Comparison of endovascular and surgical treatments for
intracranial aneurysms: an evidence-based review
Adnan I Qureshi, Vallabh Janardhan, Ricardo A Hanel, Giuseppe Lanzino
Lancet Neurol 2007; 6: 816–25 Intracranial aneurysms can be treated with endovascular or surgical techniques. We provide an objective comparison
Zeenat Qureshi Stroke Research of these treatments, using data from single-centre studies, multicentre studies with and without independent outcome
Center, Department of ascertainment, and randomised clinical trials. We compared the outcomes of patients who were candidates for
Neurology, University of
endovascular treatment, surgical treatment, or both. In patients with ruptured intracranial aneurysms, rates of
Minnesota, Minneapolis, MN,
USA (A I Qureshi MD, aneurysm obliteration were higher, and need for second treatment was lower, after surgery than after endovascular
V Janardhan MD); Division of treatment. However, in observational studies and randomised trials, outcome at discharge, at 2–6 months, and at
Neurological Surgery, Barrow 1 year, and later survival, were all better after endovascular treatment than after surgery. The results suggest that the
higher rates of incomplete obliteration and retreatment after endovascular treatment do not aﬀect patients’ clinical
St Joseph’s Hospital and
Medical Center, Phoenix, AZ, outcome. In observational studies of patients with unruptured intracranial aneurysms, discharge outcomes were
USA (R A Hanel MD); and better and hospital costs were lower after endovascular treatment than after surgery. These patients showed no
Department of Neurosurgery, diﬀerence between the two treatments in 1-year outcomes and later rebleeding, although few data were available for
Illinois Neurological Institute,
University of Illinois College of
Medicine, Peoria, IL, USA
(G Lanzino MD) Introduction such as detachable coils and intravascular stents. However,
Correspondence to: Intracranial aneurysms are focal dilatations in medium- the use of these treatments varies considerably among
Adnan I Qureshi, Department of sized arteries. They are a substantial health problem, and institutions and practitioners. National organisations and
Neurology, University Of
aﬀect roughly 2% of the population worldwide.1 In 1937, medical institutions are trying to ensure that the new
Minnesota, 12-100 Phillips
Wangensteen Building, MMC Walter Dandy performed the ﬁrst surgical treatment of technology is adapted in a uniform and evidence-based
295, 420 Delaware Street SE an aneurysm using a vascular clip designed by Harvey way. Over the past 5 years, as endovascular treatments have
Minneapolis, MN 55455, USA Cushing.2,3 Subsequent advances in neurosurgical become more widely available, practitioners have been
techniques (eg, the development of operating constantly seeking comprehensive and objective sources
microscopes, microsurgical instruments, improved clips, of information to help them select patients for a particular
neuroanaesthesia, and perioperative management for treatment. In this article, we review: comparisons of
complications such as hydrocephalus and symptomatic endovascular treatment with surgery; how evidence is
vasospasm) enabled neurosurgeons to treat most cerebral being incorporated into professional guidelines; and
aneurysms, and surgery was the predominant treatment implications for the future, including deﬁciencies in some
for almost four decades. Attempts were made to place of the present data. Panel 1 shows how we have classiﬁed
iron particles, detachable balloons, and platinum coils surgical and endovascular treatments.
into intracranial aneurysms through endovascular routes1
but, although such treatment was successful in some Pathophysiology and rates of aneurysm rupture
patients, its applicability was limited by high rates of Intracranial aneurysms result from degeneration of the
particle migration, balloon deﬂation, and aneurysm arterial wall, which is caused by congenital and acquired
rupture. In the late 1980s, Guglielmi and colleagues4 medical defects8 and factors such as hypertension and
developed a device in which a soft platinum coil soldered cigarette smoking.9,10 Enlargement and rupture of
onto a stainless steel wire was successfully delivered aneurysms results from interplay between continuing
through a microcatheter into the aneurysm sac—the coil degeneration and haemodynamics. A major rupture can
mass protected against rupture by buﬀering the be preceded by inﬁltration of the artery wall by ﬁbrin and
haemodynamic stress against the fundus of the leucocytes, bleb formation, and a minor haemorrhage.9,10
aneurysm.5,6 The development and subsequent approval Some intracranial aneurysms rupture early in their
of such detachable coils by the US Food and Drug development and are commonly detected as small
Administration (FDA) in 1995 mandated a reassessment ruptured aneurysms (aneurysms that show early
of intracranial aneurysm treatment. vulnerability); others rupture late in their development
Initially, endovascular treatment was used in patients and are commonly detected in the unruptured stage,
who were thought to be poor candidates for surgical rupturing only after growing to a critical size (aneurysms
treatment,1,7 such as people who: had severe neurological that show late vulnerability). The factors that cause
deﬁcits; had an aneurysm in the posterior circulation or in aneurysms to have early rather than late vulnerability are
the cavernous segment of internal carotid artery; were aged unclear.
