Biomedical subjects

B L Hoh

Publications and source records attributed to B L Hoh.

12 recordsLinked to original sources

PubMed2004

Computed tomographic demonstrated infarcts after surgical and endovascular treatment of aneurysmal subarachnoid hemorrhage.

BACKGROUND: Cerebral infarction is a sequela of vasospasm. Other etiologies for infarction after subarachnoid hemorrhage (SAH), however, have not been well-studied. To determine the incidence and etiologies for infarction after SAH, we reviewed the head CT scans of all SAH patients at our center from 1993-2000. METHODS: From 1993-2000, 679 consecutive patients were admitted with SAH, of which 619 patients underwent surgical or endovascular treatment. Two reviewers examined the head CT scans of all 619 patients for new infarct. Clinical outcome was collected from a prospective database. FINDINGS: 505 patients were treated with surgical clipping; 114 with endovascular coiling. There were CT findings of new infarct in 189 patients (30%): 140 in the surgical group (28%) and 49 in the endovascular group (43%). The etiologies for infarct in the surgical group were vasospasm 79 (15%), perforator occlusion 40 (8%), large vessel occlusion 14 (3%), elevated intracranial pressure 4 (1%), thromboembolism 2 (0.4%), and systemic hypotension 1 (0.2%). Infarcts in the endovascular group were due to vasospasm 20 (18%), thromboembolism 12 (11%), large vessel occlusion/dissection 9 (8%), elevated intracranial pressure 4 (4%), perforator occlusion 3 (3%), and systemic hypotension 1 (1%). Hunt Hess Grade (P < 0.001), Fisher Score (P < 0.0001), and MGH Grade (P < 0.001) were significantly associated with CT-demonstrated infarct. There was no significant difference in incidence of CT-infarcts when the period 1993-1996 was compared to 1997-2000. CONCLUSIONS: Despite advances in the treatment of SAH, there is still a significant incidence of associated radiographic infarcts. Hunt Hess Grade, Fisher Score, and MGH Grade were significantly associated with CT-demonstrated infarct.

Brain Infarction↗

PubMed2004

A modified technique for using elastase to create saccular aneurysms in animals that histologically and hemodynamically resemble aneurysms in human.

BACKGROUND: Treatment of intracranial aneurysms is evolving with the development of novel therapies. It is important to have an animal model which simulates human aneurysms. We describe a new modified technique to the elastase aneurysm model which creates aneurysms that histologically and hemodynamically resemble human aneurysms. METHODS: Twelve New Zealand white rabbits underwent the aneurysm creation procedure, and 2 underwent a control procedure. In the aneurysm creation procedure, the right common carotid artery (RCCA) origin is surgically exposed and temporarily occluded with a temporary aneurysm clip. The RCCA is ligated distally, and the trapped segment is infused with elastase for 20 minutes, after which the clip is removed. In the control procedure, the RCCA is ligated distally with no elastase. Animals were assessed neurologically using a previously described rabbit neurologic grading scale and food intake scale. Intravenous digital subtraction angiography (IVDSA) was performed 21 days after the procedure. Aneurysms were harvested and stained with H&E and Verhoeff's stain. FINDINGS: All 14 rabbits had normal neurologic and food intake assessments. All 12 rabbits that underwent aneurysm creation procedures demonstrated saccular aneurysms on IVDSA. Mean aneurysm size was 5.9+/-1.9 mm; range 4.3-10.8 mm. The close proximity of the LCCA to the origin of the RCCA on the aortic arch of the New Zealand white rabbit closely resembles a bifurcation aneurysm. Both rabbits that underwent control procedures showed no aneurysm and retrograde thrombosis of the RCCA. Histologic analysis showed the aneurysms had histology characteristic of true human aneurysms. CONCLUSION: We have developed a new modified technique to the elastase aneurysm model which creates aneurysms that hemodynamically and histologically resemble human aneurysms. There have been previous elastase models described, however we find our model is easier to perform and highly reproducible. The aneurysms can be accessed transfemorally making the model ideal for testing endovascular therapies.

Animals↗

PubMed2003

Incidence of residual intracranial AVMs after surgical resection and efficacy of immediate surgical re-exploration.

