The detection and management of unruptured intracranial aneurysms

Non-aneurysm subarachnoid hemorrhage in young adults

OBJECTIVE

The incidence of subarachnoid hemorrhage (SAH) in the young is increasing recently. Among the young patients, some of them do not have detectable aneurysms, so the cause of the disease may be non-aneurysmal. In this study, we analyzed some clinical cases of subarachnoid hemorrhage in young adults and discussed the possible causes other than present aneurysm and arteriovenous malformation (AVM).

METHODS

We reviewed 11 patients with SAH below 45 years of age enrolled in our hospital from January 2007 to June 2008. Their clinical characteristics, imaging examination results were analyzed in details: nine patients were found with no obvious cause for their hemorrhage. Four of them were followed up for 1 year and the other three were followed up for half a year. We telephoned the seven patients to gain the information on their recovery by questionnaire.

RESULTS

With an average onset age of 38 years old, all patients had similar symptoms and onset behavior according to their clinical characteristics. Based on the imaging results, two had confirmed vascular malformation; the other nine did not present detectable aneurysm or AVM, but with different morphological changes of their cerebral arteries. By 1-year or half-year follow-up, the seven patients were found to have good recovery.

CONCLUSION

Pathological changes of cerebral vessels due to smoking, genetic, or as an early version of formation of aneurysm, might be contributed to SAH in the young. Repeated angiogram is necessary for young patients to confirm the cause of SAH.

An ounce of prevention is worth a pound of cure: a cost-effectiveness analysis of incidentally detected aneurysms in functional MRI research

PURPOSE

Despite ongoing debate about best practices for managing incidentally detected findings in brain research studies using magnetic resonance imaging (MRI), this issue has not been investigated from a health economics viewpoint. We applied a decision-analytic approach to assess the benefit of various strategies for functional MRI (fMRI) studies using intracranial aneurysms (IA) as a model.

METHODS

A decision tree and Markov model were created to simulate the impact on the lifetime costs and quality-adjusted life-years (QALY) of four different strategies for review of scans for the presence of IA. To populate the decision model, we used current evidence from the literature and results from a survey of experts.

RESULTS

Review of the anatomical scans by a nonspecialist is not cost-effective in any of the subgroups of participants. Full clinical examination of women with a positive family history before enrollment in a study is cost-effective. Cost-effectiveness of reviewing scans obtained from women without a family history and men with a positive family history of IA depends on the willingness-to-pay (λ) for a QALY: at λ of $50,000/QALY, review of scans by a specialist is cost-effective, whereas at λ of $100,000/QALY, a full clinical workup is the best option. Compared with not reviewing any scans, a customized strategy for each subgroup of participants results in an incremental cost-effectiveness ratio of $12,503 for λ=$50,000/QALY and $32,767 for λ=$100,000/QALY.

CONCLUSION

Tailored strategies based on the characteristics of research participants and λ for one QALY are needed to address the problem of incidental findings in research fMRI studies.

Biomarkers and vasospasm after aneurysmal subarachnoid hemorrhage

Subarachnoid hemorrhage from the rupture of a saccular aneurysm is a devastating neurological disease that has a high morbidity and mortality not only from the initial hemorrhage, but also from the delayed complications, such as cerebral vasospasm. Cerebral vasospasm can lead to delayed ischemic injury 1 to 2 weeks after the initial hemorrhage. Although the pathophysiology of vasospasm has been described for decades, the molecular basis remains poorly understood. With the many advances in the past decade in the development of sensitive molecular biological techniques, imaging, biochemical purification, and protein identification, new insights are beginning to reveal the etiology of vasospasm. These findings will not only help to identify markers of vasospasm and prognostic outcome, but will also yield potential therapeutic targets for the treatment of this disease. This review focuses on the methods available for the identification of biological markers of vasospasm and their limitations, the current understanding as to the utility and prognostic significance of identified biomarkers, the utility of these biomarkers in predicting vasospasm and outcome, and future directions of research in this field.

Abrupt-onset severe headaches

Thunderclap headache, a severe headache which is maximal in intensity at onset, is associated with numerous underlying disorders, including subarachnoid hemorrhage, unruptured intracranial aneurysm, cervical artery dissection, cerebral venous sinus thrombosis, stroke, intracranial hemorrhage, reversible cerebral vasoconstriction syndrome, and reversible posterior leukoencephalopathy. After exclusion of all possible causes, thunderclap headache may be considered a primary headache. This review summarizes the diagnostic considerations and clinical approach to thunderclap headache, with particular emphasis on the reversible cerebral vasoconstriction syndromes.

Current and evolving management of subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a catastrophic event that carries a mortality rate of 25% to 50%, with 10% to 15% of patients dying before reaching a hospital. Approximately 30,000 aneurysms rupture each year in the United States. Aneurysmal SAH accounts for 2% to 5% of all new strokes each year. Unlike other types of strokes, the incidence of SAH has not declined over time. As many as 46% of SAH survivors have long-term cognitive impairment, with impact on functional status and quality of life. Modern therapy offers the opportunity to reduce the morbidity of SAH by reducing secondary injury, preventing complications, and reducing the risk of future bleeding events. For most people, an aneurysmal rupture is a life-changing event.

Treatment of unruptured intracranial aneurysms in South Korea in 2006 : a nationwide multicenter survey from the korean society of cerebrovascular surgery

OBJECTIVE

There have been no clinical studies regarding the epidemiology and treatment outcome for unruptured intracranial aneurysm (UIA) in South Korea yet. Thus, The Korean Society of Cerebrovascular Surgery (KSCVS) decided to evaluate the clinical and epidemiological characteristics, and outcome of the treatment of UIA in 2006, using the nationwide multicenter survey in South Korea.

METHODS

A total of 1,696 cases were enrolled retrospectively over one year at 48 hospitals. The following data were obtained from all patients : age, sex, presence of symptoms, location and size of the aneurysm, treatment modality, presence of risk factors for stroke, and the postoperative 30-day morbidity and mortality.

