A retrospective review of sex differences of white matter hyperintensities in brain MRI of patients with migraine.

OBJECTIVES: The primary objective of this study was to evaluate the prevalence of white matter hyperintensities (WMHs) in patients who experience migraine and compare findings between adult male and female patients. Specific symptoms and comorbidities also were analyzed to determine whether they were associated with WMH prevalence or the sex of patients with migraine. We hypothesized that females would have a higher prevalence of WMHs, experience more frequent and more severe migraine headaches, and be more likely to have certain comorbidities associated with migraine than males. BACKGROUND: An increased prevalence of WMHs in patients with migraine has been proposed, although this relation is not well-supported by data from population-based MRI studies. The difference in brain morphology between males and females is of research interest, and females in the general population appear to have a higher prevalence of WMHs. Sex differences and various comorbidities in patients with migraine relative to the number of WMHs on brain imaging have not been fully investigated. METHODS: This was a cross-sectional study of 177 patients aged 18 years and older with a diagnosis of migraine who were seen in the Lehigh Valley Fleming Neuroscience Institute's Headache Center between January 1, 2000, and January 1, 2017. Patients' baseline characteristics were extracted from electronic medical records, including demographics, review of systems documentation, and brain imaging from MRI. Variables including headache severity, frequency of head pain, insomnia, and comorbidities (anxiety, depression, diabetes, hyperlipidemia, hypertension, and neck pain) also were analyzed for associations with the presence of WMHs. RESULTS: Females were found to have a significantly higher number of WMHs than males (median 3 [IQR: 0-7] vs. 0 [IQR: 0-3], p = 0.023). Patients with WMHs were significantly more likely than those without WMHs to have hypertension (39.8% of patients with WMHs vs. 20.3% without WMHs, p = 0.011), constipation (20.9% vs. 8.3%, p = 0.034), and sleep disorder (55.7% vs. 37.3%, p = 0.022). Females with migraine were significantly more likely to experience constipation than males (20.0% vs. 2.9%, p = 0.015). None of the migraine characteristics studied (frequency, severity, presence of aura) were different between sexes, nor were they significantly associated with the presence of WMHs. CONCLUSION: This study suggests that females with migraine may be more likely to have WMHs and experience constipation than males with migraine. Migraine frequency and severity were not different between sexes, nor were they significantly associated with the presence of WMHs. The findings of this study do not support a specific etiology of WMH development in individuals with migraine that differs from findings in the general population. Further studies are warranted.

The role of carotid ultrasound in patients with non-lateralizing neurological complaints.

OBJECTIVES: In the United States, approximately 18-25% of carotid duplex ultrasound (CUS) studies are ordered to assess patients with non-lateralizing neurological complaints such as syncope, blurry vision, lightheadedness, headache, and altered mental status. The purpose of this study is to evaluate the benefit of CUS in the evaluation of patients presenting with non-lateralizing signs or symptoms. MATERIALS AND METHODS: We conducted a retrospective analysis to assess the degree and laterality of carotid stenosis among patients with non-lateralizing neurological complaints who underwent CUS interpreted by certified vascular neurologists over a period of 3 years. The primary endpoint was to identify the prevalence of moderate-to-severe carotid artery stenosis among 280 patients who met inclusion criteria. RESULTS: A total of 17.7% of CUS studies were ordered for non-lateralizing symptoms. Two hundred and sixty-one patients (93.21%) had either normal imaging or mild carotid stenosis of <50%. Nineteen patients (6.79%) were found to have stenosis of ≥50%. In this subgroup, age and known preexisting carotid artery atherosclerotic disease were the only variables found to have a statistically significant association with the level of stenosis found on CUS. Two patients with asymptomatic stenosis of >70% underwent a revascularization procedure. CONCLUSION: At least 17.7% of CUS studies were completed for non-lateralizing symptoms. The study is of low-yield with the prevalence of moderate-to-severe stenosis being comparable to that in the general asymptomatic population. We conclude that there is minimal clinical value in the use of CUS to investigate non-lateralizing neurological complaints, resulting in unnecessary healthcare costs.

