energy depletion, reduces intracellular acidosis, and lessens the ischemic overdose of excitatory neurotransmitters. This attenuates the influx of intracellular calcium, the herald of subsequent neuronal death. Additionally, hypothermia suppresses synthesis of oxygen free radicals involved in secondary damage associated with reperfusion. It also suppresses the mechanisms related to blood-brain barrier degeneration and post-ischemic remodeling. Animal and human data show that deep hypothermia is primarily protective and is used in several cardiothoracic and neurosurgical applications, and that mild hypo...

Research paper thumbnail of Acute ischemic stroke: is there a role for hypothermia?

Cleveland Clinic journal of medicine, 2002

Preliminary clinical trials suggest that therapeutic hypothermia might improve the outcomes of pa... more Preliminary clinical trials suggest that therapeutic hypothermia might improve the outcomes of patients with acute stroke. Definitive trials are under way.

Research paper thumbnail of Outcomes after endovascular treatment for anterior circulation stroke presenting as wake-up strokes are not different than those with witnessed onset beyond 8 hours

Journal of neurointerventional surgery, Jan 17, 2014

Previous studies have suggested that patients with wake-up stroke (WUS) may have superior outcome... more Previous studies have suggested that patients with wake-up stroke (WUS) may have superior outcomes compared with patients with a witnessed late time of onset after revascularization. We sought to test this hypothesis in patients with anterior circulation large vessel occlusion stroke (ACLVOS) treated with endovascular therapy beyond 8 h from time last seen well (TLSW). A single center retrospective review of a prospectively acquired database of consecutive patients was performed to identify patients presenting beyond 8 h of TLSW with radiographic evidence of ACLVOS, small core, and large penumbra who subsequently underwent endovascular treatment. We identified 206 patients. Patients were divided into two groups: (1) patients with WUS (38%, n=78) and (2) patients with witnessed onset beyond 8 h (62%, n=128). The groups were similar in age, baseline National Institutes of Health Stroke Scale score, TLSW to reperfusion, baseline infarct volume, and rate of successful recanalization. Ra...

Research paper thumbnail of Differentiating Hemodynamic Compromise by the OEF Response to Acetazolamide in Occlusive Vascular Disease

Advances in Experimental Medicine and Biology, 2005

Identification of increased stroke risk in a population of symptomatic patients with occlusive va... more Identification of increased stroke risk in a population of symptomatic patients with occlusive vascular disease (OVD) is presently accomplished by measurement of oxygen extraction fraction (OEF) or cerebrovascular reserve (CVR). However, many regions identified by compromised CVR are not identified by OEF. Our aim was to determine whether the response of OEF to acetazolamide, namely, oxygen extraction fraction response (OEFR) would identify those hemispheres in hemodynamic compromise with normal OEF. Nine patients symptomatic with transient ischemic attacks and strokes, and with occlusive vascular disease were studied. Anatomical MRI scans and T2-weighted images were used to identify and grade subcortical white matter infarcts. PET cerebral blood flow (CBF) and OEF were measured after acetazolamide. The relationship between CVR and oxygen extraction fraction response (OEFR) showed that positive OEFR occurred after acetazolamide despite normal baseline OEF values. The two hemispheres with positive OEFR were also associated with severe (> 3 cm) subcortical white matter infarcts. We found that the OEFR was highly correlated with CVR and identified hemispheres that were hemodynamically compromised despite normal baseline OEF.

Research paper thumbnail of Lower pretreatment cerebral blood volume affects hemorrhagic risks after intra-arterial revascularization in acute stroke

Neurosurgery, 2008

Intra-arterial therapies are being used more frequently in patients presenting with acute cerebra... more Intra-arterial therapies are being used more frequently in patients presenting with acute cerebral occlusions, but they have been limited by the potential for hemorrhage. We sought to determine whether pretreatment computed tomography perfusion parameters might help to identify patients at a higher risk of developing intracranial hemorrhage after intra-arterial stroke revascularization treatment. We retrospectively reviewed all patients at the University of Pittsburgh Medical Center and Michigan State University who underwent computed tomography perfusion imaging of the brain before intra-arterial thrombolysis between January 2006 and June 2007. Demographic information, angiographic variables, and types of endovascular interventions were recorded. The mean transit time and cerebral blood volumes were recorded for the ipsilateral and contralateral middle cerebral artery territories. A binary logistic regression model was constructed to determine the independent predictors of developing intracranial hemorrhage. A total of 57 patients (33 from the University of Pittsburgh and 24 from Michigan State University) with a mean age of 66 +/- 13 years and mean National Institutes of Health Stroke Scale scores of 16 +/- 5 were studied. The overall recanalization (Thrombolysis in Myocardial Infarction Trial scale 2 or 3 flow) was 72% for the cohort, and the overall rate of parenchymal hemorrhage was 5 of 57 (9%) patients. The overall hemorrhage rate was 19 of 57 (33%) patients. The only variable found to be predictive of the development of hemorrhage after intervention was reduced pretreatment cerebral blood volume (odds ratio, 0.49; 95% confidence interval, 0.35-0.91; P < 0.022). A reduced pretreatment ipsilateral cerebral blood volume value before endovascular revascularization of an acute middle cerebral artery or internal carotid artery occlusion significantly increases the risk of an intracranial hemorrhage.

