Unruptured intracranial aneurysms: benign curiosity or ticking bomb?

Management of Unruptured Intracranial Aneurysms

Unruptured intracranial aneurysms (UIAs) are common and are being detected with increasing frequency given the improved quality and higher frequency of cross-sectional imaging. The long-term natural history of UIAs remains poorly understood. To date, there is relative lack of clear guidelines for selection of patients with UIAs for treatment. Surveillance imaging for untreated UIAs is frequently performed, but frequency, duration, and modality of surveillance imaging need clearer guidelines. The authors review the current evidence on prevalence, natural history, role of treatment, and surveillance and screening imaging and highlight the areas for further research.

Modeling of the acute effects of primary hypertension and hypotension on the hemodynamics of intracranial aneurysms

Hemodynamics is a risk factor in intracranial aneurysms (IA). Hypertension and pharmacologically induced hypotension are common in IA patients. This study investigates how hypertension and hypotension may influence aneurysmal hemodynamics. Images of 23 IAs at typical locations were used to build patient-specific Computational Fluid Dynamics models. The effects of hypotension and hypertension were simulated through boundary conditions by modulating the normotensive flow and pressure waveforms, in turn produced by a 1D systemic vascular model. Aneurysm location and flow pattern types were used to categorize the influence of hypotension and hypertension on relevant flow variables (velocity, pressure and wall shear stress). Results indicate that, compared to other locations, vertebrobasilar aneurysms (VBA) are more sensitive to flow changes. In VBAs, space-averaged velocity at peak systole increased by 30% in hypertension (16-21% in other locations). Flow in VBAs in hypotension decreased by 20% (10-13% in other locations). Momentum-driven hemodynamic types were also more affected by hypotension and hypertension, than shear-driven types. This study shows how patient-specific modeling can be effectively used to identify location-specific flow patterns in a clinically-relevant study, thus reinforcing the role played by modeling technologies in furthering our understanding of cardiovascular disease, and their potential in future healthcare.

Should patients with autosomal dominant polycystic kidney disease be screened for cerebral aneurysms?

Autosomal dominant polycystic kidney disease is a genetic disorder affecting 1 in 1000 people worldwide and is associated with an increased risk of intracranial aneurysms. It remains unclear whether there is sufficient net benefit to screening this patient population for IA, considering recent developments in imaging and treatment and our evolving understanding of the natural history of unruptured aneurysms. There is currently no standardized screening protocol for IA in patients with ADPCKD. Our review of the literature focused on the above issues and presents our appraisal of the estimated value of screening for IA in the setting of ADPCKD.

Risk factors for multiple intracranial aneurysms rupture: a retrospective study

BACKGROUND AND PURPOSE

The presence of predicting the rupture risk of intracranial aneurysms has recently generated considerable controversy. We retrospectively investigated the risk factors for multiple intracranial aneurysms related to rupture.

METHODS

Between July 2007 and July 2011, 134 patients with 294 aneurysms were identified after review. Every patient had two or more aneurysms. Univariate and multivariate logistic regression models were used to analyze the risk factors for multiple intracranial aneurysms with age, gender, site and size.

RESULTS

134 patients were divided into three groups according to patient age category (<45, 45-65, >65 years of age). The incidence of aneurysms ruptured in the second group was significantly higher. Three groups showed significant difference (P=0.001 versus >65 years of age). Thirteen of 35 AComA aneurysms were ruptured, accounting for 26% of all ruptured aneurysms, and the rate of rupture at AComA aneurysms in patients was 37.1%. The rate of aneurysm rupture in the AComA was significantly higher than that in other sites (P=0.001). In all 294 aneurysms, 88.1% of the aneurysms were 5mm or less, of which 58.2% were less than 3mm. In the ruptured aneurysms, 68% were 5mm or less.

CONCLUSIONS

Our study reveals the pattern of ruptured multiple intracranial aneurysms, in terms of age, size and location of aneurysms. Age, size, and site of aneurysm should be considered in the decision whether to treat an unruptured aneurysm or not. Especially, in cases of multiple aneurysm, the AComA aneurysm is most prone to hemorrhage.

Management of incidentally discovered intracranial vascular abnormalities

With the widespread use of brain imaging studies, neurosurgeons have seen a marked increase in the number of incidental intracranial lesions, including vascular abnormalities. Specifically, the detection of incidentally discovered aneurysms, arteriovenous malformations, cavernous angiomas, developmental venous anomalies, and capillary telangiectasias has increased. The best management strategy for most of these lesions is controversial. Treatment options include observation, open surgery, endovascular procedures, and radiosurgery. Multiple factors should be taken into account when discussing treatment indications, including the natural history of the disease and the risk of the treatment. In this article, the authors focus on the natural history of these lesions and the risk of the treatment, and they give recommendations regarding the most appropriate management strategy based on the current evidence in the literature and their experience with intracranial vascular abnormalities.