Perioperative Stroke.

PURPOSE OF REVIEW: This review overviews perioperative stroke as it pertains to specific surgical procedures. RECENT FINDINGS: As awareness of perioperative stroke increases, so does the opportunity to potentially improve outcomes for these patients by early stroke recognition and intervention. Perioperative stroke is defined to be any stroke that occurs within 30 days of the initial surgical procedure. The incidence of perioperative stroke varies and is dependent on the specific type of surgery performed. This chapter overviews the risks, mechanisms, and acute evaluation and management of perioperative stroke in four surgical populations: cardiac surgery, carotid endarterectomy, neurosurgery, and non-cardiac/non-carotid/non-neurological surgeries.

The Effect of Regional Anesthetic Sphenopalatine Ganglion Block on Self-Reported Pain in Patients With Status Migrainosus.

BACKGROUND: Status migrainosus (SM) is defined as a debilitating migraine attack lasting more than 72 hours in patients previously known to suffer from migraine headache. Typically, these attacks fail to respond to over the counter and abortive medications. The sphenopalatine ganglion (SPG) plays a critical role in propagating both pain and the autonomic symptoms commonly associated with migraines. SPG block via transnasal lidocaine is moderately effective in reducing migraine symptoms, but this approach is often poorly tolerated and the results are inconsistent. We proposed that an SPG block using a suprazygomatic injection approach would be a safe and effective option to abort or alleviate pain and autonomic symptoms of SM. METHODS: Through a retrospective records review, we identified patients with a well-established diagnosis of migraine, based on the International Headache Society criteria. Patients selected for study inclusion were diagnosed with SM, had failed to respond to 2 or more abortive medications, and had received a suprazygomatic SPG block. Patients had also been asked to rate their pain on a 1-10 Likert scale, both before and 30 minutes after the injection. RESULTS: Eighty-eight consecutive patients (20 men and 68 women) received a total of 252 suprazygomatic SPG block procedures in the outpatient headache clinic after traditional medications failed to abort their SM. At 30 minutes following the injections, there was a 67.2% (±26.6%) reduction in pain severity with a median reduction of 5 points (IQR= -6 to -3) on the Likert scale (ranging from 1 to 10). Overall, patients experienced a statistically significant reduction in pain severity (P < .0001). CONCLUSION: The SPG is known to play an integral role in the pathophysiology of facial pain and the trigeminal autonomic cephalalgias, although its exact role in the generation and maintenance of migraine headache remains unclear. Regional anesthetic suprazygomatic SPG block is potentially effective for immediate relief of SM. We believe the procedure is simple to perform and has minimal risk.

Central Hypoventilation: A Rare Complication of Wallenberg Syndrome.

Central alveolar hypoventilation disorders denote conditions resulting from underlying neurologic disorders affecting the sensors, the central controller, or the integration of those signals leading to insufficient ventilation and reduction in partial pressures of oxygen. We report a patient who presented with a left lateral medullary ischemic stroke after aneurysm repair who subsequently developed a rare complication of CAH. Increased awareness of this condition's clinical manifestations is crucial to make an accurate diagnosis and understand its complications and prognosis.

Neurologic complications of arrhythmia treatment.

An arrhythmia is defined as an abnormal heart rhythm. Certain arrhythmias have much higher rates of neurologic complications, including stroke, cognitive impairment, and dementia. The purpose of this paper is to review both the direct and indirect causes of neurologic problems caused by arrhythmias. Direct complications from arrhythmia can include stroke, transient ischemic attack (TIA), and varying disorders of cognition. According to the Stroke Data Bank, which divided potential direct causes of cardioembolic stroke into strong and weak sources, both atrial fibrillation and sick-sinus syndrome were considered to be strong sources of this type of ischemic stroke. Indirect causes of neurologic complications include cardiopulmonary resuscitation, medications, cardiology procedures, and cardiac surgical procedures used to treat arrhythmias.