RESULTS

The demographic data showed female predominance and peak age of seventh and sixth decades. Supraclinoid internal carotid artery was the most common site of aneurysms with a mean size of 5.6 mm. Eight-hundred-forty-six patients (49.9%) were treated with clipping, 824 (48.6%) with coiling, and 26 with combined method. The choice of the treatment modalities was related to hospital (p = 0.000), age (p = 0.000), presence of symptom (p = 0.003), and location of aneurysm (p = 0.000). The overall 30-day morbidity and mortality were 7.4% and 0.3%, respectively. The 30-day mortality was 0.4% for clipping and 0.2% for coiling, and morbidity was 8.4% for clipping and 6.3% for coiling. Age (p = 0.010), presence of symptoms (p = 0.034), size (p = 0.000) of aneurysm, and diabetes mellitus (p = 0.000) were significant prognostic factors, while treatment modality was not.

CONCLUSION

This first nation-wide multicenter survey on UIAs demonstrates the epidemiological and clinical characteristics, outcome and the prognostic factors of the treatment of UIAs in South Korea. The 30-day postoperative outcome for UIAs seems to be reasonable morbidity and mortality in South Korea.

[Treatment of grade 0 intracranial aneurysms: Retrospective study of 79 cases]

AIM

Without precise international recommendations, despite the advances of the ISUAA study, the superiority of microsurgery or endovascular treatment for unruptured intracranial aneurysm (UIA) over the natural history of this disease has not been proved. In this context, the authors evaluate their experience with the aim of assessing the results and risks of the different therapeutics and comparing them with the natural risk of this disease.

MATERIAL AND METHOD

From January 1993 to July 2000, 79 patients harboring 110 UIAs were treated. These patients were divided retrospectively into two groups. Group A included 45 operated patients. Group B included 37 patients treated with endovascular coiling. The therapeutic choice was not randomized and was approved by a multidisciplinary neurovascular staff.

RESULTS

The two populations were homogeneous in terms of age and sex. In group A, 12 patients presented early complications (26.6 %), with one death. In group B, 15.6 % of the patients presented an ischemic complication. After 1 year of follow-up, morbidity was 11.4 % in group A and 4.8 % for group B. Angiography found a partial recanalization in 12.5 % of the operated patients and in 33 % of the patients treated with endovascular coiling.

DISCUSSION

Many factors are involved in the therapeutic decision: UIA location and size and individual risks. Progress in both surgery and interventional neuroradiology has led to good results conforming with the data reported in the literature but does not demonstrate the superiority of one technique over another.

Neuroimaging in assessment of risk of stroke in children with sickle cell disease

PURPOSE

Stroke and subclinical "silent infarcts" are major causes of morbidity in children with Sickle Cell Disease (SCD). Ischemic strokes are more common in younger children while hemorrhagic strokes are more frequent in adults. The goal of neuroimaging in acute stroke is to document whether the stroke is ischemic or hemorrhagic, to assess the extent of parenchymal abnormalities and to determine the presence of other cerebrovascular lesions. Computed Tomography (CT) is the primary modality for the assessment of acute stroke patients because of its 24/7 availability and ability to exclude hemorrhagic causes. Magnetic resonance imaging (MRI) and MR angiography (MRA) are recommended to determine precisely extent of infarction and detect cerebrovascular abnormalities. The goal of neuroimaging in patients with hemorrhagic stroke is to identify an arteriovenous malformation or aneurysm(s) amenable to surgery or catheter intervention.The risk of first stroke is very high in asymptomatic children with intracranial arterial mean velocities over 200 cm/s on transcranial Doppler (TCD) examination. The risk can be substantially reduced if chronic blood transfusions are timely implemented. Large cerebral vessel disease detected by TCD can be confirmed or excluded by MRI/MRA. Those with evidence of parenchymal and/or cerebrovascular lesions should be followed by preventive therapy. In patients with neurologic symptoms and negative MRI/MRA findings Positron Emission Tomography or single photon emission CT is recommended. There are no specific neuroimaging findings that suggest that blood transfusions can be safely halted in children with SCD.

Primary thunderclap headache

Thunderclap headache is an uncommon type of headache, but recognition and diagnosis are important because of the possibility of a serious underlying brain disorder. In this chapter, primary thunderclap headache in relation to other primary headache disorders and secondary, symptomatic headache disorders are discussed. Most importantly, subarachnoid hemorrhage should be excluded. The first investigation is a computed tomography (CT) scan, and, if the CT scan is negative, investigation of the cerebrospinal fluid. Other symptomatic vascular causes are intracranial hemorrhage, cerebral venous sinus thrombosis, cervical artery dissection, or a reversible vasoconstriction syndrome. These and other serious underlying intracranial disorders should be detected by magnetic resonance imaging or the appropriate investigations. The remaining patients with thunderclap headache most likely represent a primary headache disorder, including migraine, primary cough headache, primary exertional headache, or primary headache associated with sexual activity. Within the group of primary headache disorders, primary thunderclap headache represents a distinct clinical entity; it is characterized by a sudden severe headache lasting from 1h up to 10 days and not attributed to another disorder. The pathogenesis of primary thunderclap headache is still not known, but the sympathetic nervous system may play an important role.

Imaging of intracranial aneurysms causing isolated third cranial nerve palsy

Isolated third cranial nerve palsies may be caused by compressive intracranial aneurysms located at the junction of the internal carotid and posterior communicating arteries or, less commonly, at the apex of the basilar artery or its junction with the superior cerebellar or posterior cerebral arteries. Such aneurysms typically measure at least 4 mm in diameter. Technical improvements in noninvasive techniques, including CT and MRA, have yielded a detection rate of such aneurysms that approaches that of catheter cerebral angiography (CCA), which itself carries a small but serious risk. Multidetector technology, which allows a rapid scan time, has promoted CT to the first choice for investigating aneurysms in this setting except when dye or radiation exposure is unacceptable, as with pregnant women, children, and those with renal or severe cardiac disease. Major impediments to accurate detection are a lack of availability of trained technicians, who must perform manipulation of the raw imaging data ("post-processing"), and a paucity of certified neuroradiologists with the time, skill, and experience to devote to interpreting difficult cases. To avoid diagnostic mishaps, noninvasive studies should be reviewed by at least one neuroradiologist before aneurysm is rejected as the cause or before the patient undergoes CCA.