75 years or over; presented 3–10 days after aneurysm The rupture rate of aneurysms varies with location, as
rupture; or had active cerebral vasospasm. Over the past reported by the International Study of Unruptured
decade, treatment of intracranial aneurysms has evolved Intracranial Aneurysms (ISUIA), which investigated
rapidly, with new developments in endovascular treatments 2686 unruptured, untreated intracranial aneurysms in
816 http://neurology.thelancet.com Vol 6 September 2007
1692 patients (mean follow-up 4·1 years).11 Patients who
did not have a history of subarachnoid haemorrhage who Panel 1: Variations of surgical and endovascular treatments for intracranial aneurysms
had aneurysms in the anterior circulation (ie, in the Surgical treatments
internal carotid artery, anterior communicating or Direct clipping (clips vary in strength, shape, and size)
anterior cerebral artery, or middle cerebral artery) had Direct clipping with decompression of the aneurysmal sac (can include thrombectomy)
cumulative 5-year rupture rates of 0%, 2·6%, 14·5%, and Direct clipping with neuroprotection (barbiturate anaesthesia or hypothermia)
40% for aneurysms of less than 7 mm, 7–12 mm, Proximal ligation (abrupt or gradual) or trapping with or without use of bypass
13–24 mm, and 25 mm or greater, respectively. Rupture Wrapping or coating
rates for aneurysms of the same sizes in the posterior Direct clipping of remnant aneurysm following endovascular treatment
circulation and posterior communicating artery were
2·5%, 14·5%, 18·4%, and 50%, respectively. Patients Endovascular treatments
with a history of subarachnoid haemorrhage had a 5-year Detachable coil placements (coils vary in strength, shape, and size)
cumulative rupture rate of 1·5% for aneurysms of less Detachable coil placements with temporary balloon assistance
than 7 mm in the anterior circulation, compared with Detachable coils and intravascular stent placement
3·4% for aneurysms of the same size in the posterior Liquid embolic agent injection with intravascular balloon or stent assistance
circulation and posterior communicating artery. The Occlusion of parent vessel
reason for the diﬀerent rates of rupture between the Detachable coil placements in remnant aneurysm following surgical treatment
anterior and posterior circulation is unclear.
There are few data on the risk of rupture 5 years after and associated outcomes in various settings. However,
detection of an unruptured aneurysm. Juvela and the comparative value of these studies is limited by
colleagues12 followed 142 patients with 181 unruptured prominent heterogeneity in selection of patients and
aneurysms for a median period of 20 years (range 1–39 imbalances in baseline characteristics between the two
years). Six patients had a single symptomatic aneurysm, treatment groups. Some single-centre studies have
ﬁve had a single incidentally discovered aneurysm, and reported higher rates of incomplete obliteration with
131 had a history of rupture and subsequent treatment of endovascular treatment than with surgery,16,17 although
another intracranial aneurysm. During 2575 person- the eﬀect of incomplete obliteration on overall outcome
years of follow-up, there were 33 ﬁrst-time episodes of was small, and there was no diﬀerence in risk of early
haemorrhage from previously unruptured aneurysms, rebleeding between the treatment groups.15,17 Studies that
with an average yearly incidence of 1·3%. The cumulative reported better outcomes with surgery also reported
rate of rupture among these 142 patients was 10·5% at more unfavourable baseline characteristics in patients
10 years, and 30·3% at 30 years. who received endovascular treatment.21,22 Conversely, in
Following rupture of an intracranial aneurysm, studies that used endovascular treatment as the ﬁrst
recurrent rupture and subarachnoid haemorrhage occur choice,16,17 many patients who were considered unsuitable
with much higher frequency. For example, Jane and for endovascular treatment subsequently underwent
colleagues13 reported that the rate of rebleeding among surgery.
patients with ruptured aneurysms was 50% within the Johnston and colleagues14 reduced the eﬀects of these
ﬁrst 6 months and 3% per year thereafter. The goal of imbalances between baseline characteristics using a
obliterative treatment is to prevent primary subarachnoid blinded comparison of patients with unruptured
haemorrhage in patients with unruptured aneurysms, intracranial aneurysms who received surgical (n=68) or
and recurrent subarachnoid haemorrhage in patients endovascular (n=62) treatment. All 130 aneurysms were
with ruptured aneurysms. judged by a panel of neurosurgeons and neuro-
interventional radiologists to be treatable by either
Comparisons of endovascular and surgical surgery or endovascular treatment. A higher frequency
treatments of post-procedural disability (score on the modiﬁed
Single-centre comparisons Rankin scale [mRS] ≥2) was reported in patients who
An important point to note before we compare treatments underwent surgery compared with those who underwent
for intracranial aneurysms is that some patients are endovascular treatment (25% vs 8%). The length of stay
candidates for surgery only or endovascular treatment in hospital, number of days in intensive care, and hospital
only, whereas for other patients, either treatment is an costs were all greater for surgical patients. There were
acceptable option. This distinction depends on the three delayed subarachnoid or intracranial haemorrhages
clinical condition of the patient, the morphology and in the endovascular group and one in the surgical group
location of the aneurysm, and institutional expertise. after follow-up of 3·9 years per patient.
