J Neurosurg 84:63–70, 1996

Intraoperative endovascular surgery for cerebral aneurysms
GRANT SINSON, M.D., MATTHEW F. PHILIPS, M.D., AND EUGENE S. FLAMM, M.D.
Division of Neurosurgery, University of Pennsylvania School of Medicine,
Philadelphia, Pennsylvania
U The application of a number of procedures that can be considered intraoperative endovascular neurosurgery has
enhanced our ability to treat cerebral aneurysms from the abluminal surface. This study identifies a role for these techniques in the management of difficult aneurysms. A review of the last 1202 aneurysms undergoing direct clipping by
the authors disclosed that these methods were used in 62 cases. Of these aneurysms, 36 arose from the internal carotid artery, 12 from the middle cerebral artery, eight from the vertebrobasilar distribution, and six from the anterior cerebral artery.
The indications for applying these methods were large size (12–60 mm), intraluminal thrombus, broad neck, plaque
at the neck, the potential compromise of branches at the base of the aneurysm, or a combination of these problems.
The most frequently chosen intraoperative technique was suction decompression with direct removal of plaque and
thrombus using suction, dissection, and/or ultrasonic aspiration. The application of temporary clips was required in all
cases in which the aneurysm was opened before definitive clipping. No special pharmacological cerebral protective
regimen was used. In one case in which a greater occlusion time was anticipated, cardiopulmonary bypass with profound hypothermia was performed.
A favorable outcome was achieved in 73% of these difficult cases. An increased neurological deficit after surgery
was seen in 11%, and the mortality rate was 8%. These methods should be considered and can be anticipated before
surgery for unusual aneurysms. Many cases now being considered for embolization may be more suitable for definitive surgical obliteration.

KEY WORDS • cerebral aneurysm • endaneurysmectomy • endovascular therapy •
giant aneurysm • surgical technique • thrombectomy

ROXIMAL artery ligation to treat intracranial aneurysms has been shown to be less effective than the
direct surgical clipping of these aneurysms.26,36,54
Direct obliteration results in excellent long-term outcomes
and is now the preferred treatment.1,12,13,37,41,49,54,57 Interventional neuroradiological procedures have recently produced encouraging short-term results in treating some
of these lesions.9,19–24,34,35,51 These neuroradiological endovascular techniques have been used most commonly in
those aneurysms that are considered too difficult to approach surgically. An important adjunct in the treatment of
difficult aneurysms is the use of intravascular and intraluminal surgical maneuvers to facilitate the definitive surgical clipping of these lesions. Our experience with a variety of intraoperative techniques is reviewed.

P

Clinical Material and Methods
All cases of cerebral aneurysms treated surgically by
the senior author (E.S.F.) between 1973 and 1993 were
evaluated. Those cases in which intraoperative endovascular techniques were used before or during clip placement are the subject of this review. These endovascular
J. Neurosurg. / Volume 84 / January, 1996

techniques include: suction decompression, endaneurysmectomy, thrombectomy, and aneurysmorrhaphy. Aneurysm size alone was not a criterion for inclusion in the
study group. A subset of these cases was examined in
greater detail. This subset included patients who underwent surgery at the Hospital of the University of Pennsylvania during the 6-year period from 1988 through
1993. These patients represent cases treated in the setting
of readily available magnetic resonance (MR) imaging,
MR angiography (MRA), and modern interventional neuroradiological techniques.
All patients received perioperative phenytoin and
methylprednisolone and intraoperative mannitol. No other
pharmacological agent was used for cerebral protection.
Mild-to-moderate intraoperative hypothermia (core body
temperature to 32˚C) was induced in some cases. Temporary clips were used in most cases. During periods of
temporary occlusion the systolic blood pressure was
maintained above 130 mm Hg. Many patients had neurophysiological monitoring during the procedure.
Outcome was graded on a five-point scale. An excellent
outcome was defined as the patient returning to baseline
neurological status. A good outcome implied the presence
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G. Sinson, M. F. Philips, and E. S. Flamm
TABLE 1
Location of 1202 aneurysms treated surgically during the period
from 1973 to 1993*
Treatment

