Advances in Acute Ischemic Stroke Treatment: Current Status and Future Directions

The management of acute ischemic stroke has undergone a paradigm shift in the past decade. This has been spearheaded by the emergence of endovascular thrombectomy, along with advances in medical therapy, imaging, and other facets of stroke care. Herein, we present an updated review of the various stroke trials that have impacted and continue to transform stroke management. It is critical for the radiologist to stay abreast of the ongoing developments to provide meaningful input and remain a useful part of the stroke team.

Quantifying Intra-Arterial Verapamil Response as a Diagnostic Tool for Reversible Cerebral Vasoconstriction Syndrome

BACKGROUND AND PURPOSE

There is mounting evidence supporting the benefit of intra-arterial administration of vasodilators in diagnosing reversible cerebral vasoconstriction syndrome. We prospectively quantified the degree of luminal diameter dilation after intra-arterial administration of verapamil and its accuracy in diagnosing reversible cerebral vasoconstriction syndrome.

MATERIALS AND METHODS

Patients suspected of having intracranial arteriopathy on noninvasive imaging and referred for digital subtraction angiography were enrolled in a prospective registry. Intra-arterial verapamil was administered in vascular territories with segmental irregularities. The caliber difference (Caliber_post - Caliber_pre) and the proportion of caliber change ([(Caliber_post - Caliber_pre)/Caliber_pre] × 100%) were used to determine the response to verapamil. The diagnosis of reversible cerebral vasoconstriction syndrome was made on the basis of clinical and imaging features at a follow-up appointment, independent of the reversibility of verapamil. Receiver operating characteristic curve analysis was performed to determine the best threshold.

RESULTS

Twenty-six patients were included, and 9 (34.6%) were diagnosed with reversible cerebral vasoconstriction syndrome. A total of 213 vascular segments were assessed on diagnostic angiography. Every patient with a final diagnosis of reversible cerebral vasoconstriction syndrome responded to intra-arterial verapamil. The maximal proportion of change (P < .001), mean proportion of change (P = .002), maximal caliber difference (P = .004), and mean caliber difference (P = .001) were statistically different between patients with reversible cerebral vasoconstriction syndrome and other vasculopathies. A maximal proportion of change  ≥32% showed a sensitivity of 100% and a specificity of 88.2% to detect reversible cerebral vasoconstriction syndrome (area under the curve = 0.951). The Reversible Cerebral Vasoconstriction Syndrome-2 score of  ≥5 points achieved a lower area under the curve (0.908), with a sensitivity of 77.8% and a specificity of 94.1%.

CONCLUSIONS

Objective measurement of the change in the arterial calibers after intra-arterial verapamil is accurate in distinguishing reversible cerebral vasoconstriction syndrome from other vasculopathies. A proportion of change  ≥32% has the best diagnostic performance.

Preserving Access: A Review of Stroke Thrombectomy during the COVID-19 Pandemic

Thrombectomy for large-vessel-occlusion stroke is a highly impactful treatment. The spread of coronavirus 19 (COVID-19) across the United States and the globe impacts access to this crucial intervention through widespread societal and institutional changes. In this document, we review the implications of COVID-19 on the emergency care of large-vessel occlusion stroke, reviewing specific infection-control recommendations, available literature, existing resources, and expert consensus. As a population, patients with large-vessel occlusion stroke face unique challenges during pandemics. These are broad in scope. Responses to these challenges through adaptation of stroke systems of care and with imaging, thrombectomy, and postprocedural care are detailed. Preservation of access to thrombectomy must be prioritized for its public health impact. While the extent of required changes will vary by region, tiered planning for both escalation and de-escalation of measures must be a part of each practice. In addition, preparations described serve as templates in the event of future pandemics.

Imaging of Patients with Suspected Large-Vessel Occlusion at Primary Stroke Centers: Available Modalities and a Suggested Approach

The overwhelming benefit of endovascular therapy in patients with large-vessel occlusions suggests that more patients will be screened than treated. Some of those patients will be evaluated first at primary stroke centers; this type of evaluation calls for standardizing the imaging approach to minimize delays in assessing, transferring, and treating these patients. Here, we propose that CT angiography (performed at the same time as head CT) should be the minimum imaging approach for all patients with stroke with suspected large-vessel occlusion presenting to primary stroke centers. We discuss some of the implications of this approach and how to facilitate them.

Hemodynamic Impairment Measured by Positron-Emission Tomography Is Regionally Associated with Decreased Cortical Thickness in Moyamoya Phenomenon

BACKGROUND AND PURPOSE

Impaired cerebrovascular reactivity has been associated with decreased cortical thickness in patients with arterial occlusive diseases. This study tests the hypothesis that severe hemodynamic impairment, indicated by increased oxygen extraction fraction ratios on positron-emission tomography with ¹⁵O tracers, is associated with decreased cortical thickness in patients with Moyamoya phenomenon.

MATERIALS AND METHODS

Patients with unilateral or bilateral idiopathic Moyamoya phenomenon were recruited. Oxygen extraction fraction ratio maps were generated from cerebral images of O[¹⁵O] counts divided by H₂[¹⁵O] counts with normalization by corresponding cerebellar counts. The normal range of the oxygen extraction fraction ratio was estimated from historically available healthy control subjects. Cortical thickness was estimated from T1-weighted MR imaging and FreeSurfer. Regional samples of oxygen extraction fraction ratios and cortical thicknesses were drawn using FreeSurfer parcellations, retaining only parcellations from the vascular territory of the middle cerebral artery.

RESULTS

Complete MR imaging and PET datasets were available in 35 subjects, including 23 women; the mean age at scanning was 44 years. Patients with Moyamoya phenomenon had a significantly increased regional oxygen extraction fraction ratio compared with 15 healthy control subjects (P < .001). Regional oxygen extraction fraction ratio and age were significant predictors of cortical thickness (P < .001 for each) in a generalized linear mixed-effects model. Using hemisphere averages and patient averages, we found that only age was a significant predictor of cortical thickness (P < .001).

CONCLUSIONS

Chronic hemodynamic impairment, as indicated by a higher regional oxygen extraction fraction ratio, was significantly predictive of reduced cortical thickness in mixed-effects analysis of FreeSurfer regions. This phenomenon may be related to reversible metabolic down-regulation.