Single-centre studies of endovascular and surgical
treatments14–25 (table 1) are valuable because the overall Multicentre comparisons
treated population and periprocedural care do not vary Observational studies that use multicentre databases
within each study. These studies thus provide an estimate show consistently lower rates of in-hospital death and
of the proportion of patients treated with each modality disability after endovascular treatment than after
http://neurology.thelancet.com Vol 6 September 2007 817
surgery.26,27 One procedure cannot be said to be better Adverse outcomes (in-hospital death, or discharge to a
than another without knowledge of the baseline nursing home or rehabilitation hospital) were more
characteristics that aﬀect outcome, but, as reported in frequent in the 1669 patients treated with surgery (25%)
the single-centre studies, shorter hospital stays and than in the 400 who received endovascular therapy
lower hospital costs lend support to the use of (10%). In-hospital death was more frequent after
endovascular treatment in selected patients. Johnston surgery than after endovascular treatment (3·5% vs
and colleagues26 compared complications of surgical and 0·5%), and length of stay and hospital costs were
endovascular treatment for unruptured intracranial greater after surgery. During the study period, adverse
aneurysms at 60 hospitals in the US University Health outcomes declined for endovascular therapy (26% in
System Consortium between 1994 and 1997. Adverse 1991 vs 4% in 1998) but not for surgery (26% in 1991 vs
outcomes, deﬁned as in-hospital death or transfer to a 21% in 1998).
nursing home or rehabilitation hospital, were more Berman and colleagues28 evaluated the eﬀect of
common in 2357 patients who underwent surgery (19%) hospital characteristics on outcome in 2200 patients
than in 255 who received endovascular treatment (11%). with ruptured cerebral aneurysms and 3763 patients
In-hospital mortality was higher in surgical patients with unruptured aneurysms treated in New York state,
(2·3% vs 0·4%) but there was no diﬀerence in the USA, from 1995 to 2000. More frequent use of
multivariate analysis. Lengths of stay and hospital costs endovascular treatment in a hospital was associated
were greater for surgical patients after adjustment for with fewer adverse outcomes (death or discharge to a
confounding factors. rehabilitation hospital or long-term facility). Hospital
Johnston and co-workers27 reviewed 2069 patients procedural volume and the propensity to use
with unruptured intracranial aneurysms using a state- endovascular treatment were both independently
wide database of hospital discharges in California, USA. associated with a good outcome.
Aneurysm Endovascular Surgery Imbalance between treatment Conclusion
characteristics treatment groups
n Good outcome n Good outcome
Kaku, 2007 24
79 ruptured 47 81% 32 78% None documented A team of experts in microsurgery and endovascular treatment
should assess each aneurysm
Helland, All ruptured 83 66% 203 48% None documented Endovascular treatment led to better clinical outcome than did
Taha, 200622 53 ruptured and 71 80% 62 66% Endovascular group had worse Endovascular treatment is a safe alternative to surgery for both
80 unruptured baseline characteristics ruptured and unruptured aneurysms.
Kato, 200521 All ruptured 59 44% 120 69% Endovascular group had worse Surgery led to better outcome than did endovascular treatment in
baseline characteristics patients with poor-grade aneurysms
Hoh, 200423 All ruptured 102 33% 413 55% Endovascular group had worse Surgery led to better outcome and lower mortality at discharge than
baseline characteristics did endovascular treatment in patients with good-grade aneurysms,
but symptomatic vasospasm in patients with good-grade or poor-
grade aneurysms was unaﬀected by treatment type
Bairstow, All ruptured 10 Median GOS 1 12 Median GOS 2 None documented Endovascular treatment led to better functional outcome than did
Johnston, All unruptured 62 92% 68 75% None documented Endovascular treatment had higher rates of favourable outcomes
200014 than surgery in patients with unruptured aneurysms
Raftopoulos, 59 ruptured and 64 87% 63 94% Endovascular treatment was the ﬁrst Surgery led to better outcome than endovascular treatment
200016 68 unruptured choice; surgery was used for patients
who could not be treated with
Lot, 199917 280 ruptured 293 92% 102 85% Endovascular treatment was the ﬁrst With appropriate selection of patients, endovascular treatment is a
and 115 choice; surgery was used for patients good alternative for treatment of aneurysms
unruptured who could not be treated with
Gruber, 26 ruptured and 21 95% 20 75% Endovascular group had worse Endovascular treatment is an alternative to surgery in patients with
199815 15 unruptured baseline characteristics basilar artery apex aneurysms
Kahara, 130 ruptured 44 91% 106 85% Endovascular treatment was the ﬁrst Endovascular treatment is feasible, eﬀective, and safe in small
199918 and 20 choice for unruptured aneurysms aneurysms with a small neck
Gruber, All ruptured 111 Mean GOS 2·3 45 Mean GOS 2·4 Endovascular group had worse Delayed ischaemic neurological deﬁcits are more common with
199819 baseline characteristics endovascular treatment than with surgery
GOS=Glasgow outcome scale. The deﬁnition of good outcome varied between studies.