Research paper thumbnail of Increased Cerebral Oxygen Metabolism and Ischemic Stress in Subjects with Metabolic Syndrome-Associated Risk Factors: Preliminary Observations

Translational Stroke Research, 2010

Hypertension, diabetes, obesity, and dyslipidemia are risk factors that characterize metabolic sy... more Hypertension, diabetes, obesity, and dyslipidemia are risk factors that characterize metabolic syndrome (MetS), which increases the risk for stroke by 40%. In a preliminary study, our aim was to evaluate cerebrovascular reactivity and oxygen metabolism in subjects free of vascular disease but with one or more of these risk factors. Volunteers (n=15) 59±15 (mean±SD)years of age clear of cerebrovascular disease by magnetic resonance angiography but with one or more risk factors were studied by quantitative positron emission tomography for measure ment of cerebral blood flow, oxygen consumption, oxygen extraction fraction (OEF), and acetazolamide cerebrovascular reactivity. Eight of ten subjects with MetS risk factors had OEF >50%. None of the five without risk factors had OEF >50%. The presence of MetS risk factors was highly correlated with OEF >50% by Fisher's exact test (p<0.007). The increase in OEF was significantly (P<0.001) correlated with cerebral metabolic rate for oxygen. Increased OEF was not associated with compromised acetazolamide cerebrovascular reactivity. Subjects with one or more MetS risk factors are characterized by increased cerebral oxygen consumption and ischemic stress, which may be related to increased risk of cerebrovascular disease and stroke.

Research paper thumbnail of The fate of neglected stimuli

Research paper thumbnail of Mechanical Approaches Combined With Intra-Arterial Pharmacological Therapy Are Associated With Higher Recanalization Rates Than Either Intervention Alone in Revascularization of Acute Carotid Terminus Occlusion

Stroke, 2009

Background and Purpose-Acute stroke attributable to internal carotid artery terminus occlusion ca... more Background and Purpose-Acute stroke attributable to internal carotid artery terminus occlusion carries a poor prognosis.

Research paper thumbnail of Endovascular treatment of basilar artery occlusion by manual aspiration thrombectomy

Journal of NeuroInterventional Surgery, 2010

Basilar artery occlusion remains one of the most devastating subtypes of stroke. Intravenous and ... more Basilar artery occlusion remains one of the most devastating subtypes of stroke. Intravenous and intra-arterial therapy have altered the natural history of this disease; however, clinical results remain poor. Therefore, exploring more aggressive and innovative management is warranted. Six consecutive patients presenting with a basilar artery occlusion were treated with the same general algorithm of intra-arterial tissue plasminogen activator and mechanical thrombectomy with the Merci retrieval system. If complete recanalization was not achieved after two passes, manual syringe aspiration through a 4.3F catheter was employed. All interventions utilizing aspiration thrombectomy resulted in recanalization, with five out of six cases displaying TIMI3/TICI3 flow and one patient resulting in complete recanalization of the basilar artery with persistent thrombus in one P2 segment (TIMI2/TICI2B). All patients survived, with five out of six independent in activities of daily living at 3 months (mRS 0-2). Our small case series indicates that aspiration thrombectomy performed manually through a 4.3F catheter can facilitate recanalization of basilar artery occlusion with acceptable clinical outcomes.

Research paper thumbnail of Brain Death and Withdrawal of Support

Surgical Clinics of North America, 2006

The definition of death has evolved to include the concept of brain death. The brainstem is an in... more The definition of death has evolved to include the concept of brain death. The brainstem is an indispensable central integrative unit for all vital functions. The clinical criteria for brain death consist of the demonstration of the absence of function of the brainstem. Confirmatory testing, which mostly evaluates higher clinical function, is usually not required for the diagnosis of brain death.