Computer-aided detection of intracranial aneurysms in MR angiography

Intracranial aneurysms represent a significant cause of morbidity and mortality. While the risk factors for aneurysm formation are known, the detection of aneurysms remains challenging. Magnetic resonance angiography (MRA) has recently emerged as a useful non-invasive method for aneurysm detection. However, even for experienced neuroradiologists, the sensitivity to small (<5 mm) aneurysms in MRA images is poor, on the order of 30~60% in recent, large series. We describe a fully automated computer-aided detection (CAD) scheme for detecting aneurysms on 3D time-of-flight (TOF) MRA images. The scheme locates points of interest (POIs) on individual MRA datasets by combining two complementary techniques. The first technique segments the intracranial arteries automatically and finds POIs from the segmented vessels. The second technique identifies POIs directly from the raw, unsegmented image dataset. This latter technique is useful in cases of incomplete segmentation. Following a series of feature calculations, a small fraction of POIs are retained as candidate aneurysms from the collected POIs according to predetermined rules. The CAD scheme was evaluated on 287 datasets containing 147 aneurysms that were verified with digital subtraction angiography, the accepted standard of reference for aneurysm detection. For two different operating points, the CAD scheme achieved a sensitivity of 80% (71% for aneurysms less than 5 mm) with three mean false positives per case, and 95% (91% for aneurysms less than 5 mm) with nine mean false positives per case. In conclusion, the CAD scheme showed good accuracy and may have application in improving the sensitivity of aneurysm detection on MR images.

Effect of Non-Newtonian Behavior on Hemodynamics of Cerebral Aneurysms

Blood flow dynamics near and within cerebral aneurysms have long been implicated in aneurysm growth and rupture. In this study, the governing equations for pulsatile flow are solved in their finite volume formulation to simulate blood flow in a range of three-dimensional aneurysm geometries. Four constitutive models are applied to investigate the influence of non-Newtonian behavior on flow patterns and fluid mechanical forces. The blood’s non-Newtonian behavior is found to be more significant, in particular, vascular geometries, and to have pronounced effects on flow and fluid mechanical forces within the aneurysm. The choice of constitutive model has measurable influence on the numerical prediction of aneurysm rupture risk due to fluid stresses, though less influence than aneurysm morphology.

Circle of Willis artery diameters on MR angiography: an Australian reference database

The aim was to establish a reference range of measurements for all major Circle of Willis (COW) arteries for an Australian population of patients presenting for brain magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) that is typical of a tertiary referral hospital; and to report the prevalence and disease associations of COW variants in our patient population. All technically diagnostic MRI and MRA studies performed at our magnetic resonance (MR) centre in the calendar year 2006 were re-read by one reader who classified the COW anatomical layout and measured diameters of all the major vessels at defined locations. A subset of 30 was independently re-read by another reader and the interobserver measurement variability analyzed. Graphical analysis, with 95% confidence intervals (95CI), summary statistics reporting, t-testing for unpaired and for paired means, Hauck-Anderson (H-A) clinical equivalence testing and logistic regression analysis for categorical variables was performed as relevant. One hundred and seventy-one studies (of 187 eligible) formed the analysis population. All of our patients had vessels of comparable calibre regardless of MRI disease status, gender or COW variant (P > 0.05). Basilar artery (BA) diameter showed significant association with age, but other vessel diameters did not. The reference range is widely applicable, methodology straightforward and appears tolerant of interobserver variability. A number of discontinuous COW variants become more prevalent with age, perhaps from atherosclerotic occlusive disease. There was no association between COW variants, gender, aneurysm location or MRI disease status.

The investigation of acute severe headache suggestive of probable subarachnoid haemorrhage: a hospital-based study

We reviewed the diagnostic approach to patients presenting with headache suggestive of subarachnoid haemorrhage (SAH) and normal cranial imaging, both locally and using a questionnaire, in other units throughout the United Kingdom. We emphasize the correct timing of cranial imaging and lumbar puncture (LP), the importance of proceeding to LP and utilizing spectrophotometry in patients with normal cranial imaging, and the appropriate use of angiography.

Treatment of Intracranial Aneurysms

The management of intracranial aneurysms (IAs) remarkably improved due to the development of diagnostic and surgical procedures. Subarachnoid hemorrhage (SAH) from IA rupture constitutes a devastating event, whose prognosis remains unsatisfactory. At present, several researchs are targeted to individuate subjects harboring unruptured IAs and those presenting a higher risk for rupture. Numerous risk factors for the rupture of lAs have been individuated. The prevalence of intracranial saccular aneurysms in the general population is estimated from 0.2% to 6.8%, with an incidence of SAH at 10/100,000/year. The most relevant morbidity and mortality rates after SAH are related to rebleeding and vasospasm. The primary therapeutic target consists in prevention of rebleeding. At present, therapeutic opportunities for intracranial aneurysms are microsurgery and endovascular treatment.