BACKGROUND: The true incidence of residual lesions after surgical resection of AVMs is not well documented in the literature. Partial surgical resection is thought to not confer any improvement over the natural history risk of hemorrhage of AVMs, and in certain cases may actually increase the risk of hemorrhage. Over the past 11 years, we have adopted a policy of immediate postoperative angiography with immediate surgical re-exploration if a residual lesion is seen. The purpose of the present study was to review our experience to determine the incidence of residual lesions and subsequent outcome. METHODS: From June 1991 to June 2002, 324 patients underwent craniotomy and surgical AVM resection. As per protocol, all patients underwent immediate postoperative angiography. We have a protocol for immediate surgical re-exploration if a residual lesion is seen on postoperative angiographic exam. FINDINGS: There were total six patients (1.8% of patients operated with intracranial AVMs) with residual lesions on postoperative angiography. All six patients underwent immediate surgical re-exploration with complete 100% obliteration; two patients required two re-exploration procedures. There was one operative complication: posterior cerebral artery and superior cerebellar artery infarcts after re-exploration of residual lesion after surgical resection of a large occipito-temperal-parietal AVM. There were no other morbidities and no mortalities. CONCLUSIONS: The incidence of residual lesions seen on postoperative angiography after AVM surgery at an experienced center is 1.8%. Because of the potential imminent danger of hemorrhage from a residual lesion, we recommend a policy of immediate postoperative angiography (or intraoperative angiography if image quality is satisfactory) for all AVM surgery and early surgical re-exploration if a residual lesion is seen.

Adult↗

PubMed2001

Results after surgical and endovascular treatment of paraclinoid aneurysms by a combined neurovascular team.

OBJECTIVE: Advances in surgical and endovascular techniques have improved treatment for paraclinoid aneurysms. A combined surgical and endovascular team can formulate individualized treatment strategies for patients with paraclinoid aneurysms. Patients who are considered to be at high surgical risk can be treated endovascularly to minimize morbidity. We reviewed the clinical and radiographic outcomes of 238 paraclinoid aneurysms treated by our combined surgical and endovascular unit. METHODS: From 1991 to 1999, the neurovascular team treated 238 paraclinoid aneurysms in 216 patients at the Massachusetts General Hospital. The modality of treatment for each aneurysm was chosen based on anatomic and clinical risk factors, with endovascular treatment offered to patients considered to have higher surgical risks. One hundred eighty aneurysms were treated by direct surgery, 57 were treated by endovascular occlusion, and one was treated by surgical extracranial-intracranial bypass and endovascular internal carotid artery balloon occlusion. Locations were transitional, 12 (5%); carotid cave, 11 (5%); ophthalmic, 131 (55%); posterior carotid wall, 38 (16%); and superior hypophyseal 46 (19%). Lesions contained completely within the cavernous sinus were excluded from this analysis. RESULTS: Using the Glasgow Outcome Scale (GOS), overall clinical outcomes were excellent or good (GOS 5 or 4), 86%; fair (GOS 3), 7%; poor (GOS 2), 4%; and death (GOS 1), 3%. Among the surgically treated patients, 90% experienced excellent or good outcomes (GOS 5 or 4), 6% had fair outcomes (GOS 3), 2% had poor outcomes (GOS 2), and 3% died (GOS 1). Among the endovascularly treated patients, 74% had excellent or good outcomes (GOS 5 or 4), 12% had fair outcomes (GOS 3), 10% had poor outcomes (GOS 2), and 4% died (GOS 1). The overall major and minor complication rate from surgery was 29%, with a 6% surgery-related permanent morbidity rate and a mortality rate of 0%. The overall major and minor complication rate from endovascular treatment was 21%, with a 3% endovascular-related permanent morbidity rate and a 2% mortality rate. Visual outcomes for patients who presented with visual symptoms were as follows: improved, 69%; no change, 25%; worsened, 6%; and new visual deficits, 3%. In general, angiographic efficacy was lower in the endovascular treatment group. CONCLUSION: A combined team approach of direct surgery and endovascular coiling can lead to good outcomes in the treatment for paraclinoid aneurysms, including high-risk lesions that might not have been treated in previous surgical series.

