GIANT ANEURYSMS
Ricardo A. Hanel, M.D., Ph.D. Department of Neurosurgery, Mayo Clinic, Jacksonville, Florida
Robert F. Spetzler, M.D. Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona Reprint requests: Robert F. Spetzler, M.D., c/o Neuroscience Publications, Barrow Neurological Institute, 350 West Thomas Road, Phoenix, AZ 85013. Email:
[email protected] Received, December 18, 2007. Accepted, March 31, 2008.
ONLINE DIGITAL VIDEO
SURGICAL TREATMENT OF COMPLEX INTRACRANIAL ANEURYSMS COMPLEX INTRACRANIAL ANEURYSMS include not only giant aneurysms (classically larger than 25 mm in diameter) but also smaller aneurysms in difficult locations of the human brain and cranial base. Such lesions are associated with a high risk of subarachnoid hemorrhage and progressive neurological deterioration or death caused by mass effect or stroke. In the past 30 years, the understanding and treatment of these lesions have progressed considerably. Nonetheless, a deep understanding of these lesions, including the nuances of blood flow dynamics, natural history, and potential therapeutic options, is necessary when one is managing such aneurysms. The senior author’s (RFS) clinical experience with more than 5000 brain aneurysms was reviewed. We also reviewed recent literature on the surgical management of giant cerebral aneurysms, focusing on the most up-to-date microsurgical techniques. Combinations of therapies can be used in an attempt to provide a solution to various clinical dilemmas associated with the management of these difficult lesions. The synergistic association between microsurgery and endovascular modalities is also illustrated. On the basis of the knowledge obtained over the years, indirect and multimodality approaches are becoming more common as neurosurgeons strive to improve patient outcomes. KEY WORDS: Cerebral revascularization, Complex aneurysm, Giant aneurysm, Microneurosurgery Neurosurgery [SHC Suppl 3]:SHC1289–SHC1299, 2008
G
iant and complex intracranial aneurysms are among the most challenging lesions faced by neurosurgeons. The poor natural history of these lesions is related to their mass effect on the surrounding brain tissue, to emboli that can dislodge to downstream vascular territory, and to their high risk for rupture compared with that of other aneurysms. The complexity of these lesions usually makes their treatment more difficult, and they are associated with a high incidence of complications. Consequently, considerable expertise is required to manage such lesions. Detailed preoperative planning includes magnetic resonance imaging (MRI), computed tomographic angiography (CTA), and catheter-based angiography. Balloon test occlusion of the parent vessel can often provide additional valuable information for surgical planning. The treatment of complex aneurysms should be based on a balance between the risks associated with each treatment and its benefit to the patient. Although preoperative planning serves as a guide for each procedure, surgeons must be prepared to respond to clinical scenarios as they arise. Depending on intraoperative findings, procedures often begin with the options of direct clipping, wrapping, and potential bypass. Thus, surgeons should be familiar with all aspects of cerebrovascular surgery, including cranial base approaches for ideal exposure, proximal and dis-
NEUROSURGERY
DOI: 10.1227/01.NEU.0000318092.86562.F
tal control, advanced clipping and wrapping skills, and bypass and microsuturing techniques. We reviewed the senior author’s (RFS) experience with complex intracranial aneurysms obtained from more than 5000 treated aneurysms. Strategies for treating these lesions are emphasized, including the decision to treat, preoperative planning, use of cranial base approaches, and surgical techniques.
DEFINITION Classically, giant intracranial aneurysms are defined as lesions with a diameter of greater than 25 mm (15). Many other features also play a critical role in defining the complexity of an aneurysm: its location, previous treatments, and the presence or absence of collateral circulation, intraluminal thrombus, and calcification of the aneurysmal wall. Similar technical challenges are found with some lesions smaller than 25 mm, which are termed complex intracranial aneurysms. The same principles of treatment are applicable to both giant and complex intracranial aneurysms. The biological nature and behavior of saccular and fusiform aneurysms probably differ from those of complex aneurysms. For the sake of simplicity, however, we consider both in the discussion of the general principles that follows.
VOLUME 62 | NUMBER 6 | JUNE 2008 SUPPLEMENT | SHC1289
HANEL AND SPETZLER
EPIDEMIOLOGY Only about 5% of intracranial aneurysms are giant (1, 9, 23). A significantly greater proportion of giant aneurysms occur in the pediatric population (5). Typically, these lesions involve segments of the internal carotid artery (ICA), especially the cavernous and paraclinoid segments, followed by the vertebrobasilar region. The remainder involve primarily the middle cerebral artery (MCA) and anterior cerebral artery (1, 5). Morphologically, giant aneurysms are typically divided into saccular and fusiform types. Fusiform aneurysms tend to arise in the territories of the vertebrobasilar arteries and MCAs. The most common clinical presentations are subarachnoid hemorrhage, intracerebral hemorrhage, or both (1, 9, 17). Other manifestations include mass effect, occlusion of perforating vessels, distal embolic events, and seizures. Occasionally, asymptomatic lesions are found incidentally on noninvasive imaging.
NATURAL HISTORY The natural history of untreated giant cerebral aneurysms is remarkably poor. In the International Study for Unruptured Intracranial Aneurysms, Wiebers et al. (25) reported that the 5year incidence of rupture was 40% for anterior and 50% for posterior circulation giant aneurysms or 8 to 10% per year. In the series of Peerless et al. (18), the mortality rate of patients who did not present with hemorrhage was higher than 60% within 2 years, and all surviving patients had marked neurological disabilities. The prognosis was even worse for patients who became symptomatic with subarachnoid hemorrhage.