ICA

MCA

ACA

VB

Total

all aneurysms
525
243
treated surgically
aneurysms in which
36 (6.9) 12 (4.9)
surgical endovascular
techniques were used (%)

256

178

1202

6 (2.3)

8 (4.5) 62 (5.2)

* Abbreviations: ACA = anterior cerebral artery; ICA = internal carotid
artery; MCA = middle cerebral artery; VB = vertebrobasilar distribution.

of minimal deficit that did not significantly hinder the patient’s lifestyle. Fair outcomes were defined as patients
requiring some assistance with daily activities, whereas
those with poor outcomes needed significant amounts of
support. Death was the fifth outcome.
Results
A total of 1202 cases of cerebral aneurysms were treated. One or more intraoperative endovascular technique
was used in 62 (5.2%) of these cases. The aneurysm arose
from the internal carotid artery (ICA) in 36 (58.1%), the
middle cerebral artery (MCA) in 12 (19.4%), the vertebrobasilar distribution in eight (12.9%), and the anterior
cerebral artery (ACA) in six (9.7%) (Table 1).
A favorable outcome (excellent or good) was achieved
in 45 cases (72.6%). There were 12 (19.4%) fair or poor
outcomes and 5 (8.1%) deaths (Table 2). Seven patients
(11.3%) had increased neurological deficits after surgery.
These seven cases plus the five deaths result in a combined morbidity and mortality of 19.4% (12 patients).
During the 6 years reviewed in greater detail, 391
aneurysms were treated surgically. Surgical endovascular
techniques were used in 27 (6.9%) of these cases. The age
of the patients ranged from 19 to 74 years with a mean
of 54 years. The patients presented after hemorrhage
(44%), with symptoms of local mass effect (26%), or the
aneurysm was found incidentally (30%). The size of the
aneurysms ranged from 12 to 60 mm with a mean size of
33 mm. The outcomes of these patients were similar to the
entire population of patients (Table 2).
Also during this 6-year period, six patients underwent
radiological endovascular treatment for cerebral aneurysms. These cases represent 1.5% of all aneurysms treatTABLE 2
Outcome in patients with aneurysms treated by
intraoperative endovascular techniques
Treatment

all aneurysms treated surgically
1988 to 1993
aneurysms in which surgical
endovascular techniques were used
1973 to 1993
1988 to 1993

64

Good/
Excellent (%)

Poor/Fair
(%)

Dead
(%)

78.8

17.1

4.1

72.6
74.1

19.4
18.5

8.1
7.4

FIG. 1. Case 1. Contrast-enhanced computerized tomography
scan (left) demonstrating the right internal carotid artery aneurysm
extending upward and across the midline. Right anteroposterior
angiogram (right) revealing that only a 2-cm portion of the aneurysm remains patent.