Adult↗

PubMed2001

Surgical and endovascular flow disconnection of intracranial pial single-channel arteriovenous fistulae.

INTRODUCTION: Intracranial pial single-channel arteriovenous (AV) fistulae are rare vascular lesions of the brain. They differ from AV malformations in that they lack a true "nidus" and are composed of one or more direct arterial connections to a single venous channel. They often are associated with a venous varix because of their high-flow nature. The pathological aspects of pial AV fistulae arise from their high-flow dynamics; therefore, we think that disconnection of the AV shunt is enough to obliterate the lesion, and that lesion resection is unnecessary. Flow disconnection can be accomplished via surgical or endovascular means. Certain lesions have angiogeometric configurations, however, that are unfavorable for endovascular treatment. We reviewed the experience in our combined neurosurgical and neuroendovascular unit in the treatment of patients with pial single-channel AV fistulae. METHODS: From 1991 to 1999, the combined neurovascular unit at the Massachusetts General Hospital treated nine consecutive patients with nontraumatic intracranial pial single-channel AV fistulae. Carotid-cavernous fistulae and vein of Galen malformations were excluded from this analysis. The combined neurovascular team planned the treatment strategy for each patient on the basis of the anatomic location and the angiogeometry of each lesion. We retrospectively reviewed the medical records, office charts, operative reports, endovascular reports, and x-rays for each patient. Radiographic outcome was assessed by use of posttreatment angiography. Clinical outcome was assessed by an independent nurse practitioner. RESULTS: A treatment strategy of flow disconnection was used in all nine patients and was accomplished surgically in six patients, endovascularly in two patients, and by combined techniques in one patient. All nine lesions were completely obliterated as demonstrated radiographically, including obliteration of the venous varices associated with three of the lesions. With a mean long-term clinical follow-up of 3.2 years (range, 0.3-8.4 yr), four patients were neurologically excellent with no deficits, two patients had pretreatment neurological deficits that did not worsen after treatment, one patient had transient dysphonia and dysphagia postoperatively that resolved, one patient had mild weakness after treatment, and one patient had moderate homonymous hemianopia after treatment. CONCLUSION: Single-channel pial AV fistulae can be treated by a strategy of flow disconnection. Resection of the lesion is not necessary. Flow disconnection can be accomplished either surgically or endovascularly; however, certain angiogeometric configurations are more favorable for surgical treatment. An experienced combined neurosurgical and neuroendovascular team can carefully determine the most appropriate treatment modality on the basis of patient-specific and angiospecific factors.

Adult↗

PubMed2001

Combined surgical and endovascular techniques of flow alteration to treat fusiform and complex wide-necked intracranial aneurysms that are unsuitable for clipping or coil embolization.

OBJECT: Certain intracranial aneurysms, because of their fusiform or complex wide-necked structure, giant size, or involvement with critical perforating or branch vessels. are unamenable to direct surgical clipping or endovascular coil treatment. Management of such lesions requires alternative or novel treatment strategies. Proximal and distal occlusion (trapping) is the most effective strategy. In lesions that cannot be trapped, alteration in blood flow to the "inflow zone," the site most vulnerable to aneurysm growth and rupture, is used. METHODS: From 1991 to 1999 the combined neurosurgical-neuroendovascular team at the Massachusetts General Hospital (MGH) managed 48 intracranial aneurysms that could not be clipped or occluded. Intracavernous internal carotid artery aneurysms were excluded from this analysis. By applying a previously described aneurysm rupture risk classification system (MGH Grades 0-5) based on the age of the patient, aneurysm size, Hunt and Hess grade, Fisher grade, and whether the aneurysm was a giant lesion located in the posterior circulation, the authors found that a significant number of patients were at moderate risk (MGH Grade 2; 31.3% of patients) and at high risk (MGH Grades 3 or 4; 22.9%) for treatment-related morbidity. The lesions were treated using a variety of strategies--surgical, endovascular, or a combination of modalities. Aneurysms that could not be trapped or occluded were treated using a paradigm of flow alteration, with flow redirected from either native collateral networks or from a surgically performed vascular bypass. Overall clinical outcomes were determined using the Glasgow Outcome Scale (GOS). A GOS score of 5 or 4 was achieved in 77.1%, a GOS score of 3 or 2 in 8.3%, and death (GOS 1) occurred in 14.6% of the patients. Procedure-related complications occurred in 27.1% of cases; the major morbidity rate was 6.3% and the mortality rate was 10.4%. Three patients experienced aneurysmal hemorrhage posttreatment; in two patients this event proved to be fatal. Aneurysms with MGH Grades 0, 1, 2, 3, and 4 were associated with favorable outcomes (GOS scores of 5 or 4) in 100%, 92.8%, 71.4%, 50%, and 0% of instances, respectively. CONCLUSIONS: Despite a high incidence of transient complications, intracranial aneurysms that cannot be clipped or occluded require alternative surgical and endovascular treatment strategies. In those aneurysms that cannot safely be trapped or occluded, one approach is the treatment strategy of flow alteration.