An Update on the Adjunctive Neurovascular Support of Wide-Neck Aneurysm Embolization and Reconstruction Trial: 1-Year Safety and Angiographic Results

BACKGROUND AND PURPOSE

The safety and efficacy of the PulseRider for the treatment of wide-neck, bifurcation aneurysms at the basilar and carotid terminus locations were studied in a prospective trial, the Adjunctive Neurovascular Support of Wide-Neck Aneurysm Embolization and Reconstruction (ANSWER) trial, reporting on initial 6-month angiographic and clinical results. This report provides insight into the longer term durability and safety with 12-month data.

MATERIALS AND METHODS

Aneurysms treated with the PulseRider among enrolled sites were prospectively studied. Updated 12-month data on clinical and imaging end points are included.

RESULTS

Thirty-four patients were enrolled (29 women, 5 men) with a mean age of 60.9 years. The mean aneurysm height ranged from 2.4 to 15.9 mm with a mean neck size of 5.2 mm (range, 2.3-11.6 mm). At 1 year, there were no device migrations or symptomatic in-stent stenoses. Raymond-Roy I occlusion was achieved in 53% of cases at the time of treatment and progressed to 61% and 67% at 6 and 12 months, respectively. Adequate occlusion (Raymond-Roy I/II) progressed from 88% at 6 months to 90% at 12 months. No recanalizations were observed. There was 1 delayed ischemic event. Good outcome (mRS 0-2) was achieved in 90% of patients.

CONCLUSIONS

The updated 1-year results from the ANSWER trial demonstrate aneurysm stability and an acceptable safety profile for aneurysms treated at the basilar apex and carotid terminus. Prospective data from a larger set of aneurysms treated at other locations are required to assess how treatment with PulseRider compares with alternatives for treating wide-neck bifurcation aneurysms.

Hemodynamic effects of developmental venous anomalies with and without cavernous malformations

BACKGROUND AND PURPOSE

Association between developmental venous anomalies is well known, but remains unexplained. Our aim was to study possible hemodynamic differences around developmental venous anomalies with and without cavernous malformations.

MATERIALS AND METHODS

In this prospective study approved by the institutional review board, PWI was performed in 24 patients with 25 DVAs (10 with and 15 without CMs) who consented to participate. We calculated relative cerebral blood volume, relative cerebral blood flow, and relative mean transit time for the brain surrounding the DVA tributaries in reference to contralateral mirror image locations. Corresponding control values (cCBV, cCBF, and cMTT) were generated in a similar fashion for remote ipsilateral regions with normal venous drainage, also in reference to contralateral mirror image locations. Perfusion parameters for DVAs and control regions were tested for differences between groups with the t test for independent or paired samples (or the nonparametric equivalents). Similar testing was done for perfusion parameters for DVAs with and without CMs.

RESULTS

Normal-appearing brain surrounding DVAs showed increased rCBV (median = 2.98; range = 1.39-6.61), increased rCBF (median = 2.00, range = 0.79-4.43), and increased rMTT (mean = 1.46; 95% confidence interval, 1.32-1.59). These were significantly higher than median cCBV (0.99; 95% confidence interval, 0.89-1.06; P < .01), median cCBF (1.00; 95% confidence interval, 0.94-1.27; P < .01), and mean cMTT (1.00; 95% confidence interval, 0.98-1.02; P < .01), respectively. Mean rMTT (1.70; 95% confidence interval, 1.46-1.93) for DVAs with CMs was higher than mean rMTT (1.29; 95% confidence interval, 1.19-1.40; P < .01) for DVAs without CMs.

CONCLUSIONS

DVAs are strongly associated with altered hemodynamics. Significant differences in these hemodynamic alterations for DVAs with and without CMs suggest their possible role in the formation of CMs.

Retrospective review of cerebral mycotic aneurysms in 26 patients: focus on treatment in strongly immunocompromised patients with a brief literature review

BACKGROUND AND PURPOSE

Cerebral mycotic aneurysms are a rare and deadly type of aneurysm that have no definitive treatment guidelines. Our purpose was to retrospectively review known or suspected cases of CMA in order to identify patient populations that may be associated with higher morbidity and mortality. We hope that the identification of patients with these risk factors will lead to early stratification upon presentation, and more urgent treatment of their CMAs. We also hoped to identify any benefit or complication that was specific to either the endovascular or neurosurgical repair of CMAs.

MATERIALS AND METHODS

A retrospective multi-institutional study was performed examining cases of CMA during a 15-year period. Patients were considered strongly immunocompromised if there were long-term severely immunocompromised states: AIDS, chemotherapy, or steroid immunosuppression. Patients were excluded if angiographic findings suggested an alternative diagnosis or if an infectious etiology was unknown. Antibiotics were considered "noninvasive treatment." Endovascular and neurosurgical repair were considered "invasive treatment." Data were recorded by reviewing electronic medical records and imaging reports.

RESULTS

Twenty-six patients with 40 CMAs were included. Three patients were considered strongly immunocompromised and presented with 4 CMAs, which demonstrated larger average size and more rapid growth; 3 of these patients' aneurysms were treated invasively in the acute period, with the one that was not ruptured causing death. Technical success (aneurysm occlusion without rupture or recanalization) and clinical success (no neurologic complication attributable to the intervention) were obtained equally endovascularly and neurosurgically. Clipping was aborted in favor of coiling for 1 patient. Anticoagulation needed reversal before 2 patients underwent craniotomy for clipping after valve replacement. For CMAs treated with antibiotics alone with angiographic follow-up (n=11), initial aneurysm size was unrelated to persistence and 64% completely regressed.

CONCLUSIONS

We recommend initial invasive treatment for CMAs in strongly immunocompromised patients. Testing for underlying immunocompromised states is warranted in patients with CMAs. Endovascular treatment is favored over neurosurgical treatment in patients requiring acute cardiac valve repair due to delays with anticoagulation reversal.

The Kety-Schmidt technique for quantitative perfusion and oxygen metabolism measurements in the MR imaging environment

SUMMARY

The Kety-Schmidt technique provides quantitative measurement of whole-brain CBF. CBF is measured as the area between the arterial and venous washout curves of a diffusible tracer. Oxygen extraction and metabolism may be calculated from arterial and venous samples. In this report, we present a method for performing these measurements in an MR imaging environment. This technique could be useful for validation of MR imaging methods of hemodynamic and metabolic measurements in humans.