Research paper thumbnail of Quantitative Perihematomal Blood Flow in Spontaneous Intracerebral Hemorrhage Predicts In-Hospital Functional Outcome

Stroke, 2007

Background and Purpose-Few data on xenon computed tomography-based quantitative cerebral blood fl... more Background and Purpose-Few data on xenon computed tomography-based quantitative cerebral blood flow (CBF) in spontaneous intracerebral hemorrhage have been reported. We correlated perihematomal CBF in a retrospective series of 42 subacute spontaneous intracerebral hemorrhage patients undergoing xenon computed tomography with in-hospital discharge status and mortality. Methods-We calculated 3 area-weighted mean CBF values: (1) within the computed tomography-visible rim of perihematomal edema, (2) within a 1-cm marginal radius around the hematoma, and (3) all cortical regions of interest immediately adjacent to the hematoma. Primary outcomes were in-hospital mortality and discharge status (ordinally as 0ϭhome, 1ϭacute rehabilitation, 2ϭnursing home, 3ϭdeath). Discharge status was used as a surrogate for in-hospital functional outcome. Results-Median hematoma volume was 14.4 cm 3 (range, 2 to 70). Median perihematomal (low-attenuation rim) CBF was 21.9 cm 3 ⅐100 g Ϫ1 ⅐min Ϫ1 (range, 6.1 to 81.1), and the median 1-cm marginal radius CBF was 26.8 cm 3 ⅐100 g Ϫ1 ⅐min Ϫ1 (range, 10.8 to 72.8). The median regional cortical CBF was 26.7 cm 3 ⅐100 g Ϫ1 ⅐min Ϫ1 (range, 6.9 to 72.6). Eight patients had 1-cm marginal radius or regional cortical CBF values Ͻ20 cm 3 ⅐100 g Ϫ1 ⅐min Ϫ1 . Hematoma volume (odds ratio [OR], 1.68 per 10-cm 3 volume; Pϭ0.036) and intraventricular hemorrhage (OR, 1.88 per grade of intraventricular hemorrhage; Pϭ0.036) predicted mortality. Two CBF measures, hydrocephalus, and IVH predicted poor in-hospital functional outcome in bivariate analysis. Each CBF measure (OR, 0.34 to 0.43; PϽ0.001 to 0.003) and intraventricular hemorrhage (OR, 3.42; PϽ0.001) predicted in-hospital functional outcome in multivariable analyses. Conclusions-Most spontaneous intracerebral hemorrhage patients lack perihematomal penumbra. Perihematomal CBF independently predicts in-hospital discharge status but not in-hospital mortality. Further studies are warranted to determine whether perihematomal CBF predicts long-term functional outcomes. (Stroke. 2007;38:319-324.)

Research paper thumbnail of Endovascular Treatment of Tandem Extracranial/Intracranial Anterior Circulation Occlusions: Preliminary Single-Center Experience

Stroke, 2011

Background and Purpose-Acute ischemic stroke due to tandem occlusions of the extracranial interna... more Background and Purpose-Acute ischemic stroke due to tandem occlusions of the extracranial internal carotid artery and intracranial arteries has a poor natural history. We aimed to evaluate our single-center experience with endovascular treatment of this unique stroke population. Methods-Consecutive patients with tandem occlusions of the internal carotid artery origin and an intracranial artery (ie, internal carotid artery terminus, M1 middle cerebral artery, or M2 middle cerebral artery) were studied retrospectively. Treatment consisted of proximal revascularization with angioplasty and stenting followed by intracranial intervention. Endpoints were recanalization of both extracranial and intracranial vessels (Thrombolysis In Myocardial Ischemia Ն2), parenchymal hematoma, and good clinical outcome (modified Rankin Scale Յ2) at 3 months. Results-We identified 77 patients with tandem occlusions. Recanalization occurred in 58 cases (75.3%) and parenchymal hematoma occurred in 8 cases (10.4%). Distal embolization occurred in 3 cases (3.9%). In 18 of 77 patients (23.4%), distal (ie, intracranial) recanalization was observed after proximal recanalization, obviating the need for distal intervention. Good clinical outcomes were achieved in 32 patients (41.6%). In multivariate analysis, Thrombolysis In Myocardial Ischemia Ն2 recanalization, baseline National Institutes of Health Stroke Scale score, baseline Alberta Stroke Programme Early CT score, and age were significantly associated with good outcome. Conclusions-Endovascular therapy of tandem occlusions using extracranial internal carotid artery revascularization as the first step is technically feasible, has a high recanalization rate, and results in an acceptable rate of good clinical outcome. Future randomized, prospective studies should clarify the role of this approach. (Stroke. 2011;42:1653-1657.)

