M. Zuccarello et al. (eds.), Cerebral Vasospasm: Neurovascular Events After Subarachnoid Hemorrhage,
Acta Neurochirurgica Supplementum, Vol. 115, DOI 10.1007/978-3-7091-1192-5_48, © Springer-Verlag Wien 2013
Abstract Background : In spite of its common occurrence,
the factors predictive of the rupture of intracranial aneurysms
(IAs) remain poorly de fi ned.
Method : A retrospective analysis of patients admitted
with a primary diagnosis of cerebral aneurysm in a single
institution was done. The factors studied were age, sex, size,
site, side, multiplicity, neck type, aspect ratio, positive fam-
ily history, smoking and drinking habits, and hypertension.
The morphological parameters were evaluated for a total of
5,138 aneurysms obtained from the 2,347 patients. Factors
found signi fi cant on univariate analysis were further tested
on a multivariate model.
Findings : We found 1,088 patients (46.36%) had at least
a single aneurysmal rupture. Among the morphologic fac-
tors, size greater than 10 mm, right sidedness, aspect ratio
greater than 1.6, deviated neck type, and multiplicity were
found to be associated with higher incidences of rupture.
Aneurysms on posterior communicating and middle cere-
bral arteries were found to be more prone to rupture. The
demographic factors that were more linked with the ruptured
aneurysms were positive family history, smoking, and
Conclusions : Relevant cases should be started on inten-
sive lifestyle modi fi cation, and extensive screening of those
with a positive family history is highly warranted. All “at-
risk” patients should be evaluated for early surgical
Keywords Cerebral aneurysms • Risk factors • Familial
cerebral aneurysms • Hypertension • Smoking
Intracranial aneurysms (IAs) affect 2–5% of the entire popu-
lation [ 18 ] . But, despite their expected common occurrence,
only 1% of all IAs actually rupture [ 20 ] . Ruptured IAs clas-
sically cause subarachnoid hemorrhage (SAH) but may cause
intraventricular hemorrhage and subdural blood [ 8 ] . About
65% of patients die of the fi rst SAH, and a further 20–25%
experience complications [ 22 ] . Hence, understanding of the
pattern of rupture in IAs is helpful in predicting the rupture
risk in patients and would result in earlier and better manage-
ment of this disease.
Although there have been clinical studies in the past con-
cerning the various factors leading to aneurysmal rupture,
including those involving absolute size [ 12, 18, 24 ] ; various
angles, indices, and size ratios [ 6, 21 ] ; fl uid dynamic studies
[ 3, 9, 19 ] ; location of the aneurysm [ 4, 15 ] ; age and sex [ 5 ] ;
family history [ 14 ] ; hypertension [ 16 ] ; and smoking and alco-
hol consumption [ 11 ] , there has been little large-scale research
taking all the factors together. Hence, we took the 12 most
controversial yet vital factors and compared them for ruptured
and unruptured cases to discover their actual signi fi cance.
Methods and Materials
Retrospective review was made of all patients admitted in the
cerebrovascular facility of Philadelphia’s Thomas Jefferson
University from March 2006 to January 2010, irrespective of
when or where their aneurysms were operated on; this made us
include many people having their surgeries prior to 2006. Only
patients with a radiographically con fi rmed diagnosis of cere-
bral aneurysm by computed tomographic angiography (CTA),
magnetic resonance angiography (MRA), or digital subtraction
angiography (DSA) were included. There were 2,347 patients
who met the criteria, among which 1,088 had rupture of at least
a single IA. There were 884 patients with multiple aneurysms,
so a total of 5,138 IA s were obtained from the 2,347 cases.
S. Ghosh , MBBS , S. Dey , MBBS (?), S. Tjoumakaris , M.D., FACS ,
F. Gonzalez , M.D., FACS , R. Rosenwasser , M.D., FACS , J. Pascal ,
M.D., FACS , and J. Jallo , M.D., Ph.D., FACS
Department of Neurological Surgery ,
Thomas Jefferson University ,
Philadelphia , PA , USA
Association of Morphologic and Demographic Features of
Intracranial Aneurysms with Their Rupture: A Retrospective Analysis
Sayantani Ghosh , Saugat Dey , Stavropoula Tjoumakaris , Fernando Gonzalez , Robert Rosenwasser , Jabbour Pascal ,