Adolescent↗

PubMed2000

Multimodality treatment of nongalenic arteriovenous malformations in pediatric patients.

OBJECTIVE: Previously reported series of arteriovenous malformations (AVMs) in pediatric patients have primarily used a single-modality treatment approach of either surgery, radiosurgery, or embolization, with significant treatment-related morbidity and mortality. At our institution, we have used a combined multidisciplinary team approach of all three treatment modalities, alone or in combination, to minimize complications and to maximize efficacy in the management of these lesions. METHODS: We retrospectively reviewed 40 consecutive pediatric patients with AVMs seen at our institution from 1991 to 1999. A multidisciplinary team planned the treatment for each AVM. The treatment modality consisted of the following approaches: surgery alone in 14 patients, a combination of endovascular embolization and surgery in 6 patients, radiosurgery alone in 11 patients, a combination of endovascular embolization and radiosurgery in 2 patients, and a combination of radiosurgery and surgery in 2 patients. Four patients are receiving ongoing multistaged treatment for reduction of the nidus size for eventual surgical resection or radiosurgical obliteration of large, complex lesions. In one patient, no treatment was recommended. RESULTS: The clinical outcomes for the overall series were 95.0% excellent or good (Glasgow Outcome Scale score 5 or 4), 2.5% fair (Glasgow Outcome Scale score 3), and 2.5% dead. Radiographic efficacy in the patients who have completed treatment was 92.9% complete obliteration of their AVMs and 7.1% incomplete obliteration. Of the 10 patients who had seizures, 9 are seizure-free. CONCLUSION: A combined multimodality approach of surgery, radiosurgery, and embolization in managing AVMs in pediatric patients can improve outcomes and minimize morbidity and mortality.

Adolescent↗

PubMed1999

Targeted inhibition of intrinsic coagulation limits cerebral injury in stroke without increasing intracerebral hemorrhage.

Agents that restore vascular patency in stroke also increase the risk of intracerebral hemorrhage (ICH). As Factor IXa is a key intermediary in the intrinsic pathway of coagulation, targeted inhibition of Factor IXa-dependent coagulation might inhibit microvascular thrombosis in stroke without impairing extrinsic hemostatic mechanisms that limit ICH. A competitive inhibitor of native Factor IXa for assembly into the intrinsic Factor X activation complex, Factor IXai, was prepared by covalent modification of the Factor IXa active site. In a modified cephalin clotting time assay, in vivo administration of Factor IXai caused a dose-dependent increase in time to clot formation (3.6-fold increase at the 300 micrograms/kg dose compared with vehicle-treated control animals, P < 0.05). Mice given Factor IXai and subjected to middle cerebral artery occlusion and reperfusion demonstrated reduced microvascular fibrin accumulation by immunoblotting and immunostaining, reduced 111In-labeled platelet deposition (42% decrease, P < 0.05), increased cerebral perfusion (2.6-fold increase in ipsilateral blood flow by laser doppler, P < 0.05), and smaller cerebral infarcts than vehicle-treated controls (70% reduction, P < 0.05) based on triphenyl tetrazolium chloride staining of serial cerebral sections. At therapeutically effective doses, Factor IXai was not associated with increased ICH, as opposed to tissue plasminogen activator (tPA) or heparin, both of which significantly increased ICH. Factor IXai was cerebroprotective even when given after the onset of stroke, indicating that microvascular thrombosis continues to evolve (and may be inhibited) even after primary occlusion of a major cerebrovascular tributary.