Research paper thumbnail of Comparison of Safety and Clinical and Radiographic Outcomes in Endovascular Acute Stroke Therapy for Proximal Middle Cerebral Artery Occlusion With Intubation and General Anesthesia Versus the Nonintubated State

Stroke, 2010

There is considerable heterogeneity in practice patterns between sedation in the intubated state ... more There is considerable heterogeneity in practice patterns between sedation in the intubated state vs nonintubated state during endovascular acute stroke therapy. We sought to compare clinical and radiographic outcomes between these 2 sedation modalities. Consecutive patients with acute stroke due to middle cerebral artery-M1 segment occlusion treated with endovascular therapy between January 2006 and July 2009 were identified in our interventional acute stroke database. Level of sedation was determined as intubated (IS) vs nonintubated (NIS) state. Final infarct volumes on follow-up imaging and clinical outcomes at 3 to 6 months were obtained. A total of 126 patients were included (73 [58%] NIS vs 53 [42%] IS). In IS patients, intensive care unit length of stay was longer (6.5 vs 3.2 days, P=0.0008). Intraprocedural complications were lower in NIS patients compared with IS patients (5/73 [6%] vs 8/53 [15%], respectively), but the difference was not significant (P=0.13). In univariate and multivariate analyses, NIS was significantly associated with in-hospital mortality (odds ratio=0.32, P=0.011), good clinical outcome (odds ratio=3.06, P=0.042), and final infarct volume (odds ratio=0.25, P=0.004). In endovascular acute stroke therapy, treatment of patients in NIS appears to be as safe as treatment in IS and may result in more favorable clinical and radiographic outcomes. Our preliminary observations derived from this retrospective study await confirmation from prospective trials.

Research paper thumbnail of Three-Dimensional Representations of Objects in Dorsal Cortex are Dissociable from Those in Ventral Cortex

Cerebral cortex (New York, N.Y. : 1991), Jan 18, 2015

An established conceptualization of visual cortical function is one in which ventral regions medi... more An established conceptualization of visual cortical function is one in which ventral regions mediate object perception while dorsal regions support spatial information processing and visually guided action. This division has been contested by evidence showing that dorsal regions are also engaged in the representation of object shape, even when actions are not required. The critical question is whether these dorsal, object-based representations are dissociable from ventral representations, and whether they play a functional role in object recognition. We examined the neural and behavioral profile of patients with impairments in object recognition following ventral cortex damage. In a functional magnetic resonanace imaging experiment, the blood oxygen level-dependent response in the ventral, but not dorsal, cortex of the patients evinced less sensitivity to object 3D structure compared with that of healthy controls. Consistently, in psychophysics experiments, the patients exhibited si...

Research paper thumbnail of Abstract 3730: Length Of Hospitalization And Discharge Disposition Among Acute Ischemic Stroke Patients With Moderate To Severe Stroke by Treatment

Research paper thumbnail of Abstract 2627: Outcomes After Endovascular Treatment For Anterior Circulation Stroke Presenting Beyond 8 Hours Of Time Last Seen Well Do Not Differ In Wake-up Strokes Vs. Witnessed Onset Beyond 8 Hours

Research paper thumbnail of Intra-arterial Thrombolysis Initiated Greater than 24 Hours after Stroke Onset

Research paper thumbnail of Safety and Efficacy of Transplanting Immortalized Neural Stem Cells in Stroke Patients

Current Clinical Neurology, 2008

Research paper thumbnail of Aspirin Response Test Role in Platelet Transfusion Following Intracerebral Hemorrhage*

Clinical Neurology and Neurosurgery, 2015

Spontaneous intracerebral hemorrhage (ICH) results in high morbidity and mortality. A target for ... more Spontaneous intracerebral hemorrhage (ICH) results in high morbidity and mortality. A target for therapy might be hematoma expansion, which occurs in a significant proportion of patients, and can be exacerbated by antiplatelet medications, such as aspirin. It is not clear whether platelet transfusion neutralizes aspirin. The Aspirin Response Test (ART) is commonly ordered in this patient population, but it is not clear whether the results of this test can help select patients for transfusion of platelets. The aim of our study is to investigate whether a selected group of ICH patients, those with reduced platelet activity (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;aspirin responders&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;), will benefit from platelet transfusion. This retrospective study included 63 patients who were taking aspirin but no other antithrombotic medication prior to the ICH. For each patient, we measured hematoma size by head CT on admission and compared with follow-up head CT 1 day later. In the general cohort, 41% of transfused patients and 29% of non-transfused patients had a hematoma expansion. In the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;aspirin responders&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; group, 46% of transfused patients and 22% of non-transfused patients had an expansion. Our data suggest that platelet transfusion following an ICH in &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;aspirin responders&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; does not reduce hematoma expansion rates in those patients. A larger prospective study is needed.

