Risk of intracranial aneurysms in families with subarachnoid hemorrhage

Connective Tissue Abnormalities in Patients with Ruptured Intracranial Aneurysms and No Known Systemic Connective Tissue Disorder

BACKGROUND

Defect in internal elastic lamina, defect in tunica media, and the amount of collagen and elastin play a role in vessel wall weakening leading to aneurysm formation. A similar picture may be found in connective tissue disorders, such as Marfan syndrome, Ehlers-Danlos syndrome (EDS), neurofibromatosis type 1, and Loeys-Dietz syndrome (LDS), where there is a predominant disorder of collagen formation/maturation.

METHODS

Histopathology of skin and the superficial temporal artery (STA) was done. All specimens were obtained during craniotomy for ruptured aneurysm clipping or other indicated procedures (for control subjects). Parameters in skin biopsy seen were epithelial thickness, dermal collagen thickness, and so forth. For the STA, parameters such as intimal thickness, intimal proliferation, thickness of media, and so forth were studied.

RESULTS

Twenty cases and twenty control subjects were studied. The mean age of the study population was 40.5 years. Salient findings on skin biopsy in patients of intracranial aneurysms (IAs) (cases) were haphazard orientation of collagen, inflammation in the subepidermal layer, increased dermal collagen thickness, and reduced and/or fragmented elastic fibers. Prominent findings on vessel wall biopsy were intimal proliferation, reduplication of internal elastic lamina, reduced and/or fragmented elastin, and vacuolation of smooth muscle cells. The average number of aberrations per patient was significantly higher in cases than control subjects.

CONCLUSIONS

The histologic changes seen in skin and the STA in cases of IAs signify a weak connective tissue. Some of these findings are also seen in known connective tissue disorders such as Marfan syndrome, EDS, neurofibromatosis type 1, and LDS. The connective tissue abnormalities found in patients with IAs may be congenital, which gets further accentuated by known risk factors leading to weak vessel wall and subsequent aneurysm formation.

Subarachnoid hemorrhage in Kashmir: Causes, risk factors, and outcome

Context:

Kashmir, a snow bound and mountain locked valley, is populated by about 7 million ethnic and non-migratory Kashmiris who have specific dietary and social habits than rest of the world. The neurological disorders are common in Kashmiri population.

Aims:

To study the prevalence and outcome of spontaneous intracranial subarachnoid hemorrhage (SAH) in Kashmir compared withother parts of the world.

Settings and Design:

A retrospective and hospital based study from 1982 to 2010 in the single and only Neurosurgical Centre of the State of Jammu and Kashmir.

Materials and Methods:

A hospital based study, in which, information concerning all Kashmiri patients was collected from the case sheets, patient files, discharge certificates, death certificates, and telephonic conversations with the help of Medical Records Department and Central Admission Register of Sher–i-Kashmir Institute of Medical Sciences, Kashmir India.

Statistical Analysis:

Analysis of variance and students T-test were used at occasions.

Results:

Incidence of SAH in Kashmiris is about 13/100,000 persons per year. SAH comprises 31.02% of total strokes and aneurysmal ruptures are cause of 54.35% SAHs. The female suffers 1.78 times more than the male. Total mortality of 36.60% was recorded against a good recovery of 14.99%. The familial SAHs and multiple aneurysms were also common. Intra-operative finding of larger aneurysmal size than recorded on pre-operative computed tomography (CT) angiogram of same patients was noteworthy. In 493 patients of SAH, the angiography revealed 705 aneurysms.

Conclusion:

Spontaneous intracranial subarachnoid hemorrhage, due to aneurysmal rupture, is common in Kashmir, with worst outcome. Food habits like “salt-tea twice a day”, group-smoking of wet tobacco like “Jejeer”, winter season, female gender, hypertension, and inhalation of “Kangri” smoke are special risk factorsof SAH, in Kashmiris. The plain CT brain and CT angiography are best diagnostic tools. The preventive measures for aneurysmal formation and rupture seems most promising management of future. The detachable endovascular aneurysmal occupying video assisted micro-camera capsules or plugs may be future treatment.