ed during this period but do not include aneurysms that
were confined to the cavernous portion of the ICA. Two
of these patients underwent surgical exploration, and it
was discovered that the aneurysms could not be safely
clipped. The other four patients were treated primarily
with radiological endovascular techniques: two because
their poor neurological status precluded surgical intervention and two whose aneurysms were not believed to be
surgically approachable.
Indications cited for using surgical endovascular techniques included: 1) a broad aneurysmal neck, 2) the presence of intraluminal thrombus, 3) large aneurysm size, 4)
a firm plaque in the aneurysm neck, 5) the potential compromise of branches at the aneurysm base, or 6) a combination of these problems. The aneurysm was isolated with
temporary clips except in those cases in which the aneurysm arose from the proximal intracranial carotid artery.
In these instances proximal control of the aneurysm was
achieved by isolation of the cervical carotid artery.
Temporary clip time ranged from 0.5 to 60 minutes. Circulatory arrest with extreme hypothermia was used in one
case. The following are representative cases.
Case 1
Presentation. This 62-year-old man presented to another hospital with complaints of decreased appetite, difficulty standing, and severe headaches. These symptoms had
become most prominent during the week prior to admission. Diagnostic evaluation included: a lumbar puncture
that revealed xanthochromic cerebrospinal fluid, computerized tomography (CT) of the head demonstrating a right
hemisphere mass that extended across the midline, and a
cerebral angiogram that better defined the mass as an
aneurysm (Fig. 1). The aneurysm was 5 cm in diameter
and projected upward to the level of the foramen of
Monro. It arose from the right ICA and was partially
thrombosed, with the patent portion measuring 2 cm in
diameter. Neurological examination showed intact visual
fields, motor function, and speech. The patient was alert
and oriented but did have some difficulty with simple calculations and was noted to have a blunted affect.
Operation. After induction of general anesthesia, a lumbar subarachnoid catheter was placed and scalp electroencephalographic (EEG) electrodes were applied. The right
cervical common carotid artery and ICA were then isolatJ. Neurosurg. / Volume 84 / January, 1996

Intraoperative endovascular aneurysm surgery

FIG. 2. Illustrations showing the operative management of Case 1. A: The anterior clinoid process has been removed,
the cervical internal carotid artery is occluded (not shown), and a temporary clip is positioned on the carotid artery distal to the aneurysm. B: After incising the aneurysm, the high-speed drill is used to enter and decompress the patent portion of the aneurysm. C: The calcified thrombus is dissected away from the aneurysm neck to permit clip placement.

ed with vascular loops. A right-sided pterional craniotomy
was performed. Retraction of the frontal and temporal
lobes after widely opening the sylvian fissure allowed
adequate visualization of the intracranial carotid artery,
the third cranial nerve, and the aneurysm, which was
markedly displacing the right optic nerve. The base of the
aneurysm was noted to be densely calcified and could not
be compressed. This calcification extended 1 cm up the
neck of the aneurysm.
To permit better visualization of the proximal aspect of
the aneurysm neck, the anterior clinoid process was then
removed using a high-speed drill. The cervical ICA was
occluded, and a temporary clip was placed on the intracranial ICA distal to the aneurysm. The aneurysm dome
was opened and a small amount of backbleeding from the
ophthalmic artery was encountered but was easily controlled with suction (Fig. 2). The calcification proved to
be quite firm and required the use of rongeurs and the
high-speed drill to fragment. Gradually the calcium was
removed until a thin vascular wall remained. Two aneurysm clips were used to obliterate the aneurysm neck and
preserve the ICA. The temporary occlusion of the carotid
artery was removed (Fig. 3). The occlusion time was 20
minutes and there were no changes noted in the EEG.
Because of its large size, the remaining aneurysm mass
was removed. This was done without difficulty.
Postoperative Course. After surgery the patient was alert
and had intact visual fields. He demonstrated a mild leftsided hemiparesis and worsening of his confusion. The
weakness and mental status deficits improved over the
next few months. At his 3-month follow-up examination
he was neurologically intact.

headaches. Her neurological examination was normal.
Subsequent MR imaging and angiography revealed a 3cm aneurysm at the bifurcation of the right ICA (Fig. 4).
She underwent surgical exploration at another hospital;
however, involvement of the anterior choroidal artery
(AChA) with the aneurysm precluded its clipping. The
patient was transferred to the Hospital of the University of
Pennsylvania where it was decided that a second attempt
would be made at surgical obliteration of the aneurysm.
Operation. Scalp EEG electrodes were placed after induction of general anesthesia. The patient’s existing craniotomy incision and bone flap were then reopened.
Retraction of the frontal lobe demonstrated that the aneurysm arose from the posterior wall of the ICA. Multiple
branches of the AChA and perforating branches from the

Case 2
Presentation. This 46-year-old woman underwent a

CT scan of the head because of a 1-month history of
J. Neurosurg. / Volume 84 / January, 1996

FIG. 3. Case 1. Intraoperative photograph showing final clip
placement. The neck of the aneurysm is obliterated with two
straight clips on the remaining vascular wall.