Research paper thumbnail of Predictors of Outcome in Patients Presenting with Acute Ischemic Stroke and Mild Stroke Scale Scores

Journal of Stroke and Cerebrovascular Diseases, 2015

Although National Institutes of Health Stroke Scale (NIHSS) is a known predictor of outcome in ac... more Although National Institutes of Health Stroke Scale (NIHSS) is a known predictor of outcome in acute ischemic stroke, there are other factors like age, ambulatory status, and ability to swallow that may be predictors of outcome but are not assessed by the traditional NIHSS. The aim of this retrospective review was to identify predictors of outcome in mild ischemic stroke. Discharge outcomes from patients who presented to our large academic stroke center with acute ischemic stroke from 2005 to 2013 were retrospectively reviewed. Of 7189 patients reviewed, 2597 had initial NIHSS less than 5. Outcome measures were modified Rankin Scale (MRS) score 0-1 and discharge to home. In all, 65% of patients with NIHSS 0-4 were discharged directly home independent of treatment. Of those patients discharged to home, 74% were able to ambulate independently and 98% passed their dysphagia screen. Of patients not discharged directly home, 66% were unable to ambulate independently and 21% did not pass their dysphagia screen. Multivariate logistic regression analysis revealed a significant effect of dysphagia screen (P = .001), ability to ambulate independently (P = .002), age (P = .016), and NIHSS (P = .005) on discharge to home but not MRS of 0-1 (P = .564). In patients with mild stroke scale scores defined as NIHSS 0-4, several factors including age, NIHSS, ambulatory status, and ability to swallow may be independent predictors of functional outcome and discharge home. These data support the development of a modified grading system for assessing functional outcome in mild stroke that considers these factors.

Research paper thumbnail of Hypothermia for acute ischemic stroke: not just another neuroprotectant

The neurologist, 2003

Based on empirical experience, hypothermia has long been known to be a potent putative neuroprote... more Based on empirical experience, hypothermia has long been known to be a potent putative neuroprotectant. Recent insights into the mechanisms of central ischemia and reperfusion suggest reasons why hypothermia may be an ideal modality for extending the time window for thrombolytic stroke therapy. Hypothermia protects brain tissue from the effects of ischemia in multiple ways. It retards energy depletion, reduces intracellular acidosis, and lessens the ischemic overdose of excitatory neurotransmitters. This attenuates the influx of intracellular calcium, the herald of subsequent neuronal death. Additionally, hypothermia suppresses synthesis of oxygen free radicals involved in secondary damage associated with reperfusion. It also suppresses the mechanisms related to blood-brain barrier degeneration and post-ischemic remodeling. Animal and human data show that deep hypothermia is primarily protective and is used in several cardiothoracic and neurosurgical applications, and that mild hypo...

Research paper thumbnail of Acute ischemic stroke: is there a role for hypothermia?

Cleveland Clinic journal of medicine, 2002

Preliminary clinical trials suggest that therapeutic hypothermia might improve the outcomes of pa... more Preliminary clinical trials suggest that therapeutic hypothermia might improve the outcomes of patients with acute stroke. Definitive trials are under way.

Research paper thumbnail of Outcomes after endovascular treatment for anterior circulation stroke presenting as wake-up strokes are not different than those with witnessed onset beyond 8 hours

Journal of neurointerventional surgery, Jan 17, 2014

Previous studies have suggested that patients with wake-up stroke (WUS) may have superior outcome... more Previous studies have suggested that patients with wake-up stroke (WUS) may have superior outcomes compared with patients with a witnessed late time of onset after revascularization. We sought to test this hypothesis in patients with anterior circulation large vessel occlusion stroke (ACLVOS) treated with endovascular therapy beyond 8 h from time last seen well (TLSW). A single center retrospective review of a prospectively acquired database of consecutive patients was performed to identify patients presenting beyond 8 h of TLSW with radiographic evidence of ACLVOS, small core, and large penumbra who subsequently underwent endovascular treatment. We identified 206 patients. Patients were divided into two groups: (1) patients with WUS (38%, n=78) and (2) patients with witnessed onset beyond 8 h (62%, n=128). The groups were similar in age, baseline National Institutes of Health Stroke Scale score, TLSW to reperfusion, baseline infarct volume, and rate of successful recanalization. Ra...

