A ten percent prevalence of asymptomatic familial intracranial aneurysms: preliminary report on 110 magnetic resonance angiography studies in members of 21 Finnish familial intracranial aneurysm families

A balanced translocation truncates Neurotrimin in a family with intracranial and thoracic aortic aneurysm

BACKGROUND

Balanced chromosomal rearrangements occasionally have strong phenotypic effects, which may be useful in understanding pathobiology. However, conventional strategies for characterising breakpoints are laborious and inaccurate. We present here a proband with a thoracic aortic aneurysm (TAA) and a balanced translocation t(10;11) (q23.2;q24.2). Our purpose was to sequence the chromosomal breaks in this family to reveal a novel candidate gene for aneurysm.

METHODS AND RESULTS

Intracranial aneurysm (IA) and TAAs appear to run in the family in an autosomal dominant manner: After exploring the family history, we observed that the proband's two siblings both died from cerebral haemorrhage, and the proband's parent and parent's sibling died from aortic rupture. After application of a genome-wide paired-end DNA sequencing method for breakpoint mapping, we demonstrate that this translocation breaks intron 1 of a splicing isoform of Neurotrimin at 11q25 in a previously implicated candidate region for IAs and AAs (OMIM 612161).

CONCLUSIONS

Our results demonstrate the feasibility of genome-wide paired-end sequencing for the characterisation of balanced rearrangements and identification of candidate genes in patients with potentially disease-associated chromosome rearrangements. The family samples were gathered as a part of our recently launched National Registry of Reciprocal Balanced Translocations and Inversions in Finland (n=2575), and we believe that such a registry will be a powerful resource for the localisation of chromosomal aberrations, which can bring insight into the aetiology of related phenotypes.

Saccular intracranial aneurysm: pathology and mechanisms

Saccular intracranial aneurysms (sIA) are pouch-like pathological dilatations of intracranial arteries that develop when the cerebral artery wall becomes too weak to resist hemodynamic pressure and distends. Some sIAs remain stable over time, but in others mural cells die, the matrix degenerates, and eventually the wall ruptures, causing life-threatening hemorrhage. The wall of unruptured sIAs is characterized by myointimal hyperplasia and organizing thrombus, whereas that of ruptured sIAs is characterized by a decellularized, degenerated matrix and a poorly organized luminal thrombus. Cell-mediated and humoral inflammatory reaction is seen in both, but inflammation is clearly associated with degenerated and ruptured walls. Inflammation, however, seems to be a reaction to the ongoing degenerative processes, rather than the cause. Current data suggest that the loss of mural cells and wall degeneration are related to impaired endothelial function and high oxidative stress, caused in part by luminal thrombosis. The aberrant flow conditions caused by sIA geometry are the likely cause of the endothelial dysfunction, which results in accumulation of cytotoxic and pro-inflammatory substances into the sIA wall, as well as thrombus formation. This may start the processes that eventually can lead to the decellularized and degenerated sIA wall that is prone to rupture.

Familial Aggregation of Both Aortic and Cerebral Aneurysms: Evidence for a Common Genetic Basis in a Subset of Families

OBJECTIVE

Although previous reports have described patients with both cerebral and aortic aneurysms, any association was believed to be coincidental. In this study, we provide evidence that aortic and cerebral aneurysm formation may share a common genetic predisposition in some families.

METHODS

A prospective enrollment of consecutive patients treated for saccular cerebral aneurysm by a single surgeon was constructed. Medical and family histories were obtained. Familial syndromes were identified when two or more first-degree relatives had diagnoses of cerebral or aortic aneurysm. Pedigrees were constructed, and asymptomatic relatives were screened.

RESULTS

In 2.5 years, 274 patients were enrolled from 322 eligible patients (85%). A family history of aortic aneurysm was noted in 29 patients (10.5%). These patients were older, included more males, and were overwhelmingly Caucasian. Statistically significant demographic differences were noted when these families were compared with families affected by cerebral aneurysm only. A total of 110 affected family members were identified (average, 3.8 per family; range, 2-12); 59 had cerebral aneurysms, and 51 had aortic aneurysms. In some families, the association may have been coincidental. But in several families, pedigree analyses showed an inheritance pattern likely to represent autosomal dominance with variable penetrance. In addition, both cerebral and aortic phenotypes could be inherited from a parent with an aortic aneurysm, further evidence for a common genetic basis.

