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Guglielmi Detachable Coiling for Intracranial Aneurysms
The Story So Far
Zach Dovey, MD;
Mukesh Misra, MD;
John Thornton, MD;
Fady T. Charbel, MD;
Gerard M. Debrun, MD;
James I. Ausman, MD, PhD
Arch Neurol. 2001;58:559-564.
ABSTRACT
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Spontaneous rupture of cerebral aneurysms typically results in subarachnoid
hemorrhage. The primary goal of treatment of cerebral aneurysms is to prevent
future rupture. Surgical clipping had been the mainstay of treatment of both
ruptured and unruptured cerebral aneurysms. In 1991, Guglielmi detachable
coil (GDC) embolization was introduced as an alternative method for treating
selected patients with aneurysm. The goal of the treatment is prevent the
flow of blood into the aneurysm sack by filling the aneurysm with coils and
thrombus. Theoretically, there are several advantages of GDC over surgery.
These procedures are performed under general anesthesia with the standard
transfemoral approaches used in diagnostic angiography. Since its inception,
GDC embolization has evolved as a result of both clinical experience and the
introduction of technological improvements. We are now better at selecting
aneurysms appropriate for coiling, which also have wide necks. Advances in
GDC technology have also improved this method of treatment. Over the last
several years, the number of coil sizes has been increased, multidimensional
coils allowing safer initial coil placement have become available, and, more
recently, softer coils have been introduced. Our current approach is to have
both surgical and endovascular options for patients.
INTRODUCTION
Endovascular therapy (EVT) continues to evolve and is now challenging
surgical clipping as a genuine alternative therapy for intracranial aneurysms.
The management of subarachnoid hemorrhage (SAH) and its associated complications
remains a problem, and the need for a new relatively atraumatic treatment
option has generated much interest. The Guglielmi detachable coil (GDC) has
been particularly promising.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
This platinum coil is detached by electrolysis of the stainless steel delivery
wire.7, 8 The coil has proved simpler
to deploy than earlier techniques and is safer because it deforms more easily
to the lumen of the aneurysm.3, 4
The GDC has been studied in the treatment of acutely ruptured aneurysms2, 3, 14, 15 and
unruptured aneurysms1, 4, 5, 9, 10, 11
with a variety of morphologic features and locations. The outcome of surgical
treatment for acutely ruptured aneurysms has remained fairly constant for
the past 20 years, with only 30% of patients regaining their premorbid neurological
status.2 It was hoped that the use of EVT in
aneurysmal SAH would reduce the risks and harvest the benefits of early surgical
intervention. The geometry and location of the aneurysm and the clinical status
of the patient affect the indication for and likely success of EVT.5, 6, 12, 13, 16
Although comparison is theoretically invalid given the different patient
populations, EVT has tended to be reserved for poor surgical candidates, those
with poor Glasgow Outcome Scale scores after SAH, or those with high surgical
risks due to position or morphologic features, and the results have been similar
to those of surgical series.2, 3, 5, 12, 13
Criticism of EVT has resulted from the potential for rebleeding from
partially occluded aneurysms. The need to demonstrate complete obliteration
of the sac has been emphasized,5, 12
and the terms dog-ears, neck remnants, and residual aneurysm have been used to describe the angiographic
appearance when partial occlusion occurs. The long-term natural history of
partially occluded aneurysms is not yet clear. As the pool of data for EVT
increases, it is becoming clear that EVT is a viable alternative to surgical
clipping. Moreover, in certain situations, EVT might be regarded as the treatment
of choice. To our knowledge, there are no randomized controlled trials directly
comparing surgery with EVT, but the criteria for the ideal "EVT candidate"
are beginning to emerge. The aim of this review is to discuss the current
literature that is concerned with the comparison of surgical treatment and
EVT, detailing population demographics; outcomes; and morbidity, mortality,
rebleeding, and complication rates. In light of this, we attempted to clarify
the indications for choosing EVT for intracranial aneurysms in what is now
an established multidisciplinary approach using the expertise of neurosurgeons
and neuroradiologists.
SUMMARY OF DATA FROM THE LITERATURE
Several studies assess the use of EVT in the treatment of ruptured and
unruptured intracranial aneurysms. Five recent studies5, 6, 12, 13, 16
are worthy of more detailed attention. The summarized results of these and
other studies are shown in Table 1.
In Table 2, for comparison, a
selection of surgical series is highlighted.
