Unruptured intracranial aneurysms and the assessment of rupture risk based on anatomical and morphological factors: sifting through the sands of data

Aneurysmal subarachnoid hemorrhage continues to have high rates of morbidity and mortality for patients despite optimal medical and surgical management. Due to the fact that aneurysmal rupture can be such a catastrophic event, preventive treatment is desirable for high-risk lesions. Given the variability of the literature evaluating unruptured aneurysms regarding basic patient population, clinical practice, and aneurysm characteristics studied, such as size, location, aspect ratio, relationship to the surrounding vasculature, and the aneurysm hemodynamics, a metaanalysis is nearly impossible to perform. This review will instead focus on the various anatomical and morphological characteristics of aneurysms reported in the literature with an attempt to draw broad inferences and serve to highlight pressing questions for the future in our continued effort to improve clinical management of unruptured intracranial aneurysms.

Cavernous carotid aneurysms: to treat or not to treat?

Most cavernous carotid aneurysms (CCAs) are considered benign lesions, most often asymptomatic, and to have a natural history with a low risk of life-threatening complications. However, several conditions may exist in which treatment of these aneurysms should be considered. Several options are currently available regarding the management of CCAs with resultant good outcomes, namely expectant management, luminal preservation strategies with or without addressing the aneurysm directly, and Hunterian strategies with or without revascularization procedures. In this article, we discuss the sometimes difficult decision regarding whether to treat CCAs. We consider the natural history of several types of CCAs, the clinical presentation, the current modalities of CCA management and their outcomes to aid in the management of this heterogeneous group of cerebral aneurysms.

Cardiac troponin I and acute lung injury after subarachnoid hemorrhage

INTRODUCTION

There are few predictors of acute lung injury (ALI) or the acute respiratory distress syndrome (ARDS) after subarachnoid hemorrhage (SAH). We hypothesized that cardiac troponin I, which is associated with cardiovascular morbidity, would also predict ALI.

METHODS

We prospectively enrolled 171 consecutive patients with SAH. Troponin was routinely measured on admission and the next day and subsequently if abnormal. We prospectively recorded the maximum troponin, in-hospital events, and clinical endpoints. ALI and ARDS were defined by standard criteria.

RESULTS

Acute lung injury was found in 10 patients (6%), ARDS in an additional 14 (8%), and pulmonary edema without lung injury in 9 (5%). Maximum troponin was different in patients without lung injury or pulmonary edema (0.03 [0.02-0.12] mcg/l), ALI (0.17 [0.04-1.4]), or ARDS (0.31 [0.9-1.8], P < 0.001). In ROC analysis, a cutoff of 0.04 mcg/l had 91% sensitivity and 42% specificity for ALI or ARDS (AUC = 0.75, P < 0.001). Troponin was associated with ALI or ARDS after accounting for neurologic grade in multivariate models without further contribution from pneumonia, packed red cell transfusion, gender, tobacco use, coronary artery disease, vasospasm, depressed ejection fraction on echocardiography, or CT grade. Lung injury was associated with worse functional outcome at 14 days, but not at 28 days or 3 months.

CONCLUSION

Troponin I is associated with the development of ALI after SAH.

Endovascular options in the treatment of delayed ischemic neurological deficits due to cerebral vasospasm

The second leading cause of death and disability in patients with aneurysmal subarachnoid hemorrhage (SAH) is delayed cerebral ischemia due to vasospasm. Although up to 70% of patients have been shown to have angiographic evidence of vasospasm, only 20-30% will present with clinical changes, including mental status changes and neurological deficits that necessitate acute management. Endovascular capabilities have progressed to become viable options in the treatment of cerebral vasospasm. The rationale for intraarterial therapy includes the fact that morbidity and mortality rates have not changed in recent years despite optimized noninvasive medical care. In this report, the authors discuss the most common endovascular options-namely intraarterial vasodilators and transluminal balloon angioplasty-from the standpoint of mechanism, efficacy, limitations, and complications as well as the treatment algorithms for cerebral vasospasm used at our institution.

Fever burden and functional recovery after subarachnoid hemorrhage

OBJECTIVE

Fever is associated with worse outcome after subarachnoid hemorrhage, but there are few prospective data to quantify this relationship.