Animals↗

PubMed1998

Reduced microvascular thrombosis and improved outcome in acute murine stroke by inhibiting GP IIb/IIIa receptor-mediated platelet aggregation.

Treatment options in acute stroke are limited by a dearth of safe and effective regimens for recanalization of an occluded cerebrovascular tributary, as well as by the fact that patients present only after the occlusive event is established. We hypothesized that even if the site of major arterial occlusion is recanalized after stroke, microvascular thrombosis continues to occur at distal sites, reducing postischemic flow and contributing to ongoing neuronal death. To test this hypothesis, and to show that microvascular thrombosis occurs as an ongoing, dynamic process after the onset of stroke, we tested the effects of a potent antiplatelet agent given both before and after the onset of middle cerebral arterial (MCA) occlusion in a murine model of stroke. After 45 min of MCA occlusion and 23 h of reperfusion, fibrin accumulates in the ipsilateral cerebral hemisphere, based upon immunoblotting, and localizes to microvascular lumena, based upon immunostaining. In concordance with these data, there is a nearly threefold increase in the ipsilateral accumulation of 111In-labeled platelets in mice subjected to stroke compared with mice not subjected to stroke. When a novel inhibitor of the glycoprotein IIb/IIIa receptor (SDZ GPI 562) was administered immediately before MCA occlusion, platelet accumulation was reduced 48%, and fibrin accumulation was reduced by 47% by immunoblot densitometry. GPI 562 exhibited a dose-dependent reduction of cerebral infarct volumes measured by triphenyltetrazolium chloride staining, as well as improvement in postischemic cerebral blood flow, measured by laser doppler. GPI 562 caused a dose-dependent increase in tail vein bleeding time, but intracerebral hemorrhage (ICH) was not significantly increased at therapeutic doses; however, there was an increase in ICH at the highest doses tested. When given immediately after withdrawal of the MCA occluding suture, GPI 562 was shown to reduce cerebral infarct volumes by 70%. These data support the hypothesis that in ischemic regions of brain, microvascular thrombi continue to accumulate even after recanalization of the MCA, contributing to postischemic hypoperfusion and ongoing neuronal damage.

Animals↗

PubMed1998

Surgical management of high-grade intracranial dural arteriovenous fistulas: leptomeningeal venous disruption without nidus excision.

OBJECTIVE: Of intracranial dural arteriovenous malformations (AVMs), those with cortical venous drainage pose the greatest risk of hemorrhaging. Given recent advances in endovascular, surgical, and radiosurgical techniques, the optimal management of these dural AVMs is controversial. For surgical candidates, the choice of intraoperative techniques remains unclear. Several authors have suggested that surgical clipping of the draining vein close to the nidus of dural AVMs can provide adequate treatment for some lesions. However, recent reports have also promoted partial or complete surgical resection of these lesions. METHODS: We present five cases of dural AVMs with cortical venous drainage that were surgically treated by the senior author between 1993 and 1996, and we review their management. Our series includes two frontal, one temporal, and two occipital lesions. Three patients presented with intracerebral hemorrhages, one with headache and eye pain, and one without symptoms. All five patients demonstrated venous aneurysms associated with the AVMs. Two patients underwent incomplete endovascular embolization before surgery. Operative management in all cases involved clipping of the draining vein as close as possible to the AVMs, together with extensive cautery of the surrounding dura. RESULTS: Postoperative angiography demonstrated complete angiographic obliteration in all cases. The four symptomatic patients all experienced clinical improvement postoperatively. The asymptomatic patient remained asymptomatic. With a mean follow-up period of 29 months, no patient has developed recurrent symptoms. CONCLUSION: Surgical clipping of the draining vein close to dural AVMs has proven safe and effective in our experience. Given the highly vascular nature of dural AVMs, often near major dural sinuses, surgical resection of these lesions may not be indicated.

Adult↗

PubMed1997

Exacerbation of cerebral injury in mice that express the P-selectin gene: identification of P-selectin blockade as a new target for the treatment of stroke.