TREATMENT PLANNING Treatment of giant and complex aneurysms requires careful planning, with meticulous acquisition and review of all needed information before treatment. The choice of therapeutic modality and approach is based on this information. Different imaging modalities can add important information. Computed tomographic scanning is best for the evaluation of calcification. MRI is ideal for evaluation of the presence of intraluminal thrombus, perilesional edema, and possible associated infarcts. Both CTA and magnetic resonance angiography allow three-dimensional reconstruction of the lesion and its surroundings to facilitate preoperative visualization of surgical challenges. After clipping procedures, CTA is the noninvasive method of choice for evaluating residual or recurrent aneurysms. Magnetic resonance angiography is best for evaluating aneurysms in need of coiling. Although used less frequently for cerebral aneurysms in general, catheter-based angiography is often used to evaluate complex giant aneurysms as recent improvements in noninvasive images modalities (i.e., CTA and magnetic resonance angiography) have become available. This option can provide valuable information about the direction of blood flow and the possibility of assessing collateral flow to a given vascular territory. Rotational catheter-based angiography with three-dimensional
SHC1290 | VOLUME 62 | NUMBER 6 | JUNE 2008 SUPPLEMENT
reconstruction provides the most accurate evaluation of the aneurysmal neck and is important for treatment planning.
Balloon Test Occlusion and the Allcock Test Much refined since its introduction by Matas (16) in 1911, temporary carotid occlusion offers valuable information during preoperative planning for complex aneurysms. With known limitations regarding its predictive value, temporary occlusion of a major cranial vessel allows surgeons to assess the viability of collateral flow and, occasionally, to improve their understanding of the anatomy of the lesion. For example, during the treatment of giant cavernous aneurysms, the results of temporary occlusion can indicate the type of flow replacement needed. If balloon occlusion is tolerated, no replacement or, more often, a superficial temporal artery (STA)-to-MCA bypass is indicated. If, however, temporary occlusion evokes neurological deficits, a high-caliber conduit is needed to replace target vessel flow. The use of Allcock’s test (Patient 2) allows surgeons to assess the patency and caliber of the posterior communicating arteries, information that is especially important when aneurysms of the basilar artery are treated (3, 19). Balloon test occlusion was originally described as angiographic injection of the vertebral artery simultaneously with unilateral compression of the carotid artery. However, improved catheter and balloon technology now allows variations in which the basilar artery proximal to the aneurysm can be temporarily occluded safely to simulate sacrifice of the basilar artery.
TREATMENT General Considerations The goal of treatment of giant intracranial aneurysms is to exclude the lesion from the circulation while preserving function in the neural tissues fed by the parent vessel. A multidisciplinary approach that includes both surgical and endovascular expertise is often needed to manage such complex lesions. To discuss the options for endoluminal treatment and reconstruction for giant and complex intracranial aneurysms is beyond the scope of this article. However, they should be considered when treatment is planned. Advances in endovascular technology such as modified stents (covered, partially covered, or low porosity) and new embolic agents will probably improve therapeutic options for these complex lesions. Combined morbidity and mortality rates for the surgical treatment of unruptured giant aneurysms (including cognitive dysfunction) vary between 20 and 45%, depending on the location of the aneurysm and the patient’s age. Older patients and patients with posterior circulation lesions tend to have the poorest outcomes (25). Contemporary rates of surgical mortality for treated giant aneurysms, whether ruptured and unruptured, vary from 6 to 22% (6, 12, 20). Good or excellent outcomes have been reported in 61 to 87% of patients (6, 12, 20). Patients who become symptomatic with subarachnoid hemorrhage and mass effect have the worst surgical outcomes (12).
www.neurosurgery-online.com
SURGICAL TREATMENT OF COMPLEX INTRACRANIAL ANEURYSMS
Patients harboring giant aneurysms tend to be older than those with smaller aneurysms (5). They also tend to have multiple medical comorbid conditions and a higher risk for complications associated with general anesthesia. Compared with less complex lesions, giant aneurysms have a higher rate of arterial wall calcifications, atherosclerotic plaque, and intraluminal thrombus. These features complicate direct clip reconstruction. Occasionally, adjunctive treatment techniques, including profound hypothermia and circulatory arrest and flow redirection with or without flow augmentation/ replacement, are necessary. Each adjunct incurs an independent risk for complications. At our center, the decision making process for treating these lesions is individually tailored in each patient. All of the above factors are considered and weighed against the risks associated with each potential intervention. Depending on the strategy needed to secure an aneurysm, the surgical morbidity and mortality rates for these patients vary tremendously, from 10 to 15% for direct clipping and an in situ graft as needed to approximately 30% when circulatory arrest and hypoperfusion are recommended.
Cerebral Protection and Intraoperative Monitoring For many years at this institution, barbiturate-induced electroencephalographic burst suppression has been routine during the treatment of intracranial aneurysms. These agents are most effective when administered before periods of ischemia. They reduce cerebral blood volume and metabolism, which helps protect the brain. During periods of circulatory arrest, mild hypertension is also used to maximize collateral blood flow. Somatosensory evoked potentials and motor evoked potentials are recorded in all vascular procedures; additional monitoring is used on the basis of the anatomic area being manipulated.
TABLE 1. Selection of surgical approach based on location of complex aneurysma Cranial base approach OZ craniotomy tailored to lesion (mini-modified, modified, or full OZ)
Location Supraclinoid ICA, ICA bifurcation, proximal ACA, MCA
OZ, interhemispheric
Distal ACA
OZ
Basilar artery apex, SCA
Far lateral
Vertebral artery
Far lateral, suboccipital
PICA
Far lateral, petrosal
VB junction
OZ, petrosal or far lateral
AICA, midbasilar trunk
a OZ, orbitozygomatic; ICA, internal carotid artery; ACA, anterior cerebral artery; MCA, middle cerebral artery; SCA, superior cerebellar artery; PICA, posterior inferior cerebellar artery; VB, vertebrobasilar; AICA, anterior inferior cerebellar artery.
Surgical Technique Fundamental principles of aneurysm surgery are especially important when one is treating the most challenging aneurysms. Obtaining proximal and distal vascular control, sharp dissection, meticulous preservation of perforators, circumferential dissection of the aneurysm, and the surgical exposure that minimizes neural damage is far more difficult to achieve with giant aneurysms, which often have a calcified neck and intraluminal thrombus.