Table 1: Characteristics and outcomes of surgical and endovascular treatments in 12 single-centre studies
818 http://neurology.thelancet.com Vol 6 September 2007
Multicentre studies with independent outcome respectively. At 12 months, good or moderate recovery on
ascertainment the Glasgow outcome scale was observed in 79% of
Rates of periprocedural morbidity and mortality for either patients after endovascular treatment and 75% of patients
treatment were higher in multicentre observational after surgery (p=0·3). Neuropsychiatric tests at 3 and
studies with independent assessment of outcome than in 12 months did not reveal any diﬀerences between the
self-reported studies14–25 (table 1); this indicates that study groups. Crossover from endovascular to surgical
design can lead to reporting bias. Independently assessed treatment (n=12) was greater than crossover from surgical
multicentre studies also suggest that the higher rates of to endovascular treatment (n=4; p=0·03). No rebleedings
retreatment after endovascular treatment do not have an occurred after the ﬁrst hospitalisation. There was no
eﬀect on outcome. For example, in ISUIA,11 in which diﬀerence in cumulative survival times between the
endpoints were adjudicated by a central committee, endovascular (mean survival time 1575 days, 95% CI
periprocedural morbidity and mortality was 12% for 1917 1403–1746) and surgical (1572 days, 1400–1745) treatment
patients who underwent surgery and 10% for 451 patients groups (p=0·9). In MRI at 12 months after intervention,
who underwent endovascular treatments. However, these superﬁcial brain retraction deﬁcits (p<0·001) and
results should be interpreted with the understanding that ischaemic lesions in the territory of the ruptured
ISUIA was not designed for comparison of treatment aneurysm (p=0·025) were more frequent in patients
modalities, and patients who received endovascular treated with surgery than in those who received
treatment were at a higher risk of morbidity and mortality endovascular treatment.
than those who received surgery, because of greater The randomised, multicentre phase III International
patient age, greater aneurysm size, and more aneurysms Subarachnoid Aneurysm Trial (ISAT)32 compared the
in the posterior circulation. Importantly, patient age did eﬃcacy of endovascular treatment with that of surgery in
not aﬀect outcome after endovascular treatment to the patients with ruptured aneurysms who were suitable for
same extent as it did after surgery. either treatment. The aim was to determine whether
In an ambidirectional cohort study,29 all patients with endovascular treatment could reduce the rate of death or
ruptured intracranial aneurysms at nine institutions that disability (deﬁned as mRS 3–6) by 25% or more at 1 year
had expertise in endovascular and surgical treatment in patients with ruptured intracranial aneurysms for
were followed up for early and delayed (>1 year) rerupture whom both endovascular and surgical treatments were
and retreatment. 2·7% of the 299 endovascular-treated acceptable options. A total of 1070 and 1073 patients were
patients and 1·0% of the 711 surgery-treated patients had randomly assigned to surgical and endovascular
rebleeding during the ﬁrst month after treatment. After treatments, respectively. Recruitment was prematurely
1 year, the yearly rate of rebleeding of the index aneurysm stopped after a planned interim analysis showed reduced
was low in both treatment groups: 0·1% after endovascular disability in the endovascular treatment group. The
treatment (904 person-years of follow-up) and 0% after proportion of patients who were dependent or dead at
surgery (2666 person-years). Retreatment after 1 year was 1 year was lower in those allocated to endovascular
more frequent after endovascular treatment, but major treatment (24% of 801) than in those allocated to surgery
complications during this retreatment were rare. The (31% of 793) (relative reduction in risk of dependency or
investigators concluded that the low rates of late death was 23% [95% CI 9–34]; absolute risk reduction
rebleeding and periprocedural complications associated was 7% [3–11]). However, the requirement for a second
with retreatment mean that the beneﬁts of the procedures procedure was higher after endovascular than after
are unlikely to diﬀer after 1 year. surgical treatment. The risk of rebleeding from the
ruptured aneurysm after 1 year was two per 1276 patient-
Randomised comparisons years and zero per 1081 patient-years for patients allocated
A prospective randomised trial30,31 compared endovascular to endovascular and surgical treatments, respectively.
and surgical treatment of intracranial aneurysms within ISAT32,33 assessed survival and long-term outcome by
72 h of subarachnoid haemorrhage. The study assessed reviewing the certiﬁed causes of death, case record
the angiographic outcome and clinical outcome forms, clinical records, and post-mortem details, if
(including neuropsychiatric evaluation) at 3 and available, supplemented at 1 year and yearly thereafter
12 months in 109 patients who were suitable for both with a questionnaire mailed to surviving patients. The
endovascular and surgical treatment. Angiographic early survival advantage with endovascular treatment
outcomes in patients with aneurysms in the anterior was maintained for up to 7 years (log-rank p=0·03). The
cerebral artery were signiﬁcantly better after surgery than risk of epilepsy was substantially lower with
after endovascular treatment, whereas those in patients endovascular treatment than with surgery, but the risk
with aneurysms in the posterior circulation were of rebleeding after 1 year was non-signiﬁcantly higher:
signiﬁcantly better after endovascular treatment than of nine patients who had conﬁrmed rebleeding from
after surgery. One patient had early rebleeding after the target aneurysm, seven had been allocated
endovascular treatment. Technique-related mortality was endovascular treatment and two had been allocated
2% and 4% in the endovascular and surgical groups, surgery. Follow-up of the ISAT patients34 showed that
http://neurology.thelancet.com Vol 6 September 2007 819
191 of 1096 (17·4%) patients were retreated after treatment in ISAT. There were no diﬀerences in the total
endovascular treatment and 39 of 1012 patients (3·8%) cost of treatment between the endovascular-treated
were retreated after surgery. The rate of follow-up (n=30) and the surgery-treated (n=32) patients: the
angiography was higher in the endovascular-treated beneﬁts of shorter hospital stays for the endovascular-
patients than in surgery-treated patients; this might in treated patients were oﬀset by higher procedure costs.
part have increased the rate of detection of asymptomatic There were no diﬀerences in clinical outcomes between
aneurysm regrowth, and subsequently retreatment the groups at 2 months and at 1 year.