Endovascular carotid artery stenting and early coronary artery bypass grafting for asymptomatic carotid artery stenosis: long-term outcomes and neurologic events.

BACKGROUND: Optimal management of patients with asymptomatic critical carotid artery stenoses prior to coronary artery bypass grafting (CABG) has no clear consensus. Further, optimal timing for surgical coronary revascularization has not been defined after or with any carotid revascularization. METHODS: We reviewed the data from 2002 to 2007, of all patients in our institution who underwent carotid artery stenting (CAS) for critical carotid artery stenoses, prior to CABG. Twenty patients with critical carotid disease were referred for preoperative carotid intervention prior to CABG. Carotid duplex demonstrated evidence of critical stenoses in all patients. Patients were serially assessed by a stroke neurologist before and after the procedure (immediately, at 24 hr, at 48 hr, immediately following CABG, and at 30 days). We evaluated initial procedural success as well as freedom from periprocedure stroke. RESULTS: Prior to undergoing CABG, 20 patients had stents placed in a single carotid artery for unilateral asymptomatic critical carotid artery stenoses. All the procedures, except one, were performed with distal embolic protection. Patients received aspirin and clopidogrel. There were no strokes or deaths up to a mean follow up of 486 days. The mean time from CAS to CABG performed in the same hospital admission was 6.4 days. Transfusion rates were not excessive despite dual antiplatelet therapy. CONCLUSION: In a real-world setting, endovascular extracranial CAS for asymptomatic carotid artery stenosis by experienced operators, prior to CABG was safe and permitted early coronary revascularization without increased risk of strokes or death in this high-risk cardiovascular patient population.

Cardioembolic stroke: An update on etiology, diagnosis and management.

Stroke and ischemic heart diseases are among the most common causes of death and disability throughout the world. Even more worrisome is the suggestion that stroke rates may further increase in certain developing nations. The purpose of this article is to review the particular subtype of stroke known as cardioembolic stroke. A cardioembolic stroke occurs when the heart pumps unwanted materials into the brain circulation, resulting in the occlusion of a brain blood vessel and damage to the brain tissue. The etiology, clinical manifestations, diagnosis and management of cardioembolic stroke are reviewed.

Technology insight: brain MRI and cardiac surgery--detection of postoperative brain ischemia.

Annually, an estimated 1 million patients undergo heart surgery worldwide. Unfortunately, stroke continues to be a frequent complication of cardiac surgery, with the specific cerebrovascular risk depending upon the particular surgical procedure performed. Neuroimaging has an integral role in the initial evaluation and management of patients who present with acute stroke symptoms following cardiac surgery. The aim of this paper is to review the role brain MRI has in detecting postoperative brain ischemia in these patients. Multimodal MRI--using diffusion-weighted MRI (DWI), perfusion-weighted MRI, and gradient-recalled echo imaging--has an excellent capacity to identify and delineate the size and location of acute ischemic strokes as well as intracerebral hemorrhages. This differentiation is critical in making appropriate treatment decisions in the acute setting, such as determining patient eligibility for thrombolytic or hemodynamic therapies. At present, DWI offers prognostic value in patients with strokes following cardiac surgery. Additionally, DWI could be a valuable tool for evaluating stroke preventive measures as well as therapeutic interventions in patients undergoing CABG surgery.

Use of stents to treat extracranial cerebrovascular disease.

Stent-assisted carotid angioplasty (CAS) is increasingly utilized for hemodynamically significant stenoses of the extracranial carotid artery. Carotid endarterectomy (CEA) is still considered the gold standard in the management of symptomatic hemodynamically significant carotid stenoses. However, endovascular device technology is rapidly evolving and the recent introduction of embolic filtration devices (EFD) proved to reduce periprocedural stroke rates in CAS considerably. Several randomized multicenter trials are currently recruiting patients to compare CAS with EFD to carotid endarterectomy in different cohorts, such as patients at high surgical risk for CEA and those with asymptomatic stenosis. The review presents current developments in CAS.