Susceptibility-weighted imaging: a new tool in the diagnosis and evaluation of abnormalities of the vein of Galen in children

We retrospectively identified 9 consecutive children, 3 males and 6 females (age 5.2 ± 6.3 years, range 1 day to 18 years), with known or suspected AVGs who underwent MR imaging, including SWI, at our institution between January 2007 and March 2011. On the SWI sequence, arterialized blood flow was considered to be present in the vein of Galen or its tributaries when these showed abnormal signal hyperintensity from arteriovenous shunting. SWI findings were correlated with findings from DSA studies or findings from time-of-flight or contrast-enhanced MR angiography sequences. SWI was found to accurately differentiate between high-flow and low-flow AVGs and was also useful in characterizing the arterial supply and venous drainage patterns associated with high-flow AVGs.

Cerebral hemodynamics and cognitive impairment: baseline data from the RECON trial

OBJECTIVE

To determine whether unihemispheral hemodynamic failure is independently associated with cognitive impairment among participants in the National Institute of Neurological Disorders and Stroke-sponsored, multicenter, randomized clinical trial, Randomized Evaluation of Carotid Occlusion and Neurocognition (RECON).

METHODS

Forty-three patients were randomized into RECON after recent symptomatic carotid artery occlusion and asymmetrically increased oxygen extraction fraction (OEF) by PET (OEF ratio >1.13), indicating stage II hemodynamic failure on the side of occlusion. The PET-positive patients were compared with 28 RECON-enrolled patients who met all clinical and radiographic inclusion/exclusion criteria but had no OEF asymmetry. A multivariable regression compared patients with PET OEF >1.13 or ≤1.13, stratifying by TIA vs. stroke as the qualifying event. The dependent variable was a composite neurocognitive score derived from averaging age-normalized z scores on a test battery that included global and internal carotid artery (ICA) side-relevant hemisphere-specific tests.

RESULTS

There were no differences in demographic, clinical, or radiologic characteristics between the PET-positive and PET-negative patients except for PET OEF asymmetry. The unadjusted average neurocognitive z score was -1.45 for the PET-positive and -1.25 for the PET-negative patients, indicating cognitive impairment in both groups but no difference between them (p = 0.641). After adjustment for age, education, side of occlusion, depression, and previous stroke, there was a significant difference between PET-positive and PET-negative patients among those with TIA as a qualifying event (average z score = -1.41 vs. -0.76, p = 0.040). Older age and right ICA side were also significant in this model.

CONCLUSION

Hemodynamic failure is independently associated with cognitive impairment in patients with carotid occlusion. This finding establishes the physiologic parameter upon which the extracranial-intracranial bypass will be tested.

Improvement in angiographic cerebral vasospasm after intra-arterial verapamil administration

BACKGROUND AND PURPOSE

Endovascular options for therapy for patients with vasospasm after SAH include angioplasty and intra-arterial vasodilator infusion. Preliminary studies of the effects of the calcium channel antagonist verapamil on angiographic vasospasm have yielded mixed and/or qualitative results. In this study, improvement in angiographic vasospasm after intra-arterial verapamil administration is demonstrated with quantitative, blinded methods.

MATERIALS AND METHODS

This retrospective observational case series includes 12 patients with vasospasm after SAH who collectively received 16 treatments with intra-arterial verapamil during a 2-year period at our institution. The exclusion criterion was concurrent treatment with angioplasty. Blinded reviewers quantitatively evaluated angiograms from each patient and/or treatment after presentation with SAH and before and after intra-arterial treatment of vasospasm.

RESULTS

Patients were treated with intra-arterial verapamil for vasospasm 9 ± 4 days after SAH with a range from 1 to 16 days. For the 34 arterial distributions treated, the segment with the worst angiographic vasospasm from each arterial distribution averaged 51 ± 13% stenosis, which improved to 29 ± 18% stenosis (P < .001). There was no significant difference in treatment effect in proximal arterial segments, which may be amenable to angioplasty, compared with distal segments (P > .05). There was no significant difference in treatment effect in arterial segments previously subjected to angioplasty compared with other segments (P > .05).

CONCLUSIONS

Intra-arterially administered verapamil improves angiographic vasospasm after SAH when administered at 10 ± 3 mg per arterial distribution. Optimal dose, infusion rate, and retreatment interval remain to be determined. Randomized controlled trials are needed to prove efficacy in the treatment of clinical vasospasm.

Performance and training standards for endovascular ischemic stroke treatment

Stroke is the third leading cause of death in the USA, Canada, Europe, and Japan. According to the American Heart Association and the American Stroke Association, there are now 750,000 new strokes that occur each year, resulting in 200,000 deaths, or 1 of every 16 deaths, per year in the USA alone. Endovascular therapy for patients with acute ischemic stroke is an area of intense investigation. The American Stroke Association has given a qualified endorsement of intra-arterial thrombolysis in selected patients. Intra-arterial thrombolysis has been studied in two randomized trials and numerous case series. Although two devices have been granted FDA approval with an indication for mechanical stroke thrombectomy, none of these thrombectomy devices has demonstrated efficacy for the improvement of patient outcomes. The purpose of the present document is to define what constitutes adequate training to perform neuroendovascular procedures in patients with acute ischemic stroke and what performance standards should be adopted to assess outcomes. These guidelines have been written and approved by multiple neuroscience societies which historically have been directly involved in the medical, surgical and endovascular care of patients with acute stroke. The participating member organizations of the Neurovascular Coalition involved in the writing and endorsement of this document are the Society of NeuroInterventional Surgery, the American Academy of Neurology, the American Association of Neurological Surgeons/Congress of Neurological Surgeons Cerebrovascular Section, and the Society of Vascular & Interventional Neurology.

Reporting standards for endovascular repair of saccular intracranial cerebral aneurysms

BACKGROUND AND PURPOSE

The goal of this article is to provide consensus recommendations for reporting standards, terminology, and written definitions when reporting on the radiological evaluation and endovascular treatment of intracranial, cerebral aneurysms. These criteria can be used to design clinical trials, to provide uniformity of definitions for appropriate selection and stratification of patients, and to allow analysis and meta-analysis of reported data.