(88% vs 46%, respectively). 87 patients were retreated in Cost-utility analysis37—in which beneﬁts of an
the absence of rebleeding 3 months after their initial intervention are quantiﬁed in terms of quality-adjusted
endovascular treatment. Although retreatment was 6·9 life-years (QALYs)—has become the standard analysis of
times more likely after endovascular treatment than cost-eﬀectiveness. An incremental cost-eﬀectiveness of
after surgery, no permanent complications were below US$20 000 per additional QALY is exceptionally
reported with the retreatment. The mean time to beneﬁcial, values of $20 000–40 000 are acceptable, and
retreatment was 21 months after endovascular treatment values greater than $100 000 are not desirable. Most
and 6 months after surgery, suggesting that recurrences currently accepted programmes have an incremental cost-
occur after longer periods in endovascular-treated eﬀectiveness of $60 000–100 000 per additional QALY.
patients. This beneﬁt of endovascular treatment on In a cost-utility analysis, Johnston and colleagues38
long-term survival was not oﬀset by periprocedural compared surgical and endovascular treatment with no
complications, because occurrence of these was low for treatment for unruptured aneurysms in a hypothetical
retreatment. cohort of 50-year-old women. For an asymptomatic
The eﬀects of the two treatments on patient outcome unruptured aneurysm less than 10 mm in diameter in
were further compared in a meta-analysis35 of three patients with no history of subarachnoid haemorrhage,
randomised trials in 2272 patients with subarachnoid both procedures resulted in a net loss in QALYs (surgery,
haemorrhage. After 1 year of follow-up, the relative risk loss of 1·6 QALY; endovascular treatment, loss of
of poor outcome after endovascular treatment versus 0·6 QALY). For aneurysms of 10 mm diameter or larger,
surgery was 0·76 (95% CI 0·67–0·88) and the absolute treatment was cost-eﬀective for aneurysms that produced
risk reduction was 7% (4–11). For patients with an symptoms by compressing neighbouring nerves and
aneurysm in the anterior circulation, the relative risk brain structures, and for patients with a history of
of poor outcome after endovascular treatment versus subarachnoid haemorrhage. Cost per additional QALY
surgery was 0·78 (0·68–0·90) and the absolute risk was $11 000–38 000 for surgery and $5000–42 000 for
reduction was 7% (3–10). For patients with an aneurysm endovascular treatment. The investigators concluded that
in the posterior circulation, the relative risk was 0·41 both treatments are cost-eﬀective for aneurysms that are
(0·19–0·92) and the absolute decrease in risk was 27% symptomatic or 10 mm in diameter or larger, and for
(6–48). The investigators concluded that endovascular patients with a history of subarachnoid haemorrhage.
treatment is associated with a better outcome for The higher cost of endovascular procedures might be
patients who had ruptured aneurysms in either the balanced by cost saved in reduced length of stay in
anterior or posterior circulation and who were hospital.20 However, the studies that support this idea
otherwise in good health and considered suitable for used short-term follow-up and do not take into account
both surgical and endovascular treatment. other factors such as lost productivity of patients at work.
Another important and unaddressed issue is how the
Cost-eﬀectiveness cost-eﬀectiveness of new and more expensive endo-
As new and potentially more expensive technology is vascular technology compares with that of older
introduced, the diﬀerence in outcome should be assessed endovascular techniques.
against the diﬀerence in cost. Bairstow and colleagues20
compared the cost and outcome of endovascular (n=10) Quality of life and functional measures
and surgical (n=12) treatments for ruptured intracranial In a prospective multicentre observational study, Brilstra
aneurysms. Despite incurring higher procedural costs and colleagues39 measured the eﬀect of surgical or
than surgery, endovascular treatment was associated with endovascular treatment of unruptured aneurysms on
lower costs for staﬃng and the stay in hospital. This functional health, quality of life, anxiety, and depression.
study also reported that patients tended to return to In the surgical group of 32 patients, 36 of all 37 aneurysms
normal activity or paid employment sooner, and have a (97%) were successfully treated and four patients (12%)
more favourable functional outcome, after endovascular had a permanent complication. At 3 months post-surgery,
procedures than after surgery, although these ﬁndings quality of life was worse than before treatment, and at
were not included in the cost analysis.20 Javadpour and 12 months post-surgery the quality of life had improved
colleagues36 compared the cost-eﬀectiveness of surgery but had not completely returned to baseline. In the
with that of endovascular treatment for 62 patients endovascular group of 19 patients, 16 of all 19 aneurysms
randomly assigned to either surgery or endovascular (84%) were occluded by 90% or more, and none of the
820 http://neurology.thelancet.com Vol 6 September 2007
surviving patients had complications with permanent aneurysms unsuitable for endovascular treatment should
deﬁcits. However, one patient died from rupture of an be treated surgically if that option is judged to be viable
aneurysm previously treated by endovascular intervention. by a vascular neurosurgeon.