Molecular Genetics of Human Intracranial Aneurysms

Intracranial aneurysms (IAs) are the dilatations of blood vessels in the brain and pose potential risk of rupture leading to subarachnoid hemorrhage. Although the genetic basis of IAs is poorly understood, it is well-known that genetic factors play an important part in the pathogenesis of IAs. Therefore, the identifying susceptible genetic variants might lead to the understanding of the mechanism of formation and rupture of IAs and might also lead to the development of a pharmacological therapy. To elucidate the molecular pathogenesis of diseases has become a crucial step in the development of new treatment strategies. Although extensive genetic research and its potential implications for future prevention of this often fatal condition are urgently needed, efforts to elucidate the susceptibility loci of IAs are hindered by the issues bewildering the most common and complex genetic disorders, such as low penetrance, late onset, and uncertain modes of inheritance. These efforts are further complicated by the fact that many IA lesions remain asymptomatic or go undiagnosed. In this review, we present and discuss the current status of genetic studies of IAs and we recommend comprehensive genome-wide association studies to identify genetic loci that underlie this complex disease.

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 < 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 < 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.

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.

Unruptured intracranial aneurysms: benign curiosity or ticking bomb?

15 years ago, the treatment of incidentally discovered intracranial aneurysms was straightforward with a good evidence base behind it. When intracranial aneurysms were identified, people were referred to neurosurgeons who would offer surgical repair if the patient was in reasonable health and had a good life expectancy. Since that time, several studies have given contradictory evidence for what should be done with these lesions, and a new technique for the repair of aneurysms, endovascular coil embolisation, has been developed. Here we review the research and make several recommendations. First, incidentally discovered aneurysms in the anterior circulation less than 7 mm in size in people with no personal or family history of subarachnoid haemorrhage should be left untreated. Second, people with remaining life expectancy of less than 20 years or so (ie, those over age 60 years) should be informed that from a statistical point of view the benefits of treatment do not outweigh the risks. Third, in all other cases treatment with surgical clipping or coil embolisation should be advised. And finally, if surgical treatment is not feasible then medical hypotensive treatment may be a viable alternative.

Ultrastructural connective tissue aberrations in patients with intracranial aneurysms

BACKGROUND AND PURPOSE

An unknown connective tissue defect might predispose for the development and rupture of intracranial aneurysms in some patients. This study of connective tissue samples of a series of patients with intracranial aneurysms investigates the morphology of the extracellular matrix with methods that are currently used in the routine diagnosis of inherited connective tissue disorders.

METHODS

Skin biopsies from 21 patients with intracranial aneurysms, many with multiple aneurysms, were studied by electron microscopy. None of the patients included in this study showed clinical signs of a known connective tissue disorder.

RESULTS

In 7 patients (33%), we observed repetitive aberrations in the morphology of collagen fibrils and elastic fibers of the reticular dermis. The observed ultrastructural findings were somewhat similar to those typically observed in patients with Ehlers-Danlos syndrome (EDS) and in a subgroup of patients with spontaneous cervical artery dissections. The patterns of abnormalities fell into 2 classes: 4 patients displayed abnormalities that resembled those found in patients with EDS type III, and the electron microscopic findings in the skin biopsies from 3 patients resembled those of EDS type IV patients. The sequence of the COL3A1 gene from the patients with EDS type IV-like alterations of the connective tissue morphology was analyzed. No mutation was detected.

CONCLUSIONS

Connective tissue alterations were found in skin biopsies from a minority of patients with intracranial aneurysms. Electron microscopic investigation of skin biopsies from patients and their relatives might become valuable for clinical diagnostics, identification of persons at risk, and basic studies of the pathogenesis of this vascular disease.

Influence of smoking, hypertension, and sex on the phenotypic expression of familial intracranial aneurysms in siblings

OBJECTIVE

To investigate the effects of smoking, hypertension, and sex on the phenotypic expression of familial intracranial aneurysms (FIAs).

METHODS

We retrospectively reviewed the case records of 806 consecutive patients undergoing aneurysm surgery at our institution (1986-1995) and discovered 24 families with at least two affected siblings. Prevalence rates for the smoking, hypertension, and sex risk factors in these nuclear families were compared with those of patients with sporadic intracranial aneurysms (SIAs) and population-based control patients.