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G. Sinson, M. F. Philips, and E. S. Flamm

FIG. 4. Case 2. Coronal T1-weighted magnetic resonance image (left) showing a right internal carotid bifurcation aneurysm that is fully patent. Lateral (center) and anteroposterior (right) angiograms better define the origin of the aneurysm.

top of the carotid artery bifurcation and the posterior
communicating artery (PCoA) were seen draped over the
dome of the aneurysm. These branches were dissected
from the aneurysm dome to permit passage of clip blades.
At this point the patient’s temperature had been cooled to
32˚C and her systolic blood pressure was raised to 130
mm Hg. Temporary clips were applied to the proximal
ICA, the ACA, and the MCA. Despite the temporary
clips, the aneurysm remained tense; therefore, a fourth
temporary clip was placed on the large PCoA (Fig. 5 left).
Three fenestrated clips were used to obliterate the aneurysm neck while preserving flow in the ICA and its
branches. To facilitate final clip adjustments, suction decompression was performed using a 23-gauge butterfly
needle. After each clip adjustment the patency of the
aneurysm was tested by releasing only the temporary clip
on the PCoA. All temporary clips were then removed after
an occlusion time of 15 minutes (Fig. 5 right). There were
no EEG changes seen during the period of temporary
occlusion. A microvascular Doppler probe was used to

confirm flow in the major branches arising from the carotid artery.
Postoperative Course. The patient was neurologically
normal after surgery except for a palsy of the third cranial
nerve. At her 2-month follow-up examination her third
nerve dysfunction had completely resolved and she remained neurologically intact.
Case 3
Presentation. This 54-year-old man presented to another hospital after experiencing an extremely severe headache. Neurological examination revealed a short-term
memory deficit and mild confusion. There were no focal
signs on the examination. He had also been receiving
psychiatric treatment for a 2-year history of altered personality.
A CT scan revealed a 6-cm left hemisphere mass with
calcifications and fresh subarachnoid blood. An MR image demonstrated a large flow void within the partially

FIG. 5. Case 2. Intraoperative photographs. Left: Placement of temporary clips to completely isolate the aneurysm
prior to final dissection and clip placement. Temporary clips are placed on (clockwise from the upper right) the posterior communicating artery, middle cerebral artery, anterior cerebral artery, and proximal internal carotid artery (ICA).
Right: After final clip placement, three fenestrated aneurysm clips have reconstructed the ICA without compromising
patency of the branches.

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Intraoperative endovascular aneurysm surgery

FIG. 6. Case 3. Sagittal T1-weighted magnetic resonance (MR) image (A) showing the patent portion of the aneurysm
arising from the left internal carotid bifurcation, surrounded by a large amount of thrombosed aneurysm. Axial T2-weighted MR image (B) also demonstrating the patent portion of the aneurysm as well as the surrounding edema from this large
lesion. A lateral (C) and anteroposterior (D) angiogram better highlight the origin of the aneurysm from the carotid bifurcation.