Quality of life in the other 18 patients after 3 months and The German Society of Neurosurgery44 stated that the
1 year was similar to that before treatment. Thus, in the outcome after a speciﬁc treatment (surgical or
short term, surgical treatment, but not endovascular endovascular) of ruptured intracranial aneurysms is
treatment, of patients with an unruptured aneurysm determined by both the periprocedural complication rate
seems to have a negative eﬀect on functional health and and the success of preventing rebleeding from the treated
quality of life. aneurysm. Endovascular treatment is a safe method
associated with fewer complications than surgery in
Recommendations from professional experienced hands. The success of complete obliteration
organisations is higher after surgery than after endovascular treatment,
There have been several sets of guidelines about but whether incompletely occluded aneurysms have a
endovascular treatments for aneurysms since September higher rate of rerupture, and therefore the deﬁnitive
1995, when the FDA approved Guglielmi detachable coils long-term rerupture rate, is unknown.
for treatment of high-risk or inoperable ruptured and Also in 2003, the UK National Institute for Health and
unruptured brain aneurysms.40 Panel 2 summarises the Clinical Excellence (NICE)45 stated that endovascular
recommendations made in these guidelines, together with treatment seems to be eﬃcacious in obliteration of
recommendations made by published reports (table 2). unruptured intracranial aneurysms and that the safety of
In 1997, guidelines from the Canadian Neurosurgical this treatment is similar to that of surgery. However, the
Society41 recommended early surgery for aneurysm risks of treating unruptured intracranial aneurysms by any
treatment unless the aneurysm location or size makes procedure might be greater than the yearly risk of rupture
this diﬃcult. According to this report, aneurysm without treatment. In the same year, NICE similarly stated46
obliteration is best accomplished with open microsurgery that evidence on safety and eﬃcacy lends support to use of
and clipping, although other options include proximal endovascular treatment for ruptured intracranial
parent artery occlusion, trapping of the segment of the aneurysms, provided that standard arrangements are used
artery that contains the aneurysm, and embolisation of for consent, audit, and clinical governance.
the aneurysm using endovascular techniques. In 2000, The Brain Attack Coalition47 recommended in 2005 that
the Stroke Council of the American Heart Association42 endovascular treatment of aneurysms is a safe and
recognised endovascular treatment as an option for eﬀective alternative to surgery in selected patients. These
unruptured intracranial aneurysms. However, although guidelines also recommended that surgical and
the technique was being used with increasing frequency, endovascular treatments should be done in a
the council decided that the eﬃcacy of endovascular comprehensive stroke centre, and that if a centre cannot
treatment for unruptured intracranial aneurysms should oﬀer these treatments, protocols should be developed for
not be judged until there had been a case-controlled, the rapid transfer of patients to a facility that can.
randomised prospective trial.
In 2002, the Committee on Cerebrovascular Imaging
of the American Heart Association Council on Panel 2: Guidelines for use of endovascular treatment
Cardiovascular Radiology7 recommended endovascular Recommendations discussed in the main text and studies summarised in table 2 together
coils as a treatment option for ruptured and unruptured suggest the following:
intracranial aneurysms. The council also suggested that • Both endovascular and surgical treatment options must be available in any centre that
endovascular treatment should be used for patients in treats patients with intracranial aneurysms
whom surgery is impossible or high risk, such as those • There is evidence that endovascular treatment can be an initial treatment option for
with aneurysms in the posterior circulation. In 2003, the all ruptured and unruptured intracranial aneurysms. However, only part of this
year in which the FDA approved Guglielmi detachable evidence is derived from randomised trials, and further studies are needed
coils for use to treat all aneurysms, four reports further • Endovascular treatment should be the preferred option only with the understanding
encouraged use of endovascular treatment. After the that certain aneurysms are better treated with surgery. Physicians with endovascular
results of ISAT were published, the American Society of expertise must also be familiar with the strengths of surgical treatment if they are to
Interventional and Therapeutic Neuroradiology and the recommend the best treatment option
American Society of Neuroradiology43 recommended that • Although signiﬁcant emphasis has been placed on selecting the appropriate
endovascular therapy be considered for every patient with endovascular or surgical treatment, conservative management might be the best option
a ruptured cerebral aneurysm, preferably following for some patients. Therefore, physicians involved in the care of patients with aneurysms
consultation with a neuroendovascular specialist. These must understand the natural history of intracranial aneurysms in various settings
guidelines also proposed that the reasons for • Physicians and people who are responsible for institutions that treat aneurysms should
recommendation of one treatment over another should think about cost-eﬀectiveness before incorporating new and expensive technology
be documented, in accordance with the usual standards into their practices
for informed consent, and that patients who have
http://neurology.thelancet.com Vol 6 September 2007 821
Implications of the comparisons of endovascular haemorrhage in central Finland are candidates for
and surgical treatments aneurysm treatment.