Surgical Exposure The use of cranial base approaches (Fig. 1) to enhance exposures and to minimize damage to and retraction of neural tissue has been standard for 15 years. Many articles from this institution have addressed the application and value of such approaches for common locations involving giant aneurysms (Table 1) (4, 7, 8, 11–14, 22). For lesions involving the anterior circulation, we routinely use the orbitozygomatic (OZ) craniotomy and its variants (mini-modified, modified, or full OZ) (Fig. 2) tailored to the amount of exposure necessary for a given lesion. For lesions involving the posterior circulation, one or a combination of the following approaches is used (Fig. 3): OZ craniotomy and its variants, the transpetrosal approach (Fig. 4), and the far-lateral approach. When necessary, additional dissection with removal of the posterior clinoid and clivus (i.e., the transcavernous approach) can be used to enhance exposure of the proximal basilar artery (2, 4).
Proximal and Distal Vascular Control FIGURE 1. Cranial base approaches (shaded areas) for giant aneurysms. The appropriate approach can provide access to almost all vascular lesions. Courtesy of Barrow Neurological Institute.
NEUROSURGERY
Proximal and distal vascular control is a basic principle of aneurysm surgery that is especially important when complex lesions are treated. The aneurysmal wall of giant lesions is often thick, atherosclerotic, and relatively unlikely to rupture intraoperatively. Nonetheless, the size of the body of the aneurysm
VOLUME 62 | NUMBER 6 | JUNE 2008 SUPPLEMENT | SHC1291
HANEL AND SPETZLER
A
B
FIGURE 2. Comparison of pterional (A) and orbitozygomatic (OZ) (B) craniotomies. The OZ craniotomy increases the angle of attack and minimizes brain retraction. Courtesy of Barrow Neurological Institute.
FIGURE 3. Illustration of selected approach for each area of the vertebrobasilar system, which can be divided into five segments. The upper two-fifths of the basilar artery can be accessed via an OZ craniotomy, the middle fifth via a petrosal approach, and the lower twofifths via a far-lateral craniotomy. Courtesy of Barrow Neurological Institute.
FIGURE 4. Variants of the transpetrosal approach to access aneurysms of the posterior circulation. Courtesy of Barrow Neurological Institute.
SHC1292 | VOLUME 62 | NUMBER 6 | JUNE 2008 SUPPLEMENT
itself precludes visualization of the circumference of the lesion, preventing appropriate circumferential dissection. When vascular control is achieved, the surgeon can arrest blood flow to the lesion and proceed with one of several maneuvers, such as suction decompression, opening and resection of the aneurysmal contents, and endarterectomy of the aneurysmal wall. For aneurysms of the ICA, such as ophthalmic and other aneurysms of the paraclinoid region, proximal control can be obtained by exposing the cervical carotid artery. Other options, such as exposure of the petrous carotid artery via Glasscock’s triangle, exposure of the clinoid segment with an anterior clinoidectomy, and endoluminal occlusion with balloons at different levels, including at the neck of the aneurysm, have been described (13, 24). For lesions of the anterior cerebral arteries and MCAs, proximal control can often be obtained without difficulty. Exposure of a proximal segment of vessel to enable vascular control of lesions of the posterior circulation is far more difficult to obtain. For these lesions, maximal surgical exposure is essential to obtain successful vascular control. Hypothermic circulatory arrest offers the ultimate in vascular control. The indications for this technique are decreasing as advances are made in bypass techniques and endovascular neurosurgery. Nonetheless, circulatory arrest permits the surgeon to work in a bloodless surgical field with no risk of aneurysmal rupture. The aneurysmal wall can be collapsed to gain a crucial few millimeters of exposure. Relaxation of the aneurysm also allows dissection and preservation of the perforating arteries. Ponce et al. (unpublished data) recently summarized the senior author ’s (RFS) experience with this technique. These authors retrospectively reviewed 105 patients (65 women and 40 men; mean age, 44.8 yr) who underwent 107 deep hypothermic circulatory arrest procedures between 1985 and 2005. Of 97 posterior circulation aneurysms, 60 involved the basilar apex. Seven patients harbored anterior circulation aneurysms. The perioperative mortality rate was 13.3% (14 patients). Follow-up was available from 84 of the 91 patients discharged after the procedure (92.3%). Of these, 65 patients were the same or better after surgical intervention (77% of those who survived), 10 patients were worse, and nine patients had died. The mean postoperative Glasgow Outcome Scale score was 4. If the perioperatively deceased group is analyzed with the patients available for follow-up, the combined morbidity and mortality rate was 33%. However, the cause of death for the nine patients deceased at the time of follow-up cannot be known precisely, and these patients could skew the data. An encouraging result was that at the time of follow-up the annual hemorrhage rate after microsurgical clipping under cardiac standstill was 0.5% per year, and 92% of the patients had required no further treatment of their aneurysm. These data demonstrate that deep hypothermic circulatory arrest remains an important treatment for complex and giant posterior circulation aneurysms. When compared with the natural history of these aneurysms, the risks associated with cardiac standstill are acceptable. Given the relatively high morbidity and mortality rates associated with this technique, it is
www.neurosurgery-online.com
SURGICAL TREATMENT OF COMPLEX INTRACRANIAL ANEURYSMS
reserved for highly selected patients for whom all other surgical and endovascular options have been exhausted.
operative ultrasonography and routine intraoperative cerebral angiography have been used (10). More recently, the advent of indocyanine green (ICG) videoangiography (21) has allowed surgeons to assess the same parameters with this less-invasive method. ICG videoangiography consists of an intravenous injection of a fluorescent dye (ICG) that can be visualized through the vessel wall on the areas exposed to light from a surgical microscope. A special infrared filter allows the fluorescent dye in the vessel lumen to be recorded. This method has allowed us to reduce the use of intraoperative angiography to about 20% of the aneurysms operated on (RF Spetzler, unpublished data). Angiography is reserved for patients in whom ICG videoangiography does not clarify the presence of stenosis or occlusion in the parent vessel or filling of residual aneurysm because the parent vessel cannot be visualized or because of heavy calcification or atheromatous plaque in the vessel. The main goal of this article is to illustrate the principles discussed above that are well known to many vascular and general neurosurgeons through selected videos, which provide a live demonstration of many of these strategies and direct application on a case-by-case basis.
