Aneurysm, Intracranial Berry, 1

Description

Rupture of an intracranial aneurysm, an outpouching or sac-like widening of a cerebral artery, 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 (summary by Krischek and Inoue, 2006).

Genetic Heterogeneity of Intracranial Berry Aneurysm

Intracranial berry aneurysm-1 (ANIB1) has been mapped to chromosome 7q11.2.

Other mapped loci for intracranial berry aneurysm include ANIB2 (608542) on chromosome 19q13, ANIB3 (609122) on 1p36.13-p34.3, ANIB4 (610213) on 5p15.2-14.3, ANIB5 (300870) on Xp22, ANIB6 (611892) on 9p21, ANIB7 (612161) on 11q24-q25, ANIB8 (612162) on 14q23, ANIB9 (612586) on 2q, ANIB10 (612587) on 8q, and ANIB11 (614252) on 8p22.

Clinical Features

Ullrich and Sugar (1960) reported 4 families, in each of which 2 members had cerebral aneurysms. McKusick (1964) observed a 34-year-old man and his 13-year-old daughter, both of whom died of intracranial berry aneurysm. Graf (1966) reported 2 pairs of affected sibs. Beumont (1968) described 3 affected sisters. Thierry et al. (1972) reviewed 10 reports and documented autosomal dominant inheritance. Edelsohn et al. (1972) reported a family with affected father and 3 affected daughters and an affected son.

Brisman and Abbassioun (1971) raised the question of prophylactic investigations in a family with a high frequency of mortality from ruptured aneurysms. Toglia and Samii (1972) suggested that familial aneurysms may have favored locations and that multiple aneurysms may be more often familial than are single aneurysms. They reported 2 families: 2 black sisters and 2 white brothers with intracranial aneurysms. One sister, aged 38, developed 6 intracranial aneurysms, the largest at the left middle cerebral artery. Her sister suffered an aneurysm at the right anterior cerebral artery at age 43. In the second family, a 31-year-old male developed an aneurysm at the bifurcation of the basilar artery. His brother, at age 34, developed an aneurysm at the same site, as well as a smaller one at the left middle cerebral artery. Their father died of a subarachnoid hemorrhage at age 39. Berry aneurysm appears to have a lower frequency in blacks than in whites in the US and elsewhere.

Intracranial aneurysm occurs in some cases of polycystic kidney disease (Jankowicz et al., 1971) and with coarctation of the aorta (120000).

Bromberg et al. (1995) found a higher relative risk for poor outcome in patients with familial subarachnoid hemorrhage from those of sporadic cases. Of their 14 families, 2 were segregating autosomal dominant polycystic kidney disease (see 173900). The mean age of subarachnoid hemorrhage in familial cases in their series was 44.7 years compared to 53.4 years in sporadic cases. The authors recommended screening individuals at risk for familial intracranial aneurysms with catheter and angiography between the ages of 40 and 60 and with MR angiography between the ages of 20 and 70.

Inheritance

Ronkainen et al. (1993) investigated the frequency of either aneurysmal subarachnoid hemorrhage or incidental intracranial aneurysms in the relatives of 1,150 subarachnoid hemorrhage patients from east Finland who had proven intracranial aneurysms. They found a 10% incidence of familial intracranial aneurysm.

Leblanc et al. (1995) found higher than expected concordance of the age at rupture in a prospective study of 30 individuals in 13 families with multiple affected individuals. A specific pattern of inheritance could not be ascertained from these pedigrees, nor was there an abnormality demonstrated in type 3 collagen in any of these patients. Bromberg et al. (1995) suggested that subarachnoid hemorrhage in consecutive generations occurred at an earlier age as compared to previous generations.

Struycken et al. (2003) analyzed anticipation, sex ratio, and mode of inheritance in 10 families in which at least 2 persons in consecutive generations were affected by subarachnoid hemorrhage, symptomatic intracranial aneurysm (SIA), or a presymptomatic intracranial aneurysm (PIA). They found that the age at SIA onset in the parental generation (mean, 55.5 years) differed significantly from the age at onset in their children (mean, 32.4 years). In the parental generation, 11 men and 37 women were affected (including both SIA and PIA); in the consecutive generation, 28 men and 32 women were affected. There was a significant difference in sex ratio of affected family members when the generations were compared (P less than 0.02). There was no evidence of SIA or PIA in 3 consecutive generations in any family.