Implications for clinical practice
On the basis of results from ISAT, we estimated that if a Implications for patient outcomes
new treatment for ruptured aneurysms had a 6% higher To evaluate the eﬀect of endovascular treatment on
rate of discharge of patients home from hospital after patient outcomes, we used data from the National
subarachnoid haemorrhage than did an older procedure, Hospital Discharge Survey to identify changes in
use of the new procedure for 20% and 50% of patients morbidity and mortality rates in adult patients who were
with subarachnoid haemorrhage could lead to yearly admitted to hospital for ruptured and unruptured
savings of $11·4 million and $28·6 million, respectively intracranial aneurysms.48 Variables pertaining to hospital
(Qureshi AI, unpublished). However, the cost savings admission were compared for three distinct time periods.
and reduction in death and disability are obscured by the In-hospital mortality rates for patients with subarachnoid
relatively small proportion of patients with subarachnoid haemorrhage demonstrated no signiﬁcant change across
haemorrhage who are considered for any aneurysm the diﬀerent periods (27·6%, 24·6%, and 26·3% in
treatment. We have reported that a third of patients 1986–90, 1991–95, and 1996–2001, respectively), but rates
admitted to hospital in the USA with subarachnoid decreased across the three periods for patients with
haemorrhage and half of those admitted with unruptured unruptured intracranial aneurysms (5·9%, 6·3%, and
intracranial aneurysms underwent either surgical or 1·4%, respectively; p=0·07).
endovascular treatment.48 Cross and colleagues49 reported A UK-based single-centre study51 investigated changes
that 34% of 16 399 admissions for subarachnoid in clinical therapy and outcome of 1609 patients with
haemorrhage in 18 US states from 1998 to 2000 resulted subarachnoid haemorrhage over 9 years (1990–98).
in either surgical (29%) or endovascular (5%) treatment Overall, 54% of patients (ranging from 35% to 66%) were
for intracranial aneurysms. However, the proportion of surgically treated, 8% had endovascular treatment
patients eligible for such treatment is likely to be (0·6%–18%), and 38% (28%–46%) were managed without
higher—for example, Fogelholm and colleagues50 surgical treatment for the aneurysm. The proportion of
estimated that about 60% of patients with subarachnoid patients undergoing surgery decreased from 1994
Patients with ruptured intracranial aneurysms Patients with unruptured intracranial aneurysms
Candidates for any treatment* Candidates for either treatment† Candidates for any treatment* Candidates for either treatment†
Aneurysm obliteration Higher with surgical treatment (SCS)17,18 Higher with surgical treatment (RCT)32 Higher with surgical treatment ··
Cerebral vasospasm Higher with endovascular treatment (SCS)19 ·· ·· ··
Discharge outcome Better with endovascular treatment (SCS)‡17 ·· Better with endovascular treatment Better with endovascular treatment
Hospital charges No diﬀerence (SCS)20 No diﬀerence (SCS)36 Lower with endovascular treatment Lower with endovascular treatment
2–6 month outcome ·· Better with endovascular treatment ·· ··
1-year outcome ·· Better with endovascular treatment No diﬀerence (MOSI)11 ··
Neuropsychiatric ·· No diﬀerence (RCT)30 No diﬀerence (MOSI)11 ··
Perioperative and long- ·· Lower with endovascular treatment (RCT)33 ·· ··
term risk of seizures
Quality of life (1-year ·· ·· Better with endovascular treatment ··
Early rebleeding§ ·· No diﬀerence (RCT)33 ·· ··
Late rebleeding No diﬀerence (MOSI)29 No diﬀerence (RCT)33 ·· No diﬀerence (SCS)15
Second treatment Higher with endovascular treatment Higher with endovascular treatment (RCT)34 ·· ··
Late survival ·· Better with endovascular treatment (RCT)33 ·· ··
*Includes patients who were candidates for only surgical or only endovascular treatment. Endovascular treatment was preferentially used for patients with poor clinical and angiographic characteristics. †Patients
for whom both endovascular and surgical treatments were acceptable options. ‡Not consistently demonstrated. §Rate of rebleeding was higher within 1 month after treatment in the endovascular-treated
patients, but overall rate of rebleeding within 1 month was similar in the two groups because the rate of rebleeding was higher before the procedure in surgery-treated patients than in endovascular-treated
patients. SCS=single-centre study. MOS=multicentre observational study. Double dots indicate that we found no relevant studies. MOSI=multicentre observational study with independent outcome
ascertainment. RCT=randomised controlled trial.
Table 2: Comparison of endovascular and surgical treatments
822 http://neurology.thelancet.com Vol 6 September 2007
onwards, owing to improvements in endovascular
treatment and higher rates of admission for patients with Search strategy and selection criteria
poor-grade aneurysms. This change in admissions can We based the review on personal knowledge of the subject
also explain an increase in mortality rate during the supplemented by data from multicentre randomised trials,
period of review (from 18% to 32%). non-randomised controlled studies with independent
The beneﬁts of endovascular treatment are obscured in outcome ascertainment, and selected observational studies.