CONCLUSION

This study, which represents the largest and most complete characterization of families affected by both cerebral and aortic aneurysms, provides evidence that a single gene defect may lead to the development of either lesion.

IS ASPECT RATIO A RELIABLE PREDICTOR OF INTRACRANIAL ANEURYSM RUPTURE?

OBJECTIVE

This study was undertaken to assess the reliability of the aspect ratio (AR) (i.e., aneurysm depth to aneurysm neck) in predicting aneurysm rupture. It has been shown that the AR is a key factor in predicting intraaneurysmal blood flow and aneurysm rupture.

METHODS

Seventy-five patients with subarachnoid hemorrhage and multiple aneurysms were studied. The sizes of the aneurysms and their ARs were determined by examining the angiographic films. By comparing the difference between ruptured and unruptured aneurysms in the same individual, each patient in effect served as his or her own control. Each ruptured aneurysm was confirmed during surgery.

RESULTS

There were 75 ruptured and 107 unruptured aneurysms. The mean AR was 2.70 for ruptured aneurysms, compared with 1.8 for unruptured aneurysms. This difference between the ARs was statistically significant (P < 0.001). The difference in aneurysm sizes in the two groups also was significant (P < 0.001).

CONCLUSION

AR on its own is as reliable a variable as the size of the aneurysm for predicting aneurysm rupture.

Diagnostic fidelity of the Z-buffer segmentation algorithm: preliminary assessment based on intracranial aneurysm detection

We have developed an algorithm known as the Z-buffer segmentation (ZBS) algorithm for segmenting vascular structures from 3D MRA images. Previously we evaluated the accuracy of the ZBS algorithm on a voxel level in terms of inclusion and exclusion of vascular and background voxels. In this paper we evaluate the diagnostic fidelity of the ZBS algorithm. By diagnostic fidelity we mean that the data preserves the structural information necessary for diagnostic evaluation. This evaluation is necessary to establish the potential usefulness of the segmentation for improved image display, or whether the segmented data could form the basis of a computerized analysis tool. We assessed diagnostic fidelity by measuring how well human observers could detect aneurysms in the segmented data sets. ZBS segmentation of 30 MRA cases containing 29 aneurysms was performed. Image display used densitometric reprojections with shaded surface highlighting that were generated from the segmented data. Three neuroradiologists independently reviewed the generated ZBS images for aneurysms. The observers had 80% sensitivity (90% for aneurysms larger than 2mm) with 0.13 false positives per image. Good agreement with the gold standard for describing aneurysm size and orientation was shown. These preliminary results suggest that the segmentation has diagnostic fidelity with the original data and may be useful for improved visualization or automated analysis of the vasculature.

Incidence of familial intracranial aneurysms in 200 patients: comparison among Caucasian, African-American, and Hispanic populations

OBJECTIVE

Although the cause of cerebral aneurysms remains unclear, there is clear evidence that genetic predisposition plays a role. Ten percent of patients report an aneurysm in a first-degree family member. However, studies to date have largely involved Caucasian populations. Our goal was to characterize the familial aggregation of intracranial aneurysms in different ethnic groups.

METHODS

We began a prospective, single-center study on patients treated for intracranial aneurysms. Consenting subjects completed a detailed questionnaire regarding the medical history of family members. In families with two or more affected members, asymptomatic first-degree relatives were screened using computed tomographic or magnetic resonance angiography.

RESULTS

In a 2-year period, 292 patients with intracranial aneurysms were treated and 200 were enrolled; these included 124 Caucasians (62%), 34 African-Americans (17%), 38 Hispanics (19%), and 4 Asian-Americans (2%). Forty patients had a family history (20%). The incidence of family history among the different ethnic groups was similar; it was 19.4% in Caucasians, 20.6% in African-Americans, and 21.6% in Hispanics. One Asian-American patient had a family history. Visual inspection of the pedigrees supported autosomal-dominant inheritance with variable penetrance in all ethnic groups.