Majamaa et al. (1994) investigated the familial aggregation of cervical artery dissection and cerebral aneurysm in 22 consecutively diagnosed patients with spontaneous carotid artery dissection and 38 randomly selected controls. Of the sibs of dissection patients, 3.5% had either an intracranial aneurysm or carotid artery dissection, compared with only 1 of 189 sibs of control patients. This suggested to the authors that spontaneous carotid dissection in cerebral aneurysms may have a common pathogenetic factor.

Schievink et al. (1994) reported a 3-generation family in which there were 7 individuals affected with intracranial aneurysms with male-to-male transmission. They also reviewed the literature of familial intracranial aneurysms and found 238 families with 560 affected members, of which 56% were female and 44% were male. The most commonly affected relatives were sibs. Segregation analysis revealed several patterns of inheritance with no single mendelian model showing a best overall fit. Schievink et al. (1994) suggested that genetic heterogeneity may be important. Twenty-two percent of sibs of male probands had an intracranial aneurysm compared with 9% of sibs of female probands. Angiographic screening in 12 families detected an intracranial aneurysm in 29% of 51 asymptomatic relatives.

In a complete survey of the families of patients with aneurysmal subarachnoid hemorrhage in Rochester, Minnesota, between 1970 and 1979, Schievink et al. (1995) found that 15 of 76 patients (20%) had a first- or second-degree relative with aneurysmal subarachnoid hemorrhage. The number of observed first-degree relatives with aneurysmal subarachnoid hemorrhage was 11, compared to an expected number of 2.66, giving a relative risk of 4.14.

In the Saguenay-Lac-Saint-Jean (SLSJ) region of the Province of Quebec, Canada, Mathieu et al. (1997) found that sibs of patients with ruptured intracranial aneurysm had a greater risk of ruptured intracranial aneurysm than the general population. Nevertheless, the largest part of the familial occurrence observed in the SLSJ region could be explained by accidental aggregation due to large kinships. Mathieu et al. (1997) proposed that in this population an underlying genetic predisposition can be suspected only when 3 or more cases of ruptured intracranial aneurysm are identified among first- to third-degree relatives.

Nakagawa et al. (1999) studied the incidence of asymptomatic, unruptured cerebral aneurysms among Japanese patients with a family history of subarachnoid hemorrhage within the second degree of consanguinity. Thirty-four of the 244 patients (13.9%) had unruptured cerebral aneurysms, significantly higher than that found in a control group of healthy volunteers (6%). Patients with a family history of subarachnoid hemorrhage combined with more than one other risk factors, such as history of cerebral infarction, hypertension, diabetes mellitus, hyperlipidemia, and habitual smoking, were found to have the highest incidence.

Among 429 families with definite or probable intracranial aneurysm, Woo et al. (2009) found that 54 (12.5%) had a parent-offspring pair or aunt/uncle-niece/nephew pair with ruptured aneurysm. In this group, although the F1 generation was more likely to have an aneurysm rupture at a younger age than the F0 generation, this was largely because of a lack of follow-up time in the F1 generation. After controlling for duration of follow-up, the authors found no evidence for anticipation.

Diagnosis

The Magnetic Resonance Angiography in Relatives of Patients with Subarachnoid Hemorrhage Study Group (1999) screened 626 first-degree relatives of 160 patients with sporadic subarachnoid hemorrhage from a prospective series of 193 consecutive index patients. Magnetic resonance angiography was the screening tool; conventional angiography was used as the reference test in subjects thought to have aneurysms. Aneurysms were found in 25 (4.0%) of 626 first-degree relatives (95% confidence interval, 2.6 to 5.8%). Surgery was performed in 18, resulting in a decrease in function in 11 (disabling in 1). Medium-sized aneurysms (5 to 11 mm in diameter) were found in 5, and both small- and medium-sized aneurysms were found in 2. On average, surgery increased estimated life expectancy by 2.5 years for these 18 subjects (or by 0.9 months per person screened) at the expense of 19 years of decreased function per person. The number of relatives who would need to be screened in order to prevent 1 subarachnoid hemorrhage on a lifetime basis was 149, and 298 would have to be screened in order to prevent 1 fatal subarachnoid hemorrhage. The group concluded that a screening program did not seem warranted at the time of report, since the resulting slight increase in life expectancy did not offset the risk of postoperative sequelae.