METHODS

We prospectively enrolled consecutive aneurysmal or cryptogenic subarachnoid hemorrhage patients and recorded the highest core temperature each calendar day for Day 0 (the day of hemorrhage) through Day 13. Fever burden was defined as the daily highest core temperature minus 100.4 degrees F, summed from admission through Day 13 (temperatures <100.4 degrees F did not contribute to or subtract from fever burden). Outcomes were assessed at 14 days or at the time of hospital discharge with the National Institutes of Health Stroke Scale and modified Rankin Scale, and at 28 days and 3 months with the modified Rankin Scale. Improvement was analyzed with repeated measures analysis of variance.

RESULTS

We prospectively enrolled 94 patients. From 14 days to 28 days to 3 months, functional improvement was related to cumulative fever burden, admission neurological grade, aneurysm obliteration procedure, admission computed tomographic score, vasospasm, and external ventricular drainage. Good-grade patients had worse functional outcomes with increased fever burden, and poor-grade patients improved more over time when fever burden was higher (time by World Federation of Neurological Surgeons grade by fever burden interaction, P < 0.001). Patients with vasospasm (P = 0.04) and patients with higher computed tomographic scores (P = 0.002) had worse 14-day outcomes but improved more over time. Bacteremia and ventriculitis were uncommon (<or=5%) and were not associated with higher fever burden.

CONCLUSION

Cumulative fever burden was associated with worse outcomes in good-grade patients and potential late recovery in poor-grade patients. Effective fever control in febrile subarachnoid hemorrhage patients may improve functional outcomes and hasten recovery.

Advanced noninvasive imaging of spinal vascular malformations

Spinal vascular malformations (SVMs) are an uncommon, heterogeneous group of vascular anomalies that can render devastating neurological consequences if they are not diagnosed and treated in a timely fashion. Imaging SVMs has always presented a formidable challenge because their clinical and imaging presentations resemble those of neoplasms, demyelination diseases, and infection. Advancements in noninvasive imaging modalities (MR and CT angiography) have increased during the last decade and have improved the ability to accurately diagnose spinal vascular anomalies. In addition, intraoperative imaging techniques have been developed that aid in the intraoperative assessment before, during, and after resection of these lesions with minimal and/or optimal use of spinal digital subtraction angiography. In this report, the authors review recent advancements in the imaging of SVMs that will likely lead to more timely diagnoses and treatment while reducing procedural risk exposure to the patients who harbor these uncommon spinal lesions.

Acute symptomatic cerebellar tonsillar herniation following intraoperative lumbar drainage

Complications of tonsillar herniation associated with lumbar drainage have been reported in the literature. However, acutely symptomatic tonsillar herniation after intraoperative lumbar drainage is rare. The following case illustrates the risk associated with cerebrospinal fluid (CSF) drainage in the setting of tonsillar herniation. The use of lumbar drainage during cranial surgery is a common practice for reducing intracranial pressure and enhancing exposure, but is not without complications. In addition to the complications of the insertion procedure itself, the change in pressure gradient between the intracranial and the suboccipital compartments is of key importance.

The authors present the case of a patient who underwent a subtemporal craniotomy for resection of mesial temporal cavernous malformation with intraoperative lumbar drainage. The patient had a preexisting, asymptomatic 4-mm Chiari malformation and progressive neurological deficits resulting from further cerebellar tonsillar herniation in the early postoperative period developed, which required a lumbar blood patch, decompressive suboccipital craniectomy, and C-1 laminectomy with duroplasty. After placement of the lumbar drain and subsequent CSF drainage, the change in CSF pressure gradient above and below the foramen magnum probably led to the herniation. Unfortunately, the patient has lasting neuropathic pain and cervical cord signal changes on MR images.

Immune response in human cerebral cavernous malformations

BACKGROUND AND PURPOSE

Preliminary observations suggesting the presence of B and plasma cells and oligoclonality of immunoglobulin (Ig) G in cerebral cavernous malformations (CCM) have motivated a systematic study correlating the infiltration of the immune cells with clinical activity and antigen-triggered immune response in surgically excised lesions.

METHODS

Infiltration of plasma, B, T, and human leukocyte antigen-DR-expressing cells and macrophages within 23 excised CCM was related to clinical activity. Relative amounts of Ig isotypes were determined. IgG clonality of mRNA from CCM was assessed by spectratyping, cloning, and sequencing.