Unruptured Cerebral Aneurysm Detected after Intravenous Tissue Plasminogen Activator for Stroke

Therapeutic guidelines of intravenous thrombolysis with tissue plasminogen activator (tPA) for hyperacute ischemic stroke are very strict. Because of potential higher risk of bleeding complications, the presence of unruptured cerebral aneurysm is a contraindication for systemic thrombolysis with tPA. According to the standard CT criteria, a 66-year-old woman who suddenly developed aphasia and hemiparesis received intravenous tPA within 3 h after ischemic stroke. Magnetic resonance angiography during tPA infusion was performed and the presence of a small unruptured cerebral aneurysm was suspected at the anterior communicating artery. Delayed cerebral angiography confirmed an aneurysm with a size of 7 mm. The patient did not experience any adverse complications associated with the aneurysm. Clinical experiences of this kind of accidental off-label thrombolysis may contribute to modify the current rigid tPA guidelines for stroke.

Pathogenesis of cerebral vasospasm following aneurysmal subarachnoid hemorrhage: putative mechanisms and novel approaches

Cerebral vasospasm is a potentially incapacitating or lethal complication in patients with aneurysmal subarachnoid hemorrhage (SAH). The development of effective preventative and therapeutic interventions has been largely hindered by the fact that the underlying pathogenic mechanisms of cerebral vasospasm remain poorly understood. However, intensive research during the last 3 decades has identified certain mechanisms that possibly play a role in its development. Experimental data suggest that calcium-dependent and -independent vasoconstriction is taking place during vasospasm. It appears that the breakdown products of blood in the subarachnoid space are involved, through direct and/or indirect pathways, in the development of vasospasm after SAH. Free radicals reactions, an imbalance between vasoconstrictor and vasodilator substances (endothelium derived substances, e.g., nitric oxide, endothelin; arachidonic acid metabolites, e.g., prostaglandins, prostacyclin), inflammatory processes, an upheaval of neuronal mechanisms that regulate vascular tone, endothelial proliferation, and apoptosis have all been put forward as causative and/or pathogenic factors. Translational research in the field of vasospasm has traditionally aimed to identify agents/interventions in order to block the cascades initiated after SAH. The combination of novel approaches such as cerebral microdialysis, magnetic resonance spectroscopy, proteomics, and lipidomics could serve a dual purpose: elucidating the complex pathobiochemistry of vasospasm and providing clinicians with tools for early detection of this feared complication. The purpose of this Mini-Review is to provide an overview of the pathogenesis of cerebral vasospasm and of novel approaches used in basic and translational research.

TNF-alpha and sICAM-1 in intracranial aneurismal rupture

Introduction

Subarachnoidal hemorrhage (SAH) occurring after aneurismal rupture produces an inflammatory response in the cerebral circulation. Tumor necrosis factor (TNF)-α is a major cytokine in this process. Adhesion molecules provide information on inflammatory reactions taking place in the walls of blood vessels. Clinical evidence suggests a role of soluble intercellular adhesion molecule (sICAM)-1 in early hemorrhagic events. This study aimed to evaluate the implementation of early TNF-α and sICAM-1 serum measurement for the prognosis of patient outcome after intracranial aneurismal rupture.

Materials and Methods

The study consisted of 27 patients with a diagnosis of intracranial aneurysm. SAH was evaluated on admission according to the Fisher scale, patients-consciousness with the Glasgow Coma Scale, clinical grading with the Hunt and Hess scale, and clinical outcome with the Glasgow Outcome Scale (GOS). Blood samples were drawn within 72 h after arrival at the emergency room. Serum concentrations of TNF-α and sICAM-1 were assayed with the ELISA method.

Results

The initial serum TNF-α concentration in the aneurismal patients was low and did not correlate with radiological and clinical scores. The serum sICAM-1 level positively correlated with the severity of bleeding assessed by the Fisher scale and negatively with the patient’s scoring in the GOS.

Conclusions

This study demonstrated the absence of a systemic TNF-α-mediated inflammatory response at the onset of subarachnoid hemorrhage. Early measurement of serum sICAM-1 levels offers a potential prognostic value in the assessment of patients-outcome after brain aneurismal rupture.

Growth rates of intracranial aneurysms: exploring constancy

OBJECT

The annual rate of rupture of intracranial aneurysms is often assumed to be constant, but it is unknown whether this assumption is true. Recent case reports have suggested that aneurysms grow fast in a short period of time. The authors of the present report investigated the plausibility of a constant growth rate for intracranial aneurysms.

METHODS

Assuming a constant aneurysm growth rate within an individual and varying rates between individuals, a hypothetical cohort was simulated. Individuals with high growth rates will display aneurysm formation and rupture at a young age; such persons disappear early from the hypothetical cohort. As a result the mean lesion growth rate varies over time. In hypothetical cohorts with different initial mean growth rates, the authors calculated age-specific incidence rates (per 100,000 person-years) of subarachnoid hemorrhage and compared these rates with population-based data on the incidence of subarachnoid hemorrhage (per 100,000 person-years).

RESULTS

A hypothetical cohort with a mean initial growth rate of 0.18 mm/year reproduced most closely the incidence rates observed in the population. However, even for this most plausible hypothetical cohort, age-specific incidence rates in the model differed substantially and statistically significantly from those observed in the population.

CONCLUSIONS

Based on the results of this study, it is unlikely that intracranial aneurysms in general grow at a constant time-independent rate. The authors hypothesized that the actual growth process is irregular and discontinuous, which results in periods with and without aneurysm growth and with high and low risks of rupture.

Numerical simulation of pre- and postsurgical flow in a giant basilar aneurysm

Computational modeling of the flow in cerebral aneurysms is an evolving technique that may play an important role in surgical planning. In this study, we simulated the flow in a giant basilar aneurysm before and after surgical takedown of one vertebral artery. Patient-specific geometry and flowrates obtained from magnetic resonance (MR) angiography and velocimetry were used to simulate the flow prior to and after the surgery. Numerical solutions for steady and pulsatile flows were obtained. Highly three-dimensional flows, with strong secondary flows, were computed in the aneurysm in the presurgical and postsurgical conditions. The computational results predicted that occlusion of a vertebral artery would result in a significant increase of the slow flow region formed in the bulge of the aneurysm, where increased particle residence time and velocities lower than 2.5 cms were computed. The region of slow flow was found to have filled with thrombus following surgery. Predictions of numerical simulation methods are consistent with the observed outcome following surgical treatment of an aneurysm. The study demonstrates that computational models may provide hypotheses to test in future studies, and might offer guidance for the interventional treatment of cerebral aneurysms.

