CLINICAL STUDIES GIANT VERTEBROBASILAR ANEURYSMS: ENDOVASCULAR TREATMENT AND LONG-TERM FOLLOW-UP Boris Lubicz, M.D. Department of Neuroradiology, Roger Salengro Hospital, University Hospital of Lille, Lille, France Xavier Leclerc, M.D., Ph.D. Department of Neuroradiology, Roger Salengro Hospital, University Hospital of Lille, Lille, France Jean-Yves Gauvrit, M.D. Department of Neuroradiology, Roger Salengro Hospital, University Hospital of Lille, Lille, France Jean-Paul Lejeune, M.D., Ph.D. Department of Neurosurgery, Roger Salengro Hospital, University Hospital of Lille, Lille, France Jean-Pierre Pruvo, M.D., Ph.D. Department of Neuroradiology, Roger Salengro Hospital, University Hospital of Lille, Lille, France Reprint requests: Boris Lubicz, M.D., Service de Neuroradiologie (EA 2691), Hôpital Roger Salengro, Centre Hospitalier Régional Universitaire Lille, Boulevard J. Leclercq, 59037 Lille Cédex, France. Email: blubicz@hotmail.com Received, July 21, 2003. Accepted, March 1, 2004. OBJECTIVE: To report long-term imaging follow-up and clinical outcome of 13 patients with a giant vertebrobasilar aneurysm treated by parent artery occlusion (PAO). METHODS: From 1994 to 2000, 13 consecutive patients with a giant vertebrobasilar aneurysm were treated by PAO. Symptoms were related to mass effect in nine patients and to a subarachnoid hemorrhage in four. Endovascular treatment consisted of aneurysm trapping in nine patients and occlusion of one or both vertebral arteries in four. We assessed the clinical outcome and imaging findings in all patients during a 28-month period. RESULTS: Endovascular treatment resulted in clinical improvements in eight patients, worsening of symptoms in four, and death in one. One woman with a ruptured vertebral aneurysm died from a rebleeding after PAO without trapping. One man developed a brainstem infarction after lower basilar artery occlusion and incurred hemiparesis. In three patients, symptoms of mass effect increased after the procedure. Long-term follow-up revealed good or excellent clinical outcome in all patients and a sharp decrease in size of the thrombosed aneurysm in nine patients. One basilar aneurysm recanalized despite selective coiling and subsequent bilateral vertebral artery occlusion; one vertebral aneurysm and one basilar aneurysm did not decrease in size despite complete occlusion. CONCLUSION: Giant vertebrobasilar aneurysms are rare and challenging lesions for both neurosurgeons and neurointerventionalists. Their treatment by endovascular PAO remains safe and effective. Early clinical worsening may be observed, but long-term follow-up shows good or excellent results in most patients. This treatment can be carried out with minimal morbidity and mortality using clinical and angiographic monitoring. KEY WORDS: Endovascular treatment, Giant intracranial aneurysm, Parent artery occlusion Neurosurgery 55:316-326, 2004 G DOI: 10.1227/01.NEU.0000129477.15636.AE iant vertebrobasilar aneurysms (GVBAs) are rare and are associated with a poor prognosis (36, 39, 41, 42, 44, 47). Surgical clipping of giant aneurysms is considered a high-risk procedure because of the size of the aneurysm and of its neck, which is usually wide, leading to anticipated surgical difficulties (7, 17, 28, 39, 41, 48). Selective embolization with Guglielmi detachable coils (GDCs) constitutes another therapeutic option that has proven to be effective in small lesions (24, 32, 56). However, in the case of a giant aneurysm, complete occlusion is rarely achieved and, in time, the aneurysm often recurs (12, 35, 43). Previous studies have 316 | VOLUME 55 | NUMBER 2 | AUGUST 2004 www.neurosurgery-online.com shown that nonselective parent artery occlusion (PAO) was the most effective technique in cases of unclippable giant aneurysms, facilitating aneurysm thrombosis and symptom resolution (1, 5, 6, 9, 10, 19, 29, 47, 51). The purpose of this article is to report the longterm clinical and imaging findings of 13 consecutive patients with 13 GVBAs treated by nonselective embolization. PATIENTS AND METHODS Patients From January 1994 to July 2000, nonselective endovascular treatment was considered www.neurosurgery-online.com TREATMENT AND FOLLOW-UP OF GIANT VERTEBROBASILAR ANEURYSMS in 13 consecutive patients with a GVBA. There were 10 men and 3 women with a mean age of 48 