Tactics for Aneurysm Repair Many strategies can be used to repair aneurysms. The selection of the optimal technique for any given lesion is the essence of maximizing outcomes. Direct exposure of the aneurysm and clip reconstruction of the parent vessel is the most common strategy. Variations include clip-wrapping or wrapping only. When the direct approach is infeasible or judged to have an exceedingly high risk, alternative approaches can be used (13). Primary proximal vessel occlusion (Hunterian ligation), distal vessel occlusion, and trapping with or without flow replacement (bypass) are often common options. When the anatomy permits, aneurysms can be excised with or without an interposition graft to reestablish blood flow. Aneurysmorrhaphy can also be applied.
Intraoperative Imaging To minimize complications, many different modalities have been used intraoperatively to assess the results of aneurysmal repair and preservation of the parent vessel. Traditionally, intra-
A
B
E
F
FIGURE 5. Giant aneurysm of the midbasilar trunk treated via a transpetrosal approach with direct clipping under hypothermic circulatory arrest (see text for description). A, C–H, courtesy of Barrow Neurological Institute, Phoenix, Arizona. B, from, Bambakadis NC, Gonzalez LF, Amin-
NEUROSURGERY
C
G
D
H
Hanjani S, Deshmukh VR, Porter RW, Daspit PC, Spetzler RF: Combined skull base approaches to the posterior fossa. Technical note. Neurosurg Focus 19:E8, 2005.
VOLUME 62 | NUMBER 6 | JUNE 2008 SUPPLEMENT | SHC1293
HANEL AND SPETZLER
A
B
stem compression. CTA (Fig. 5C) and diagnostic cerebral angiography (Fig. 5, D and E) confirmed the presence of a giant saccular aneurysm of the basilar artery just above the origin of the anterior inferior cerebellar arteries. Given the location of the lesion at midclivus, a decision was made to use a right-sided transpetrosal approach. Because the size of the aneurysm would probably preclude vascular control, hypothermic circulatory arrest was used. The parent vessel was reconstructed by direct clipping (Fig. 5, F–H).
Learning Points
D C
F
Arrest of blood flow to an aneurysm through temporary occlusion of the proximal vessel, temporary proximal and distal occlusion, or circulatory arrest allows an aneurysm to relax and provides the surgeon the opportunity to complete circumferential dissection of the aneurysm while preserving adjacent neurovascular structures. When formulating a clipping strategy, surgeons should consider the possibility that occlusion with a single large clip may be ineffective because the closing force at the tip of the clip is low. Placing clips in series takes advantage of the relatively high closing forces of smaller clips and increases surgeons’ freedom to design the reconstruction of the parent vessel. Ideally, as illustrated in this patient, the clip or clips should be applied parallel to the direction of blood flow. The use of a fenestrated clip allows manipulation of the aneurysm sac through the open area of the clip. Additional clips can be used to close the remaining neck at the area of the fenestration.
Patient 2: Parent Vessel Occlusion
E
(see video at web site)
G
An 11-year-old boy presented with progressive headaches but no neurological deficits. Computed tomographic scanning of the head (Fig. 6A) showed a 25-mm, partially thrombosed aneurysm of the basilar apex. Conventional angiography (Fig. 6B) and CTA (Fig. 6C) showed a lesion with a broad base, involving the origin of both superior cere-
A
FIGURE 6. Giant aneurysm of the partially thrombosed basilar apex treated via an OZ craniotomy, posterior clinoid drilling, and sacrifice of the basilar artery (see text for description). Courtesy of Barrow Neurological Institute.
ILLUSTRATIVE CASES Patient 1: Direct Clipping Under Circulatory Arrest
(see video at web site)
B
C FIGURE 7. Giant aneurysm of the left cavernous internal carotid artery (ICA) treated with a left cervical ICA-to-middle cerebral artery (MCA) radial graft bypass and proximal occlusion of the carotid artery (see text for description). Courtesy of Barrow Neurological Institute.
A 51-year-old man presented with complaints of headache and double vision. Computed tomographic scans (Fig. 5A) and MRI (Fig. 5B) scans showed the presence of a large aneurysm with significant brain-
SHC1294 | VOLUME 62 | NUMBER 6 | JUNE 2008 SUPPLEMENT
www.neurosurgery-online.com
SURGICAL TREATMENT OF COMPLEX INTRACRANIAL ANEURYSMS
A
B
D
C
E
F
communicating artery, a left OZ approach was chosen. Proximal vascular control required drilling the posterior clinoid process. Once the aneurysm was exposed, the parent vessel was sacrificed by placing a clip proximal to the origin of the superior cerebellar arteries. Postoperative angiography (Fig. 6F) performed 24 hours after surgery showed changes in blood flow that lead to aneurysmal thrombosis. There was no blood flow inside the aneurysm (arrow at origin of posterior cerebral artery). After basilar artery sacrifice, blood flow on the apex of the basilar artery up to the origin of the SCAs was redirected and was no longer directed by the basilar artery into the aneurysm. The flow in the proximal basilar artery via the vertebral artery was good (Fig. 6G), with the aneurysm clip occluding the vessel (arrow).
Learning Points As illustrated in the video, the transcavernous dissection can be tailored to the exposure needed in each patient. In this patient, only the posterior clinoid needed to be drilled to expose the basilar artery proximal to the aneurysm. Although direct clipping of the aneurysm under hypothermic cardiac arrest was an option for this patient, many features led to the decision to sacrifice the basilar artery instead. Good collateral blood flow to the basilar apex via the right posterior communicating artery, involvement of the aneurysm with one superior cerebellar artery, and the effectiveness of sacrificing the basilar artery guided the intraoperative decision. The change in blood flow through the aneurysm induced by proximal or distal occlusion or both can be applied effectively in many different situations, in association with flow replacement, if necessary. In these complex cases, the vertebral and basilar arteries can also be sacrificed (19).