CONCLUSION

This study examined the incidence of familial cerebral aneurysms in three ethnic groups common to the United States: Caucasian, African-American, and Hispanic. We noted an equivalent rate of familial aneurysms, a finding that has immediate clinical implications. In families that have two or more members with cerebral aneurysms, screening of asymptomatic members should be recommended, regardless of ethnic background.

Search for intracranial aneurysm susceptibility gene(s) using Finnish families

BACKGROUND

Cerebrovascular disease is the third leading cause of death in the United States, and about one-fourth of cerebrovascular deaths are attributed to ruptured intracranial aneurysms (IA). Epidemiological evidence suggests that IAs cluster in families, and are therefore probably genetic. Identification of individuals at risk for developing IAs by genetic tests will allow concentration of diagnostic imaging on high-risk individuals. We used model-free linkage analysis based on allele sharing with a two-stage design for a genome-wide scan to identify chromosomal regions that may harbor IA loci.

METHODS

We previously estimated sibling relative risk in the Finnish population at between 9 and 16, and proceeded with a genome-wide scan for loci predisposing to IA. In 85 Finnish families with two or more affected members, 48 affected sibling pairs (ASPs) were available for our genetic study. Power calculations indicated that 48 ASPs were adequate to identify chromosomal regions likely to harbor predisposing genes and that a liberal stage I lod score threshold of 0.8 provided a reasonable balance between detection of false positive regions and failure to detect real loci with moderate effect.

RESULTS

Seven chromosomal regions exceeded the stage I lod score threshold of 0.8 and five exceeded 1.0. The most significant region, on chromosome 19q, had a maximum multipoint lod score (MLS) of 2.6.

CONCLUSIONS

Our study provides evidence for the locations of genes predisposing to IA. Further studies are necessary to elucidate the genes and their role in the pathophysiology of IA, and to design genetic tests.

Unruptured intracranial aneurysms: a review

OBJECT

In this article, pathological, radiological, and clinical information regarding unruptured intracranial aneurysms is reviewed.

METHODS

Treatment decisions require that surgeons and interventionists take into account information obtained in pathological, radiological, and clinical studies of unruptured aneurysms. The author has performed a detailed review of the literature and has compared, contrasted, and summarized his findings. Unruptured aneurysms may be classified as truly incidental, part of a multiple aneurysm constellation, or symptomatic by virtue of their mass, irritative, or embolic effects. Unruptured aneurysms with clinical pathological profiles resembling those of ruptured lesions should be considered for treatment at a smaller size than unruptured lesions with profiles typical of intact aneurysms, as has been determined at autopsy in patients who have died of other causes. The track record of the surgeon or interventionist and the institution in which treatment is to be performed should be considered while debating treatment options. In cases in which treatment is not performed immediately, ongoing periodic radiological assessment may be wise. Radiological investigations to detect unruptured aneurysms in asymptomatic patients should be restricted to high-prevalence groups such as adults with a strong family history of aneurysms or patients with autosomal dominant polycystic kidney disease. All patients with intact lesions should be strongly advised to discontinue cigarette smoking if they are addicted.

CONCLUSIONS

The current state of knowledge about unruptured aneurysms does not support the use of the largest diameter of the lesion as the sole criterion on which to base treatment decisions, although it is of undoubted importance.

Clinical features of intracranial aneurysms in siblings

OBJECTIVE

Among the family members of patients with aneurysmal subarachnoid hemorrhage (SAH), siblings have been documented to be at high risk of SAH and to have a high prevalence of unruptured aneurysms. We studied the distinctive features of aneurysms in siblings and attempted to determine the risk of rupture.

METHODS

We analyzed detailed data on 159 patients with siblings who had ruptured and unruptured aneurysms in 77 families from throughout Japan.