METHODS

This article was written under the auspices of the Joint Writing Group of the Technology Assessment Committee, Society of NeuroInterventional Surgery, Society of Interventional Radiology; Joint Section on Cerebrovascular Neurosurgery of the American Association of Neurological Surgeons and Congress of Neurological Surgeons; and Section of Stroke and Interventional Neurology of the American Academy of Neurology. A computerized search of the National Library of Medicine database of literature (PubMed) from January 1991 to December 2007 was conducted with the goal to identify published endovascular cerebrovascular interventional data about the assessment and endovascular treatment of cerebral aneurysms useful as benchmarks for quality assessment. We sought to identify those risk adjustment variables that affect the likelihood of success and complications. This article offers the rationale for different clinical and technical considerations that may be important during the design of clinical trials for endovascular treatment of cerebral aneurysms. Included in this guidance article are suggestions for uniform reporting standards for such trials. These definitions and standards are primarily intended for research purposes; however, they should also be helpful in clinical practice and applicable to all publications.

CONCLUSIONS

The evaluation and treatment of brain aneurysms often involve multiple medical specialties. Recent reviews by the American Heart Association have surveyed the medical literature to develop guidelines for the clinical management of ruptured and unruptured cerebral aneurysms. Despite efforts to synthesize existing knowledge on cerebral aneurysm evaluation and treatment, significant inconsistencies remain in nomenclature and definition for research and reporting purposes. These operational definitions were selected by consensus of a multidisciplinary writing group to provide consistency for reporting on imaging in clinical trials and observational studies involving cerebral aneurysms. These definitions should help different groups to publish results that are directly comparable.

Effect of antiplatelet therapy on thromboembolic complications of elective coil embolization of cerebral aneurysms

BACKGROUND AND PURPOSE

Thromboembolic events are the most common complications of elective coil embolization of cerebral aneurysms. Administration of oral clopidogrel and/or aspirin could lower the thromboembolic complication rate.

MATERIALS AND METHODS

Records over a 10-year period were reviewed in a retrospective cohort study. For 369 consecutive elective coil embolization procedures, 25 patients received no antiplatelet drugs, 86 received antiplatelet drugs only after embolization, and 258 received antiplatelet drugs before and after embolization.

RESULTS

Symptomatic thromboembolic complications (transient ischemic attack or stroke within 60 days) occurred in 4 (16%) of 25 when no antiplatelet drugs were given, in 2 (2.3%) of 86 when antiplatelet drugs were administered only after embolization, and in 5 (1.9%) of 258 when antiplatelet drugs were administered before and after embolization. The lower symptomatic thromboembolic complication rate in the patients who received any antiplatelet therapy was statistically significant (P = .004). Clots were visible intraprocedurally in 5 (4.5%) of 111 when no antiplatelet drugs were administered before procedures and in 4 (1.6%) of 258 when they were (P value not significant). None of the 9 was symptomatic postprocedurally, but 7 were lysed or mechanically disrupted. Extracerebral hemorrhagic complications occurred in 0 (0%) of 25 when no antiplatelet drugs were given and in 11 (3.2%) of 344 when they were (P value not significant).

CONCLUSION

Oral clopidogrel and/or aspirin significantly lowered the symptomatic thromboembolic complication rate of elective coil embolization of unruptured cerebral aneurysms. There were trends toward a lower rate of intraprocedural clot formation in patients given antiplatelet drugs before procedures and a higher hemorrhagic complication rate in patients given antiplatelet drugs. Benefits of antiplatelet therapy appear to outweigh risks.

Single-institution experience with matrix coils in the treatment of intracranial aneurysms: comparison with same-center outcomes with the use of platinum coils

BACKGROUND AND PURPOSE

This study was undertaken to analyze the outcomes and treatment-related complications of the polyglycolic/polylactic acid (PGLA)-coated Matrix platinum coils in the treatment of intracranial aneurysms and compare these results with those derived from the same single-institutional experience with use of uncoated, bare platinum coils.

MATERIALS AND METHODS

In this study, we compared 2 groups of patients in a retrospective fashion. The first group consisted of 70 consecutive patients who underwent 82 aneurysm treatments with Matrix coils during the 14-month period of study, from January 2003 to February 2004. We compared this cohort with 70 consecutive patients who underwent a total of 80 aneurysm treatments with bare platinum coils in the 12 months immediately preceding the use of PGLA-coated coils, from January through December 2002. We then recorded the treatment characteristics, angiographic outcomes, and any complications.

RESULTS

There were similar baseline demographic characteristics between the 2 study groups except in age, anatomic location, and length of follow-up. The overall recurrence rate of aneurysms was 41% among the Matrix-treated group and 32% among the patients treated with bare platinum. Among the 42 patients treated with 100% Matrix, the rate of recurrence was 31%. Of the recurrences, 21% of the Matrix group, 19% of the 100% Matrix group, and 9% of the bare platinum group required retreatment. The overall rate of complications was 10% in the Matrix-treated group and 7% in the bare platinum group. There was not a statistically significant difference in the rate of recurrence of aneurysms or complications between the 2 groups.

CONCLUSIONS

On the basis of our single-center experience, there is insufficient evidence to support the use of Matrix coils over bare platinum coils, given their disadvantages.

Frequency of spinal arteriovenous malformations in patients with unexplained myelopathy

The authors reviewed charts of 78 myelopathy patients who underwent spinal angiography for possible arteriovenous malformations (AVMs). Twenty-two patients had an AVM. No neurologic complications from angiography were observed. MRI findings of increased T2 signal or flow voids were strongly associated with AVMs. Spinal angiography should be performed in all patients with unexplained myelopathy after neurologic evaluation and an MRI demonstrating increased T2 signal or flow voids.

Rapid enlargement of a posterior communicating artery aneurysm after Guglielmi detachable coil treatment of ipsilateral carotid artery aneurysms

This case illustrates rapid aneurysm enlargement, presumably due to altered hemodynamics resulting from endovascular treatment of aneurysms on the same artery. We postulate that increased hemodynamic force directed to the inflow zone of the posterior communicating artery aneurysm was caused by the treatment of the two ophthalmic artery aneurysms. Originally, many of the flow vectors may have been directed into the larger ophthalmic segment aneurysm, located on the outside of the curve of the internal carotid artery. After treatment, flow may have been directed more smoothly around the carotid siphon and into the posterior communicating artery aneurysm.