Reproducibility of haemodynamical simulations in a subject-specific stented aneurysm model--a report on the Virtual Intracranial Stenting Challenge 2007

This paper presents the results of the Virtual Intracranial Stenting Challenge (VISC) 2007, an international initiative whose aim was to establish the reproducibility of state-of-the-art haemodynamical simulation techniques in subject-specific stented models of intracranial aneurysms (IAs). IAs are pathological dilatations of the cerebral artery walls, which are associated with high mortality and morbidity rates due to subarachnoid haemorrhage following rupture. The deployment of a stent as flow diverter has recently been indicated as a promising treatment option, which has the potential to protect the aneurysm by reducing the action of haemodynamical forces and facilitating aneurysm thrombosis. The direct assessment of changes in aneurysm haemodynamics after stent deployment is hampered by limitations in existing imaging techniques and currently requires resorting to numerical simulations. Numerical simulations also have the potential to assist in the personalized selection of an optimal stent design prior to intervention. However, from the current literature it is difficult to assess the level of technological advancement and the reproducibility of haemodynamical predictions in stented patient-specific models. The VISC 2007 initiative engaged in the development of a multicentre-controlled benchmark to analyse differences induced by diverse grid generation and computational fluid dynamics (CFD) technologies. The challenge also represented an opportunity to provide a survey of available technologies currently adopted by international teams from both academic and industrial institutions for constructing computational models of stented aneurysms. The results demonstrate the ability of current strategies in consistently quantifying the performance of three commercial intracranial stents, and contribute to reinforce the confidence in haemodynamical simulation, thus taking a step forward towards the introduction of simulation tools to support diagnostics and interventional planning.

Intracranial aneurysms treated with Guglielmi detachable coils: long-term imaging follow-up with contrast-enhanced magnetic resonance angiography

OBJECT

The aim of this study was to assess the long-term results of intracranial aneurysms treated with Guglielmi detachable coils (GDCs) with the aid of contrast-enhanced magnetic resonance (MR) angiography.

METHODS

Between January 1998 and August 2001, 92 patients with 92 aneurysms treated by endovascular coiling with GDCs underwent contrast-enhanced MR angiography. These patients underwent long-term follow-up (range 32-78 months, mean 42.1 +/- 11.9 months [standard deviation]) after endovascular treatment. All images were compared with digital subtraction angiograms and contrast-enhanced MR angiograms that had been obtained during the short-term follow-up (range 5-25 months, mean 13 +/- 5.1 months after treatment). The MR angiograms were analyzed independently by 2 senior radiologists. Findings were assigned to 1 of 3 categories: complete obliteration (Class 1), residual neck (Class 2), or residual aneurysm (Class 3).

RESULTS

Of 92 contrast-enhanced MR angiograms obtained at the long-term follow-up, complete obliteration of the aneurysm was noted in 57 patients (Class 1), a residual neck was seen in 22 (Class 2), and a residual aneurysm was observed in 13 (Class 3). One patient experienced aneurysm rehemorrhaging during the follow-up period. The comparison of short- and long-term follow-up angiograms demonstrated a change in aneurysm classification in 7 patients (7.6%), including 4 that progressed from Class 1 to Class 2 and 3 from Class 2 to Class 3. However, 4 (14.2%) of the 28 long-term recurrences were not detected on the short-term control images.

CONCLUSIONS

Long-term follow-up with contrast-enhanced MR angiography after selective embolization of intracranial aneurysms can identify late aneurysm recanalization that is undetected at short-term follow-up.

GUIDELINES FOR THE SURGICAL TREATMENT OF UNRUPTURED INTRACRANIAL ANEURYSMS

THE MANAGEMENT OF unruptured cerebral aneurysms remains one of the most controversial topics in neurosurgery. To this end, we discuss the diagnosis and estimated prevalence of these lesions as well as review the literature regarding the rate of rupture for cerebral aneurysms and risks of operative intervention. Our interpretation of the literature concludes that aneurysms are present in approximately 1% of the adult population, varying between less than 1% in young adults to 4% in the elderly. The yearly risk of subarachnoid hemorrhage for an unruptured intracranial aneurysm is approximately 1% for lesions 7 to 10 mm in diameter. Based on these assumptions, we recommend that 1) with rare exceptions, all symptomatic unruptured aneurysms should be treated; 2) small, incidental aneurysms less than 5 mm in diameter should be managed conservatively in virtually all cases; 3) aneurysms larger than 5 mm in patients younger than 60 years of age should be seriously considered for treatment; 4) large, incidental aneurysms larger than 10 mm should be treated in nearly all patients younger than 70 years of age; and 5) microsurgical clipping rather than endovascular coiling should be the first treatment choice in low-risk cases. Critical to our guidelines is collaboration by a highly experienced cerebrovascular team of microneurosurgeons and endovascular neurosurgeons working at a tertiary medical center with a high case volume and using a decision-making paradigm designed to offer only low-risk treatments. In certain patients for whom both treatment and natural history carry high risks, such as those with giant aneurysms, nonoperative management is typically elected.

Clinical spectrum of thunderclap headache

Headaches of the thunderclap variety become severe in intensity within seconds to a minute of onset. Patients with thunderclap headache are to be evaluated in an emergent fashion as many of the underlying causes are associated with significant morbidity and mortality. Although subarachnoid hemorrhage is usually the initial consideration, a multitude of other etiologies have been identified and are discussed herein. In accordance with the increased utilization of cerebral imaging, availability of noninvasive techniques to image the cerebral vasculature and interest in identifying causes of thunderclap headaches, the list of potential causes is growing rapidly. Included in this growth are the reversible cerebral vasoconstriction syndromes, terminology recently introduced to unify several disorders all presenting with thunderclap headache and similar diagnostic findings including reversible vasoconstriction of the intracranial arteries.