Differential Effects of Chromosome 9p21 Variation on Subphenotypes of Intracranial Aneurysm

Background and Purpose— Recently, a genome-wide association study identified associations between single nucleotide polymorphisms on chromosome 9p21 and risk of harboring intracranial aneurysm (IA). Aneurysm characteristics or subphenotypes of IAs, such as history of subarachnoid hemorrhage, presence of multiple IAs and location of IAs, are clinically important. We investigated whether the association between 9p21 variation and risk of IA varied among these subphenotypes.

Methods— We conducted a case-control study of 981 cases and 699 controls in Japanese. Four single nucleotide polymorphisms tagging the 9p21 risk locus were genotyped. The OR and 95% CI were estimated using logistic regression analyses.

Results— Among the 4 single nucleotide polymorphisms, rs1333040 showed the strongest evidence of association with IA ( P =1.5×10 −6 ; per allele OR, 1.43; 95% CI, 1.24–1.66). None of the patient characteristics (gender, age, smoking, and hypertension) was a significant confounder or effect modifier of the association. Subgroup analyses of IA subphenotypes showed that among the most common sites of IAs, the association was strongest for IAs of the posterior communicating artery (OR, 1.69; 95% CI, 1.26–2.26) and not significant for IAs in the anterior communicating artery (OR, 1.22; 95% CI, 0.96–1.57). When dichotomizing IA sites, the association was stronger for IAs of the posterior circulation–posterior communicating artery group (OR, 1.73; 95% CI, 1.32–2.26) vs the anterior circulation group (OR, 1.28; 95% CI, 1.07–1.53). Heterogeneity in these ORs was significant ( P =0.032). The associations did not vary when stratifying by history of subarachnoid hemorrhage (OR, 1.42; 95% CI, 1.18–1.71 for ruptured IA; OR, 1.27; 95% CI, 1.00–1.62 for unruptured IA) or by multiplicity of IA (OR, 1.57; 95% CI, 1.21–2.03 for multiple IAs; OR, 1.36; 95% CI, 1.15–1.61 for single IA).

Conclusions— Our results suggest that genetic influence on formation may vary between IA subphenotypes.

Differences in anatomical distribution, gender, and sidedness between ruptured and unruptured intracranial aneurysms in a defined patient population

BACKGROUND

Working with patients with intracranial aneurysms, we have developed a clinical suspicion that there may be differences in the rupture rate of aneurysms depending on the aneurysm's anatomical location. The aim of the study was to examine the anatomical distribution of ruptured and unruptured intracranial aneurysms in a defined population.

METHOD

We retrospectively included all patients with an aneurysm treated in our institution between 1 January 1990 and 31 December 1999, and collected the relevant data from the individual patient files. With the Koivisto categories for aneurysm location, we gathered the aneurysms into four categories: ACA, MCA, ICA, and VBA.

FINDINGS

Four hundred forty-four aneurysms were included in the study: 361 in SAH patients and 83 in patients without SAH. ACA aneurysms were over-represented in the ruptured group (36.0% vs. 9.6%, p < 0.0001). MCA aneurysms were more frequent in the unruptured group (51.8% vs. 29.6%, p < 0.0002). Ruptured ACA aneurysms were over-represented among males (p < 0.0001), whereas ruptured ICA aneurysms were more frequent among females (p < 0.0001). Ruptured aneurysms in the posterior circulation were more frequently found on the left side (p < 0.0001).

CONCLUSION

This study shows that the anatomical distribution of aneurysms is different in SAH patients compared with patients with unruptured aneurysms. Haemodynamic features of the vessel of origin may explain the differences we have found. Furthermore, this study suggests that it is of particular importance to treat patients with incidentally found ACA aneurysms.

Size and location of ruptured intracranial aneurysms

OBJECTIVE

The aim of study was to review our patient population to determine whether there is a critical aneurysm size at which the incidence of rupture increases and whether there is a correlation between aneurysm size and location.

METHODS

We reviewed charts and radiological findings (computed tomography (CT) scans, angiograms, CT angiography, magnetic resonance angiography) for all patients operated on for intracranial aneurysms in our hospital between September 2002 and May 2004. Of the 336 aneurysms that were reviewed, measurements were obtained from angiograms for 239 ruptured aneurysms by a neuroradiologist at the time of diagnosis in our hospital.