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Table 1. Summary of Coiling Series*
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Table 2. Summary of Surgical Series
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Debrun et al6 present data from 144 patients
split into groups 1 and 2 representing their early and late experience, respectively.
The former group was chosen for GDC based on surgical exclusion and the latter
based on aneurysm geometry (specifically, dome-to-neck ratios >2). For 55
patients with SAH (Hunt and Hess grade I, 24%; II, 29%; III, 25%; IV, 14%;
and V, 7%), an excellent outcome (Glasgow Outcome Scale score 1) was seen
in 74%, with procedure-related morbidity and mortality of 3.6% and 1.8%, respectively
(overall morbidity and mortality, 7.2% and 17.8%, respectively). For 89 patients
who presented nonacutely, an excellent outcome was observed in 90%, with procedure-related
morbidity of 2.2% and no procedure-related mortality (overall morbidity and
mortality, 2.2% and 7.8%, respectively). The significance of subgrouping into
those treated based on aneurysmal geometry is addressed later in this article.
Kuether et al16 published their data
from 74 patients—40% presented with SAH over a 4 -year period.
After coiling, they found that of patients with Hunt and Hess grade I/II,
81% were independent; of those with grade III, 100% were independent; and
of those with grade IV/V, 50% were independent. Procedure-related morbidity
and mortality were 9.1% and 7.8%, respectively.
Cognard et al5 performed EVT on 182 patients,
150 of whom had SAH (Hunt and Hess grade I, 61%; II, 17%; III, 9%; IV, 3%;
and V, 9%) and 58 of whom had unruptured aneurysms. Of 167 patients who survived
to long-term follow-up, 83% had Glasgow Outcome Scale scores of 1, with overall
morbidity and mortality of 6.5% and 8.7%, respectively.
Viñuela et al13 treated 403 patients
with GDC divided into Hunt and Hess grade I, 20.3%; II, 26.1%; III, 30.0%;
IV, 17.1%; and V, 6.5%. They found that 84.9% of patients improved or remained
neurologically unchanged, with overall morbidity and mortality of 8.9% and
6.2%, respectively. In discussing these results they were compared with previous
surgical series with similar distributions of Hunt and Hess grades and overall
morbidity and mortality of 23% and 21%, respectively,18
and 14% and 27%, respectively,20 and 16% mortality.17, 18, 19, 20, 21, 22, 23, 24, 25
Raymond and Roy12 treated 75 patients
with EVT, with a Hunt and Hess grading distribution of I, 24%; II, 17%; III,
40%; IV, 15%; and V, 4%. They found that 82% of patients with grades I through
III had good outcomes, with procedure-related morbidity and mortality of 8%.
Although these populations are different from those of surgical series,
their results compare favorably.17, 18, 19, 20, 23, 24, 25
It seems that overall the ability of EVT to secure aneurysms after hemorrhage
(thus preventing rebleeding and allowing treatment of associated vasospasm)
and achieve high good outcome scores is similar to that of surgical clipping.
The tabulated surgical results (Table 2) are by no means comprehensive but give an idea of figures obtained
through the late 1980s and 1990s. The discussion and comparison of these 2
treatments is complicated not only by the differing nature of the population
characteristics but also by the presentation of variable outcome measures
and morbidity and mortality rates: overall rates and procedure-related rates
can only be compared with like rates. Furthermore, these observational comparisons
are hardly scientific, and more detailed analysis requires a randomized controlled
trial.
DRAWBACKS AND REASONS FOR EVT FAILURE
Drawbacks of EVT include the potential for bleeding from nonobliterated
aneurysms after the procedure, its effect on the incidence of vasospasm, and
the inherent complications of the technique.
Remnant Rebleeding
Experience from surgical clipping has shown that aneurysmal neck remnants
seen on the postoperative angiogram might dilate to form another aneurysm
and represent a significant risk for rebleeding.26
In view of this, the aim of EVT has been to achieve total occlusion. Total
occlusion rates of 70% to 85% have been quoted,3, 4, 5, 6, 12, 13
sometimes requiring more than one procedure.10, 25
Generally, it has been easier to achieve total occlusion in aneurysms with
small necks, and aneurysmal geometry is emerging as an important predictive
factor.6
In the study by Keuther et al16 of 74
patients, 40% of aneurysms exhibited complete occlusion (100%), 52% near complete
occlusion (90%-99%), and 8% incomplete occlusion (<90%). They reported
after 1.9 years of follow-up that no completely occluded aneurysm hemorrhaged
after GDC treatment, and of near complete occlusions, 2.6% hemorrhaged at
a rate of 1.4% per year. In the incomplete occlusion group, 16.7% (1 of 6
patients) bled after 2.3 years at a rate of 7.3% per year. In the context
of acutely ruptured aneurysms, other studies have quoted rebleeding rates
from partially occluded or residual aneurysms (which are presumably <90%
occluded) of 6.25%,3 27.0%,4
and 25.0%.12
In the study by Raymond and Roy,12 the
angiographic terms dog-ears and residual necks are used to differentiate incomplete occlusion from
residual aneurysms, which are classified as any opacification of the sac.