Patient 3: Parent Vessel Occlusion with Radial Artery Bypass A 61-year-old woman presented with complete left ophthalmoplegia. Cerebral angiography showed bilateral giant aneurysms of the cavernous ICA (Fig. 7, A and B). Given the symptomatic nature of the lesion, a decision was made to treat the left-sided aneurysm first. A left OZ craniotomy was performed with a cervical ICA-to-MCA bypass and occlusion of the ICA proximal to the aneurysm (Fig. 7C).
G
FIGURE 8. Giant aneurysm of the left M2 resected via a left OZ craniotomy by direct anastomosis of M2 and two M3 branches (figureeight and superficial temporal artery (STA)-to-M3 anastomosis) (see text for description). Courtesy of Barrow Neurological Institute.
bellar arteries. Allcock’s test variant with temporary occlusion of the basilar artery and injections of the right (Fig. 6D) and left ICA (Fig. 6E) showed a patent posterior communicating artery on the right side. The decision was made to approach the lesion for possible direct clipping under hypothermic circulatory arrest rather than sacrificing the proximal basilar artery. On the basis of the contralateral posterior
NEUROSURGERY
Learning Points Whether cerebral bypass is or is not associated with parent vessel occlusion, this technique is an appealing option for treating giant aneurysms in many locations. Revascularization, which has traditionally been used when the collateral circulation was judged insufficient after test occlusion, can be used when collateral blood flow is present. In fact, in some patients, the change in blood flow induced by the graft can lead to thrombosis of the aneurysm. In the present patient, we selected the cervical ICA as the proximal site of anastomosis. A shorter interposition graft can be used, and the ICA can be occluded proximal to the aneurysm.
Patient 4: Aneurysm Excision with Figure-eight Anastomosis of M2 to Two Separate M3 Branches Plus an STA-to-M3 End-to-end Anastomosis (see video at web site) A 39-year-old man presented with memory loss, occasional trouble finding words, and unremarkable results for a neurological examina-
VOLUME 62 | NUMBER 6 | JUNE 2008 SUPPLEMENT | SHC1295
HANEL AND SPETZLER
A
B
C
D
F
G
H
I
J
E
FIGURE 9. Giant partially thrombosed aneurysm of the left MCA treated via a left OZ craniotomy, double-barrel STA-to-MCA bypass, partial distal occlusion of the parent vessel, and complete coil occlusion of the aneurysm (see text for description). Courtesy of Barrow Neurological Institute.
tion. MRI of the head (Fig. 8A) showed a giant partially thrombosed aneurysm of the left MCA. Conventional angiography showed an M2 aneurysm (Fig. 8, B and C). A left OZ craniotomy was performed to explore the aneurysm. During dissection, two large branches were found arising from the aneurysm, one of which was a short trunk, next to a bifurcation point. Proximal and distal vascular control was obtained. The aneurysm was dissected circumferentially and removed. While one of the distal branches was being prepared for anastomosis, the short trunk was resected. Two individual branches were then left for anastomosis to the proximal M2. A figure-eight anastomosis was used (Fig. 8D) to join these two branches to the proximal M2. The STA was used to revascularize the other M3 branch. Postoperative angiography confirmed patency of the figure-eight anastomosis between M2 and two separate M3 branches (Fig. 8, E and F; arrows, anastomosis site) as well as patency of the STA-to-M3 anastomosis (Fig. 8G).
Learning Points Depending on the local anatomy, an aneurysm can be resected via a primary in situ end-to-end anastomosis. A short arterial graft interposition can also be used. When the craniotomy is performed, preservation of the STA, which can serve as a versatile donor for grafting, should always be attempted. When treating such challenging lesions,
SHC1296 | VOLUME 62 | NUMBER 6 | JUNE 2008 SUPPLEMENT
surgeons should be ready to create solutions for potential misadventures during surgery.
Patient 5: Combined Microsurgical and Endovascular Approach with a Double-barrel STA-to-MCA Bypass Plus Endovascular Aneurysm Occlusion (see video at web site) A 51-year-old man presented with a transitory loss of speech. The differential diagnoses were seizure and a transient ischemic attack. Results of MRI of the brain were unremarkable for ischemic lesions. However, a large mass in the left sylvian fissure, highly suggestive of a giant partially thrombosed MCA aneurysm (Fig. 9A), was seen. CTA (Fig. 9, B and C), conventional angiography (Fig. 9D), and a threedimensional angiographic reconstruction (Fig. 9E) showed a giant partially thrombosed aneurysm with a serpiginous vascular channel as the residual lumen of the aneurysm. A left OZ craniotomy was performed with the intention of performing a double-barrel STA bypass into both branches of the left MCA distal to the aneurysm followed by partial clip occlusion of the MCA branches distal to the aneurysm (Fig. 9F). Postoperatively, the patient had a new episode of speech loss that responded to elevating his blood pressure with vasoactive drugs.
www.neurosurgery-online.com
SURGICAL TREATMENT OF COMPLEX INTRACRANIAL ANEURYSMS
Angiography showed residual flow in the serpiginous channel of the left MCA. Temporary balloon occlusion (Fig. 9G) dramatically increased blood flow in the bypass (Fig. 9H). A decision was made to proceed with coil occlusion of the residual aneurysm lumen (Fig. 9I). Computed tomographic perfusion after coil occlusion of the left MCA showed no evidence of hypoperfusion (Fig. 9J).
Learning Points Again, this patient illustrates the utility of the STA for cerebral revascularization in patients with giant aneurysms. A double-barrel graft, divided to each branch of the MCA distal to the aneurysm, was used to increase blood flow. To reduce the risk of a postoperative ischemic event, we decided to occlude the MCA branches distal to the aneurysm only partially. This maneuver decreased the demand on the bypass because the patient’s symptoms resolved when perfusion was augmented. Endovascular coil occlusion of the residual conduit lumen created demand for the bypass, improving perfusion and resolving the patient’s symptoms. This aneurysm nicely illustrates the synergy between microneurosurgery and endovascular neurosurgery as complementary methods. A wise combination of available therapeutic modalities improves overall outcomes for this patient population. Although current endoluminal treatment for giant intracranial aneurysms has several limitations, it can be considered as an initial therapeutic modality or in association with microsurgery on a case-by-case basis.