RESULTS

There were 115 male and 221 female patients assessed in this study. The locations of aneurysms were the middle cerebral artery (MCA, 61), anterior communicating artery (ACoA, 66), posterior communicating artery (PCoA, 52), the top of the basilar artery (15), internal carotid artery (ICA) including the cavernous portion (13), anterior choroidal artery (AChA, 7), A1 segment of the anterior cerebral artery (3), A2 segment of the anterior cerebral artery (11), posterior inferior cerebellar artery (PICA, 8), superior cerebellar artery (SCA, 2), P2 segment of the posterior cerebral artery (1), and the vertebral artery (2). The mean diameter of aneurysms was 5.47+/-2.536 mm in anterior cerebral artery (ACA), 6.84+/-3.941 mm in ICA, 7.09+/-3.652 mm in MCA and 6.21+/-3.697 mm in vertebrobasilar artery. The ACA aneurysms were smaller than the MCA aneurysms. Aneurysms less than 6 mm in diameter included 37 (60.65%) in patients with aneurysms in the MCA, 43 (65.15%) in patients with aneurysms in the ACoA and 29 (55.76%) in patients with aneurysms in the PCoA.

CONCLUSION

Ruptured aneurysms in the ACA were smaller than those in the MCA. The most prevalent aneurysm size was 3-6 mm in the MCA (55.73%), 3-6 mm in the ACoA (57.57%) and 4-6 mm in the PCoA (42.30%). The more prevalent size of the aneurysm to treat may differ in accordance with the location of the aneurysm.

Cost-effectiveness of treatment of unruptured intracranial aneurysms in patients with a history of subarachnoid hemorrhage

RATIONALE AND OBJECTIVES

The study goal was to evaluate the cost-effectiveness of surgery and endovascular treatment of unruptured intracranial aneurysms in patients with a history of subarachnoid hemorrhage from a previous aneurysm, incorporating the results of the prospective International Study of Unruptured Intracranial Aneurysms.

MATERIALS AND METHODS

Using a Markov model, we performed a decision and cost-effectiveness analysis comparing surgery or endovascular treatment with no treatment. Twelve clinical scenarios were defined based on aneurysm size and location. Probabilistic sensitivity analyses were performed for 50- and 40-year-old cohorts. Treatment was considered to be cost-effective at an incremental cost-effectiveness ratio less than $100,000 per quality-adjusted life-year.

RESULTS

In 50-year-old patients, no treatment was the most cost-effective strategy for aneurysms located in the cavernous carotid artery. For aneurysms less than 7 mm located in the anterior circulation, no treatment was the most cost-effective strategy. Endovascular treatment was the most cost-effective option for 7- to 24-mm aneurysms, whereas surgery was the most cost-effective option for aneurysms of 25 mm or larger. For aneurysms less than 7 mm and located in the posterior circulation, endovascular treatment was the most cost-effective option, whereas surgery was the most cost-effective option for 7- to 12-mm aneurysms. No treatment was the most cost-effective strategy for aneurysms of 13 mm or larger.

CONCLUSION

For 50-year-old patients with a history of aneurysmal subarachnoid hemorrhage, treatment of unruptured aneurysms that are located in the cavernous carotid artery, or small (<7 mm) and located in the anterior circulation, or large (>or=13 mm) and located in the posterior circulation is ineffective or not cost-effective.

Could late rebleeding overturn the superiority of cranial aneurysm coil embolization over clip ligation seen in the International Subarachnoid Aneurysm Trial?

OBJECT

The present purpose is to define the sensitivity of the superiority of coil embolization observed in the International Subarachnoid Aneurysm Trial (ISAT) according to the rate of late rebleeding over a reasonable range, and to find the range of rebleeding rates for which it may be overturned. In the ISAT, coil embolization appears to be safer than clip ligation at 1 year, and clip occlusion has better long-term efficacy at preventing rebleeding. This leaves open the question of which is better in the longer term.

METHODS

The authors calculate the life expectancy of patients following a subarachnoid hemorrhage (SAH) and compare the life expectancy of those who underwent coil embolization with those who underwent clip ligation in the ISAT cohort.

RESULTS

The 1-year poor outcome rate following treatment climbs rapidly with advancing age. A consequence is that the absolute difference between the poor outcome rates after coil embolization and clip occlusion is lower in those < 50 years of age (3.3%) than it is for those > 50 years of age (10.1%). This difference may be enough to give clip application the advantage in the < 40-year-old group despite the small size of the difference in 1-year rebleeding rates thus far observed (0.152%).