RESULTS

Infiltration of the immune cells ranged widely within CCM lesions, and cells were generally coexpressed with each other. Immune cell infiltration did not associate with recent bleeding and lesion growth. Significantly more B lymphocytes in CCM lesions were associated with venous anomaly. More T cells were present in solitary lesions. More T cells and less macrophages were present in CCM from younger subjects. IgG isotype was present in all CCM lesions. Most lesions also expressed IgM and IgA, with IgM predominance over IgA correlating with recent CCM growth. Oligoclonality was shown in IgG mRNA from CCM, but not from peripheral blood lymphocytes, with only 8 complementary-determining region 3 sequences observed among 134 clones from 2 CCM lesions.

CONCLUSIONS

An antigen-directed oligoclonal IgG immune response is present within CCM lesions regardless of recent clinical activity. Apparent differences in immune response in younger patients and in lesions with recent growth will need confirmation in other series. The pathogenicity of oligoclonal immune response will require systematic hypothesis testing in recently available CCM murine models.

OUTCOME PREDICTORS AND SPECTRUM OF TREATMENT ELIGIBILITY WITH PROSPECTIVE PROTOCOLIZED MANAGEMENT OF INTRACEREBRAL HEMORRHAGE

OBJECTIVE

Risk predictors, spectrum of treatment eligibility, and range of expected outcomes have not been validated in consecutive series including all cases of intracerebral hemorrhage (ICH) subjected to a prospective management protocol based on current guidelines.

METHODS

Eighty-six cases of ICH were prospectively identified in conjunction with screening for a clinical trial during an 18-month period. All patients were subjected to protocolized management based on published “best practice” guidelines for ICH. Medical records were reviewed by trained researchers, and outcomes were assessed at various time points including latest follow-up (range, 0–24 months; mean, 3.97 months). Initial assessment parameters, treatment eligibility, and outcomes were based on standardized criteria.

RESULTS

In accordance with past literature, mortality and functional outcomes were significantly worse in older patients, those with a larger ICH volume, and worse Glasgow Coma Scale scores, in univariate and multivariate models. The presence and severity of associated intraventricular hemorrhage also correlated with mortality and outcome. Significantly lower mortality (P = 0.024) and better functional outcomes (P = 0.018) were achieved at 30 days in patients with an ICH volume of less than 30 cm3 in this series than in previously published community-based historical controls without protocolized care. A tight correspondence between treatment eligibility and treatment administered was found.

CONCLUSION

Previous estimates of poorer outcome in patients with ICH might not apply to contemporary management protocols, especially in patients with a smaller ICH volume. Outcome ranges in various risk categories and modeling of treatment eligibility will help project more realistic prognostication and assist with the design of future trials.

How patients die after intracerebral hemorrhage

INTRODUCTION

Severity of illness scores predict all-cause mortality after intracerebral hemorrhage (ICH), but do not differentiate between proximate mechanisms or predict the timing. We hypothesized that death by neurologic criteria [brain death (BD)], withdrawal of life support, and cardiovascular death would be distinct after ICH.

METHODS

We prospectively enrolled patients with spontaneous ICH without underlying vascular malformation or neoplasm. We recorded clinical data and the proximate mechanism of death (BD, withdrawal of life support, cardiovascular death, or other cause). Time to death was compared with Kaplan-Meier methods (log-rank test). Data are median (IQR).

RESULTS

Among 89 patients, 15 had withdrawal of life support, 5 had BD, 2 died from cardiac arrest, and 3 died from other causes. Among patients who died, ICH score, age, Glasgow Coma Scale, NIH Stroke Scale, and proximate cause were not associated with the proximate mechanism of death. The time to death was different (P < 0.001) depending on the proximate mechanism. Patients with BD died 1 [0-1] 1 day after ICH, withdrawal of life support led to death 5 [1-13] days after ICH, cardiac death occurred 35 [35-85] days after ICH, and other causes led to death 33 [26-33] days after ICH. Among patients where life support was withdrawn, a higher ICH score on admission was related to earlier death (P = 0.002).

CONCLUSIONS

Proximate mechanisms of death after ICH occur at distinct times. Withdrawal of life support leads to earlier death in patients with a higher severity of injury. Medical causes of death can be effectively prevented after ICH.