years (range, 15–65 yr). Clinical findings are summarized in Table 1. Nine patients had symptoms of mass effect including headaches, gait disturbance, and pain. Four patients were admitted on an emergent basis with a subarachnoid hemorrhage (SAH) and were classified according to the Hunt and Hess scale (21): three patients were Grade II and one was Grade IV. The aneurysm involved the intracranial segment of the vertebral artery (VA) in 10 cases: proximal to the origin of the posteroinferior cerebellar artery (PICA) in five, distal to the origin of the PICA in four, and at the vertebrobasilar junction (VBJ) in one. The basilar artery (BA) was involved in three cases (basilar tip in one, middle third of the BA in one, and lower third of the BA in one). Allcock test (6, 39). A test occlusion was performed under neuroleptic analgesia in the remaining six patients treated by occlusion of the dominant VA or both VAs, or by lower BA occlusion. Patients received a bolus of 5000 IU at the start of the procedure, followed by a continuous infusion of 2500 to 3000 IU/h, with the aim of maintaining the activated clotting time at more than 300 seconds. Before balloon test occlusion, an Allcock test (6, 39) was performed and carotid arteries were compressed to demonstrate the patency and the size of the respective posterior communicating arteries. Then, patients underwent clinical and angiographic test occlusion. Femoral catheterization with a 4-French catheter was carried out to obtain selective angiograms and to confirm the collateral circulation from the contralateral vertebral artery. An 8-French catheter guide was inserted into the contralateral femoral artery and placed into the V1 segment of the VA. Through this catheter, a balloon was introduced and inflated into the extracranial segment of the VA or at the initial portion of the BA. Before 1996, we used a detachable latex balloon (Goldvalve Test Occlusion Seven patients who had a giant aneurysm of the nondominant VA underwent only four-vessel angiography with an TABLE 1. Characteristics of 13 patients with 13 giant vertebrobasilar aneurysmsa Clinical followup Aneurysm on followup MRA None Excellent 36 mo, size reduced VA occlusion None Good 48 mo, unchanged Yes Bilateral VA ⫹ basilar artery occlusion Brainstem infarction Good 48 mo, disappearance Yes VA occlusion None Good 36 mo, size reduced 0 VA occlusion None Good 12 mo, size reduced SAH IV VA occlusion None Death 45 SAH II Bilateral VA occlusion None Excellent 36 mo, recanalization VA 40 Headaches 0 VA occlusion None Excellent 36 mo, size reduced 64/F VA 30 Headaches, gait disturbance 0 VA occlusion None Excellent 24 mo, size reduced 10 42/M VA 25 SAH II VA occlusion None Excellent 24 mo, size reduced 11 65/M VA 30 Headaches, gait disturbance 0 Yes VA occlusion None Excellent 12 mo, size reduced 12 50/M BA 25 Headaches 0 Yes Bilateral VA occlusion None Excellent 12 mo, size reduced 13 60/M BA 30 SAH II Yes Bilateral VA occlusion None Excellent 12 mo, unchanged Hunt and Hess grade Test occlusion Patient no. Age (yr)/sex Aneurysm location Aneurysm size (mm) 1 47/M VA 40 Laterocervical pain 0 VA occlusion 2 48/M VA 40 Gait disturbance 0 3 15/M VBJ 60 Gait disturbance 0 4 52/M VA 40 Gait disturbance 0 5 36/F VA 25 Gait disturbance 6 50/F VA 25 7 65/M BA 8 29/M 9 a Symptoms Yes Treatment Complications MRA, magnetic resonance angiography; VA, intracranial segment of the vertebral artery; BA, basilar artery; VBJ, vertebrobasilar junction; SAH, subarachnoid hemorrhage. NEUROSURGERY VOLUME 55 | NUMBER 2 | AUGUST 2004 | 317 LUBICZ ET AL. No. 17 or 19; Nycomed, Paris, France). Since 1996, we have been using a latex balloon (X-ray, No. 1; Balt Extrusion, Montmorency, France) glued to a flow-directed microcatheter. To ensure temporary occlusion, the balloon was inflated until stasis of contrast material was apparent. The 30-minute VA test occlusion protocol included angiographic assessment of both contralateral VA and carotid arteries with continuous clinical monitoring. Collateral circulation was judged appropriate when the intracranial frontal view of the contralateral vertebral angiogram showed no delay between the cerebellar hemispheres at the venous phase of the angiogram. If the venous filling in the vascular territory of the occluded vessel occurred more than 0.5 second later, the