CONCLUSIONS

When treating ruptured cerebral aneurysms, the advantage of coil embolization over clip ligation cannot be assumed for patients < 40 years old. In this age range the difference in the safety of the 2 procedures is small, and the better long-term protection from SAH afforded by clip placement may give this treatment an advantage in life expectancy for patients < 40 years of age.

Endovascular embolization of intracranial aneurysms

Intracranial aneurysm (ICA) is a common condition but with a high mortality rate when rupture occurs. The treatment of ruptured or unruptured ICA, especially with an endovascular approach, has been evolving rapidly. The current generally accepted opinion suggests that endovascular embolization is an effective technique for preventing the recurrence of aneurysm rupture, but the rebleeding rate after endovascular embolization is found to be higher than that after surgical clipping. In addition, long-term follow-up data are required for the evaluation of the effectiveness of endovascular treatment in unruptured ICA. This review presents the current understanding of ICA, the selection of optimal treatment approaches, and in particular, the advances in endovascular embolization in the treatment of ICA, including embolic materials, therapeutic and assisting techniques, long-term effectiveness, and limitations.

Screening for familial intracranial aneurysms: decision and cost-effectiveness analysis

RATIONALE AND OBJECTIVES

To evaluate the potential benefits, harms, and cost-effectiveness of screening for asymptomatic, unruptured intracranial aneurysms in family members of patients with aneurysmal subarachnoid hemorrhage (SAH).

MATERIALS AND METHODS

Using a Markov model, we performed a decision and cost-effectiveness analysis comparing magnetic resonance (MR) angiography screening for asymptomatic, unruptured intracranial aneurysms to no screening in family members of patients with aneurysmal SAH. Treatment of unruptured intracranial aneurysms was determined according to patient age and aneurysm size and location. Cohort age was taken as 40 years.

RESULTS

In family members with two or more affected first-degree relatives, screening compared with no screening had an incremental cost-effectiveness ratio (ICER) of $37,400 per quality-adjusted life-year (QALY). With screening, life expectancy increased from 39.44 years to 39.55 years. The ICER of screening was >$50,000 per QALY if age at screening was > or =50 years. In family members with one affected first-degree relative, screening compared with no screening had an ICER of $56,500 per QALY.

CONCLUSIONS

The results suggest that MR angiography screening for asymptomatic, unruptured intracranial aneurysms in family members with two or more affected first-degree relatives is cost-effective. The benefit and cost-effectiveness are dependent on age at screening.

MORPHOLOGICAL DIFFERENCES BETWEEN RUPTURED AND UNRUPTURED CASES IN MIDDLE CEREBRAL ARTERY ANEURYSMS

OBJECTIVE

To elucidate the morphological differences between ruptured and unruptured aneurysms, three-dimensional digital subtraction angiography was performed in 44 cases (20 unruptured, 24 ruptured) of middle cerebral artery aneurysm.

METHODS

When the neck was located on the extension of the midline of the parent artery, it was defined as Type C; when it was not, it was defined as Type D. Aspect ratio (AP ratio; dome/neck ratio) and daughter artery ratio (DA ratio; diameter of the larger daughter artery/diameter of the smaller daughter artery) were calculated, and these ratios were compared for ruptured and unruptured cases.

RESULTS

Nineteen cases were Type C and 25 cases were Type D. χ2 test revealed that there were significantly more ruptured cases among Type C (14 out of 19) compared with Type D (10 out of 25) (P &lt; 0.05). AP ratios were 2.24 ± 0.75 for ruptured cases and 1.56 ± 0.58 for unruptured cases. DA ratios were 1.53 ± 0.54 in ruptured cases and 2.14 ± 0.80 for unruptured cases. Both showed significant differences (P &lt; 0.01). In cases with an AP ratio of 1.8 or greater and a DA ratio less than 1.7, 13 out of 15 (87%) were ruptured cases. On the contrary, in cases with an AP ratio less than 1.8 and a DA ratio of 1.7 or greater, 12 out of 13 (92%) were unruptured cases.

CONCLUSION

Type C and equality of the diameters of two daughter arteries, together with high AP ratios, seem to be morphological factors that associate with aneurysmal rupture.

Endovascular treatment of unruptured intracranial aneurysms with Guglielmi detachable coils: short- and long-term results of a single-centre series

BACKGROUND AND PURPOSE

Purpose of the present study is to evaluate the clinical outcome of endovascular treatment of unruptured intracranial aneurysms and to address the question of long-term stability and protection against future subarachnoid hemorrhage.