RESULTS

Affected family members with FIAs exhibited prevalence rates of smoking and hypertension (74% and 43%, respectively) that tended to be higher than those of population-based control patients (52% [P < 0.005] and 36% [P = not significant (NS)], respectively) and comparable to those of patients with SIAs (64% [P = NS] and 40% [P = NS], respectively). A positive association existed between FIA formation and female sex but was somewhat less strong than that observed in the SIAs (59% FIAs, 71% SIAs, 50% control patients). In addition, the prevalence rates of smoking, hypertension, and female sex were higher in affected family members with FIAs than in their unaffected siblings (58% [P < 0.05], 28% [P = 0.06], and 39% [P < 0.05], respectively). Individuals in families with expressed FIAs who had high aneurysmal penetrance had a greater tendency to be smokers, hypertensive, and female (74%, 59%, and 55%, respectively) than did their low-penetrance counterparts (61% [P = 0.1], 27% [P < 0.05], and 45% [P = NS], respectively).

CONCLUSION

Together these data suggest that hypertension, smoking, and female sex increase the likelihood that a member of a family with an expressed FIA will have an aneurysm. These observations may prove helpful in guiding the use of screening studies and encouraging education about the potential risks of continued tobacco use and untreated hypertension in this patient cohort.

The ACE I allele is associated with increased risk for ruptured intracranial aneurysms

Genetic and environmental factors play roles in the aetiology of ruptured intracranial aneurysms. Hypertension has been reported as a risk factor for intracranial aneurysm haemorrhage. We have tested if genotypes at the angiotensin converting enzyme (ACE) gene locus are associated with ruptured intracranial aneurysms. The insertion/deletion polymorphism in the ACE gene was genotyped in 258 subjects presenting in East Anglia with ruptured intracranial aneurysms (confirmed at surgery or angiographically) and 299 controls from the same region. ACE allele frequencies were significantly different in the cases and the controls (alleles chi(2)(1)=4.67, p=0.03). The I allele was associated with aneurysm risk (odds ratio for I allele v D allele = 1.3 (95% CI=1.02-1-65); odds ratio for II v DD genotype = 1.67 (95% CI=1.04-2.66)). The I allele at the ACE locus is over-represented in subjects with ruptured intracranial aneurysms. These data are supported by non-significant trends in the same direction in two previous smaller studies. Thus, this allele may be associated with risk for ruptured intracranial aneurysms.

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.

The detection and management of unruptured intracranial aneurysms

The incidence of subarachnoid haemorrhage (SAH) is 6-8 per 100 000 person years, peaking in the sixth decade. SAH, mostly due to rupture of an intracranial aneurysm, accounts for a quarter of cerebrovascular deaths. Aneurysms increase in frequency with age beyond the third decade, are 1.6 times more common in women and are associated with a number of genetic conditions. Prospective autopsy and angiographic studies indicate that between 3.6 and 6% of the population harbour an intracranial aneurysm. Studies have found an increased rate of SAH in first degree relatives of SAH patients (relative risk 3.7-6.6). In affected families, the most frequent relationship between sufferers is sibling to sibling. The rupture rate of asymptomatic aneurysms was thought to be 1-2% per annum, but the recent International Study of Unruptured Intracranial Aneurysms found that the rupture rate of small aneurysms was only 0.05% per annum in patients with no prior SAH, and 0.5% per annum for large (>10 mm diameter) aneurysms and for all aneurysms in patients with previous SAH. Non-invasive tests such as magnetic resonance angiography (MRA), computed tomographic angiography (CTA) and transcranial Doppler (TCD) have been advocated as alternatives to intra-arterial digital subtraction angiography to screen for aneurysms. Although all are promising techniques, the quality of data testing their accuracy is limited. Overall reported sensitivity for CTA and MRA (TCD is poorer) was 76-98% and specificity was 85-100%, but many subjects had an aneurysm or recent SAH, which could overestimate accuracy. CTA and MRA are much poorer methods for the detection of aneurysms <5 mm diameter, which account for up to one-third of unruptured aneurysms. Elective surgical clipping of asymptomatic aneurysms has a morbidity of 10.9% and mortality of 3. 8%. Treatment of aneurysms by Guglielmi coils, for which there is less long-term follow-up available, has a 4% morbidity and 1% mortality, but only achieves complete aneurysm occlusion in 52-78% of cases. There has been interest in screening for aneurysms, but the indication for, and cost effectiveness of screening are unclear because aneurysm prevalence varies, rupture rate is low, non-invasive imaging tests are not yet accurate enough to exclude small aneurysms and the morbidity and mortality for elective surgical treatment of unruptured aneurysms is high. There may be a limited role for investigation of high risk subgroups. Ideally, screening in such subgroups should be tested in a randomized trial. The avoidance of risk factors for aneurysms such as smoking, hypertension and hypercholesterolaemia should be part of the management of at-risk subjects.