angiogram was repeated after several minutes. If, after 30 minutes, no simultaneous venous filling was observed, the arterial suppleance was judged inefficient and no permanent occlusion was performed. The BA test occlusion included both carotid artery angiograms that assessed the retrograde filling of the BA through the posterior communicating arteries. The neurological status of the patients was continuously monitored by a trained neurologist who assessed speech, motor strength, sensory extinction, and level of alertness. Endovascular Procedure Patients with a GVBA who tolerated the test occlusion or had appropriate collateral circulation during the Allcock test (6, 39) underwent permanent PAO. Procedures were performed under full heparinization with the same protocol as the test occlusion. Heparin therapy was administered for 48 hours after occlusion, with patients receiving subsequent aspirin therapy for 6 months to avoid a distal embolism secondary to thrombosis. VA occlusions were performed with GDCs and/or detachable balloons (Goldvalve No. 17 or 19). The details of the GDC procedure have already been published (13, 56). Of 10 patients with a VA aneurysm, 8 underwent a trapping of the aneurysm by coils (Fig. 1), 1 was treated by occlusion of the parent vessel with coils placed proximal to the aneurysm, and 1 with a VBJ aneurysm underwent bilateral VA and lower BA occlusion (Fig. 2). This last patient was first treated by unilateral VA occlusion (detachable balloons), but angiographic control, performed 2 days later, showed an opacification of the aneurysm. A lower BA test occlusion was performed and tolerated before lower BA and bilateral VA occlusion with coils. In three patients with a giant BA aneurysm, staged (2–12 wk) bilateral VA occlusions were performed. One of these patients was initially treated by selective embolization in another institution, but a subsequent bilateral VA occlusion was performed because of regrowth of the aneurysm. After endovascular treatment, patients were transferred to the intensive care unit, and fluid balance, neurological status, and blood pressure were carefully monitored. Clinical and Imaging Follow-up Immediately after treatment, patients were evaluated by angiography to document aneurysm exclusion and patency of 318 | VOLUME 55 | NUMBER 2 | AUGUST 2004 FIGURE 1. Patient 4. Progressive gait disturbance in a 52-year-old man. A, axial T1-weighted MRI scan after gadolinium administration showing a partially thrombosed mass in front of the medulla. B, left vertebral angiogram showing a giant dysplastic aneurysm proximal to the PICA origin. C and D, right vertebral angiograms with (C) and without (D) subtraction showing the absence of aneurysm opacification after endovascular trapping with coils. E, control MRI scan 36 months after treatment showing a decrease in size of the thrombosed aneurysm. the parent vessel. Magnetic resonance imaging (MRI) follow-up was performed at 6, 12, 24, 36, and 48 months after treatment and included axial and coronal spin-echo T1- and T2-weighted sequences and three-dimensional time-of-flight magnetic resonance angiograms. Some patients were lost to follow-up after 12 or 24 months, so the mean duration of follow-up was 28 months (range, 12–48 mo). Conventional angiography was performed only in the case of MRI contraindications or if a recanalization was observed on magnetic resonance angiograms. A clinical examination by a senior neurosurgeon was obtained simultaneously with the imaging control examination. Clinical outcome was graded according to the Glasgow Outcome Scale (25), modified as follows: ex- www.neurosurgery-online.com TREATMENT AND FOLLOW-UP OF GIANT VERTEBROBASILAR ANEURYSMS cellent (neurologically intact); good (mild hemiparesis, cranial nerve palsy, or other deficit that does not interfere with daily functioning or work); fair (significant hemiparesis, aphasia, confusion, or other deficit that interferes with daily activities or prevents a return to work); and poor (coma or severe neurological deficit rendering the patient dependent on family or nursing staff). Angiographic films and MRI scans were reviewed by two senior neuroradiologists together (BL and XL). ILLUSTRATIVE CASES Case 1 A 52-year-old man (Patient 4) who complained of progressive gait disturbance underwent brain