by Christopher S.
Aneurysm & AVM Center
INTRACRANIAL ANEURYSMS: CURRENT STRATEGIES OF MANAGEMENT:
affecting management decisions | Management
scheme | Figures
| Other sources of information
A giant intracranial aneurysm
is defined as one larger than 2.5 cm in diameter. Treatment of large (2-2.5 cm)
and giant aneurysms has traditionally been associated with a higher morbidity
and mortality than smaller lesions. Giant aneurysms are thought to represent about
5-8% of all intracranial aneurysms. Size does not influence the hemorrhage rate,
and approximately 25% of patients present with subarachnoid hemorrhage. Seventy
to seventy-five percent of patients with giant aneurysm present with mass effect,
usually manifest by visual failure, cranial nerve dysfunction, hemiparesis, seizure
or headache. Thrombosis and stroke due to blood clot formation within the aneurysm
and subsequent distant embolus, occurs in some 2-5% of patients with giant aneurysms.
Sixty percent of giant aneurysms occur on the internal carotid artery. An additional
10% occur in the anterior communicating artery region, with 10% occurring in the
middle cerebral artery. Fifteen percent of these giant lesions occur at the top
of the basilar artery, and approximately 5% arise from the vertebral artery.
Several different strategies are currently available
to manage giant aneurysms. This stems from the fact that no single technique is
effective in dealing with all giant aneurysms. Current treatment options for these
lesions include direct surgical techniques, endovascular techniques, and combined
approaches. Regarding surgery, the aneurysm can be attacked directly with clipping
and resection of the mass lesion, or aneurysmorrhaphy with vessel reconstruction.
Indirect surgical techniques include proximal occlusion and trapping of the aneurysm
using clips or ligature above and below the lesion. Alternatively, if the patient
is unable to tolerate occlusion of the parent vessel in relation to a giant aneurysm,
an extracranial to intracranial bypass procedure can be performed with subsequent
trapping or proximal occlusion of the vessel. This typically arises as an issue
in internal carotid artery aneurysms. More recently, intracranial bypass procedures
have been described for reconstruction of the carotid artery with saphenous vein
grafts or aneurysm resection with middle cerebral artery reconstructions.
Endovascular techniques include balloon trapping
with balloons placed intravascularly above and below the giant aneurysm. Proximal
balloon occlusion is a useful and often used technique for giant internal carotid
artery aneurysms, specifically those arising within the cavernous sinus. If the
balloon occlusion is tolerated anywhere in the intracranial circuit, this technique
can be useful if the balloon can be placed adjacent to the aneurysm. Balloon placement
within the aneurysm was a technique which was associated with a significant morbidity
and therefore has largely been replaced by coil embolization of giant lesions.
Guglielmi detachable coils are another means of endovascular occlusion of giant
intracranial aneurysms. While there are some concerns regarding reshaping of the
coils once they are packed in giant aneurysms, and coil migration into thrombus
which is present in giant aneurysms, this overall strategy may provide a means
of treating carefully selected lesions.
Other treatment options for giant aneurysms include combined techniques. In this
approach, a surgical procedure such as an intracranial to extracranial bypass
can be performed prior to endovascular occlusion of the parent vessel. Alternatively,
bypass techniques can be combined with endovascular trapping of certain giant
aneurysms or intra-aneurysmal endovascular techniques.
consideration should be given prior to treatment of any giant aneurysm regarding
specific anatomic features. It is well known that critical perforating vessels
can arise from the aneurysm itself. In addition, parent vessels of origin may
be included in the aneurysmal wall as the aneurysm grows over time. Consideration
in direct surgical attack is that a thick, calcified wall may not accept an aneurysm
clip. In this instance, aneurysmorrhaphy (opening of the aneurysm and removing
intra-aneurysmal clot) may be necessary. If this is to be performed in an elderly
patient, careful consideration of risk must be balanced against other available
strategies to treat the aneurysm.
adjuncts have been developed to aid direct surgery for giant aneurysms. Techniques
of cardiac arrest allow for a slack aneurysm which can be dissected from surrounding
cerebral tissue. Temporary occlusion of the parent vessel can also allow decompression
of the aneurysm.