thrombosed aneurysm (Fig. 6A and B). Angiography confirmed the aneurysm arising from the bifurcation of the
left ICA (Fig. 6C and D). Approximately one-third of the
aneurysm was patent.
Operation. After induction of general anesthesia, a left
pterional craniotomy was performed. Care was taken to
preserve the superficial temporal artery. Fresh subarachnoid clot was visualized. The supraclinoid ICA was exposed, the PCoA identified, and the AChA was seen and
dissected from the body of the aneurysm. The ACA and
MCA were then isolated distal to the aneurysm. After
cooling the patient to 32˚C, temporary clips were applied
to the supraclinoid ICA (distal to the PCoA) and the
MCA and ACA. The aneurysm ceased pulsating but remained tense. Suction decompression was performed with
a 19-gauge needle. Despite decompression, the aneurysm
could not be clipped because of the clot within the aneurysm neck. The aneurysm was then incised and the thrombus in the region of the neck was removed with a combination of gentle dissection and ultrasonic aspiration. This
permitted placement of the aneurysm clip parallel to the
parent vessel, which preserved flow into the vessel’s
branches (Fig. 7). Temporary clips were removed after a
20-minute occlusion time.
Because of the significant mass effect of the aneurysm
on the left hemisphere, the ultrasonic aspirator was then
used to remove a large amount of thrombosed material
from the aneurysm dome. No attempt was made to remove the dome of the aneurysm or to separate it from the
brain.
Postoperative Course. The patient had no new deficits
after surgery. His confusion resolved within 1 week and
the short-term memory deficit improved over the next 6
months. He was then able to return to work.
Discussion
Treatment Options for Difficult Cerebral Aneurysms
Operative obliteration of aneurysms by placing a clip at
the neck was first introduced by Dandy11 in 1937. Advances in neurosurgery since then have made this surgical
J. Neurosurg. / Volume 84 / January, 1996

intervention much safer than it was in Dandy’s time. The
concept, however, of curing the defect in the vessel wall
by reapposing two portions of the normal endothelial surface has been very successful. Large series of aneurysms
repaired in this way have shown very low recurrence
rates. Yasargil57 reported the results of operations in 355
patients between 1979 and 1983, with a rerupture rate
of 0.6%. Other groups have shown a rerupture rate from
0.14% to 1.0%.13,29,41 Many of these cases of recurrent
hemorrhage have been shown to occur in aneurysms that
had residual angiographic filling after clipping.12,13,29,41 In
fact, many consider that a completely clipped aneurysm
has no significant chance of recurring.37,54,56
Extraordinary aneurysms exist that challenge our ability to apply this standard approach. Recent advances in
neuroangiography have led to the capability of approaching these aneurysms from a different direction, the in-

FIG. 7. Case 3. Intraoperative photograph demonstrating final
clip placement. The remaining aneurysm wall can be seen on both
sides of the aneurysm clip and the hole in the aneurysm is blocked
by the hub of the clip. Prior to decompression of the aneurysm, the
rigid wall continued to force the clip blades downward and thereby obstructed flow in the middle cerebral artery.

67

G. Sinson, M. F. Philips, and E. S. Flamm
travascular space. The placement of coils into the aneurysm itself can halt any angiographic filling.25 Some institutions have documented significant experience with these
techniques;9,19–22,34,51 however, long-term data do not yet
exist which demonstrate that the outcome in these patients
is as good as in those who have had the aneurysm completely obliterated surgically. These techniques clearly
remain experimental.19,24,35
This review includes aneurysms that were treated surgically, yet required specialized techniques in addition to
adequate dissection and clip application. We believe that
being prepared to perform a number of intraoperative endovascular treatments increases the chances of successfully obliterating these aneurysms without compromising
normal blood flow. Many of these techniques require preoperative preparations and therefore their use must be
anticipated during surgical planning rather than during
aneurysm dissection.
Specific Intraoperative Endovascular Techniques
Cerebral Protection. Many of these cases require intraoperative regional or local circulatory arrest, which places
portions of the brain at risk for ischemia. Some authors
advocate the use of barbiturate coma during periods of
ischemia.45,49 Others use etomidate for cerebral protection,
citing fewer cardiovascular side effects.4,5 Laboratory data
and recent data from both neural trauma and ischemia
experience have suggested a beneficial effect of mild
hypothermia on cerebral ischemia and outcome.8,10,18,27,31,
38,55
A decrease of 1˚C can result in a reduction of cerebral
metabolism by 7%.40 Currently we induce hypothermia to
32˚C in all cases that may require temporary vessel occlusion. The potentially adverse cardiac or coagulation effects reported with more severe hypothermia are avoided
by not lowering the temperature further.28,46 During periods of temporary vessel occlusion the systolic blood pressure is also maintained above 130 mm Hg to maximize
collateral flow to regions of potential ischemia. Patients
receive mannitol and phenytoin perioperatively for their
effects on brain relaxation and seizures, respectively.
Circulatory Control. Circulatory control can be achieved
by many methods: locally with temporary clips, regionally with occlusion of the cervical carotid artery, or systemically using cardiopulmonary bypass. All of these techniques achieve the same goal of reducing or halting blood
flow through the aneurysm. This permits additional dissection around the slack aneurysm, reduces the risk of
hemorrhage during this dissection, and allows for opening
of the aneurysm to evacuate plaque or clot that may prevent accurate clip placement. Whereas many aneurysms
can be isolated with temporary clips alone, those located
on the proximal intracranial carotid artery require an alternative approach. We prefer to achieve temporary occlusion and proximal control during early dissection of
the aneurysm by exposure of the cervical carotid artery.
Having the ability to perform cardiopulmonary bypass for
systemic circulatory arrest during aneurysm surgery is
important.2,47,49 In this series, however, only one case that
required endovascular access necessitated the use of a
bypass.
Various attempts have been made to quantify the period
of time that vessels can be safely occluded.5,50,54 Different
68