Advanced magnetic resonance imaging of cerebral cavernous malformations: part I. High-field imaging of excised human lesions

OBJECTIVE

We hypothesized that structural details that have not been described previously would be revealed in cerebral cavernous malformations (CCM) through the use of high-field magnetic resonance and confocal microscopy. The structural details of CCMs excised from patients were sought by examination with high-field magnetic resonance imaging (MRI) and correlated with confocal microscopy of the same specimens. Novel features of CCM structure are outlined, including methodological limitations, venues for future research, and possible clinical implications.

METHODS

CCM lesions excised from 4 patients were fixed in 2% paraformaldehyde and subjected to high-resolution MRI at 9.4 or 14.1-T by spin echo and gradient recalled echo methods. Histological validation of angioarchitecture was conducted on thick sections of CCM lesions using fluorescent probes to endothelium under confocal microscopy.

RESULTS

Images of excised human CCM lesions were acquired with proton density-weighted, T1-weighted, T2-weighted spin echo, and T2*-weighted gradient recalled echo MRI. These images revealed large "bland" regions with thin-walled caverns and "honeycombed" regions with notable capillary proliferation and smaller caverns surrounding larger caverns. Proliferating capillaries and caverns of various sizes were also associated with the walls of apparent larger blood vessels in the lesions. Similar features were confirmed within thick sections of CCMs by confocal microscopy. MRI relaxation times in different regions of interest suggested the presence of different states of blood breakdown products in areas with apparent angiogenic proliferative activity.

CONCLUSION

High-field MRI techniques demonstrate novel features of CCM angioarchitecture, visible at near histological resolution, including regions with apparently different biological activity. These preliminary observations will motivate future research, correlating lesion biological and clinical activity with features of MRI at higher field strength.

Giant intracranial aneurysms: endovascular challenges

The treatment of giant aneurysms remains a formidable challenge for endovascular and surgical strategies. The use of endovascular techniques in a deconstructive (e.g., parent vessel occlusion) and reconstructive (e.g., stent coiling) methodology is reviewed. The results of endovascular coiling as a primary therapy for giant aneurysm occlusion have been disappointing. Hunterian strategies have had more success in published series, but recent developments in coil, glue, and stent technology show great promise in allowing parent vessel reconstruction as a primary endovascular target, with acceptable morbidity, mortality, and durability. A literature review of giant aneurysm endovascular treatment strategies was undertaken after 1994, when Guglielmi detachable coils were approved by the Food and Drug Administration. Where possible, follow-up, durability, and occlusion rates are also reviewed.

Medical complications drive length of stay after brain hemorrhage: a cohort study

INTRODUCTION

Longer length of stay (LOS) is associated with higher complications and costs in ICU patients, while hospital protocols may decrease complications and LOS. We hypothesized that medical complications would increase LOS after spontaneous subarachnoid (SAH) and intracerebral (ICH) hemorrhage after accounting for severity of neurologic injury in a cohort of consecutively admitted patients.

METHODS

We prospectively recorded admission characteristics, hospital complications, and LOS for 122 patients with SAH and 56 patients with ICH from February 2006 through March 2008. A multidisciplinary Neuro-ICU team included a dedicated pharmacist and intensivist on daily rounds. Hospital protocols set glucose control with intravenous insulin, ventilator bundles, pharmacist involvement, and hand hygiene. Associations were explored with univariate statistics (t-tests, ANOVA, or non-parametric statistics as appropriate) and linear regression (repeated after log transformation of ICU and hospital LOS).

RESULTS

Factors associated with longer LOS after SAH and ICH were similar. In both SAH and ICH the strongest drivers of LOS were infection, fever, and acute lung injury. For SAH, vasospasm and Glasgow Coma Scale were also significant in some models, while in patients with ICH the volume of the initial bleed was significant in some models.

CONCLUSION

LOS after spontaneous brain hemorrhage is driven by medical complications even after the adoption of dedicated intensive care medical staff, pharmacist involvement, and evidence-based protocols for ICU care. Further alterations in care will be necessary to eliminate "preventable" complications and minimize LOS after brain hemorrhage.

Thalamic and basal ganglia arteriovenous malformations: redefining "inoperable"

Deep arteriovenous malformations of the basal ganglia and thalamus have an aggressive natural history and present a therapeutic challenge. More often than not, these lesions are deemed "inoperable" and are treated expectantly or with stereotactic radiosurgery. In some cases, clinical details combined with an opportune route of access dictate surgical resection. History of hemorrhage, small lesion size, and deep venous drainage each add to the aggressive natural history of these malformations. Interestingly, these same factors can point toward surgery. We present a discussion of the microsurgical techniques involved in managing these lesions, with an emphasis on situations that allow these lesions to be approached surgically.