METHODS

Retrospective analysis of all patients treated in a 12-year period (173 patients: age 26 to 76 yr, mean 52.2+/-10.8/202 aneurysms: size 3 to 50 mm, mean 10.0+/-8.3).

RESULTS

The mortality was 0.5%; the overall morbidity was 3.5%. The most frequent complications were thromboembolic events (10.9%). Of these, 3.0% of patients suffered a stroke, leading to severe disability in 1 patient (0.5%). In 1 patient, the aneurysm ruptured during treatment, resulting in relevant neurological disability. Another patient suffered a fatal aneurysm rupture hours after treatment. The occlusion rate depended on aneurysm and neck size. Follow-up angiography revealed a decrease of the occlusion rate over time. This trend was obvious in all size categories and was most pronounced in giant aneurysms. In 3 patients (1.5%) with partially thrombosed giant aneurysms of the posterior circulation, embolization could not prevent later aneurysm rupture. There were no ruptures of any other aneurysms in the follow-up period (3.7+/-3.4 yr).

CONCLUSIONS

Endovascular treatment is a highly safe procedure with low intervention-related morbidity and mortality. Long-term data for nongiant aneurysms showed good protection against rupture in the observation period. In contrast, the risk of rupture for giant aneurysms of the posterior circulation was as high as expected in observational studies.

Intracranial and abdominal aortic aneurysms: similarities, differences, and need for a new class of computational models

Intracranial saccular and abdominal aortic aneurysms (ISAs and AAAs, respectively) result from different underlying disease processes and exhibit different rupture potentials, yet they share many histopathological and biomechanical characteristics. Moreover, as in other vascular diseases, hemodynamics and wall mechanics play important roles in the natural history and possible treatment of these two types of lesions. The goals of this review are twofold: first, to contrast the biology and mechanics of intracranial and abdominal aortic aneurysms to emphasize that separate advances in our understanding of each disease can aid in our understanding of the other disease, and second, to suggest that research on the biomechanics of aneurysms must embrace a new paradigm for analysis. That is, past biomechanical studies have provided tremendous insight but have progressed along separate lines, focusing on either the hemodynamics or the wall mechanics. We submit that there is a pressing need to couple in a new way the separate advances in vascular biology, medical imaging, and computational biofluid and biosolid mechanics to understand better the mechanobiology, pathophysiology, and treatment of these lesions, which continue to be responsible for significant morbidity and mortality. We refer to this needed new class of computational tools as fluid-solid-growth (FSG) models.

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.

Treatment of unruptured intracranial aneurysms: decision and cost-effectiveness analysis

PURPOSE

To prospectively perform a decision and cost-effectiveness analysis of surgical and endovascular treatments of unruptured intracranial aneurysms, with incorporation of the results of the prospective International Study of Unruptured Intracranial Aneurysms.

MATERIALS AND METHODS

With use of a Markov model, a decision and cost-effectiveness analysis was performed for comparison of surgical or endovascular treatment with no treatment. Twelve clinical scenarios were defined on the basis of aneurysm size and location. Probabilistic sensitivity analyses were performed for 50- and 40-year-old patient cohorts. Treatment was considered to be cost-effective at an incremental cost-effectiveness ratio less than $100,000 per quality-adjusted life-year.

RESULTS

In 50-year-old patients, no treatment was the most cost-effective strategy for aneurysms located in the cavernous carotid artery. For aneurysms smaller than 7 mm located in the anterior circulation, no treatment was the most cost-effective strategy. Endovascular treatment was the most cost-effective option for 7-24-mm aneurysms, whereas surgical treatment was the most cost-effective option for aneurysms 25 mm or larger. For aneurysms smaller than 7 mm or 25 mm or larger located in the posterior circulation, no treatment was the most cost-effective strategy. Surgical treatment was the most cost-effective option for 7-12-mm aneurysms, whereas endovascular treatment was the most cost-effective option for 13-24-mm aneurysms.

CONCLUSION

For 50-year-old patients, treatment of aneurysms that are small (<7 mm), that are located in the cavernous carotid artery, or that are large (>or=25 mm) and located in the posterior circulation is ineffective or not cost-effective.