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

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

Cerebrovascular Complications of Fibromuscular Dysplasia.

Patients with cerebral ischemia or hemorrhage due to fibromuscular dysplasia (FMD) should be admitted to a monitored hospital bed and receive supportive stroke care. Based on our personal clinical experience, we recommend antiplatelet agents for future stroke prevention in patients with symptomatic FMD. In patients with watershed stroke due to hemodynamically significant FMD, our opinion is that hypertensive, hypervolemic therapy should be initiated immediately. Additionally, we suggest that potential revascularization therapies, such as intraoperative or primary percutaneous angioplasty, should be discussed.

Acute basilar artery occlusion: diffusion-perfusion MRI characterization of tissue salvage in patients receiving intra-arterial stroke therapies.

BACKGROUND AND PURPOSE: Diffusion-perfusion MRI in patients with anterior circulation occlusions has demonstrated salvage of threatened tissue after thrombolytic therapy. Similar studies have not been reported with posterior circulation occlusions. METHODS: Patients with acute basilar artery occlusion treated with intra-arterial thrombolytics were studied with multimodal MRI before treatment, several hours after treatment, and at day 7. RESULTS: Ten patients were studied (9 men, 1 woman). Mean age was 70 years, and median pretreatment National Institutes of Health Stroke Scale (NIHSS) score was 14. In 6 patients imaged before treatment and at day 7, mean pretreatment diffusion-weighted imaging (DWI) lesion volume was 11 cm(3), and day 7, lesion volume was 2.6 cm(3). Significant mismatch was visualized in all 5 patients with pretreatment perfusion-diffusion imaging (mean, 73%; range, 49% to 99%). Late imaging obtained in 4 of these 5 patients demonstrated that mean posttreatment DWI lesion volume (21 cm(3)) was less than the mean initial perfusion lesion volume (62 cm(3)). Although there was no direct correlation between pretreatment DWI volume and initial NIHSS (r=-0.113), there was good correlation between pretreatment perfusion-weighted imaging volume and initial NIHSS (r=0.72). CONCLUSIONS: In this first report of diffusion-perfusion MRI in patients with acute basilar artery occlusions treated with intra-arterial thrombolysis, significant mismatch was visualized on pretreatment studies, suggesting that large volumes of salvageable tissue were present. Final infarct volumes were smaller than pretreatment perfusion volumes, suggesting that substantial volumes of tissue were salvaged by thrombolytic reperfusion.

The Los Angeles Motor Scale (LAMS): a new measure to characterize stroke severity in the field.

OBJECTIVE: To develop and retrospectively analyze an instrument that rapidly characterizes pretreatment stroke severity for use in prehospital acute stroke clinical trials. METHODS: The Los Angeles Motor Scale (LAMS) was constructed by assigning point values to Los Angeles Prehospital Stroke Screen (LAPSS) items of facial weakness, arm strength, and grip to yield a total 0-5 scale. The concurrent, discriminant, and predictive validities of the LAMS were probed using data from 90 patients enrolled in acute stroke clinical trials. Predictive performance of the LAMS was compared with that of the initial full National Institutes of Health Stroke Scale (NIHSS) and the five-item shortened NIHSS (sNIHSS) in projecting long-term outcomes on standard functional end points. RESULTS: LAMS score at entry averaged mean 2.6, median 2. Entry LAMS scores correlated closely with entry NIHSS scores (r=0.75). LAMS score correlations with three-month functional outcome measures were robust. Receiver operator curve analyses (c statistic) for performance in predicting three-month outcomes were: three-month modified Rankin-LAMS 0.75, sNIHSS 0.69, NIHSS 0.74; three-month Barthel Index-LAMS 0.77, sNIHSS 0.76, NIHSS 0.82; three-month NIHSS-LAMS 0.76, sNIHSS 0.62, NIHSS 0.70; and three-month GOS-LAMS 0.55, sNIHSS 0.67, NIHSS 0.76. Considering dichotomized three-month measures, entry LAMS scores were markedly lower in patients destined for excellent outcome, e.g., three-month modified Rankin score

Validation of computed tomographic middle cerebral artery "dot"sign: an angiographic correlation study.