CONCLUSION The use of microneurosurgical techniques in the treatment of complex intracranial aneurysms continues to be crucial to successful outcomes. A team approach that includes both microsurgical and endovascular techniques should be used to optimize treatment for patients on a case-by-case basis to ensure the best possible outcomes for this challenging population. The evolution of techniques and technology and their judicious use in both microsurgery and endovascular neurosurgery are key to improving the results of treating these lesions.
REFERENCES 1. Barrow DL, Alleyne C: Natural history of giant intracranial aneurysms and indications for intervention. Clin Neurosurg 42:214–244, 1995. 2. Dolenc VV, Skrap M, Sustersic J, Skrbec M, Morina A: A transcavernoustranssellar approach to the basilar tip aneurysms. Br J Neurosurg 1:251–259, 1987. 3. Drake CG: The treatment of aneurysms of the posterior circulation. Clin Neurosurg 26:96–144, 1979. 4. Figueiredo EG, Zabramski JM, Deshmukh P, Crawford NR, Preul MC, Spetzler RF: Anatomical and quantitative description of the transcavernous approach to interpeduncular and prepontine cisterns. Technical note. J Neurosurg 104:957–964, 2006. 5. Fox JL: Intracranial Aneurysms. New York, Springer-Verlag, 1983. 6. Gewirtz RJ, Awad IA: Giant aneurysms of the anterior circle of Willis: Management outcome of open microsurgical treatment. Surg Neurol 45:409–421, 1996. 7. Henn JS, Lemole GM Jr, Ferreira MA, Schornak M, Preul M, Spetzler RF: Black holes of the brain: How to reach challenging areas of the cerebrum. Clin Neurosurg 49:19–26, 2002. 8. Hsu FP, Clatterbuck RE, Spetzler RF: Orbitozygomatic approach to basilar apex aneurysms. Neurosurgery 56:172–177, 2005. 9. Khurana VG, Piepgras DG, Whisnant JP: Ruptured giant intracranial aneurysms. Part I—A study of rebleeding. J Neurosurg 88:425–429, 1998.
NEUROSURGERY
10. Klopfenstein JD, Spetzler RF, Kim LJ, Feiz-Erfan I, Han PP, Zabramski JM, Porter RW, Albuquerque FC, McDougall CG, Fiorella DJ: Comparison of routine and selective use of intraoperative angiography during aneurysm surgery: A prospective assessment. J Neurosurg 100:230–235, 2004. 11. Lawton MT, Daspit CP, Spetzler RF: Technical aspects and recent trends in the management of large and giant midbasilar artery aneurysms. Neurosurgery 41:513–521, 1997. 12. Lawton MT, Spetzler RF: Surgical management of giant intracranial aneurysms: Experience with 171 patients. Clin Neurosurg 42:245–266, 1995. 13. Lawton MT, Spetzler RF: Surgical strategies for giant intracranial aneurysms. Neurosurg Clin N Am 9:725–742, 1998. 14. Lemole GM Jr, Henn JS, Spetzler RF, Riina HA: Surgical management of giant aneurysms. Oper Tech Neurosurg 3:239–254, 2000. 15. Locksley HB: Natural history of subarachnoid hemorrhage, intracranial aneurysms and arteriovenous malformations. Based on 6368 cases in the cooperative study. J Neurosurg 25:219–239, 1966. 16. Matas R: Testing the efficiency of the collateral circulation as a preliminary to the occlusion of the great surgical arteries. Ann Surg 53:1–43, 1911. 17. Onuma T, Suzuki J: Surgical treatment of giant intracranial aneurysms. J Neurosurg 51:33–36, 1979. 18. Peerless SJ, Wallace MD, Drake CG: Giant intracranial aneurysms, in Youmans JR (ed): Neurological Surgery: A Comprehensive Reference Guide to the Diagnosis and Management of Neurosurgical Problems. Philadelphia, W.B. Saunders Co., 1990, ed 3, pp 1742–1763. 19. Pelz DM, Viñuela F, Fox AJ, Drake CG: Vertebrobasilar occlusion therapy of giant aneurysms. Significance of angiographic morphology of the posterior communicating arteries. J Neurosurg 60:560–565, 1984. 20. Piepgras DG, Khurana VG, Whisnant JP: Ruptured giant intracranial aneurysms. Part II—A retrospective analysis of timing and outcome of surgical treatment. J Neurosurg 88:430–435, 1998. 21. Raabe A, Nakaji P, Beck J, Kim LJ, Hsu FP, Kamerman JD, Seifert V, Spetzler RF: Prospective evaluation of surgical microscope-integrated intraoperative near-infrared indocyanine green videoangiography during aneurysm surgery. J Neurosurg 103:982–989, 2005. 22. Spetzler RF, Riina HA, Lemole GM Jr: Giant aneurysms. Neurosurgery 49:902–908, 2001. 23. Sundt TM Jr, Piepgras DG, Fode NC, Meyer FB: Giant intracranial aneurysms. Clin Neurosurg 37:116–154, 1991. 24. Thorell W, Rasmussen P, Perl J, Masaryk T, Mayberg M: Balloon-assisted microvascular clipping of paraclinoid aneurysms. Technical note. J Neurosurg 100:713–716, 2004. 25. Wiebers DO, Whisnant JP, Huston J 3rd, Meissner I, Brown RD Jr, Piepgras DG, Forbes GS, Thielen K, Nichols D, O’Fallon WM, Peacock J, Jaeger L, Kassell NF, Kongable-Beckman GL, Torner JC: Unruptured intracranial aneurysms: Natural history, clinical outcome, and risks of surgical and endovascular treatment. Lancet 362:103–110, 2003.
COMMENTS
G
iant aneurysms have always been a formidable challenge for vascular neurosurgeons. The field continues to evolve, and the drive for direct neck clipping in every case has been softened by the adoption of alternative approaches. In this report, Dr. Spetzler focuses on the array of options available to treat complex and giant aneurysms as demonstrated by his extensive experience. Returning to the days of Hunterian ligation, proximal occlusion, or trapping, with or without bypass, has been applied more liberally in recent years. Even with cardiac standstill techniques, some giant aneurysms, especially at the basilar apex and at the MCA trifurcation, cannot be safely clipped. The presence of perforators or involved branches often limits our ability to perform safe clip reconstructions. As shown in Illustrative Case 2, proximal basilar occlusion is probably the best approach for true giant basilar apex aneurysms. With direct clipping, even under ideal circumstances, sparing the thalamoperforates is only a 50/50 proposition.