In Vitro Evaluation of Flow Divertors in an Elastase-Induced Saccular Aneurysm Model in Rabbit

Endovascular coiling is an acceptable treatment of intracranial aneurysms, yet long term follow-ups suggest that endovascular coiling fails to achieve complete aneurysm occlusions particularly in wide-neck and giant aneurysms. Placing of a stentlike device across the aneurysm neck may be sufficient to occlude the aneurysm by promoting intra-aneurysmal thrombosis; however, conclusive evidence of its efficacy is still lacking. In this study, we investigate in vitro the efficacy of custom designed flow divertors that will be subsequently implanted in a large cohort of animals. The aim of this study is to provide a detailed database against which in vivo results can be analyzed. Six custom designed flow divertors were fabricated and tested in vitro. The design matrix included three different porosities (75%, 70%, and 65%). For each porosity, there were two divertors with one having a nominal pore density double than that of the other. To quantify efficacy, the divertors were implanted in a compliant elastomeric model of an elastase-induced aneurysm model in rabbit and intra-aneurysmal flow changes were evaluated by particle image velocimetry (PIV). PIV results indicate a marked reduction in intra-aneurysmal flow activity after divertor implantation in the innominate artery across the aneurysm neck. The mean hydrodynamic circulation after divertor implantation was reduced to 14% or less of the mean circulation in the control and the mean intra-aneurysmal kinetic energy was reduced to 29% or less of its value in the control. The intra-aneurysmal wall shear rate in this model is low and implantation of the flow divertor did not change the wall shear rate magnitude appreciably. This in vitro experiment evaluates the characteristics of local flow phenomena such as hydrodynamic circulation, kinetic energy, wall shear rate, perforator flow, and changes of these parameters as a result of implantation of stentlike flow divertors in an elastomeric replica of elastase-induced saccular aneurysm model in rabbit. These initial findings offer a database for evaluation of in vivo implantations of such devices in the animal model and help in further development of cerebral aneurysm bypass devices.

Genetics Of Intracranial Aneurysms

Despite advances in the treatment of intracranial aneurysms (IA) in recent years, the overall outcome of patients with aneurysmal subarachnoid hemorrhage has shown only modest improvement. Given this poor prognosis, diagnosis of IA before rupture is of paramount importance. Currently, there are no reliable methods other than screening imaging studies of high-risk individuals to diagnose asymptomatic patients. Multiple levels of evidence suggest that environmental factors acting in concert with genetic susceptibilities lead to the formation, growth, and rupture of aneurysms in these patients. Epidemiological studies have already identified aneurysm-specific risk factors such as size and location, as well as patient-specific risk factors, such as age, sex, and presence of medical comorbidities, such as hypertension. In addition, exposure to certain environmental factors such as smoking have been shown to be important in the formation of IA. Furthermore, substantial evidence proves that certain loci contribute genetically to IA pathogenesis. Genome-wide linkage studies using relative pairs or rare families that are affected with the Mendelian forms of IA have already shown genetic heterogeneity of IA, suggesting that multiple genes, alone or in combination, are important in the disease pathophysiology. The linkage results, along with association studies, will ultimately lead to the identification of IA susceptibility genes. Identification of the genes important in IA pathogenesis will not only provide novel insights into the primary determinants of IA, but will also result in new opportunities for early diagnosis in the preclinical setting. Ultimately, novel therapeutic strategies based on biology will be developed, which will target these newly elucidated genetic susceptibilities.

Computed tomographic angiography for the evaluation of aneurysmal subarachnoid hemorrhage

OBJECTIVES

Computed tomography (CT) followed by lumbar puncture (LP) is currently the criterion standard for diagnosing subarachnoid hemorrhage (SAH) in the emergency department (ED); however, this is based on studies involving a limited number of patients. The authors sought to assess the ability of CT angiography (CTA), a new diagnostic modality, in conjunction with CT/LP to detect SAH.

METHODS

Consecutive patients presenting to the ED with symptoms concerning for SAH were approached. All patients had an intravenous catheter placed and underwent a noncontrast head CT followed by CTA. Patients whose CT did not reveal evidence of SAH or other pathology underwent LP in the ED. CTAs were read within 24 hours by a neuroradiologist blinded to the patient's history.

RESULTS

A total of 131 patients were approached, 116 were enrolled, and 106 completed the study. In six of 116 patients (5.1%), aneurysm was found on CTA with normal CT and positive findings on LP; three had a positive CTA with normal CT and LP findings (one of which had a negative cerebral angiogram), and there was one false-positive CTA. Follow-up of all 131 patients showed no previously undiagnosed intracranial pathology. In this patient population, 4.3% (5/116) were ultimately found to have an SAH and/or aneurysm.

CONCLUSIONS

In this pilot study, CTA was found to be useful in the detection of cerebral aneurysms and may be useful in the diagnosis of aneurysmal SAH. A larger multicenter study would be useful to confirm these results.