It was from the residual aneurysms that the rebleeding occurred. They also
note that at angiographic follow-up, 12 patients had recurrences from coil
compaction that was more commonly associated with narrow necks than wide necks.
Recurrences during this short period were not associated with hemorrhage,
mortality, or morbidity. We need to determine whether patients who rebleed
from the features of their postprocedure angiography (ie, dog-ears, residual
necks, or percentage of incomplete occlusion) can be predicted so that in
these patients further embolization or surgical clipping can be performed
prophylactically. This information will come to light as long-term follow-up
studies are published.
Vasospasm
The incidence of vasospasm in patients treated with EVT is a controversial
issue. A recent study by Gruber et al17 suggests
an increase in infarction rates after acute SAH in those treated with EVT
compared with those treated with surgery. However, the increased rate of infarction
is only significant in patients with Fischer grade 4 and Hunt and Hess grade
V. They conclude that the presence of retained intracerebral clots in patients
treated with EVT increases the delayed ischemic infarction rate secondary
to vasospasm. In patients without intracerebral clot, there was no significant
difference between those treated with surgery or EVT, although there was a
trend toward higher rates in the EVT-treated group. Theoretically, even in
groups with less severe grades of SAH, early surgery has been suggested to
reduce the incidence of vasospasm by removal of vasoactive blood products
at the time of surgery using cisternal lavage.27, 28
This was not confirmed in the International Cooperative Study on the Timing
of Aneurysm Surgery,29, 30 in which
early surgery did not seem to affect the incidence of morbidity and mortality
from chronic cerebral vasospasm. Murayama et al,31
studying a group of patients with Hunt and Hess grades I through III treated
with EVT, found the incidence of symptomatic vasospasm to be 23%, which compares
favorably with conventional surgical series14, 32
and is confirmed by other EVT studies.6 More
recently, Yalamanchili et al22 compared patients
of similar Hunt and Hess and Fischer grades treated with surgery or EVT within
48 hours of aneurysmal SAH. They found that 22% of the EVT group developed
vasospasm, whereas 74% of the surgical group developed vasospasm. Those in
the EVT group responded to maximal medical management with significant improvement
or resolution of their deficit: in the surgical group, 3 patients (30%) required
endovascular angioplasty; ultimately, 2 died and 1 experienced a residual
hemiparesis. They suggest, in contrast to Gruber et al,21
that blood, lipid peroxides, and free radicals released into the subarachnoid
space because of surgical trauma, in addition to the spastic response of the
cerebral vasculature to manipulation, predisposes craniotomy patients to vasospasm.
The study by Yalamanchili et al22 consisted
of a small number of patients, and, in the face of this conflicting data,
it is clear that further study is required.
Technical Considerations
Complications are well documented in all the published series and include
aneurysmal rupture, artery occlusion and thromboemboli, and coil migration.
These complications have been reported at rates of 2.1% to 8.0% for aneurysmal
perforation, 1.6% to 6.5% for thromboemboli, 3.2% to 5.0% for parent vessel
occlusion, and 1.1% to 1.3% for coil migration.6, 12, 13, 16
Vessel Tortuosity
A possible cause of failure is the inability to gain a stable position
of the microcatheter in the aneurysm for coil delivery because of tortuosity
of the access vessel.
Mass Effect
Another problem encountered is increasing mass effect after coiling
of large or giant aneurysms, which might require subsequent decompression
of the surrounding structures. In a series of 9 patients, Tsuura et al,33 performing serial magnetic resonance images after
embolization of large or giant aneurysms, found that shrinkage of approximately
30% tended to occur 2 to 12 months after treatment. Only 2 patients were coiled,
however (the rest had balloon occlusion), and these tended to shrink more
slowly, they believed, because balloon occlusion allowed thrombosis of capillary
channels within the aneurysm wall. Growth of thrombosed aneurysms has been
recorded after treatment,34, 35
possibly secondary to hemorrhage of vasa vasorum, but in each case after balloon
occlusion. It is possible that the presence of coils might produce the same
effect in addition to an inflammatory reaction and associated edema.