Positron emission tomography shows that intrathecal leptin reaches the hypothalamus in baboons

Human obesity may be caused by a resistance to circulating leptin. Evidence from rodents and humans suggests that a major component of this resistance is an impairment in the ability of the blood-brain barrier (BBB) to transport leptin from the blood to the brain. One potential way to bypass the BBB is by administering leptin into the intrathecal (i.t.) space. To be effective, i.t. leptin would have to move caudally from the site of injection, enter the cranium, and reach the hypothalamic arcuate nucleus at the base of the pituitary fossa. However, many substances, especially small, lipid-soluble molecules, do not diffuse far from the site of i.t. injection but are resorbed back into blood. To determine whether i.t. leptin can move caudally, we injected leptin conjugated to diethylenetriaminepentaacetic acid (DTPA) and labeled with (68)Ga (G-Ob) into the lumbar space of three baboons. We also studied unconjugated DTPA labeled with (68)Ga, which did not move up the spinal cord but rapidly appeared in blood after i.t. injection. In contrast, G-Ob steadily moved toward the cranium and had reached the hypothalamus 91 and 139 min after i.t. injection in two baboons. We estimated the concentration of leptin in the hypothalamic region to be at least 8 ng/ml, which is about 40 times higher than cerebrospinal fluid levels in normal weight humans and about 4 times higher than the highest level ever recorded after the peripheral administration of leptin. In a third baboon, the leptin neither moved caudally nor appeared in the blood. We conclude that leptin administered i.t. can reach the hypothalamus in therapeutic concentrations, although there is considerable individual variation.

Wada testing reveals frontal lateralization for the memorization of words and faces

Neuroimaging studies have suggested that specific regions of the frontal and medial temporal cortex are engaged during memory formation. Further, there is specialization across these regions such that verbal materials appear to preferentially engage the left regions while nonverbal materials primarily engage the right regions. An open question, however, has been to what extent frontal regions contribute to successful memory formation. The present study investigates this question using a reversible lesion technique known as the Wada test. Patients memorized words and unfamiliar faces while portions of their left and right hemispheres were temporarily anesthetized with sodium amytal. Subsequent memory tests revealed that faces were remembered better than words following left-hemisphere anesthesia, whereas words were remembered better than faces following right-hemisphere anesthesia. Importantly, inspection of the circulation affected by the amytal further suggests that these memory impairments did not result from direct anesthetization of the medial temporal regions. Taken in the context of the imaging findings, these results suggest that frontal regions may also contribute to memory formation in normal performance.

Mannitol bolus preferentially shrinks non-infarcted brain in patients with ischemic stroke

Changes in brain tissue volume in six patients who had acute complete middle cerebral artery (MCA) infarctions and CT evidence of midline shift were measured using the brain boundary shift integral (BBSI) on sequential T1-weighted MR images acquired before and after a 1.5-g/kg bolus infusion of mannitol. At 50 to 55 minutes after the baseline scan, total brain volume decreased by 8.1 +/- 2.8 mL (0.6%, p < 0.005). Brain in the noninfarcted hemisphere shrank more (0.8 +/- 0.4%) than in the infarcted hemisphere (0.0 +/- 0.5%, p < 0.05).

Comparison of PET oxygen extraction fraction methods for the prediction of stroke risk

PET measurement of increased oxygen extraction fraction (OEF) identifies patients at high risk for subsequent stroke. OEF methodology remains controversial. In this study we compare the sensitivity and specificity of absolute OEF measurements with ipsilateral-to-contralateral ratios of absolute OEF and count-based OEF estimates.

METHODS

Multivariate analyses of OEF methods were performed using data from patients with symptomatic carotid artery occlusion (n = 68). Outcome and receiver operating characteristic (ROC) curve analyses were performed.

RESULTS

All 3 methods were predictive of stroke risk in univariate analysis. Only the count-based method remained significant in multivariate analysis. The area under the ROC curve was greatest for the count-based ratio: 0.815 versus 0.769 (absolute) and 0.737 (ratios of absolute).

CONCLUSION

All 3 methods are predictive of stroke risk in patients with unilateral carotid artery occlusion. ROC curve analysis is useful for selecting optimal thresholds for maximal sensitivity and specificity.

Severe hemodynamic impairment and border zone--region infarction

PURPOSE

To investigate the relationship between the patterns of cerebral infarction that have been associated with hemodynamic impairment and the presence of severe chronic hemodynamic compromise (increased oxygen extraction fraction) in a large prospectively enrolled group of patients with carotid artery occlusion.

MATERIALS AND METHODS

At enrollment in a prospective study of cerebral hemodynamics, 110 patients with carotid occlusion underwent (a) positron emission tomography for the measurement of cerebral oxygen extraction fraction and (b) computed tomographic (CT) or magnetic resonance (MR) examinations of the brain. Infarcts were categorized retrospectively by vascular territory, location, and pattern. The association of these findings with hemodynamic impairment (increased oxygen extraction fraction) was investigated.

RESULTS

No border zone-region infarctions were found in 35 asymptomatic patients. In 75 symptomatic patients, cortical border zone-region infarction was found in seven of 36 patients with increased oxygen extraction fraction, and in two of 39 with normal oxygen extraction fraction (P =.08, difference not significant). The pattern of multiple white matter lesions arranged parallel to the lateral ventricle was observed only in symptomatic patients with increased oxygen extraction fraction (eight of 36 patients; P =.002; sensitivity, 22%; specificity, 100%). This finding was more frequent with MR imaging (seven of 14 patients) than with CT (one of 22 patients).

CONCLUSION

Multiple white matter infarctions, arranged parallel to the lateral ventricle, are associated with severe hemodynamic impairment. This pattern of infarction is likely due to a hemodynamic mechanism.

Angioplasty and stenting is a reasonable treatment option for many patients with atherosclerotic carotid stenosis

A growing number of patients with atherosclerotic stenosis of the carotid artery are being treated endovascularly by percutaneous transluminal balloon angioplasty and vascular stent placement (angioplasty and stenting). However, there is considerable controversy surrounding the use of this procedure. Like many controversial issues in medicine, there are both political and scientific aspects to consider. If all treatment modalities for atherosclerotic carotid stenosis fell within the scope of a single specialty, much of the current hue and cry would be absent. In this short essay, I will outline the scientific issues regarding the treatment of carotid stenosis and provide a rationale for the use of angioplasty and stenting in selected patients.