Unruptured intracranial aneurysms: using evidence and outcomes to guide patient teaching

It is estimated that approximately 10 to 15 million Americans have intracranial aneurysms. Intracranial aneurysms are classified as either unruptured or ruptured. Advances in knowledge and technology are enhancing diagnosis, management, and outcomes associated with unruptured intracranial aneurysms. Optimal outcomes are achieved when aneurysms are treated before they rupture. If the aneurysm ruptures, the mortality rate ranges from 30% to 60%. A review of evidence regarding aneurysms, including the pathogenesis, risk factors, treatment options, and outcomes, is presented. Treatment options addressed include surgical clipping, endovascular coiling, or watchful waiting. Current evidence supports aggressive treatment for patients with previously ruptured aneurysms, large or symptomatic aneurysms, a family history of aneurysm rupture, a long life expectancy, and aneurysms demonstrating growth. Factors that favor watchful waiting include aneurysms that are small or located in the anterior circulation and in patients with a short life expectancy or comorbid medical conditions. Nurses are in an ideal position to use evidence and outcomes to provide accurate and current information on how to reduce the risks for rupture and evaluate treatment options.

Anévrismes intracrâniens non rompus : que proposer ?

Intracranial unruptured aneurysm (ICUA) has become a common condition for patient consultation. The mortality rate after fissuration is estimated to be between 52% and 85.7%. The final therapeutic decision results from a balance between the risk of rupture and risks related to the aneurysmal exclusion. Analysis of the risk of rupture risk enables a classification of risk factors. Depending on the circumstances of diagnosis, we considered the ICUA at high risk of rupture for incidental ICUA larger than 7 mm and in the event of associated aneurysms. Classifying by morphologic features, high-risk ICUA were located in the vertebrobasilar system (RR: 4.4; 95%CI: 2.7-6.8), those with a size between 7 and 12 mm (RR: 3.3; 95%CO: 1.3-8.2), larger than 12 mm (RR: 17; 95%CI: 8-36.1), those that were multilobular or a larger size and those ones with a index P/L superior to 3.4 (risk x20). Familial ICUA would expose to a major rupture risk (2 to 7 times sporadic ICUA). Some systemic factors were related to ICUA rupture: arterial hypertension (RR: 1.46; 95%CI: 1.01-2.11) and smoking addiction (RR: 3.04; 95%CI: 1.21-7.66). After microsurgical exclusion, the morbidity and mortality rates were 10% and 2% respectively. Some microsurgical morbidity factors were identified: age (32%>65 years), size (14%>15 mm), vertebrobasilar location and temporary occlusion. The rupture incidence after microsurgical exclusion was estimated 0.26%/year. After endovascular exclusion, the morbidity and mortality rates were 8% and 1% respectively. The complete exclusion rate varied between 47% and 67%. The rupture risk was estimated at 0.9%/year. Treatment recommendations were classified into 3 categories.

Contemporary management of incidental intracranial aneurysms

The management of unruptured intracranial aneurysms has changed significantly in recent years and continues to evolve. The three main factors that have affected the management of unruptured intracranial aneurysms are as follows: 1) increased availability of noninvasive imaging technology, resulting in increased detection of incidental aneurysms; 2) improved understanding of the natural history of unruptured aneurysms; and 3) the advent of neuroendovascular therapy. In this report, the authors discuss the implications of these factors in the diagnosis and management of truly incidental, asymptomatic aneurysms and review the current practice patterns at their institution.

Historical and current articles regarding noninvasive neuroimaging, aneurysm screening, endovascular and surgical therapy, and the natural history of unruptured aneurysms were reviewed. Current practices used for diagnosis and management of incidental aneurysms at the authors' institution were also reviewed.

The management of incidental intracranial aneurysms has become an increasingly controversial subject in recent years. Improvements in noninvasive imaging resulting in detection of an increasing number of incidental aneurysms, the establishment of endovascular therapy as an attractive alternative to surgery, and studies indicating a more benign natural history for unruptured aneurysms than previously thought have led to significant changes in neurosurgical practice. Safety and long-term efficacy are the goals of treatment for unruptured aneurysms. Until conclusive studies are completed, the experience of the neurovascular team at each institution and the art of patient selection for treatment will continue to play a fundamental role in the management of these lesions.