BACKGROUND AND PURPOSE: The middle cerebral artery (MCA) "dot" sign consists of hyperdensity of an arterial structure, seen as a dot in the sylvian fissure. The MCA dot sign has been proposed to indicate thrombosis of M2 or M3 MCA branches, analogous to the hyperdense middle cerebral artery (HMCA) sign indicating M1 thrombosis. The MCA dot sign has not been validated previously against the gold standard of conventional cerebral angiography. METHODS: Noncontrast CT scans and immediately subsequent cerebral angiograms from 54 acute stroke patients within 8 hours of symptom onset were analyzed. CT films were inspected for the MCA dot sign and HMCA sign. Vascular findings on CT were compared with findings at angiography. RESULTS: Mean patient age was 71 years; median National Institutes of Health Stroke Scale score was 16.5. Mean time from symptom onset to CT was 125 minutes, and that from CT to angiography was 117 minutes. All patients had arterial occlusion at angiography. Of the anterior circulation occlusions, M1 occlusions were noted in 28 patients, isolated M2 in 15, and isolated M3 in 4. One definite MCA dot sign was observed in 16.7% of patients, and an HMCA sign was observed in 13.9%. MCA dot sign performance in predicting the presence of M2 or M3 clot at angiography was as follows: sensitivity 38%, specificity 100%, positive predictive value 100%, negative predictive value 68%, and overall accuracy 73%. CONCLUSIONS: The MCA dot sign is a highly specific and moderately sensitive indicator of acute thrombus in the M2/M3 MCA branches, as validated by catheter angiography. The MCA dot sign is a useful additional acute stroke CT marker.

Annual incidence of first silent stroke in the United States: a preliminary estimate.

BACKGROUND: Recent estimates of stroke incidence in the US range from 760,000 to 780,000 annually, however these estimates do not reflect the incidence of silent infarcts and hemorrhages. Since population-based studies indicate the prevalence of silent stroke is substantially higher than that of symptomatic stroke, estimates of stroke incidence based solely on symptomatic events may substantially underestimate the annual stroke burden. METHODS: The prevalence of silent infarcts for different age strata were abstracted from two US population-based MRI studies, the Atherosclerosis Risk in Communities Study and the Cardiovascular Health Study. Similarly, first silent cerebral hemorrhage incidence rates were derived from population-based MRI prevalence observations in the Austrian Stroke Prevention Study. Prevalence observations in these studies and death rates from the US Census were inputted to calculate age-specific first silent MRI infarct and hemorrhage incidence. Age- specific incidence rates were projected onto 1998 US population age cohorts to calculate the annual burden of first silent MRI ischemic stroke and first silent MRI cerebral hemorrhage. RESULTS: Estimated age-specific annual incidence rates (per 100,000) of persons experiencing first silent MRI infarct ranged from 1,600 in the age 30-39 stratum to 16,400 at ages 75-79. Estimated incidence rates of first silent MRI cerebral hemorrhage ranged from 180 in the ages 30-39 to 6,900 at age >85. Overall, the projected annual incidence in 1998 of US individuals experiencing first silent MRI infarct was 9,040,000, and first silent MRI hemorrhage 1,940,000. CONCLUSIONS: In 1998, more than 11 million persons experienced stroke in the US, in whom approximately 770,000 were symptomatic and 11 million were first-ever silent MRI infarcts or hemorrhages. These findings demonstrate the incidence of stroke is substantially higher than suggested by estimates based solely on clinically manifest events.

Beyond tissue plasminogen activator: mechanical intervention in acute stroke.