In Vitro Evaluation of Platinum Guglielmi Detachable Coils at 3 T with a Porcine Model: Safety Issues and Artifacts

PURPOSE

To evaluate safety-related issues and imaging artifacts of Guglielmi detachable coils in vitro with 3-T magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Two aneurysm models were constructed: one from porcine carotid artery and the other from a pharmaceutical capsule. Both were filled with Guglielmi detachable coils. The models were tested with a 3-T MR imager for heating, deflection, and imaging artifact. Testing for heating and deflection was performed (a) at static points both inside and outside the bore, (b) during movement into the imager, and (c) during clinical imaging sequences.

RESULTS

No change in temperature was measured during movement into the imager bore or at different points within the bore. No differences in heating from radio-frequency energy were found between aneurysm models and controls. Similarly, no evidence of deflection of the coil mass (capsule model) was found. Minor susceptibility artifacts were found in the readout direction during gradient-echo sequences. Magnetic field mapping showed no induced field inhomogeneity.

CONCLUSION

MR imaging at field strengths of 3 T in patients with aneurysms treated with Guglielmi detachable coils is safe. Imaging artifacts are likely to be minimal.

Bleeding complications after basilar artery fibrinolysis with tissue plasminogen activator

BACKGROUND AND PURPOSE

Fibrinolysis with local intraarterial urokinase infusion for basilar artery thrombosis has been associated with a low rate of spontaneous symptomatic cerebral hemorrhage, even when patients have been treated late in the course of symptoms. Because urokinase is presently unavailable in the United States, this study was undertaken to determine the frequency of spontaneous cerebral hemorrhage in basilar artery fibrinolysis performed with tissue plasminogen activator (tPA).

METHODS

In a retrospective review of our initial experience with cerebral fibrinolysis for acute stroke using intraarterial tPA, four cases of basilar thrombosis were identified. Doses of the fibrinolytic agent and heparin, angiographic findings, clinical courses, and bleeding complications for these patients were determined. These results were compared with those from a prior study of 20 similar consecutive patients treated with urokinase.

RESULTS

Symptom duration before treatment was unlimited. Intraarterial doses of tPA were 20 to 50 mg. Patients received full systemic anticoagulation with heparin. Complete basilar artery recanalization was achieved in 75% of patients. Two patients treated with tPA had angioplasty and stent placement for related high-grade stenosis. Spontaneous symptomatic cerebral hemorrhage occurred in three (75%) of the four tPA-treated patients and in three (15%) of the 20 urokinase-treated patients.

CONCLUSION

The cerebral hemorrhage complication rate for intraarterial fibrinolysis with tPA was very high in cases of basilar artery thrombosis at the doses we used. Protocol adjustments should be considered.

Malignant giant-cell tumor of the parietal bone: case report and review of the literature

OBJECTIVE AND IMPORTANCE

Giant-cell tumors (GCTs) are primary bone tumors that involve long bones in 75 to 90% of patients. They seldom develop in the cranium and are very rare in patients older than 60 years of age. A GCT rarely occurs with Paget's disease; when it does, however, it is most commonly associated with the polyostotic form and tends to involve the craniofacial bones. Pagetic GCTs are less aggressive than GCTs that are not associated with Paget's disease.

CLINICAL PRESENTATION

We report the case of an 81-year-old woman with a painless left parietal mass and asymptomatic monostotic parietal Paget's disease.

INTERVENTION

Surgical resection was performed, and histological examination of the lesion demonstrated Paget's disease with a malignant GCT. An incidental, low-grade, small-cell lymphocytic lymphoma also was noted. The patient experienced local recurrence of the malignant GCT and eventually died after developing pulmonary metastases of the malignant GCT.

CONCLUSION

This case is the first reported example of a patient with a malignant GCT of the cranium associated with monostotic Paget's disease. It provides evidence that not all pagetic GCTs in the cranium are benign, as has been reported.

Reversal of focal misery perfusion after intracranial angioplasty: case report

OBJECTIVE AND IMPORTANCE

The presence of reduced blood flow and increased oxygen extraction fraction (OEF) (misery perfusion) in the hemisphere distal to an occluded carotid artery is a proven risk factor for subsequent stroke. Whether angioplasty of intracranial stenosis is sufficient to reverse this condition has not been documented.

CLINICAL PRESENTATION

A 67-year-old man exhibited progressive right hemispheric ischemic symptoms despite maximal antiplatelet and antithrombotic therapy. Angiography demonstrated focal 80% stenosis of the supraclinoid segment of the ipsilateral internal carotid artery.

TECHNIQUE

15O positron emission tomographic measurements of cerebral blood flow and OEF were made before and after transfemoral percutaneous angioplasty. OEF values measured before angioplasty were elevated in the middle cerebral artery distal to the stenosis. Angioplasty reduced the degree of luminal stenosis to 40% (linear diameter). OEF values measured 36 hours after angioplasty were normal.

CONCLUSION

Angioplasty of intracranial stenosis can restore normal cerebral blood flow and oxygen extraction, despite mild residual stenosis after the procedure. Hemodynamic measurements may be useful for the identification of patients with the greatest potential to benefit from angioplasty.

Randomized controlled trial of sheaths in diagnostic neuroangiography

PURPOSE

To determine the value of arterial sheaths in diagnostic neuroangiography in a randomized controlled trial.

MATERIALS AND METHODS

A total of 842 patients (411 men, 431 women; mean age, 59.4 years; age range, 29.5-94.3 years) undergoing diagnostic neuroangiography were randomly assigned to groups in which a sheath was introduced immediately after puncture of the femoral artery (sheath group) or in which a diagnostic catheter was introduced without a sheath (control group). Two hundred twenty-four (26.7%) of 839 patients were receiving anticoagulants immediately prior to the procedure.

RESULTS

Complications (mostly small hematomas of the groin) occurred in 106 (12.6%) of 842 patients, with no difference between groups (53 [12.6%] of 421 patients in both; P >.99). Ease of catheter manipulation was greater in the sheath group than in the control group. Incidence of bleeding at the femoral puncture site during the procedure was less in the sheath group (seven [1.7%] of 421 patients) versus the control group (150 [35.6%] of 421 patients), with a P value less than.001. Because of bleeding, sheath insertion was necessary in 165 (39.2%) of 421 patients in the control group. This crossover group also had a higher rate of local complications (28 [17.0%] of 165 patients) than the sheath and control groups. Serious complications, such as stroke (one [0.12%] of 842 patients) and transient ischemic attacks (five [0.60%] of 842 patients), occurred with equal frequency in both the sheath and control groups.