Usefulness of MR imaging for the assessment of nonophthalmic paraclinoid aneurysms

BACKGROUND AND PURPOSE

The neuroradiologic location of asymptomatic paraclinoid aneurysms is decisive for patient management. In a preliminary study, we designed a paraclinoid MR protocol (PMP) including high-resolution T2-weighted images in 2 orthogonal planes to define the inferior limit of the distal dural ring plane that represents the borderline between the intradural and extradural internal carotid artery. In this clinical study, we compared this protocol with digital subtraction angiography (DSA) for the location of paraclinoid aneurysms.

MATERIALS AND METHODS

During a 3-year period, we performed PMP and conventional angiograms in 14 consecutive patients with 17 asymptomatic paraclinoid aneurysms. Ophthalmic (superior) aneurysms were excluded. Two independent observers reviewed MR imaging data, and a third experienced neuroradiologist analyzed the conventional angiograms. MR imaging and conventional angiograms were independently analyzed, and interpretations obtained with each technique were compared.

RESULTS

PMP allowed correct visualization of the aneurysms in all patients. No significant differences (P >.05) were found between the DSA and PMP for the measurement of the aneurysmal neck or sac. Interobserver agreement was good. MR imaging was discordant with conventional angiography regarding the position around the cavernous sinus of the aneurysmal neck and sac in 5 cases. PMP images were helpful for treatment decisions in 4 cases.

CONCLUSION

PMP is an interesting tool that might be used in association with conventional angiography for the assessment of paraclinoid aneurysms.

Anesthetic considerations for intraoperative management of cerebrovascular disease in neurovascular surgical procedures

Despite new surgical methods and interventions a considerable number of patients who undergo neurovascular procedures emergently or electively have substantial mortality, morbidity, and disability. Sound knowledge of pathophysiology of cerebral hypoperfusion, reliable and timely information from monitoring devices, and appropriate choice of therapeutic intervention is essential for successful anesthetic management of these patients. The management of perioperative vasospasm and temporary ischemia during aneurysm clipping require an understanding of cerebral vascular pathophysiology and neuroprotective measures.

The radiological investigation of subarachnoid haemorrhage

Subarachnoid haemorrhage is an important condition with a high mortality, so prompt diagnosis is essential. This article will review the investigation of subarachnoid haemorrhage with a radiological bias. Appropriate clinical correlation will be included and it will look at some of the more interesting areas in the investigation of this condition.

Computer-aided diagnosis in medical imaging: historical review, current status and future potential

Computer-aided diagnosis (CAD) has become one of the major research subjects in medical imaging and diagnostic radiology. In this article, the motivation and philosophy for early development of CAD schemes are presented together with the current status and future potential of CAD in a PACS environment. With CAD, radiologists use the computer output as a "second opinion" and make the final decisions. CAD is a concept established by taking into account equally the roles of physicians and computers, whereas automated computer diagnosis is a concept based on computer algorithms only. With CAD, the performance by computers does not have to be comparable to or better than that by physicians, but needs to be complementary to that by physicians. In fact, a large number of CAD systems have been employed for assisting physicians in the early detection of breast cancers on mammograms. A CAD scheme that makes use of lateral chest images has the potential to improve the overall performance in the detection of lung nodules when combined with another CAD scheme for PA chest images. Because vertebral fractures can be detected reliably by computer on lateral chest radiographs, radiologists' accuracy in the detection of vertebral fractures would be improved by the use of CAD, and thus early diagnosis of osteoporosis would become possible. In MRA, a CAD system has been developed for assisting radiologists in the detection of intracranial aneurysms. On successive bone scan images, a CAD scheme for detection of interval changes has been developed by use of temporal subtraction images. In the future, many CAD schemes could be assembled as packages and implemented as a part of PACS. For example, the package for chest CAD may include the computerized detection of lung nodules, interstitial opacities, cardiomegaly, vertebral fractures, and interval changes in chest radiographs as well as the computerized classification of benign and malignant nodules and the differential diagnosis of interstitial lung diseases. In order to assist in the differential diagnosis, it would be possible to search for and retrieve images (or lesions) with known pathology, which would be very similar to a new unknown case, from PACS when a reliable and useful method has been developed for quantifying the similarity of a pair of images for visual comparison by radiologists.

Thunderclap headache: An approach to a neurologic emergency

Thunderclap headache (TCH) refers to an excruciating headache of instantaneous onset. Recognition and accurate diagnosis of this headache are important because it can be caused by various serious underlying brain disorders such as subarachnoid hemorrhage, intracranial hematoma, cerebral venous sinus thrombosis, cervical artery dissection, ischemic stroke, pituitary apoplexy, acute arterial hypertension, spontaneous intracranial hypotension, third ventricle colloid cyst, and intracranial infections. Patients with TCH who have evidence of reversible, segmental, cerebral vasoconstriction of circle of Willis arteries and normal or near-normal cerebrospinal fluid evaluation are considered to have reversible cerebral vasoconstriction syndrome. Primary TCH is diagnosed when no underlying etiology is identified. In this review, we discuss the differential diagnosis of TCH, outline the characteristics and diagnostic criteria for primary TCH, offer a pathophysiologic hypothesis for primary TCH, and detail the diagnostic evaluation of the patient presenting with TCH.