Research paper thumbnail of Differentiating Hemodynamic Compromise by the OEF Response to Acetazolamide in Occlusive Vascular Disease

Advances in Experimental Medicine and Biology, 2005

Identification of increased stroke risk in a population of symptomatic patients with occlusive va... more Identification of increased stroke risk in a population of symptomatic patients with occlusive vascular disease (OVD) is presently accomplished by measurement of oxygen extraction fraction (OEF) or cerebrovascular reserve (CVR). However, many regions identified by compromised CVR are not identified by OEF. Our aim was to determine whether the response of OEF to acetazolamide, namely, oxygen extraction fraction response (OEFR) would identify those hemispheres in hemodynamic compromise with normal OEF. Nine patients symptomatic with transient ischemic attacks and strokes, and with occlusive vascular disease were studied. Anatomical MRI scans and T2-weighted images were used to identify and grade subcortical white matter infarcts. PET cerebral blood flow (CBF) and OEF were measured after acetazolamide. The relationship between CVR and oxygen extraction fraction response (OEFR) showed that positive OEFR occurred after acetazolamide despite normal baseline OEF values. The two hemispheres with positive OEFR were also associated with severe (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 3 cm) subcortical white matter infarcts. We found that the OEFR was highly correlated with CVR and identified hemispheres that were hemodynamically compromised despite normal baseline OEF.

Research paper thumbnail of Lower pretreatment cerebral blood volume affects hemorrhagic risks after intra-arterial revascularization in acute stroke

Neurosurgery, 2008

Intra-arterial therapies are being used more frequently in patients presenting with acute cerebra... more Intra-arterial therapies are being used more frequently in patients presenting with acute cerebral occlusions, but they have been limited by the potential for hemorrhage. We sought to determine whether pretreatment computed tomography perfusion parameters might help to identify patients at a higher risk of developing intracranial hemorrhage after intra-arterial stroke revascularization treatment. We retrospectively reviewed all patients at the University of Pittsburgh Medical Center and Michigan State University who underwent computed tomography perfusion imaging of the brain before intra-arterial thrombolysis between January 2006 and June 2007. Demographic information, angiographic variables, and types of endovascular interventions were recorded. The mean transit time and cerebral blood volumes were recorded for the ipsilateral and contralateral middle cerebral artery territories. A binary logistic regression model was constructed to determine the independent predictors of developing intracranial hemorrhage. A total of 57 patients (33 from the University of Pittsburgh and 24 from Michigan State University) with a mean age of 66 +/- 13 years and mean National Institutes of Health Stroke Scale scores of 16 +/- 5 were studied. The overall recanalization (Thrombolysis in Myocardial Infarction Trial scale 2 or 3 flow) was 72% for the cohort, and the overall rate of parenchymal hemorrhage was 5 of 57 (9%) patients. The overall hemorrhage rate was 19 of 57 (33%) patients. The only variable found to be predictive of the development of hemorrhage after intervention was reduced pretreatment cerebral blood volume (odds ratio, 0.49; 95% confidence interval, 0.35-0.91; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.022). A reduced pretreatment ipsilateral cerebral blood volume value before endovascular revascularization of an acute middle cerebral artery or internal carotid artery occlusion significantly increases the risk of an intracranial hemorrhage.

Research paper thumbnail of Increased Cerebral Oxygen Metabolism and Ischemic Stress in Subjects with Metabolic Syndrome-Associated Risk Factors: Preliminary Observations

Translational Stroke Research, 2010

Hypertension, diabetes, obesity, and dyslipidemia are risk factors that characterize metabolic sy... more Hypertension, diabetes, obesity, and dyslipidemia are risk factors that characterize metabolic syndrome (MetS), which increases the risk for stroke by 40%. In a preliminary study, our aim was to evaluate cerebrovascular reactivity and oxygen metabolism in subjects free of vascular disease but with one or more of these risk factors. Volunteers (n=15) 59±15 (mean±SD)years of age clear of cerebrovascular disease by magnetic resonance angiography but with one or more risk factors were studied by quantitative positron emission tomography for measure ment of cerebral blood flow, oxygen consumption, oxygen extraction fraction (OEF), and acetazolamide cerebrovascular reactivity. Eight of ten subjects with MetS risk factors had OEF >50%. None of the five without risk factors had OEF >50%. The presence of MetS risk factors was highly correlated with OEF >50% by Fisher's exact test (p<0.007). The increase in OEF was significantly (P<0.001) correlated with cerebral metabolic rate for oxygen. Increased OEF was not associated with compromised acetazolamide cerebrovascular reactivity. Subjects with one or more MetS risk factors are characterized by increased cerebral oxygen consumption and ischemic stress, which may be related to increased risk of cerebrovascular disease and stroke.