CONCLUSION

Use of arterial sheaths lessens the incidence of intraprocedural bleeding at the femoral puncture site and increases ease of catheter manipulation without increasing the number of groin complications.

Cost-effectiveness analysis of therapy for symptomatic carotid occlusion: PET screening before selective extracranial-to-intracranial bypass versus medical treatment

The St. Louis Carotid Occlusion Study (STLCOS) demonstrated that increased cerebral oxygen extraction fraction (OEF) detected by PET scanning predicted stroke in patients with symptomatic carotid occlusion. Consequently, a trial of extracranial-to-intracranial (EC/IC) arterial bypass for these patients was proposed. The purpose of this study was to examine the cost-effectiveness of using PET in identifying candidates for EC/IC bypass.

METHODS

A Markov model was created to estimate the cost-effectiveness of PET screening and treating a cohort of 45 symptomatic patients with carotid occlusion. The primary outcome was incremental cost for PET screening and EC/IC bypass (if OEF was elevated) per incremental quality-adjusted life year (QALY) saved. Rates of stroke and death with surgical and medical treatment were obtained from EC/IC Bypass Trial and STLCOS data. Costs were estimated from the literature. Sensitivity analyses were performed for all assumed variables, including the PET OEF threshold used to select patients for surgery.

RESULTS

In the base case, PET screening of the cohort followed by EC/IC bypass on 36 of the 45 patients yielded 23.2 additional QALYs at a cost of $20,000 per QALY, compared with medical therapy alone. A more specific PET threshold, which identified 18 surgical candidates, gained 22.6 QALYs at less cost than medical therapy alone. The results were sensitive to the perioperative stroke rate and the stroke risk reduction conferred by EC/IC bypass surgery.

CONCLUSION

If postoperative stroke rates are similar to stroke rates observed in the EC/IC Bypass Trial, EC/IC bypass will be cost-effective in patients with symptomatic carotid occlusion who have increased OEF. A clinical trial of medical therapy versus PET followed by EC/IC bypass (if OEF is elevated) is warranted.

Absence of selective deep white matter ischemia in chronic carotid disease: a positron emission tomographic study of regional oxygen extraction

BACKGROUND AND PURPOSE

Deep white matter may be the location of an internal arterial border zone. The purpose of this study was to determine whether the deep white matter was subject to a greater degree of ischemia than was the cortex among patients with chronic carotid occlusion.

METHODS

Thirty-six patients with carotid occlusion and structurally normal deep white matter were studied with positron emission tomography. Measurements of oxygen extraction fraction were made in superficial (cortical and subcortical) regions in the middle cerebral artery territory and in deep white matter (internal border zone) regions. The presence of selective ischemia of the deep white matter was assessed by the ratio of deep white matter:superficial oxygen extraction fraction. Ipsilateral hemispheric ratios among patients were assessed as a group as compared with contralateral hemispheric ratios and as compared with normal hemispheric ratios from 15 control volunteers.

RESULTS

Mean deep white matter to superficial oxygen extraction fraction ratios (+/-95% confidence limits) were 0.99 (+/-0.07), 1.01 (+/-0.06), and 1.02 (+/-0.08) for ipsilateral, contralateral, and normal hemispheres, respectively. No statistically significant difference was found between ipsilateral and contralateral (P = .691) or normal hemispheres (P = .68), nor was any statistically significant difference found when the analysis was limited to patients with increased superficial oxygen extraction fraction (n = 9). Individual deep white matter:superficial ratios were within the normal range for all patients.

CONCLUSION

Normal deep white matter among patients with carotid occlusion is not subject to a greater degree of ischemia than is the overlying cortex. It is unlikely that deep white matter infarctions observed among patients with carotid occlusion are owing to chronic selective hemodynamic compromise occurring at an internal arterial border zone.

Benign prognosis of never-symptomatic carotid occlusion

OBJECTIVE

To determine the prognosis of asymptomatic carotid artery occlusion.

BACKGROUND

As opposed to symptomatic carotid occlusion, little information is available on the prognosis of asymptomatic carotid occlusion.

METHOD

Thirty never-symptomatic and 81 symptomatic patients with carotid occlusion underwent baseline assessment of 15 risk factors together with PET measurements of oxygen extraction fraction (OEF). Every 6-month telephone contact recorded interval medical treatment and subsequent stroke occurrence during an average follow-up of 32 months. Patients, treating physicians, and an end point adjudicator were blinded to PET results.

RESULTS

Ischemic stroke occurred in 1 of 30 of never-symptomatic patients (3.3%) and 15 of 81 of symptomatic patients (18.5%; p = 0.03). No strokes in the carotid territory distal to the occluded vessel occurred in the never-symptomatic patients. Multivariate analysis of baseline risk factors for all 111 patients revealed that age, plasma fibrinogen level, and PET findings of high OEF distal to the occluded carotid artery were the only independent predictors of subsequent stroke (p < 0.05). Previous ipsilateral hemispheric or retinal symptoms was not a significant predictive variable. The lower risk of stroke in never-symptomatic patients was associated with a lower incidence of high OEF (4 of 30) as opposed to symptomatic patients (39 of 81; p = 0.002), but there was no significant difference in age or fibrinogen level.

CONCLUSIONS

Never-symptomatic carotid occlusion carries a very low risk of subsequent ischemic stroke. This benign prognosis is associated with a low incidence of cerebral hemodynamic compromise in these patients. These data support further the importance of hemodynamic factors in the pathogenesis of ischemic stroke in patients with carotid occlusion.

Count-based PET method for predicting ischemic stroke in patients with symptomatic carotid arterial occlusion

PURPOSE

To test the ability of a count-based positron emission tomographic (PET) method, without arterial sampling, for the measurement of regional cerebral oxygen extraction fraction (OEF) to predict ischemic stroke in patients with symptomatic carotid arterial occlusion.

MATERIALS AND METHODS

The outcome analysis of a blinded prospective study designed to determine if increased OEF was an independent predictor of stroke in patients with symptoms and with carotid occlusion was repeated by substituting a count-based method of OEF measurement for the original quantitative technique. The performance of the quantitative and count-based methods was assessed by using Kaplan-Meier cumulative survival functions (log-rank, [p < .05]). Receiver operating characteristic (ROC) curves for both methods were generated.