VOLUME 62 | NUMBER 6 | JUNE 2008 SUPPLEMENT | SHC1297
HANEL AND SPETZLER
At this time, endovascular options for giant aneurysms are largely limited to proximal occlusion, often with a preliminary surgical bypass procedure. Currently approved stent technology cannot usually address the broad necks of giant aneurysms, and packing coils in giant aneurysms has not been shown to be curative or to improve the natural history of these lesions. However, future stent designs, some already under investigation, may allow for new methodology of parent vessel reconstruction, providing additional options for treating giant aneurysms. Robert A. Solomon New York, New York
T
he authors have provided a concise yet elegant review of the clinical decision making and surgical management of complex intracranial aneurysms, including several highly illustrative case studies. These rare and difficult lesions require creative management strategies utilizing all of the skills of the cerebrovascular surgeon. As illustrated by the case studies in this article, the definition of a “complex” aneurysm includes more than large size. Additional features, such as neck calcification, intraluminal thrombus, complex neck morphology, and undesirable location, may render an otherwise innocuous aneurysm a complex and highly challenging lesion to manage. Although no definition of “complex aneurysm” is universally agreed upon, the experienced cerebrovascular surgeon will generally recognize the complexity with appropriate preoperative imaging studies. As emphasized by the authors, multiple imaging techniques assist in identifying the complexity of an aneurysm prior to planning and executing treatment. Computed tomography to identify calcifications within the sac and particularly within the neck is highly valuable in determining potential intraoperative challenges. Magnetic resonance imaging will demonstrate associated intraluminal thrombus that may not be apparent on digital subtraction angiography. Balloon test occlusion is useful in determining collateral blood flow and a patient’s potential tolerance of parent vessel sacrifice. Occasionally, the complexity of an intracranial aneurysm is not recognized until the lesion is explored surgically. This fact emphasizes the need for the operating surgeon to be flexible and creative in planning and carrying out the operative procedure. We routinely attempt to preserve the superficial temporal artery when approaching most brain aneurysms and agree with the authors that utilizing this very versatile blood supply allows for creative, and often unexpected, treatment strategies that evolve during the surgical procedure. Optimal management of complex aneurysms requires close collaboration among cerebrovascular surgeons and endovascular experts. Despite the shortcomings of endovascular therapy in treating many of these complex aneurysms, new advances in endovascular technology provide innovative and novel strategies for managing many of these lesions, either alone or combined with surgical treatment. Despite the rapid advances in endovascular technology, the field of microsurgery has not been static during the past 2 decades. Many of the important adjuncts to microsurgical treatment of intracranial aneurysms are illustrated in this article and include cranial base exposures; three-dimensional rotational angiography; brain protection, including hypothermic circulatory rest; more liberal use of temporary clips; modern aneurysm clips with multiple innovative designs, including fenestrations and multiple angles; use of extracranial-to-intracranial bypass; intraoperative angiography; intraoperative indocyanine green videoangiography; and interventional neuroradiology. As care for patients with complex cases such as these becomes regionalized, neurovascular surgeons and cerebrovascular teams will
SHC1298 | VOLUME 62 | NUMBER 6 | JUNE 2008 SUPPLEMENT
be required to collaborate effectively as they are asked to deal with increasingly complex and challenging lesions. Alexander Mason Daniel L. Barrow Atlanta, GA
T
he authors provide us with a review of giant and complex aneurysms. They emphasize the complexity of these lesions and the demands that they can place on the neurosurgical team. Despite their uncommon occurrence, the lesions often do require treatment due to their high risk of rupture. These authors reinforce the value of complete understanding of the anatomy of the lesion as defined on computed tomography, magnetic resonance, and digital subtraction angiography. In addition, the value of balloon test occlusion and the Allcock test can provide further information, which is important in determining the surgical strategy and whether to incorporate a bypass and what caliber bypass. The authors illustrate cases of direct clip reconstruction, parent vessel occlusion, occlusion and bypass, in situ bypass with end-to-end anastomosis, and combined surgical and endovascular treatment. At our institution, the neurovascular team assesses giant and complex aneurysms. Imaging such as computed tomographic angiography, magnetic resonance, magnetic resonance angiography, and digital subtraction angiography are routinely performed. In addition, balloon test occlusion is often performed to further assess the consequences of vessel sacrifice (deconstructive) procedures, such as Hunterian ligation or aneurysm trapping with or without bypass (low-flow vs. high-flow). Given a favorable clinical condition, surgical therapies are favored due to the high recurrence rate from standalone endovascular therapy. Often the surgical treatment is combined with endovascular strategies during the procedure in order to provide proximal control and soften the aneurysm (suction decompression). Postoperative assessment includes conventional digital subtraction angiography. These authors have illustrated the demanding and creative strategies necessary to treat these complex and giant aneurysms. A strategy that reconstructs the normal vessel lumen is ideal, but not always achievable. When reconstructive strategies are not feasible, deconstructive techniques are deployed with or without flow augmentation to eliminate the aneurysm from the circulation and protect against the severe consequences of SAH. In the current era, endovascular treatment can be combined with open surgical techniques to improve patient outcome. Daniel Surdell H. Hunt Batjer Chicago, IL
T