RESULTS

Seventy-three percent of the patients were female, and the mean age at the time of rupture was 55.6 years. In 39 families, two or more siblings had SAH. Eighty of 107 patients with ruptured aneurysms and 28 of 52 with unruptured aneurysms had a family history of SAH in siblings (P = 0.0082). Multiple and mirror-image aneurysms were found in 42 and 21 patients, respectively. Among 218 aneurysms, middle cerebral artery aneurysms were the most common type (43%). Anterior communicating artery aneurysms were underrepresented (15%). There were significantly more ruptured than unruptured anterior communicating artery aneurysms, compared with other aneurysms (P = 0.01).

CONCLUSION

The clinical features of aneurysms in siblings in this population agreed well with those reported for familial intracranial aneurysms and SAH, except for the age at the time of rupture. It is suggested that the risk of rupture is greater when patients with unruptured aneurysms have siblings with aneurysmal SAH and/or anterior communicating artery aneurysms.

Asymptomatic familial cerebral aneurysms

PURPOSE

We evaluated the prevalence and features of cerebral aneurysms in the family members of people with asymptomatic aneurysms among 8680 participants undergoing magnetic resonance angiography.

METHODS

Of the 8680 participants, 380 had family histories of aneurysms and 8300 did not. The prevalence and features of asymptomatic aneurysms were compared in these two subgroups. In addition, the prevalence in all living first- or second-degree relatives was evaluated in 20 families.

RESULTS

The prevalence of asymptomatic aneurysms was 7.0% (606 of 8680 participants) overall and 10.5% (40 of 380 participants) and 6.8% (566 of 8300 participants) in the subgroups with and without family histories of aneurysms, respectively. The prevalence in the female participants with family histories of aneurysms (12.3%, 28 of 228 participants) was higher than that in the male participants with family histories of aneurysms (7.9%, 12 of 152 participants) (P < 0.0001). Compared with the entire group, this subgroup more commonly showed aneurysms situated at the junction of the internal carotid and posterior communicating arteries (P < 0.0005) and at the middle cerebral artery (P < 0.0001). The prevalence of aneurysms in 115 members of the 20 families was 33.9%. Although the members of 14 families with aneurysmal subarachnoid hemorrhage showed higher prevalence of ruptured and asymptomatic aneurysms (42.1%) than did the members of 6 families with only asymptomatic aneurysms (17.9%), the former had very low prevalence of asymptomatic aneurysms.

CONCLUSION

The prevalence of aneurysms is significantly elevated in family members of people with asymptomatic aneurysms. It is suggested that familial asymptomatic aneurysms are more likely to rupture in families having members with aneurysmal subarachnoid hemorrhage than in those without.

Risk of harboring an unruptured intracranial aneurysm

BACKGROUND AND PURPOSE

The purpose of the present study was to calculate the prevalence and relative risk of unruptured incidental intracranial aneurysms (IAs) among families with IA case(s) compared with the general population in one geographically defined area in East Finland and to identify the risk group that could benefit most from screening for IAs. We compared these results with our earlier study results of familial IA (FIA) cases, with two or more known IA cases in the same family.

METHODS

The study groups were collected from the catchment area of the University Hospital of Kuopio in East Finland. The inclusion criteria were age 30 to 70 years and unruptured incidental IAs > or =3 mm. Patients with previous subarachnoid hemorrhage or in whom a ruptured IA was found to be the cause of death were excluded from all study groups. During routine forensic autopsies the circle of Willis was studied for IAs to estimate the number of IAs in the general population. In the families with one known IA case and in FIA families, MR angiography was used as a preliminary screening method for IAs, followed by intra-arterial angiography to verify suspected IAs. Study populations were age and sex adjusted for the statistical calculations.

RESULTS

The relative risk for IAs among first-degree relatives in FIA families was 4.2 (95% confidence interval, 2.2 to 8.0) and among first-degree relatives in families with only one affected family member was 1.8 (95% confidence interval, 0.7 to 4.8) compared with the general population in East Finland.

CONCLUSIONS

First-degree relatives in FIA families constitute a high-risk group for incidental IAs, and this group would benefit from screening studies for IAs. Screening for IAs in families with only one affected member or in the general population is not recommended.