There is currently a stark therapeutic void in the treatment of evolving stroke. Although P-selectin is rapidly expressed by hypoxic endothelial cells in vitro, the functional significance of P-selectin expression in stroke remains unexplored. In order to identify the pathophysiological consequences of P-selectin expression and to identify P-selectin blockade as a potential new approach for the treatment of stroke, experiments were performed using a murine model of focal cerebral ischemia and reperfusion. Early P-selectin expression in the postischemic cerebral cortex was demonstrated by the specific accumulation of radiolabeled anti-murine P-selectin IgG, with the increased P-selectin expression localized to the ipsilateral cerebral microvascular endothelial cells by immunohistochemistry. In experiments designed to test the functional significance of increased P-selectin expression in stroke, neutrophil accumulation in the ischemic cortex of mice expressing the P-selectin gene (PS +/+) was demonstrated to be significantly greater than that in homozygous P-selectin-null mice (PS -/-). Reduced neutrophil influx was accompanied by greater postischemic cerebral reflow (measured by laser Doppler) in the PS -/- mice. In addition, PS -/- mice demonstrated smaller infarct volumes (5-fold reduction, P<.05) and improved survival compared with PS +/+ mice (88% versus 44%, P<.05). Functional blockade of P-selectin in PS +/+ mice using a monoclonal antibody directed against murine P-selectin also improved early reflow and stroke outcome compared with control mice, with reduced cerebral infarction volumes noted even when the blocking antibody was administered after occlusion of the middle cerebral artery. These data are the first to demonstrate a pathophysiological role for P-selectin in stroke and suggest that P-selectin blockade may represent a new therapeutic target in the treatment of stroke.

Animals↗

PubMed1997

Use of a spectrophotometric hemoglobin assay to objectively quantify intracerebral hemorrhage in mice.

BACKGROUND AND PURPOSE: There is great interest in developing novel anticoagulant or thrombolytic strategies to treat ischemic stroke. However, at present there are limited means to accurately assess the hemorrhagic potential of these agents. The present studies were designed to develop and validate a method to accurately quantify the degree of intracerebral hemorrhage (ICH) in murine models. METHODS: In a murine model, ICH was induced by stereotaxic intraparenchymal infusion of collagenase B alone (6 x 10(-6) U; n = 5) or collagenase B followed by intravenous recombinant tissue plasminogen activator (rt-PA) (0.1 mg/kg; n = 6). Controls consisted of either sham surgery with stereotaxic infusion of saline (n = 5) or untreated animals (n = 5). ICH was (1) graded by a scale based on maximal hemorrhage diameter on coronal sections and (2) quantified by a spectrophotometric assay measuring cyanomethemoglobin in chemically reduced extracts of homogenized murine brain. This spectrophotometric assay was validated with the use of known quantities of hemoglobin or autologous blood added to a separate cohort of homogenized brains. With this assay, the degree of hemorrhage after focal middle cerebral artery occlusion/reperfusion was quantified in mice treated with postocclusion high-dose intravenous rt-PA (10 mg/kg; n = 11) and control mice subjected to stroke but treated with physiological saline solution (n = 9). RESULTS: Known quantities of hemoglobin or autologous blood added to fresh whole brain tissue homogenates showed a linear relationship between the amount added and optical density (OD) at the absorbance peak of cyanomethemoglobin (r = 1.00 and .98, respectively). When in vivo studies were performed to quantify experimentally induced ICH, animals receiving intracerebral infusion of collagenase B had significantly higher ODs than saline-infused controls (2.1-fold, increase; P = .05). In a middle cerebral artery occlusion and reperfusion model of stroke, administration of rt-PA after reperfusion increased the OD by 1.8-fold compared with animals that received physiological saline solution (P < .001). When the two methods of measuring ICH (visual score and OD) were compared, there was a linear correlation (r = .88). Additional experiments demonstrated that triphenyltetrazolium staining, which is commonly used to stain viable brain tissue, does not interfere with the spectrophotometric quantification of ICH. CONCLUSIONS: These data demonstrate that the spectrophotometric assay accurately and reliably quantifies murine ICH. This new method should aid objective assessment of the hemorrhagic risks of novel anticoagulant or thrombolytic strategies to treat stroke and can facilitate quantification of other forms of ICH.

Animals↗