patients with subarachnoid haemorrhage by preferential The information was identiﬁed with multiple searches of
use of this treatment for patients with poor-grade Medline from January, 1985, to May, 2007, by cross-
aneurysms, in whom outcome is predominantly referencing key words of “intracranial aneurysms”,
determined by initial clinical condition. Similarly, “subarachnoid haemorrhage”, “embolization”, and
endovascular treatment has increased the proportion of “detachable coils”. Only papers published in English were
elderly patients who are treated for ruptured aneurysms; reviewed. We also reviewed abstracts from pertinent scientiﬁc
in these patients, short-term and long-term survival is meetings, and information about technological developments
partly inﬂuenced by comorbidities, which limits the was acquired through industrial resources available for clinical
overall beneﬁt of aneurysm treatment. Nevertheless, investigators.
endovascular treatment has greatly improved the overall
outcomes of patients with unruptured intracranial
aneurysms. to 31% following publication of the ISAT results, whereas
endovascular treatment of aneurysms increased from
Implications of ISAT 35% to 68%. During the same period, there was a non-
ISAT is to our knowledge the most comprehensive signiﬁcant improvement in outcome at 6 months and a
comparison of endovascular and surgical treatments. decrease in the mean total duration of hospital stay,
However, results suggest that the patients treated in ISAT which was related to the shorter duration of hospital stay
had more favourable baseline clinical and procedural associated with endovascular treatment than with
characteristics than do patients with aneurysms treated surgery. Another study55 analysed the therapeutic
outside this study. For example, a comparison of patients decision-making process and outcome in 100 consecutive
admitted with subarachnoid haemorrhage to a nationally patients with subarachnoid haemorrhage treated since
representative sample of hospitals in the USA48 showed the publication of ISAT. 47 patients underwent surgery,
that the mean age of patients was lower in ISAT.32 In- 41 underwent endovascular treatment, and 12 received a
hospital mortality was also lower (6% overall in ISAT32 vs combination of the two procedures. Good functional
26% for patients with subarachnoid haemorrhage in the outcome (mRS 0–2) after 6 months was achieved in 71%
USA48). Similarly, the mortality in ISAT patients was of patients. This result suggests that, in routine clinical
lower than that reported in the Japanese Standard Stroke practice, excellent functional results can be seen when
Registry Study (22%).52 surgical and endovascular treatments are assigned on the
Despite this diﬀerence, results from another study basis of data from ISAT.
suggest that ISAT can be applied to the general
population. Flett and colleagues53 reported on patients Conclusions
who were admitted to one centre that participated in Endovascular treatment has been incorporated into the
ISAT but who were not recruited into the trial (72% of all treatment of patients with subarachnoid haemorrhage
admissions to the centre; most exclusions from ISAT who are poor candidates for surgical treatment. Since the
were because one treatment was judged to be preferable emergence of endovascular treatments, reports such as
to the other by the treating physicians, on the basis of ISAT have supported the idea that endovascular treatment
morphology and location of the aneurysm or clinical is a valid alternative for many patients (table 2). However,
characteristics of the patient). Nine of these patients were the deﬁnition of these patients is arbitrary, and the
treated conservatively, 67 underwent surgical treatment, decision to use endovascular treatment for unruptured
and 46 underwent endovascular treatment. At 12 months, intracranial aneurysms can depend on the views and
72% of the patients who received endovascular treatment expertise in local institutions. A better understanding of
and 49% of those who received surgery had a good mRS the long-term risk of rupture, periprocedural results, and
(0–2). This higher rate of favourable outcomes in patients complications associated with available procedures is
who received endovascular treatment than in those who helping to clarify whether therapeutic intervention is
received surgery provides evidence that the results of beneﬁcial for unruptured intracranial aneurysms. Future
ISAT can be applied generally. research priorities include a comparison of treatments for
The proportion of patients undergoing endovascular unruptured intracranial aneurysms that can be treated by
treatment has increased since the publication of ISAT. In either surgical or endovascular treatment, and a
a report from a single neurosurgical unit in the UK,54 the comparison of treatments for ruptured intracranial
proportion of patients with subarachnoid haemorrhage aneurysms in patient populations not included in ISAT,
who underwent surgical treatment decreased from 51% with use of randomised clinical trials and prospective
http://neurology.thelancet.com Vol 6 September 2007 823
multicentre registries with independent outcome 19 Gruber A, Ungersbock K, Reinprecht A, et al. Evaluation of
ascertainment. As physicians, we should use data to guide cerebral vasospasm after early surgical and endovascular
treatment of ruptured intracranial aneurysms. Neurosurgery 1998;
our decisions on a case-by-case basis, and we should 42: 258–67.
remember that selection of appropriate patients for each 20 Bairstow P, Dodgson A, Linto J, Khangure M. Comparison of cost
therapeutic method can improve the overall results. and outcome of endovascular and neurosurgical procedures in the
treatment of ruptured intracranial aneurysms.
Contributors Australas Radiol 2002; 46: 249–51.
All authors contributed equally to the literature search, writing, and 21 Kato Y, Sano H, Dong PT, et al. The eﬀect of clipping and coiling in
revision of the manuscript. All authors have seen and approved the ﬁnal acute severe subarachnoid hemorrhage after international
version. subarachnoid aneurysmal trial (ISAT) results.
Minim Invasive Neurosurg 2005; 48: 224–27.
Conﬂicts of interest
22 Taha MM, Nakahara I, Higashi T, et al. Endovascular embolization
We have no conﬂicts of interest. vs surgical clipping in treatment of cerebral aneurysms: morbidity
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