RESULTS

Thirteen ipsilateral strokes occurred during a mean follow-up of 3.1 years for 81 patients. All ipsilateral strokes occurred in 50 patients with increased count-based OEF (P = .002, sensitivity 100%, specificity 46%). Sixty-eight patients underwent complete quantitative studies, which allowed comparison of OEF methods. Both the count-based and the quantitative methods were predictive of stroke in this subgroup (P = .005 and .025, respectively). ROC analysis demonstrated a greater area under the curve for the count-based OEF method.

CONCLUSION

Count-based PET measurement of OEF without arterial sampling accurately predicts stroke in patients with carotid occlusion.

Cerebral hemodynamic impairment: methods of measurement and association with stroke risk

Stenosis or occlusion of the major arteries of the head and neck may cause hemodynamic impairment of the distal cerebral circulation. Hemodynamic factors may play an important role in the pathogenesis of ischemic stroke for patients with cerebrovascular disease. Several neuroimaging methods are currently available for the indirect assessment of the hemodynamic effect of atherosclerotic stenosis or occlusion on the distal cerebrovasculature. Because these methods rely on different underlying physiologic mechanisms, they are not interchangeable. Two basic categories of hemodynamic impairment can be assessed with these techniques: Stage 1, in which autoregulatory vasodilation secondary to reduced perfusion pressure is inferred by the measurement of either increased blood volume or an impaired blood flow response to a vasodilatory stimulus; and Stage 2, in which increased oxygen extraction fraction (OEF) is noninvasively but directly measured. The correlation of different Stage 1 methods with each other and with Stage 2 techniques is quite variable. Clinical studies associating different manifestations of hemodynamic impairment with stroke risk often suffer from methodologic problems. The best evidence to date for such an association is for increased OEF measured in patients with symptomatic carotid occlusion. In the absence of data demonstrating improvement in patient outcome, there is currently no role for the routine use of these tools to guide clinical management in patients with cerebrovascular disease.

Progression of mass effect after intracerebral hemorrhage

BACKGROUND AND PURPOSE

While the evolution of mass effect after cerebral infarction is well characterized, similar data regarding intracerebral hemorrhage (ICH) are scant. Our goal was to determine the time course and cause for progression of mass effect after ICH.

METHODS

Patients with spontaneous supratentorial ICH who underwent >/=2 CT scans were identified in our prospectively collected database. CT lesion size and midline shift of the pineal and septum pellucidum were retrospectively measured and correlated with clinical and CT characteristics. Causes for increased midline shift were determined by 2 independent observers.

RESULTS

Seventy-six patients underwent 235 scans (3.1+/-1.3 per patient). Initial CT was obtained within 24 hours of ICH in 66. Twenty-five scans were repeated on day 1, 80 on days 2 through 7, 31 on days 8 through 14, and 24 >14 days after ICH. Midline shift was present on 88% of the initial scans. There were 17 instances of midline shift progression: 10 occurred early (0.2 to 1.7 days) and were associated with hematoma enlargement, and 7 occurred late (9 to 21 days) and were associated with edema progression. Progression of mass effect due to edema occurred with larger hemorrhages (P<0.05). Of 65 scans repeated for clinical deterioration, only 10 were associated with increased mass effect.

CONCLUSIONS

Progression of mass effect after ICH occurred at 2 distinct time points: within 2 days, associated with hematoma enlargement, and in the second and third weeks, associated with increase in edema. The clinical significance of later-developing edema is unclear.

Compensatory mechanisms for chronic cerebral hypoperfusion in patients with carotid occlusion

BACKGROUND AND PURPOSE

The purpose of this experiment was to assess long-term cerebral hemodynamic and metabolic changes in patients with increased oxygen extraction fraction (OEF) in the hemisphere distal to an occluded carotid artery who remain free of stroke. Methods--Ten patients with increased OEF and no interval stroke underwent repeated positron emission tomography examinations 12 to 59 months after the initial examination. Quantitative regional measurements of cerebral blood flow, cerebral blood volume, cerebral rate of oxygen metabolism (CMRO2), and OEF were obtained. Regional measurements of the cerebral rate of glucose metabolism (CMRGlc) were made on follow-up in 5 patients. Statistical significance (P<0.05) was measured with t tests and linear regression analysis.

RESULTS

The ipsilateral/contralateral OEF ratio declined from a mean of 1.16 to 1.08 (P=0.022). Greater reductions were seen with longer duration of follow-up (P=0.023, r=0.707). The cerebral blood flow ratio improved from 0.81 to 0.85 (P=0.021). No change in cerebral blood volume or CMRO2 was observed. CMRGlc was reduced in the ipsilateral hemisphere (P=0.001 compared with normal), but the CMRO2/CMRGlc ratio was normal.

CONCLUSIONS

Increased OEF improves in patients with carotid occlusion and no interval stroke. This improvement in OEF is due to an improvement in collateral blood flow.

Lack of correlation between pattern of collateralization and misery perfusion in patients with carotid occlusion

BACKGROUND AND PURPOSE

Misery perfusion, identified by increased oxygen extraction fraction (OEF), predicts subsequent stroke in patients with carotid occlusion. The purpose of this investigation was to determine the relationship of angiographic findings to increased OEF in these patients.

METHODS

Forty-seven patients with carotid occlusion were studied with cerebral angiography and positron emission tomography (PET). The following angiographic data were collected blind to PET results: (1) pial collateralization, defined as retrograde filling of the MCA branches to the level of the insula; (2) presence of border zone shift; (3) presence of delayed venous phase; and (4) measurement of posterior communicating artery size. Patients were divided into 2 groups based on the PET measurement of normal or increased OEF.

RESULTS

Seventeen of 47 patients had increased OEF distal to the occluded carotid artery. No significant relationship between increased OEF and any angiographic finding was found. Pial collateralization was present in only 2 patients, both with increased OEF (P=0.105). Border zone shift was equally distributed between the 2 groups (12 of 30 with normal OEF and 6 of 15 with increased OEF). Delayed venous phase was present in 4 patients, 3 of whom had increased OEF (P=0.073). The relationship between the size of the posterior communicating artery and OEF was not significant by linear regression analysis (P=0.242).

CONCLUSIONS

With the possible but infrequent exceptions of delayed venous phase and pial collateralization, anatomic findings made on routine angiographic studies of patients with carotid occlusion do not correlate with increased OEF.