intraoperative protocols make this data difficult to summarize, especially given the wide variability seen even
within specific series.50,54 Samson, et al.,43 have shown
that temporary arterial occlusion in the distribution of the
perforating arteries of the distal basilar artery and the horizontal segment of the MCA may be the most hazardous.
It is not yet clear whether intermittent reperfusion is helpful or detrimental during periods of temporary arterial
occlusion.17,42,43,48,53
Intraoperative Instrumentation. Specific instrumentation
that is useful intraoperatively includes: 1) electrophysiological monitoring; 2) a suction decompression device;
3) the ultrasonic aspirator; and 4) the microvascular Doppler monitor. The interpretation of electrophysiological
data (EEG, somatosensory evoked potentials, or brainstem auditory evoked responses) can be difficult intraoperatively, but with the aid of an experienced electrophysiologist, this information can be helpful.39 Other
groups have demonstrated the ability of evoked potential
monitoring to signal the onset of clinically significant, yet
reversible, ischemia.16,32,33,39,44 In cases that may require
prolonged intraoperative temporary vessel occlusion, preoperative temporary balloon occlusion with the patient
awake can be helpful.
Many different devices have been described for performing a suction decompression.6,14,52 Any apparatus that
does not significantly interfere with the surgeon’s view
and working area can be used. We continue to use a butterfly needle that has had the wings removed and is then
attached to a suction device, which has variable strength
and can be controlled by the surgeon.14 Although we are
comfortable with this direct technique of suction decompression, the cervical carotid artery suction decompression for proximal ICA aneurysms appears to be an excellent alternative.6,52 In those cases that require removal of
thrombus from the inside of the aneurysm, the ultrasonic
aspirator is helpful.15,37 This device permits rapid yet gentle removal of even organized thrombus.
The microvascular Doppler monitor has been useful in
many cases. We use this tool routinely to confirm the absence of flow in the aneurysm dome after clipping and
prior to puncturing the aneurysm.30 In this series the Doppler was most useful after reestablishing local blood flow
by confirming flow through the parent vessel and even
smaller vessels whose origin may have been near the aneurysm neck. This technique is rapid, noninvasive, and
easily interpreted. Intraoperative angiography is used by
others to evaluate clip placement on difficult aneurysms.3,5
With the use of the Doppler monitor we have not found
angiography to be a necessity; however, there are undoubtedly a small number of cases in which an intraoperative angiogram may be helpful.
Aneurysm Obliteration. Once confronted with an aneurysm that cannot be directly clipped, despite circulatory
isolation and maximum dissection, various endovascular
options must be considered. In those cases in which circulatory isolation cannot be completely achieved (Case 2),
the aneurysm may not slacken significantly after the application of temporary clips. The use of suction decompression can help to further decompress the aneurysm.6,14,52
Decompressing the aneurysm prior to clip application
helps achieve an accurate placement of the blades to
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Intraoperative endovascular aneurysm surgery
reconstitute the parent vessel. The puncture of the dome
should be done in a portion of the aneurysm that will not
result in the suction device interfering with eventual clip
placement or further dissection.
If thrombus is present in the aneurysm, it may also
interfere with dissection and clip placement. An MR image will reveal this preoperatively and can be useful in
surgical planning. Thrombus that is encountered after
opening an aneurysm can often be removed with gentle
dissection or the ultrasonic aspirator.15,37 Of course, the
goal of initial thrombus removal is only to allow enough
dissection to permit clip placement and then reestablish
flow through the parent artery. After this has been
achieved, additional clot may be removed, especially in
those aneurysms that have presented because of symptoms associated with the aneurysm’s mass. However, care
must be taken to avoid injury to perforating vessels that
are still adherent to the remaining aneurysm wall.
A firm plaque present in the aneurysm neck can usually be seen as yellow, atherosclerotic changes in the aneurysm wall. The presence of calcium can often be
visualized preoperatively on a CT scan. Fortunately, atherosclerotic changes do not always indicate that the neck
cannot be directly clipped. In those cases in which the
plaque is clearly preventing placement of an aneurysm
clip, an endarterectomy of the aneurysm neck can be performed.25,37,49
An injury near the aneurysm’s base may result in a
neck that cannot hold an aneurysm clip and requires an
aneurysmorrhaphy (the use of a portion of the aneurysm
wall to reconstruct the parent vessel using either fenestrated aneurysm clips or direct suturing techniques).7,37,56 This
is a difficult and time-consuming maneuver but may provide the only chance to reestablish flow through the parent vessel.
All of these techniques require a certain amount of
working room, which is not always available. Use of traditional techniques such as aneurysm trapping (with or
without a vascular bypass procedure) should be considered in cases in which there exists limited exposure for
aneurysm dissection and manipulation.1,37,56 However,
using these intraoperative endovascular techniques we
rarely resort to aneurysm trapping and vascular bypass.
Surgical Outcome