Research paper thumbnail of The fate of neglected stimuli

Research paper thumbnail of Mechanical Approaches Combined With Intra-Arterial Pharmacological Therapy Are Associated With Higher Recanalization Rates Than Either Intervention Alone in Revascularization of Acute Carotid Terminus Occlusion

Stroke, 2009

Background and Purpose-Acute stroke attributable to internal carotid artery terminus occlusion ca... more Background and Purpose-Acute stroke attributable to internal carotid artery terminus occlusion carries a poor prognosis.

Research paper thumbnail of Endovascular treatment of basilar artery occlusion by manual aspiration thrombectomy

Journal of NeuroInterventional Surgery, 2010

Basilar artery occlusion remains one of the most devastating subtypes of stroke. Intravenous and ... more Basilar artery occlusion remains one of the most devastating subtypes of stroke. Intravenous and intra-arterial therapy have altered the natural history of this disease; however, clinical results remain poor. Therefore, exploring more aggressive and innovative management is warranted. Six consecutive patients presenting with a basilar artery occlusion were treated with the same general algorithm of intra-arterial tissue plasminogen activator and mechanical thrombectomy with the Merci retrieval system. If complete recanalization was not achieved after two passes, manual syringe aspiration through a 4.3F catheter was employed. All interventions utilizing aspiration thrombectomy resulted in recanalization, with five out of six cases displaying TIMI3/TICI3 flow and one patient resulting in complete recanalization of the basilar artery with persistent thrombus in one P2 segment (TIMI2/TICI2B). All patients survived, with five out of six independent in activities of daily living at 3 months (mRS 0-2). Our small case series indicates that aspiration thrombectomy performed manually through a 4.3F catheter can facilitate recanalization of basilar artery occlusion with acceptable clinical outcomes.

Research paper thumbnail of Brain Death and Withdrawal of Support

Surgical Clinics of North America, 2006

The definition of death has evolved to include the concept of brain death. The brainstem is an in... more The definition of death has evolved to include the concept of brain death. The brainstem is an indispensable central integrative unit for all vital functions. The clinical criteria for brain death consist of the demonstration of the absence of function of the brainstem. Confirmatory testing, which mostly evaluates higher clinical function, is usually not required for the diagnosis of brain death.

Research paper thumbnail of Quantitative Perihematomal Blood Flow in Spontaneous Intracerebral Hemorrhage Predicts In-Hospital Functional Outcome

Stroke, 2007

Background and Purpose-Few data on xenon computed tomography-based quantitative cerebral blood fl... more Background and Purpose-Few data on xenon computed tomography-based quantitative cerebral blood flow (CBF) in spontaneous intracerebral hemorrhage have been reported. We correlated perihematomal CBF in a retrospective series of 42 subacute spontaneous intracerebral hemorrhage patients undergoing xenon computed tomography with in-hospital discharge status and mortality. Methods-We calculated 3 area-weighted mean CBF values: (1) within the computed tomography-visible rim of perihematomal edema, (2) within a 1-cm marginal radius around the hematoma, and (3) all cortical regions of interest immediately adjacent to the hematoma. Primary outcomes were in-hospital mortality and discharge status (ordinally as 0ϭhome, 1ϭacute rehabilitation, 2ϭnursing home, 3ϭdeath). Discharge status was used as a surrogate for in-hospital functional outcome. Results-Median hematoma volume was 14.4 cm 3 (range, 2 to 70). Median perihematomal (low-attenuation rim) CBF was 21.9 cm 3 ⅐100 g Ϫ1 ⅐min Ϫ1 (range, 6.1 to 81.1), and the median 1-cm marginal radius CBF was 26.8 cm 3 ⅐100 g Ϫ1 ⅐min Ϫ1 (range, 10.8 to 72.8). The median regional cortical CBF was 26.7 cm 3 ⅐100 g Ϫ1 ⅐min Ϫ1 (range, 6.9 to 72.6). Eight patients had 1-cm marginal radius or regional cortical CBF values Ͻ20 cm 3 ⅐100 g Ϫ1 ⅐min Ϫ1 . Hematoma volume (odds ratio [OR], 1.68 per 10-cm 3 volume; Pϭ0.036) and intraventricular hemorrhage (OR, 1.88 per grade of intraventricular hemorrhage; Pϭ0.036) predicted mortality. Two CBF measures, hydrocephalus, and IVH predicted poor in-hospital functional outcome in bivariate analysis. Each CBF measure (OR, 0.34 to 0.43; PϽ0.001 to 0.003) and intraventricular hemorrhage (OR, 3.42; PϽ0.001) predicted in-hospital functional outcome in multivariable analyses. Conclusions-Most spontaneous intracerebral hemorrhage patients lack perihematomal penumbra. Perihematomal CBF independently predicts in-hospital discharge status but not in-hospital mortality. Further studies are warranted to determine whether perihematomal CBF predicts long-term functional outcomes. (Stroke. 2007;38:319-324.)