Mapping

Onda et al. (2001) cited a prevalence of 3 to 6% for intracranial aneurysms as determined in angiographic and autopsy studies. They reported a genomewide linkage study of this phenotype in 104 Japanese affected sib pairs in which positive evidence of linkage was found on 5q22-q31 (maximum lod score, 2.24), 7q11 (MLS, 3.22), and 14q22 (MLS, 2.31). The best evidence of linkage was detected at D7S2472 in the vicinity of the elastin gene (ELN; 130160), which on other grounds was considered a candidate gene for intracranial aneurysm. Fourteen distinct SNPs were identified in ELN, and no clear allelic association between intracranial aneurysm and each SNP was observed. The haplotype between intron-20/intron-23 polymorphism of ELN was strongly associated with IA (p = 3.81 x 10(-6)), and homozygous patients were at high risk (p = 0.002), with an odds ratio of 4.39. These findings suggested that a genetic locus for intracranial aneurysm lies within or close to the ELN locus on chromosome 7q11.2.

Farnham et al. (2004) confirmed the chromosome 7q11 location found in the Japanese families by linkage analysis of 13 extended pedigrees in Utah, comprising 39 intracranial aneurysm cases. They genotyped 3 markers flanking ELN and performed 2-point multipoint parametric analyses, employing simple dominant and recessive models. Analyses using a recessive affecteds-only model yielded significant confirmation of linkage to the region.

Akagawa et al. (2006) analyzed a 4.6-Mb linkage region around D7S2472 on chromosome 7q11 in patients with intracranial aneurysm. They identified a single haplotype block in linkage disequilibrium (LD) that was associated with intracranial aneurysm in 404 Japanese patients and 458 Japanese controls. The LD block covered the 3-prime untranslated region (UTR) of the ELN gene and the entire LIMK1 gene (601329). A tagging SNP in the 3-prime UTR of ELN (+659G-C; rs8326) showed the strongest association (p = 2 x 10(-6); odds ratio of 3.11) and also served as a marker for the haplotype, which was found to contain 2 functional SNPs: an ELN 3-prime UTR +502A insertion and a -187C-T transition in the LIMK1 promoter. In vitro functional expression studies showed that both the ELN +502A insertion SNP and the LIMK1 -187C-T SNP resulted in decreased transcript levels, either through accelerated ELN mRNA degradation or through decreased LIMK1 promoter activity, respectively. The association with rs8326 was confirmed in a Korean population of 196 patients and 250 controls (p = 0.027), but the functional SNPs were not associated with aneurysm in this sample.

Associations Pending Confirmation

Yoneyama et al. (2003) focused on the 5q31 region where Onda et al. (2001) had found positive evidence of linkage for intracranial aneurysm and where 3 candidate genes were located: fibroblast growth factor-1 (FGF1; 131220), fibrillin-2 (FBN2; 612570), and lysyl oxidase (LOX; 153455). A haplotype association indicated that the causal variant for intracranial aneurysm may lie either within FGF1 or in a nearby gene; however, common variants associated with intracranial aneurysm could not be determined. Although LOX and FBN2 are also positional and functional candidate genes for intracranial aneurysm, a significant association of these genes could not be discerned.

In a genomewide association study of intracranial aneurysm with discovery and replication cohorts from Europe and Japan comprising 5,891 cases and 14,181 controls Yasuno et al. (2010) identified 3 novel loci showing a disease association: rs11661542 on chromosome 18q11.2 (odds ratio (OR) of 1.22, p = 1.1 x 10(-12)) near the RBBP8 gene (604124); rs12413409 on 10q24.32 (OR of 1.29, p = 1.2 x 10(-9)) which maps to intron 9 of the CNNM2 gene (607803); and rs9315204 on 13q13.1 (OR of 1.20, p = 2.5 x 10(-9)) in intron 7 of the STARD13 gene (609866).

In a genomewide association study of 1,383 Japanese individuals with intracranial aneurysm and 5,484 controls, followed by a replication study in 1,048 patients and 7,212 controls, Low et al. (2012) found an association with SNP rs6842241 near the EDNRA gene (131243) on chromosome 4q31.22 (combined p value of 9.58 x 10(-9), odds ratio of 1.25). Imputation analysis of this locus identified SNP rs6841581, which is located upstream of EDNRA and also associated with aneurysm. In vitro functional expression studies showed that the susceptible G allele of this SNP had higher binding activity to nuclear proteins and significantly lower transcriptional activity than the other allele, suggesting that this functional variant might affect the expression of EDNRA. Low et al. (2012) suggested that variation in EDNRA expression may alter susceptibility to aneurysm via its role in vessel hemodynamic stress.