Frequency of incidental intracranial aneurysms in neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is often mentioned among the heritable connective tissue disorders associated with intracranial aneurysms, but the association has not been firmly established. We therefore reviewed a contemporary series of hospitalized patients with NF1, many of whom underwent brain magnetic resonance imaging (MRI). We identified patients with NF1 who were hospitalized at Cedars-Sinai Medical Center, Los Angeles, California, between January 1, 1997 and December 31, 2001 through the hospital's centralized medical records system using DRG codes. The mean age of the 39 patients was 30.4 years, and 22 patients had undergone MRI of the brain for the evaluation of symptoms due to the presence of central or peripheral nervous system tumors. Incidental intracranial aneurysms were detected in 2 (5%) of the 39 patients. Limiting the patient population to the 22 patients who had undergone MRI examination, the detection rate was 9%. This was significantly (P < 0.005) higher than the aneurysm detection rate in a control population (0/526 [0%]) of patients hospitalized for primary or secondary brain tumors, all of whom had undergone MRI examination. Our study suggests that patients with NF1 are at an increased risk of developing intracranial aneurysms.

Natural history of unruptured intracranial aneurysms

Since the publication of the retrospective part of the International Study of Unruptured Intracranial Aneurysms (ISUIA) in 1998, there has been a significant focus in the neurosurgical literature on the natural history of these lesions. The prospective data from the second part of the ISUIA, which was published in 2003, provided further evidence that small, asymptomatic intracranial aneurysms may have a more benign course than previously believed. With the data from the ISUIA as a reference point, in this paper the authors strive to provide a source of practical clinical data to aid cerebrovascular physicians in the initial decision to treat or observe a patient with a small, asymptomatic intracranial aneurysm. The issues covered will include previous rupture, symptoms other than rupture, aneurysm size, site, and aspect ratio. It is the authors' goal to provide a useful practical framework on the relevant clinical issues as an aid to practitioners treating patients who present with intracranial aneurysms.

Intracranial vascular surgery

PURPOSE OF REVIEW

To review the recent literature on intracranial vascular surgery, to summarize the main findings, and to discuss the impact of these findings on clinical practice.

RECENT FINDINGS

Three areas of vascular neurosurgery literature have recently generated significant interest, controversy and heated debate: (1) The International Study of Unruptured Intracranial Aneurysms studied the natural history and treatment options of unruptured aneurysms, and reported surprisingly low aneurysm rupture rates for small asymptomatic aneurysms. The study also reported favorable morbidity rates for endovascular treatment compared with surgical treatment of unruptured aneurysms. (2) The International Subarachnoid Aneurysm Trial compared endovascular and surgical treatments for ruptured intracranial aneurysms. The study concluded that the outcome in terms of survival free of disability at one year was significantly better with endovascular coiling. (3) The Intraoperative Hypothermia for Aneurysm Surgery Trial compared intraoperative hypothermia and normothermia for potential neuroprotection during neurovascular procedures. Preliminary results suggest no difference between the treatments.

SUMMARY

The International Study of Unruptured Intracranial Aneurysms and the International Subarachnoid Aneurysm Trial have provided data on the natural history of unruptured intracranial aneurysms and on the morbidity and mortality of surgical and endovascular treatments for intracranial aneurysms. Although morbidity rates of endovascular therapy compare favorably with those of surgery, long-term data on the efficacy of endovascular coiling of aneurysms are needed to assess the overall risk-benefit ratio of these therapies.

Endovascular treatment of cerebrovascular disease

PURPOSE OF REVIEW

This review summarizes recent advances in endovascular therapy for cerebrovascular disease.

RECENT FINDINGS

For ruptured aneurysms, the only large, randomized, controlled trial comparing surgical and endovascular treatment (the International Subarachnoid Aneurysm Trial) resulted in a significant reduction in death or dependency at 1 year, compared with surgery, providing sound evidence that coiling should be the treatment of first choice. Data from the International Study of Unruptured Intracranial Aneurysms demonstrated that treatment of unruptured anterior circulation aneurysms of under 7 mm with no history of subarachnoid hemorrhage is not justified. Embolization of arteriovenous malformations, as sole therapy, is curative only in a small percentage of cases, but can be part of a multimodal approach for reducing arteriovenous malformation size prior to surgery or radiotherapy. Partial treatment of complex arteriovenous malformations may be more dangerous than no treatment. Protection devices can reduce complication rates in carotid artery stenting, but scientific evidence is still lacking. Until the results of comparative trials are available, carotid artery stenting is indicated only in selected patients. Angioplasty and stenting of intracranial arterosclerotic disease is feasible but remains a high-risk procedure, indicated only in highly selected patients. In acute stroke therapy, new thrombolytics and clot-retrieval devices may result in better recanalization rates.

SUMMARY

Advances in endovascular therapy have occurred in all areas of cerebrovascular disease. To obtain maximal patient benefit, endovascular treatment should be performed as an interdisciplinary approach in high-volume centers. Importantly, long-term follow-up review is necessary to clarify the overall role of endovascular treatment in the management of cerebrovascular disease.