Most large series of aneurysms have divided the aneurysms based on their size. This report includes aneurysms grouped by the degree of difficulty in their surgical obliteration. Therefore, larger aneurysms that could
be directly clipped are excluded, whereas smaller aneurysms that resisted a direct approach are included.
Given these parameters, we believe that a favorable outcome of 72.6% is acceptable. Ausman, et al.,1 reviewed 10
series of giant aneurysms presented between 1977 and
1990. With 690 total cases, an excellent to good outcome
occurred in 75.2%. The relative safety of these techniques
is also evident in that only 11.3% of our patients had
increased deficits postoperatively. The mortality rate of
8.1% also compares well with that seen in the 690 patients
reviewed by Ausman, et al.,1 who reported a 14.1% mortality rate.
J. Neurosurg. / Volume 84 / January, 1996

Conclusions
Radiological endovascular techniques were a useful adjunct to treatment in six of our cases. However, during the
period that these radiographic techniques were available,
98.5% of the aneurysms were treated with either traditional surgical methods or with those endovascular surgical techniques that we have described. A surgical cure for
cerebral aneurysms remains the standard by which newer
treatment modalities must be tested. The use of these
intraoperative endovascular techniques broadens the
range of aneurysms that are operable and therefore can be
obliterated surgically with an acceptable morbidity. These
techniques should be considered when planning an approach to treat difficult aneurysms.
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Manuscript received May 2, 1995.
Accepted in final form August 15, 1995.
Some of these results were presented at the 62nd annual meeting
of the American Association of Neurological Surgeons, San Diego,
California, April 9–14, 1994.
Address reprint requests to: Eugene S. Flamm, M.D., Division of
Neurosurgery, University of Pennsylvania School of Medicine,
3400 Spruce Street, Philadelphia, Pennsylvania 19104–4283.

J. Neurosurg. / Volume 84 / January, 1996