Mechanical interventions in acute ischemic stroke promise to provide emergency physicians with tools to treat patients in whom conventional thrombolysis might be ineffective or contraindicated, including most patients with stroke who arrive at the emergency department beyond the 3-hour time window for intravenous tissue plasminogen activator. A systematic MEDLINE literature review was performed. Endovascular interventions currently in early human clinical trials include the use of lasers, ultrasonography, angioplasty, microsnares, and a variety of clot-retrieval devices. Potential advantages of these approaches include more rapid recanalization of occluded vessels, reduced or no exposure to fibrinolytic agents, and a longer treatment window. Early safety trials are promising, with serial improvements in device design to minimize trauma to cerebrovascular endothelium and accelerate vessel recanalization. The purpose of this review is to provide the emergency medicine community with an understanding of these promising and emerging approaches to acute stroke therapy.

Perfusion-weighted magnetic resonance imaging thresholds identifying core, irreversibly infarcted tissue.

BACKGROUND AND PURPOSE: Identifying core, irreversibly infarcted tissue and salvageable penumbral tissue is crucial to informed, physiologically guided decision making regarding thrombolytic and other interventional therapies in acute ischemic stroke. Pretreatment perfusion MRI offers promise as a means to differentiate core from penumbral tissues. METHODS: Diffusion-perfusion MRIs were performed before treatment and on day 7 in patients undergoing successful vessel recanalization with intra-arterial thrombolytic therapy. Perfusion maps of the time to peak of the residue function (Tmax) were generated after deconvolution of an arterial input function. Initial perfusion abnormalities and final infarct regions were outlined by hand. Posttreatment images were coregistered to the pretreatment study. Voxel-by-voxel and volume analyses were performed to identify thresholds of perfusion abnormalities that best predict core, irreversibly infarcted tissue. RESULTS: Fourteen patients (4 men, 10 women) with vessel recanalization were studied. Mean age was 73 years, and median entry National Institutes of Health Stroke Scale score was 12. Mean time from symptom onset to start of intra-arterial infusion was 245 minutes and to recanalization was 338 minutes. With a voxel-by-voxel analysis, Tmax > or =6 and > or =8 seconds (sensitivity, 71% and 53%; specificity, 63% and 80%) correlated most highly with day 7 final infarct. With a volume analysis, Tmax > or =6 and > or =8 seconds (r2=0.704 and r2=0.705) correlated most highly with day 7 final infarct. CONCLUSIONS: Perfusion-weighted imaging measures of ischemia severity accurately differentiate irreversibly injured core from penumbral, salvageable tissue. The best threshold for identifying core infarcted tissue is adjusted Tmax of > or =6 to 8 seconds.

Magnetic resonance imaging detection of microbleeds before thrombolysis: an emerging application.

BACKGROUND: Hemorrhagic transformation (HT) is a major complication of thrombolytic treatment for acute ischemic stroke. Although a history of prior intracerebral hemorrhage diagnosed by head CT is a contraindication to thrombolysis, there are no guidelines or data regarding evidence of prior asymptomatic microbleeds visualized with T2*-weighted magnetic resonance imaging (MRI). METHODS: Pretreatment T2*-weighted MRI sequences were retrospectively analyzed in all patients receiving intra-arterial thrombolytic therapy and undergoing a pretreatment MRI at our institution. The frequency and location of prior microbleeds was determined and compared with the frequency and location of secondary HT after therapy. RESULTS: Five of 41 patients undergoing MRI before receiving intra-arterial thrombolytic therapy demonstrated evidence of prior microbleeds on the pretreatment MRI studies. Major symptomatic hemorrhage occurred in 1 of 5 patients with microbleeds compared with 4 of 36 patients without. Only 1 patient in the entire 41-patient cohort experienced any HT outside the acute ischemic field. In this patient, the symptomatic hemorrhage occurred directly at the site of a prior microbleed, contralateral to the acute ischemic event. CONCLUSIONS: Old silent microbleeds, visualized with T2*-weighted MRI sequences, may be a marker of increased risk of HT in patients receiving thrombolytic therapy for acute ischemic stroke. Pretreatment screening of thrombolytic candidates with these MRI sequences may be useful in the future to identify these patients.