Familial intracranial aneurysms

BACKGROUND

We set out to determine the prevalence of incidental intracranial aneurysms in first-degree relatives aged 30 years or more of people with intracranial aneurysms, and to see if polycystic kidney disease contributes to the aggregation of familial intracranial aneurysms.

METHODS

91 families with two or more affected members had previously been identified from a 14 year series of 1150 intracranial aneurysm patients treated at the University Hospital of Kuopio, Finland. Magnetic resonance angiography was used as a preliminary screening method, followed by conventional four-vessel angiography to verify suspected aneurysms. Participants were also screened for polycystic kidneys by ultrasonography.

FINDINGS

Incidental aneurysms were detected in 40 individuals: 38 of 438 individuals from 85 families without polycystic kidney disease or other diagnosed heritable disorders, and two of 22 individuals from six families known to have polycystic kidney disease. The crude and age-adjusted prevalence of incidental intracranial aneurysms among screened first-degree relatives was 8.7 (SE 1.3)% (95% CI 6.2-11.7) and 9.1 (1.4)% (6.2-11.7), respectively, for the familial group and the crude prevalence for the polycystic kidney group was 9.1 (6.1)% (1.1-29.2).

INTERPRETATION

Our results demonstrate a high prevalence of incidental intracranial aneurysms among first-degree relatives aged 30 years or older of patients with the condition and indicate that the risk of having an aneurysm is about four times higher for a close relative than for someone from the general population. Also, polycystic kidney disease families are a small fraction of the familial intracranial aneurysm families.

Three-dimensional volume rendering for magnetic resonance angiography in the screening and preoperative workup of intracranial aneurysms

This study was undertaken to evaluate the capacity of three-dimensional (3-D) time-of-flight (TOF) magnetic resonance (MR) angiography with VoxelView (VV) 3-D volume rendering to detect and characterize intracranial aneurysms and to compare this rendering technique with that of maximum intensity projection (MIP). Forty patients with a total of 53 intracranial aneurysms (10 giant and subgiant, 43 saccular) were consecutively admitted to University Hospital, Lausanne, Switzerland, and investigated with 3-D TOF MR angiography. Source images of the 43 saccular aneurysms were processed with both MIP and VV. The aneurysm detection rate of the two techniques and their ability to characterize features of an aneurysm, such as its neck and its relation to the parent vessel, were compared. Intraarterial digital subtraction angiography was used as the gold standard to which these techniques could be compared and evaluated. Four aneurysms, less than 3 mm in size, were missed using MIP compared to three missed using VV. The representation of aneurysmal morphology using VV was superior to that found using conventional angiography in nine cases, equal in 16 cases, and inferior in seven cases. The representation of the aneurysm neck using VV was superior to MIP in 21 cases, equal in 17 cases, and inferior in one case; it was superior to that shown using conventional angiography in 10 cases, equal in 18 cases, and inferior in four cases. Time-of-flight MR angiography in conjunction with both MIP and VV 3-D reconstruction was able to visualize all aneurysms that were larger than 3 mm. Compared to MIP, VV provides a better definition of the aneurysm neck and the morphology of saccular aneurysms, making VV valuable for use in a preoperative diagnostic workup.

Giant intracranial aneurysms in two sisters: case report

BACKGROUND

It is rare for intracranial aneurysms to present with cranial nerve palsy caused by the space-occupying effect of the lesion. Herein we discuss two sisters with familial intracranial aneurysms, both of whom presented with cranial nerve palsy.

CASE DESCRIPTION

Two female siblings presented with ocular movement and facial sensory disturbances caused by the space-occupying effect of giant aneurysms at the cavernous portion of the internal carotid arteries. The aneurysms were located at the identical site in both patients. Proximal occlusion of the internal carotid artery was effective in both cases, resulting in the promotion of thrombosis within the aneurysms in order to reduce their space-occupying effect.

CONCLUSION

This is considered to be the first known case of siblings, both suffering from giant internal carotid artery aneurysms.