As experience increases and microcatheter and coil technology improves,
many of these drawbacks will become less significant, and complication rates
should decline.
ANEURYSM MORPHOLOGY AND LOCATION
It is well known that the results of EVT in large and giant aneurysms
are less favorable than those in small aneurysms, with a commonly accepted
classification of small (4-10 mm), large (>10-25 mm), and giant (>25 mm).3, 4, 13, 16 Occlusion
rates in these studies have consistently been better for small aneurysms,
as defined by the previous dimensions: occlusion rates decreased for aneurysms
larger than 10 mm, and for very small aneurysms (<4 mm), packing became
technically difficult.5 The width of the neck
has also been critical. There is inherent logic in the statement that small
necks are easier to pack with coils than wide necks, and a width of less than
5 mm has been suggested as a cutoff point.36
This simple principle for EVT suitability has recently been refined by Debrun
et al,6 who examined aneurysmal geometry. Based
on the observation that a 5-mm aneurysm with a 2-mm neck would be easier to
pack than a 5-mm aneurysm with a 4-mm neck, they propose dome-to-neck ratio
as a more effective measurement. In their study, group 1 patients with dome-to-neck
ratios of less than 2 (ie, relatively wide necks) had complete occlusion rates
of 58%, whereas group 2 patients with dome-to-neck ratios of greater than
2 (ie, narrow necks relative to aneurysmal sac width) had complete occlusion
rates of 80%. They point out, however, that any aneurysm with a neck wider
than 5 mm is unlikely to be packed effectively because of coil prolapse, regardless
of the dome-to-neck ratio.
For the early studies, patients were recruited on the basis of surgical
exclusion. This could be for a variety of reasons, including poor clinical
grade after SAH, general lack of fitness for surgery, and surgical inaccessibility.
As a result, the published data contained a predominance of posterior circulation
aneurysms.3, 4 This in itself was
not a problem, and in fact some groups report easier catheterization of posterior
circulation aneurysms because the vessels are less tortuous3;
however, it made comparison of EVT and surgical series less valuable. Although
this bias is now less marked, and in some cases even reversed,5, 6, 12, 13, 16
in all of these more recent series the most common individual locations were
the basilar tip or parophthalmic aneurysms. This confirms that surgical inaccessibility
remains an important factor in the choice of EVT. As experience of coiling
at other sites grows, previously unknown situations that make coiling unsuitable
have come to light: Debrun et al6 found that
aneurysms in which multiple branches arose were particularly difficult (eg,
at the middle cerebral artery trifurcation) because the vessels obscured the
aneurysm neck, increasing risk of coil protrusion, and thus thrombosis, in
the parent artery. This observation reiterates the importance of meticulous
pretherapeutic angiography and planning before opting for EVT.
SUMMARY
There are now 2 options for the treatment of intracranial aneurysms,
and available data suggest that the outcomes for each are similar. In certain
circumstances each one has an advantage over the other, and different patients
might be more suited to one but not the other. Endovascular therapy lends
itself to small aneurysms (diameter, 4-10 mm), with neck widths less than
5 mm and dome-to-neck ratios greater than 2, in which the chances of total
angiographic occlusion are highest. The most common individual locations treated
in the published data are the basilar tip and parophthalmic aneurysms. Most
of cerebral aneurysms in the posterior circulation and a few in the anterior
circulation are better treated using endovascular coiling technique rather
than surgically. A multidisciplinary approach with free communication between
the interventional neuroradiologist and the neurosurgeon should be emphasized,
with meticulous planning on the basis of pretherapeutic angiography. We need
to continuously evaluate the data from surgical and endovascular series and
any randomized trials to ensure the continued optimal management of patients
with intracranial aneurysms. New technology will continue to make advances
in this field.
AUTHOR INFORMATION
Accepted for publication April 4, 2000.
From the Departments of Neurosurgery (Drs Dovey, Misra, Charbel, and
Ausman) and Neurointerventional Radiology (Drs Thornton and Debrun), University
of Illinois at Chicago.
Corresponding author and reprints: James I. Ausman, MD, PhD, Department
of Neurosurgery (M/C 799), University of Illinois at Chicago, 912 S Wood St,
Chicago, IL 60612 (e-mail: jausman{at}uic.edu).
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