and Jack Jallo
S. Ghosh et al.
Information on age, sex, familial preponderance, hyper-
tension (>140/90 mmHg), aneurysm size, aspect ratio, loca-
tion, multiplicity, and history of smoking and alcohol
consumption was retrieved from the database. Former smok-
ers who had quit smoking more than 2 years ago and spo-
radic alcohol consumers were excluded from the smoking
and alcohol analysis. The information about the size (the
maximum perpendicular height), neck type, and the aspect
ratio (the ratio of the maximum perpendicular height to the
average neck diameter) was either noted from the operative
and discharge notes or measured from angiographic images
obtained from iPhilips. Approval for the collection and
review of data was obtained from the institutional review
board at Thomas Jefferson University.
All data were analyzed using JMP 7.0.2 (SAS Institute, Cary,
NC). Initial univariate analysis was done to assess the statis-
tical signi fi cance of the observed difference between the rup-
tured and unruptured groups for each parameter. A chi-square
test was performed for rate versus rate, and logistic regres-
sion was used for rate versus continuous variable. The p val-
ues and 95% con fi dence intervals were calculated and
reported. Effect of age was also assessed by analysis of vari-
ance (ANOVA) with age as the dependent variable and rup-
ture, sex, and family history as the main effects. All
parameters that were found to be signi fi cant ( p < 0.05) in the
univariate analysis were further analyzed using multivariate
regression to identify those parameters that retained
signi fi cance while accounting for all relevant variables.
There were a total of 1,555 females and 792 males in the
study, so the ratio of females to males was 1.96:1. The rup-
ture rate [(number of persons having a rupture/total number
of persons) × 100] was higher in males (49.24%) than in
females (44.89%) ( p = 0.045), with 38.26% of the total num-
ber of males and 37.36% of the total number of females hav-
ing more than one IA ( p = 0.67). The rupture rate among the
884 cases with multiple aneurysms was 65.38%, while it was
34.86% for those with a single aneurysm ( p < 0.0001). Mean
age of rupture in males was 4.04 years more than that in
females. Increasing age, when considered alone, was associ-
ated with less chance of rupture (odds ratio 0.98; 95%
con fi dence interval 0.97–0.99).
Of those with a history of aneurysm in a fi rst-degree rela-
tive, 72.21% had a rupture against 38.50% of those who did
not have a single family member having an IA ( p < 0.0001).
Also, people who did have a positive family history had more
chance of having multiple aneurysms ( p < 0.0001) and had a
rupture 3.22 years (95% con fi dence interval 1.83–4.62)
before those who did not ( p < 0.0001).
Among the other demographic factors, smoking and
hypertension seemed to have a role in rupture. Of current
smokers or ex-smokers who had smoked for at least 10 pack
years and have quit smoking less than 2 years ago, 67.94%
had a rupture compared to 40.20% of nonsmokers ( p < 0.0001).
Of hypertensive people, 58.21% had a rupture compared to
40.32% of those with a normal blood pressure ( p < 0.0001).
Smoking and hypertension were also associated with
increased incidences of multiple aneurysms ( p = 0.00078 and
p = 0.032, for smoking and hypertension respectively ).
Aneurysm size was found to have the most signi fi cant effect
among all factors. Of IAs greater than 10 mm in size, 58.32%
ruptured, while only 18.97% of those with a size less than
10 mm did rupture ( p < 0.0001). Other morphologic factors
like aspect ratio also had a major role to play: 52.5% of IAs
with aspect ratio greater than 1.6 ruptured, while only 19.72%
of those with aspect ratio less than 1.6 ( p < 0.0001) did rupture.
As expected, IAs with deviated neck ruptured more (35.77%)
than those with classical necks (28.43%) ( p = 0.0003). Of
patients having a deviated neck aneurysm greater than 10 mm
size and greater than 1.6 aspect ratio, 69.21% did rupture
( p < 0.0001). Although most of the aneurysms were left sided
(69.85%), right-sided ones had a higher rupture rate of 39.38%
compared to 32.96% for the left-sided ones ( p < 0.0001).