Research paper thumbnail of Endovascular Treatment of Tandem Extracranial/Intracranial Anterior Circulation Occlusions: Preliminary Single-Center Experience

Stroke, 2011

Background and Purpose-Acute ischemic stroke due to tandem occlusions of the extracranial interna... more Background and Purpose-Acute ischemic stroke due to tandem occlusions of the extracranial internal carotid artery and intracranial arteries has a poor natural history. We aimed to evaluate our single-center experience with endovascular treatment of this unique stroke population. Methods-Consecutive patients with tandem occlusions of the internal carotid artery origin and an intracranial artery (ie, internal carotid artery terminus, M1 middle cerebral artery, or M2 middle cerebral artery) were studied retrospectively. Treatment consisted of proximal revascularization with angioplasty and stenting followed by intracranial intervention. Endpoints were recanalization of both extracranial and intracranial vessels (Thrombolysis In Myocardial Ischemia Ն2), parenchymal hematoma, and good clinical outcome (modified Rankin Scale Յ2) at 3 months. Results-We identified 77 patients with tandem occlusions. Recanalization occurred in 58 cases (75.3%) and parenchymal hematoma occurred in 8 cases (10.4%). Distal embolization occurred in 3 cases (3.9%). In 18 of 77 patients (23.4%), distal (ie, intracranial) recanalization was observed after proximal recanalization, obviating the need for distal intervention. Good clinical outcomes were achieved in 32 patients (41.6%). In multivariate analysis, Thrombolysis In Myocardial Ischemia Ն2 recanalization, baseline National Institutes of Health Stroke Scale score, baseline Alberta Stroke Programme Early CT score, and age were significantly associated with good outcome. Conclusions-Endovascular therapy of tandem occlusions using extracranial internal carotid artery revascularization as the first step is technically feasible, has a high recanalization rate, and results in an acceptable rate of good clinical outcome. Future randomized, prospective studies should clarify the role of this approach. (Stroke. 2011;42:1653-1657.)

Research paper thumbnail of Comparison of Safety and Clinical and Radiographic Outcomes in Endovascular Acute Stroke Therapy for Proximal Middle Cerebral Artery Occlusion With Intubation and General Anesthesia Versus the Nonintubated State

Stroke, 2010

There is considerable heterogeneity in practice patterns between sedation in the intubated state ... more There is considerable heterogeneity in practice patterns between sedation in the intubated state vs nonintubated state during endovascular acute stroke therapy. We sought to compare clinical and radiographic outcomes between these 2 sedation modalities. Consecutive patients with acute stroke due to middle cerebral artery-M1 segment occlusion treated with endovascular therapy between January 2006 and July 2009 were identified in our interventional acute stroke database. Level of sedation was determined as intubated (IS) vs nonintubated (NIS) state. Final infarct volumes on follow-up imaging and clinical outcomes at 3 to 6 months were obtained. A total of 126 patients were included (73 [58%] NIS vs 53 [42%] IS). In IS patients, intensive care unit length of stay was longer (6.5 vs 3.2 days, P=0.0008). Intraprocedural complications were lower in NIS patients compared with IS patients (5/73 [6%] vs 8/53 [15%], respectively), but the difference was not significant (P=0.13). In univariate and multivariate analyses, NIS was significantly associated with in-hospital mortality (odds ratio=0.32, P=0.011), good clinical outcome (odds ratio=3.06, P=0.042), and final infarct volume (odds ratio=0.25, P=0.004). In endovascular acute stroke therapy, treatment of patients in NIS appears to be as safe as treatment in IS and may result in more favorable clinical and radiographic outcomes. Our preliminary observations derived from this retrospective study await confirmation from prospective trials.