Since 1989, at
the MGH Aneurysm/AVM Center we have evaluated patients on a case by case basis
to find treatment strategies using direct microsurgical clipping or trapping,
extracranial to intracranial bypass followed by proximal endovascular parent occlusion,
or endovascular techniques alone. We have taken this approach in 56 giant aneurysms
in 54 patients. In considering each case, the patient's age, overall medical condition,
and the exact size and location of the aneurysm was taken into account prior to
deciding on the final treatment plan.
Presenting signs and symptoms were compressive (cranial nerve or cerebral tissue)
in 27 patients (50%). Subarachnoid hemorrhage was the presenting sign in 14 patients
(26%), and headache the presenting sign in 10 patients (18%). Seizures occurred
in 3 patients (6%). Most lesions occurred in the internal carotid artery (32 aneurysms)
with 7 occurring on the middle cerebral artery, 6 on the anterior cerebral artery
or anterior communicating artery, and 8 in the vertebrobasilar circulation. Three
aneurysms occurred on the posterior cerebral artery distally.
Of the 54 patients managed, 21 underwent direct surgical clipping or trapping
(39%). Eight patients (15%) had planned extracranial-intracranial bypass procedures
with proximal balloon occlusion. Endovascular balloon occlusion was used in 13
patients (24%). In these patients, 10 procedures were performed for proximal vessel
occlusion. Twelve patients (22%) had detachable coil therapy with the recently
available GDC (Guglielmi detachable coil) system.
Using a combined modality approach, excellent or good results were obtained in
48 patients (89%). A fair outcome (defined as having neurological deficit, able
to live at home but unable to return to work or previous lifestyle) occurred in
3 patients (5%), and a poor outcome occurred in 1 patient (2%). There were 2 deaths
in the series (4%).
With a variety of
techniques available to treat giant intracranial aneurysms, it seems appropriate
to try to tailor the management of each patient. As newer techniques are developed,
these must be incorporated into the standard management of giant aneurysms. Despite
advances in surgical and endovascular techniques, giant aneurysms still carry
a significant risk in terms of treatment, and in some patients, careful followup
without intervention is the best option. By using a multimodality approach in
the treatment of these lesions, it is hoped that morbidity and mortality will
Figure 1. Left. CT scan
of a 64 year old woman with a giant internal carotid artery aneurysm. A large
round density demonstrates calcification of the wall of the aneurysm with thrombus
within the lesion.
MRI scan of the patient shown in Figure A, demonstrating thrombus within the lesion
and a small area of the aneurysm which still fills with blood.
Figure 2. Left. Lateral angiogram
of the patient demonstrated in Figure 1. The internal carotid artery injection
demonstrates filling of the aneurysm. The lesion was deemed to be untreatable
with direct surgical attack, and for that reason a bypass graft was placed.
Right. Lateral angiogram of the patient
in Figure 2A after placement of an extracranial-to-intracranial bypass graft and
occlusion of the internal carotid artery using intravascular balloons proximal
to the aneurysm. Excellent filling of the middle cerebral artery was demonstrated,
and the patient had no neurologic deficit.
Figure 3. Left. Coronal MRI study
of a patient who presented with visual field cut and pituitary dysfunction. The
patient was found to have a partially thrombosed giant aneurysm.
Axial MRI study of the patient seen in Figure 3A. The hyperintense region of the
lesion is the area which remains patent. The remainder of the lesion was thrombosed.
Figure 4. Left. AP view of the
internal carotid angiogram demonstrating a giant aneurysm with a small neck. The
lesion was approachable surgically and could be clipped without difficulty.
Right. Postoperative AP angiogram demonstrating
complete obliteration of the aneurysm at the neck with an aneurysm clip. The aneurysm
could then be opened surgically and the thrombus removed, alleviating the patient's
symptoms of optic chiasm compression and endocrine abnormality.
Ojemann RG, Ogilvy CS, Heros RC, Crowell RM, eds. Surgical Management of Cerebrovascular
Disease, Third edition. Williams & Wilkins, Baltimore, in press.