Most of the IAs (71.7%) were in the anterior circulation,
with most of them in the anterior communicating artery. The
posterior circulation harbored a higher fraction of the smaller-
size IAs ( p = 0.004) than the anterior circulation, with most
of them in the posterior communicating artery. The rupture
rates for the posterior circulation IAs were also higher
(37.55%) than for the anterior circulation ones (33.85%)
( p = 0.0121). The highest rupture rate was in the posterior
communicating artery, but the maximum number of rupture
cases occurred in the middle cerebral artery.
Our study revealed that aneurysm size greater than 10 mm
was the most imperative factor for rupture, which is contrary
to recent large-scale studies, such as the International Study
of Unruptured Intracranial Aneurysms [ 10, 24 ] , which pre-
dicted extremely low rupture rates based on absolute IA size.
Numerous other studies have also disputed the role of size as
a rupture predictor by illustrating incidences of rupture from
small aneurysms [ 1, 2 ] .
Family history of ruptured IA in even one fi rst-degree
relative proved to increase the rupture risk manyfold and
277Association of Morphologic and Demographic Features of Intracranial Aneurysms with Their Rupture: A Retrospective Analysis
reduce the age at rupture. Family history of aneurysm also
increased the risk for multiple aneurysms. This should per-
suade early and regular screening for IAs in the family mem-
bers of patients with a ruptured IA. Smoking and hypertension
also increased the chance of IA multiplicity. Having multiple
aneurysms alone can also amplify the rupture risk.
Current smoking and resting blood pressure above 140/90
also seemed to be independent risk factors for aneurysmal
SAH. Alcohol intake had no de fi nite relationship with rup-
ture, whereas increasing age reduced the chances of rupture.
IAs were more widespread in females, but males were found
to have slightly higher chances of rupture, although the dif-
ference lost its signi fi cance on multivariate analysis ( p = 0.08).
Figure 1 illustrates the odds ratio for rupture for the different
demographic parameters in the multivariate model.
Higher aspect ratio also accounted for higher rupture
rates, which is in sync with the previous studies [ 21, 23 ] .
Presence of deviated neck (i.e., side-wall aneurysms),
although it was associated with higher rupture risk but was
not as important as the other factors, corroborating a recent
volumetric study that parent vessel geometry has more role
to play than type of aneurysm [ 19 ] . Right-sided aneurysms,
although less common, had higher chances of rupture.
Figure 2 illustrates the odds ratio for rupture for the different
morphologic parameters in the multivariate model.
Previous studies based on the location of IAs showed that
certain vessels, such as the posterior communicating artery
and the anterior communicating artery, have a higher inci-
dence of ruptured aneurysms when compared with other
locations, such as the internal carotid artery [ 1, 2, 7, 13, 22 ] .
In our study, we obtained the highest rupture rates in the
posterior communicating artery, followed by the middle
cerebral artery and anterior communicating artery. As a
whole, we had higher rupture rates in the posterior circula-
tion. Also, we had smaller aneurysms rupturing in the poste-
rior circulation, with most of them in the posterior
communicating artery; previous studies showed a high per-
centage of small ruptured IAs in the anterior communicating
artery [ 13, 17 ] .
Our study reignited the debate on the implication of greater
aneurysmal size in the rupture of IA again by demonstrating
a considerable proportion of larger aneurysms rupturing.
This should pilot more large-scale prospective trials in this
regard. The effects of aspect ratio and aneurysm neck type on
rupture were distinguished, although not that remarkably.
Right-sided aneurysms also seemed to be related to the rup-
ture process. Family history of ruptured IAs, aneurysm mul-
tiplicity, smoking, and hypertension also were observed to
have an enormous effect on the rupture process.
Fig. 1 Odds ratio (with 95%
con fi dence interval) for rupture
for the different demographic
parameters in the multivariate
multiplicitysmoking HypertensionMale Sex
Fig. 2 Odds ratio (with 95%
con fi dence interval) for rupture
for the different morphologic
parameters in the multivariate
Size>10mm Aspect Ration>1.6Deviated Neck Type Right Side
S. Ghosh et al.
Hence, periodic screening for IAs in the family members
of patients with ruptured IA may be done from an early age.
Large or multiple aneurysms discovered on angiograms
should be referred to immediate surgical interventions. All
at-risk patients should be motivated to quit smoking and
adopt lifestyle modi fi cations to protect against cardiovascu-
Con fl icts of Interest Statement We declare that we have no con fl ict
of interest .
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