A study of inbreeding and kinship in intracranial aneurysms in the Saguenay Lac-Saint-Jean region (Quebec, Canada)

The genealogies of 533 individuals with an intracranial aneurysm (IA) born in the Saguenay-Lac-Saint-Jean region, a geographically isolated area located in northeastern Quebec, were reconstructed using a population-based register. A control group consisting of three individuals of the same sex and born on the same day and in the same municipality than the IA patients was created; the genealogies of the 1599 controls were also reconstructed. The coefficients of inbreeding and kinship were calculated. Familial aggregation, i.e. the presence of IA in two or more first- to third-degree relatives, was also sought. The mean inbreeding coefficient was lower in the IA group than in the control group (7.92 x 10(-4) versus 10.04 x 10(-4)). The mean kinship coefficient was higher in the IA group than in the control group (2.17 x 10(-4) versus 1.55 x 10(-4)). Forty-eight IA patients (9.0%) were first-degree relatives compared to only 1.9% of the control individuals. The proportion of individuals showing familial aggregation was higher in the IA group than in the control group (29.8% and 18.6% respectively). These results strongly suggest that some IA are genetically determined in this population.

Familial cerebral aneurysms: a study of 13 families

Despite the recent interest in familial cerebral aneurysms, the epidemiology, natural history, pattern of inheritance, screening of asymptomatic relatives, and the search for a biochemical marker remain problematic. To assess these issues, we report the results of our prospective study of 30 patients with 38 aneurysms (27 ruptured) and of the angiographic screening of asymptomatic relatives, all from 13 families seen consecutively since 1986. Women were over-represented (77%), and patients with multiple aneurysms (17%) were under-represented, compared with sporadic cases. Only 16% of the aneurysms were at the anterior communicating artery. Aneurysms occurred at the same or at the mirror site in 10 of 16 siblings (62%) and in 50% of mother-daughter pairs versus 20% for randomly selected, sporadic aneurysm patients. Rupture occurred in the same decade in 10 of 12 siblings (83%) versus the expected 21% for randomly selected, sporadic aneurysms. The average age at rupture was 47.2 years, and 60% of patients with a ruptured aneurysm were 50 years of age or younger. Seventy percent of patients died or were disabled from aneurysmal rupture. Screening of 41 individuals, including 2 dizygous twins, identified 1 aneurysm and 2 infundibula. A specific pattern of inheritance could not be ascertained from the pedigrees. The presence of an aneurysm was not associated with a specific human leukocyte antigen haplotype or antigen, and collagen Type III was qualitatively and quantitatively normal. Until a biological marker is identified, angiographic screening by intra-arterial digital subtraction or magnetic resonance angiography remains the only way to identify patients at risk of harboring a familial cerebral aneurysm.

Risk of intracranial aneurysms in families with subarachnoid hemorrhage

BACKGROUND

Genetic factors may be important in the etiology of subarachnoid hemorrhage (SAH) and intracranial aneurysm (IA) formation. Several studies have reported the familial occurrence of SAH and IA, although in most cases asymptomatic family members were not studied with elective angiography. The examination of data from large sibships could provide important information about the frequency of IA occurrence in at-risk individuals and the mode of inheritance for familial SAH/IA.

METHODS

We reviewed published case series of sibships with SAH and at least four siblings, in which at least one sibling underwent elective angiography. Data were collected on age-of-onset, clinical events, presence of hypertension, angiographic findings, and outcome. Patients were classified as "affected" if they had a SAH or if an IA was detected by elective angiography, and "unaffected" if they were asymptomatic and had a negative angiogram.

RESULTS

Seven case series with 52 individuals (26 men and 26 women) met our inclusion criteria. The sibships ranged from 6 to 13 members. Most of the siblings (32 of 52, 61%) were asymptomatic, 18 (35%) had a SAH, and 2 (4%) had focal symptoms but no SAH. Elective angiography of 34 siblings showed an IA in 11 (32%) and was negative in 23 (68%). The overall rate of affecteds (SAH or IA) was 56%.

CONCLUSIONS

Based on data from these sibships, angiography of asymptomatic at-risk siblings demonstrated an IA in almost one-third of cases. Familial SAH/IA segregated with a pattern that was consistent with an autosomal dominant trait in this selected series of sibships, although other factors could produce these findings.