Anesthetic Considerations of Selective Intra-arterial Nicardipine Injection for Intracranial Vasospasm

Cerebral vasospasm after subarachnoid hemorrhage can decrease cerebral blood flow with the potential for stroke. Induction of Triple-H therapy (hypertension, hypervolemia, and hemodilution) is an accepted medical therapy to decrease the delayed cerebral ischemia related to vasospasm. Recently selective intra-arterial injection of nicardipine during angiography has also been proposed as a therapeutic modality for the management of distal vasospasm not amenable to balloon angioplasty. We are reporting the hemodynamic changes in 11 patients who underwent this procedure. A retrospective chart review of 15 procedures in 11 patients showed a significant change in blood pressure after the injection of nicardipine. Blood pressure changes were not different between sexes, but increase in heart rate was higher for females. A significantly higher drop in systolic blood pressure but not for diastolic blood pressure or mean arterial pressure after the injection was seen in patients who were not intubated in the intensive care unit before the procedure. Selective intra-arterial injection of nicardipine during angiography can cause significant hemodynamic instability and requires supportive management by the anesthesiologist.

Thunderclap headache

Thunderclap headache (TCH) is head pain that begins suddenly and is severe at onset. TCH might be the first sign of subarachnoid haemorrhage, unruptured intracranial aneurysm, cerebral venous sinus thrombosis, cervical artery dissection, acute hypertensive crisis, spontaneous intracranial hypotension, ischaemic stroke, retroclival haematoma, pituitary apoplexy, third ventricle colloid cyst, and intracranial infection. Primary thunderclap headache is diagnosed when no underlying cause is discovered. Patients with TCH who have evidence of reversible, segmental, cerebral vasoconstriction of circle of Willis arteries and normal or near-normal results on cerebrospinal fluid assessment are thought to have reversible cerebral vasoconstriction syndrome. Herein, we discuss the differential diagnosis of TCH, diagnostic criteria for the primary disorder, and proper assessment of patients. We also offer pathophysiological considerations for primary TCH.

The genetics of intracranial aneurysms

The rupture of an intracranial aneurysm (IA) leads to a subarachnoid hemorrhage, a sudden onset disease that can lead to severe disability and death. Several risk factors such as smoking, hypertension and excessive alcohol intake are associated with subarachnoid hemorrhage. IAs, ruptured or unruptured, can be treated either surgically via a craniotomy (through an opening in the skull) or endovascularly by placing coils through a catheter in the femoral artery. Even though the etiology of IA formation is mostly unknown, several studies support a certain role of genetic factors. In reports so far, genome-wide linkage studies suggest several susceptibility loci that may contain one or more predisposing genes. Studies of several candidate genes report association with IAs. To date, no single gene has been identified as responsible for IA formation or rupture. The identification of susceptible genes may lead to the understanding of the mechanism of formation and rupture and possibly lead to the development of a pharmacological therapy.

Computerized detection of intracranial aneurysms for three-dimensional MR angiography: feature extraction of small protrusions based on a shape-based difference image technique

We have improved a computerized scheme for the detection of intracranial aneurysms for three-dimensional (3-D) magnetic resonance angiography (MRA) by the use of image features of small protrusions extracted based on a shape-based difference image (SBDI) technique. Initial candidates were identified by use of a multiple gray-level thresholding technique in dot enhanced images, and by finding short branches in skeleton images. Image features related to aneurysms were determined based on candidate regions segmented by use of a region growing technique. For extracting additional features on small protrusions or small aneurysms, we have developed an SBDI technique, which was based on the shape-based difference between an original segmented vessel and a vessel with suppressed local change in thickness. The SBDI technique was useful for obtaining local changes in vessel thickness, i.e., SBD regions, which could be small aneurysms in the case of true positives, but thin or very small regions in the case of false positives. Many false positives were removed by means of rule-based schemes and linear discriminant analysis on various 3-D localized image features, including SBDI features. We tested the computerized scheme on 53 cases with 61 aneurysms and 62 nonaneurysm cases based on a leave-one-out-by-patient test method. As a result, false positives per patient decreased from 5.8 to 3.8, while a high sensitivity of 97% was maintained by use of the SBDI technique, in which SBDI features were effective for removing some false positives. The computer-aided diagnostic (CAD) scheme may be robust and useful in assisting radiologists in the detection of intracranial aneurysms for MRA.

Use of antihypertension agents for the suppression of arterial pulse pressure waveforms in patients with intracranial aneurysms

Object

Patients with intracranial aneurysms tend toward raised blood pressure and abnormal pulse pressure profiles. The authors have investigated the influence of three antihypertension agents on blood pressure and pulse pressure waveforms in patients with known intracranial aneurysms, with a view to assessing the potential benefits of longterm antihypertension therapy on the progression of unruptured intracranial aneurysms.

Methods

Nineteen patients with a mean age of 56 years (range 38–76 years) were recruited for this study. All patients had confirmed intracranial aneurysms. A double-blind, randomized, crossover study was performed using perindopril, irbesartan, isosorbide mononitrate, and a placebo. Blood pressure and pulse pressure waveforms were assessed at the end of each 4-week treatment period.

Perindopril and irbesartan were well tolerated. For all measured parameters except heart rate (p = 0.03), no significant difference between baseline and placebo was identified. Each drug when compared with placebo reduced peripheral arterial blood pressure. Perindopril significantly decreased mean blood pressure by 10 mm Hg (p = 0.004), irbesartan by 9 mm Hg (p = 0.004), and isosorbide mononitrate by 13 mm Hg (p = 0.005).

The administration of each drug effected a significant reduction in the carotid artery augmentation index (AIX) compared with baseline values (perindopril p = 0.01, irbesartan p = 0.0002, and isosorbide mononitrate p = 0.03). There was also a significant difference in the AIX between irbesartan and the placebo (p = 0.05). Compared with the placebo, there was a significant difference in AIX (adjusted for heart rate) following the administration of irbesartan (p = 0.003) and isosorbide mononitrate (p = 0.01), but not with perindopril (p = 0.17).

Conclusions

Irbesartan appears to be the most effective treatment for the combined suppression of blood pressure and AIX in patients with intracranial aneurysms and has a high degree of patient tolerance.