Thalamic and Basal Ganglia Arteriovenous Malformations: Redefining “Inoperable”

Deep Arteriovenous Malformations of the basal ganglia and thalamus have an aggressive natural history and present a therapeutic challenge. More often than not, these lesions are deemed “inoperable” and are treated expectantly or with stereotactic radiosurgery. In some cases, clinical details combined with an opportune route of access dictate surgical resection. History of hemorrhage, small lesion size, and deep venous drainage each add to the aggressive natural history of these malformations. Interestingly, these same factors can point toward surgery. We present a discussion of the microsurgical techniques involved in managing these lesions, with an emphasis on situations that allow these lesions to be approached surgically.

Symptomatic spontaneous intracranial carotid artery dissection treated with a self-expanding intracranial nitinol stent: a case report

BACKGROUND

Although extracranial carotid dissection with stroke is common, intracranial dissection with stroke is rare. Stenting has been used to treat extracranial carotid dissections. Intracranially, however, it is only recently that stents have become a feasible option for this disease. We present a case of a spontaneous intracranial CAD with progressive symptoms despite medical management treated with a self-expanding intracranial micronitinol stent.

CASE DESCRIPTION

A 47-year-old, right-handed woman presented to the emergency department after noticing left-sided face and arm weakness and numbness, along with slurred speech. The patient was started on aspirin 325 mg/d orally and lovenox 40 mg/d subcutaneously. On hospital day 2, the patient was noted to have repeated episodes of weakness and numbness on the left side and MRI evidence of a new stroke. A diagnostic cerebral angiogram from a selective right internal carotid injection revealed a flow-limiting stenosis secondary to a dissection of the supraclinoid internal carotid artery with severe flow limitation to the hemisphere. Endovascular management was decided on, and a Neuroform stent measuring 4.5 x 20 mm (Boston Scientific Corporation, Natick, Mass) was deployed across the dissection with significant improvement of flow to that hemisphere on the poststent angiogram.

CONCLUSIONS

This case illustrates the successful off-label use of a self-expanding intracranial nitinol stent to treat a symptomatic intracranial internal CAD in the setting of failure of traditional medical management. This is a promising application of novel endovascular technology.

Temporal bone dissection for neurosurgery residents: identifying the essential concepts and fundamental techniques for success

BACKGROUND

Many contemporary neurosurgery residents, cordoned by work hour restrictions and drawn to newer technologies such as endovascular therapy, lack the proper direction necessary to learn the essentials of temporal bone dissection. A thorough knowledge of temporal bone anatomy combined with guidance regarding proper surgical technique makes temporal bone dissection an efficacious and fundamental learning activity. There is currently no concise guide for neurosurgical training programs to use in teaching the essentials of this dissection.

METHODS

Over several years, the authors worked with neurosurgery residents to determine the key concepts necessary to gain a fundamental working knowledge of temporal bone dissection.

RESULTS

We have identified 5 essential surgical principles and developed a step-by-step dissection technique useful for neurosurgery residents.

CONCLUSIONS

Using this template, neurosurgery residents can make the most of their time in the skull base laboratory, becoming familiar with relevant temporal bone anatomy in situ and becoming facile with the surgical techniques necessary for its safe dissection.

4D radial contrast-enhanced MR angiography with sliding subtraction

A method is presented for high spatial and temporal resolution 3D contrast-enhanced magnetic resonance angiography. The overall technique involves a set of interrelated components suited to high-frame-rate angiography, including 3D cylindrical k-space sampling, angular undersampling, asymmetric sampling, sliding window reconstruction, pseudorandom view ordering, and a sliding subtraction mask. Computer simulations and volunteer studies demonstrated the utility of each component of the technique. Angiograms of one hemisphere of the intracranial vasculature were acquired with a pixel size of 1.1 x 1.1 x 2.8 mm and a frame rate of 0.35 sec based on a temporal resolution of 3.5 sec. Such a 3D time-resolved, or "4D," technique has the potential to noninvasively acquire diagnostic quality images of certain anatomic regions with a frame rate fast enough to not only ensure the capture of an uncontaminated arterial phase, but even demonstrate contrast bolus flow dynamics. Clinical applications include noninvasive imaging of arteriovenous shunting, which is demonstrated with a patient study.