his is a nice piece of work showing the state of the art in the changing world. The pain, but also the happiness of success in treating these challenging patients, can be seen in the text, between the lines, and in the beautiful videos. The Helsinki and Kuopio Finnish collective’s experience of more than 10,000 patients with cerebral aneurysms treated is very similar to the one presented here (1). We have selected differently in the following: 1) We have never used extracorporeal circulation, despite having done preparatory steps towards it. This might be based on the cooperation with the late Dr. Drake, and his negative experience in some of the early cases among his total of 900 giant aneurysms treated (2). 2) We never adopted wide use of orbitozygomatic approaches after an initial trial. We have found useful variations in the treatment of these difficult cases with the help of different lowand high-flow bypasses, and short-term use of transient cardiac stand-
www.neurosurgery-online.com
SURGICAL TREATMENT OF COMPLEX INTRACRANIAL ANEURYSMS
still by intravenous administration of Adenosine, and with our simple, fast approaches (3–6, 8). The current paper shows what a unit at the top of the vascular microneurosurgical world can and, in fact, should do. Patients with vascular lesions should be centralized in similar centers of excellence for better results (7). Reza Dashti Istanbul, Turkey Mika Niemelä Juha A. Hernesniemi Helsinki, Finland
1. Dashti R, Hernesniemi J, Niemelä M, Rinne J, Porras M, Lehecka M, Shen H, Albayrak BS, Lehto H, Koroknay-Pal P, Sillero R, Perra G, Ronkainen A, Koivisto T, Jääskeläinen JE: Microneurosurgical management of middle cerebral artery bifurcation aneurysms. Surg Neurol 67:441–456, 2007. 2. Drake CG, Peerless SJ, Hernesniemi JA: Early surgery for ruptured vertebrobasilar aneurysms. J Neurosurg 80:643–649, 1994. 3. Hernesniemi J, Ishii K, Niemelä M, Kivipelto L, Fujiki M, Shen H: Subtemporal approach to basilar bifurcation aneurysms: advanced technique and clinical experience. Acta Neurochir 94 [Suppl]:31–38, 2005. 4. Hernesniemi J, Ishii K, Niemelä M, Smrcka M, Kivipelto L, Fujiki M, Shen H: Lateral supraorbital approach as an alternative to the classical pterional approach. Acta Neurochir 94 [Suppl]:17–21, 2005. 5. Hernesniemi J, Niemelä M, Kivipelto L, Ishii K, Rinne J, Ronkainen J, Kivisaari R, Shen H, Karatas A, Lehecka M, Frösen J, Piippo A, Jääskeläinen J: Some collected principles of microneurosurgery: simple and fast, while preserving normal anatomy: a review. Surg Neurol 64:195–200, 2005. 6. Nagy L, Toth S, Ishii K, Shen H, Karatas A, Vajda J, Niemelä M, Jääskeläinen J, Hernesniemi J: Water dissection technique of Toth for opening neurosurgical cleavage planes. Surg Neurol 65:38–41, 2006. 7. Niemelä M, Koivisto T, Kivipelto L, Ishii K, Rinne J, Ronkainen A, Kivisaari R, Shen H, Karatas A, Lehecka M, Frösen J, Piippo A, Jääskeläinen J, Hernesniemi J: Microsurgical clipping of cerebral aneurysms after the ISAT Study. Acta Neurochir 94 [Suppl]:3–6, 2005. 8. Randell T, Niemelä M, Kyttä J, Tanskanen P, Määttänen M, Karatas A, Ishii K, Dashti R, Hernesniemi J: Principles of neuroanesthesia in aneurysmal subarachnoid hemorrhage: The Helsinki experience. Surg Neurol 66:382–388, 2006.
T
his article presents a general overview of the surgical treatment of complex intracranial aneurysms, together with a collection of five videos that demonstrate the technical skill and ingenuity of the senior author (RFS). A team approach that combines microsurgical and endovascular techniques is evident in these cases. Decreasing indications for hypothermic circulatory arrest, intraoperative angiography, and full orbitozygomatic craniotomy are noteworthy and have been accompanied by increasing indications for bypasses, endovascular
techniques, indocyanine green videoangiography, and modified orbitozygomatic approaches. Techniques like the “figure-eight anastomosis” (Illustrative Case 4) show that even though endovascular therapies evolve and expand in their scope, there is always room for more creative microsurgical solutions for complex aneurysms. Michael T. Lawton San Francisco, CA
I
n this review, Hanel and Spetzler have reviewed the status of surgical treatments for complex brain aneurysms, drawing upon the senior author’s (RFS) extensive experience, expertise, and innovation in this area. The treatment of complex and giant aneurysms is continuously evolving at present due to the innovation of various endovascular treatment methods. The most recent addition to this armamentarium is the “pipeline stent,” which works on the principle of flow diversion. However, intravascular stents are associated with long-term issues of in-stent stenosis and aneurysm recurrence, and the results of endovascular techniques are still disappointing with respect to giant aneurysms. Microsurgery is therefore expected to play a major role in the management of complex aneurysms in the next 5 to 10 years, at least. The techniques available for microsurgical management include clip reconstruction of the aneurysm, bypass with aneurysm occlusion or trapping, and deep hypothermic circulatory arrest-assisted clipping. The role of these techniques will depend upon a number of factors, which include the patient’s age and comorbidities, expected natural history of the aneurysms, and the individual surgeon’s (or surgical team’s) experience with these techniques, as well as whether the aneurysm is a recently ruptured one. Based on my personal experience and the experience in the UW Aneurysm Treatment Center in recently ruptured aneurysms, I prefer clip reconstruction or balloon-assisted coiling whenever possible, bypass techniques only when absolutely needed, and intravascular stents only for rescue during endovascular emergencies. In unruptured aneurysms, both stent-assisted coiling and bypass-assisted clipping or trapping have a greater role to play. In my view, the role of the deep hypothermic circulatory arrest technique is greatly diminished nowadays, due to both the unpredictability of the results, even when the operation goes perfectly well, and the complexity of the operation. The challenge we are faced with now is how to train a future generation of neurosurgeons who can actually perform both these complex operations and endovascular surgery. Due to the diminished operative experience available, the demand for excellent results, and the long training time needed, it is more difficult to train vascular surgeons for microsurgery than for endovascular surgery. Laligam N. Sekhar Seattle, WA
NEUROSURGERY OFFICIAL JOURNAL OF THE CONGRESS OF NEUROLOGICAL SURGEONS
NEUROSURGERY
VOLUME 62 | NUMBER 6 | JUNE 2008 SUPPLEMENT | SHC1299