Intracranial Aneurysms Treated With Guglielmi Detachable Coils

BACKGROUND AND PURPOSE

To compare the utility of contrast-enhanced MR Angiography (CE-MRA) with digital subtraction angiography (DSA) after endovascular treatment of intracranial aneurysms with Guglielmi detachable coils.

METHODS

From April 1999 to August 2002, 106 patients with 107 aneurysms treated by endovascular coiling using Guglielmi detachable coils underwent simultaneous DSA and CE-MRA at follow-up (mean: 12.9 range: 5 to 27 months). DSA was performed as the standard reference. MR angiographic images were analyzed independently by 2 senior radiologists (J.-Y.G., S.C.) and DSA by a third radiologist (X.L.). Findings were assigned to 1 of 3 categories: complete obliteration (class 1), residual neck (class 2) and residual aneurysm (class 3).

RESULTS

DSA at follow-up demonstrated 65 (60.6%) complete obliterations (group 1), 21 (19.7%) residual necks (group 2) and 21 (19.7%) residual aneurysms (group 3). One patient (0.9%) experienced aneurysm rebleed during the follow-up period. Among 101 assessable imaging comparisons, interobserver agreement was determined to be very good for CE-MRA (kappa=0.96) with only 4 discrepancies between both examiners. Comparison between CE-MRA and DSA showed an excellent agreement between techniques (kappa=0.93). Of the 21 with residual necks described on DSA, 20 were seen on CE-MRA. CE-MRA detected all 19 residual aneurysms.

CONCLUSIONS

CE-MRA after selective embolization of intracranial aneurysm is useful and comparable to DSA in the assessment of aneurysmal recanalization either as residual neck or aneurysmal sac.

Blood Flow Dynamics in Saccular Aneurysm Models of the Basilar Artery

Blood flow dynamics under physiologically realistic pulsatile conditions plays an important role in the growth, rupture, and surgical treatment of intracranial aneurysms. The temporal and spatial variations of wall pressure and wall shear stress in the aneurysm are hypothesized to be correlated with its continuous expansion and eventual rupture. In addition, the assessment of the velocity field in the aneurysm dome and neck is important for the correct placement of endovascular coils. This paper describes the flow dynamics in two representative models of a terminal aneurysm of the basilar artery under Newtonian and non-Newtonian fluid assumptions, and compares their hemodynamics with that of a healthy basilar artery. Virtual aneurysm models are investigated numerically, with geometric features defined by β=0deg and β=23.2deg, where β is the tilt angle of the aneurysm dome with respect to the basilar artery. The intra-aneurysmal pulsatile flow shows complex ring vortex structures for β=0deg and single recirculation regions for β=23.2deg during both systole and diastole. The pressure and shear stress on the aneurysm wall exhibit large temporal and spatial variations for both models. When compared to a non-Newtonian fluid, the symmetric aneurysm model (β=0deg) exhibits a more unstable Newtonian flow dynamics, although with a lower peak wall shear stress than the asymmetric model (β=23.2deg). The non-Newtonian fluid assumption yields more stable flows than a Newtonian fluid, for the same inlet flow rate. Both fluid modeling assumptions, however, lead to asymmetric oscillatory flows inside the aneurysm dome.

Outcome of Surgical Clipping of Unruptured Aneurysms as it Compares with a 10-Year Nonclipping Survival Period

OBJECTIVE

Recent studies on the natural history of unruptured intracranial aneurysms dictate that we reevaluate the risks and benefits of surgical intervention as it compares with the natural course. We analyzed the outcome of surgical clipping of a patient cohort with unruptured aneurysms as it compares with a 10 year nonclipping survival period on the basis of two previously published studies (International Study on Unruptured Intracranial Aneurysms and a study by Juvela et al. [36] from Helsinki).

METHODS

Data on 148 unruptured aneurysms in 116 consecutive surgically treated patients were prospectively recorded and retrospectively analyzed. The overall majority were diagnosed with cerebral angiography. Data analyzed included aneurysmal properties and clinical outcomes including surgical related mortalities and morbidities. The observed outcomes were compared with the expected outcome of a 10 year nonclipping survival period if the patient cohort was included in recently reported studies on unruptured aneurysms. More than 1 year follow-up was available in 93.1% (108) of patients and follow-up cerebral angiography was performed in 80% (93) of patients.

RESULTS

Mean age was 53.57 years. There were 25 (16.8%) small aneurysms (less than 7 mm), 70 (47.2%) aneurysms 7 to 12 mm in size, 41 (27.70%) large (13-24 mm), and 12 (8.10%) giant (>25 mm) aneurysms. Posterior circulation aneurysm comprised 13.51%. One hundred forty-three (96.62%) aneurysms were successfully clipped, and 3.37% were either wrapped or later coiled. Surgical-related mortality was 0.82% (1 patient because of air embolism). Surgical related permanent morbidity was 3.44% (4 patients) and transient surgical-related mild morbidities was 7.7% (9 patients). Immediate postsurgical good outcome (Glasgow Outcome Score = 4-5) was 87.93% (102 patients) and 95.68% in 3 months (111 patients). At 1 year, the modified Rankin scale scores were 0 to I = 102, II = 3, III = 2, IV = 1, and V = 0. Residual aneurysms were seen in none of the postoperative angiograms (93 patients). Using the chi method, the comparison of the expected to the observed mortality and morbidity revealed a statistically significant difference in the mortality in favor of surgical clipping (P = 0.034 when compared with the International Study on Unruptured Intracranial Aneurysms and P = 0.05 when compared with the Juvela et al. [36] study). There was no statistically significant difference in the permanent morbidity.

CONCLUSION

Studies on natural history of unruptured intracranial aneurysms suggest 10 year cumulative bleeding-related mortality and severe morbidity of no less than 7.5%. In our study, surgical clipping resulted in an 0.8% rate of mortality and 3.4% permanent morbidity. This suggests that surgical clipping has the potential of a superior outcome to the natural history of patients who have an estimated life expectancy of no less than 10 years.