imaging that revealed a partially thrombosed mass in the posterior fossa (Fig. 1A). Conventional angiography (Fig. 1B) showed a 40-mm dysplastic aneurysm of the dominant VA proximal to the PICA. The patient was referred to our department for endovascular treatment, and a test occlusion of the left VA was performed and tolerated. The aneurysm was trapped with GDCs, and angiographic control images (Fig. 1, C and D), obtained at the end of the procedure, showed an occlusion of the parent artery and the aneurysm. A few hours after the treatment, the patient developed dysphagia and progressive loss of consciousness. He was kept intubated and on a ventilator, and intravenous corticosteroid therapy was administered for 4 days. The clinical status of the patient improved, but the mild gait disturbance remained. An MRI examination at 36 months (Fig. 1E) showed a decrease in size of the thrombosed aneurysm. Case 2 FIGURE 2. Patient 3. Acute gait disturbance in a 15-year-old boy. A, sagittal T1-weighted MRI scan after gadolinium administration showing a partially thrombosed mass in front of the brainstem. B and C, right (B) and left (C) vertebral angiograms showing a giant aneurysm of the right vertebrobasilar junction. D and E, left vertebral angiograms with (D) and without (E) subtraction showing the absence of aneurysm opacification after bilateral vertebral arteries and lower basilar artery occlusion with coils and detachable balloons. F and G, control MRI scans at 48 months after treatment: F, sagittal T2-weighted MRI scan; G, three-dimensional time-of-flight magnetic resonance angiogram showing a complete disappearance of the aneurysm and a retrograde filling of the basilar artery from the anterior circulation. NEUROSURGERY A 15-year-old boy (Patient 3) was admitted to the emergency room for an acute gait disturbance. MRI revealed a partially thrombosed mass in front of the brainstem (Fig. 2A). Conventional angiography (Fig. 2, B and C) showed a 60-mm aneurysm of the right VBJ. A test occlusion of the right VA was performed, and the patient was treated by PAO with two detachable balloons. Angiographic control at 48 hours revealed an opacification of the aneurysm, and a lower BA test occlusion was performed and tolerated. The left VA and lower BA were then occluded with coils (Fig. 2, D and E), which resulted in the absence of aneurysm opacification. The patient developed a hemiparesis 24 hours after the treatment, and MRI revealed a brainstem infarct. The neurological examination showed improvement at 48 months, and MRI showed a remarkable disappearance of the aneurysm (Fig. 2, F and G). RESULTS Tolerance to Test Occlusion Among 13 patients treated by PAO for a GVBA, six patients underwent and tolerated the test occlusion. Retrograde filling of the BA or symmetrical venous drainage of the posterior fossa was observed in all cases. In the remaining seven patients, collateral blood supply from the contralateral VA and both carotid arteries was assessed by angiographic criteria. VOLUME 55 | NUMBER 2 | AUGUST 2004 | 319 LUBICZ ET AL. Clinical Outcome Table 1 lists the symptoms of all patients. In seven patients treated by nondominant VA occlusion (no test occlusion), the immediate clinical outcomes were as follows: five improvements, one worsening of symptoms, and one death. In the remaining six patients, who underwent test occlusion before bilateral VA and/or lower BA occlusion, three patients showed a clinical improvement and three experienced a worsening of symptoms. A 50-year-old woman (Patient 6) who presented with a ruptured giant vertebral aneurysm was treated by PAO with coils placed proximal to the aneurysm. Posttreatment conventional angiography revealed a partial aneurysm thrombosis, and the patient died the next day from a rebleeding. In three (Patients 4, 7, and 8) of four patients who had clinical worsening, symptoms related to mass effect on the brainstem, including dysphagia and progressive loss of consciousness, occurred a few hours after the procedure. These patients were kept intubated and on a ventilator, and intravenous corticosteroid therapy was administered for 4 to 6 days with progressive improvement of symptoms. The fourth patient (Patient 3) developed a stroke 1 day after endovascular treatment and underwent an MRI examination that showed a brainstem infarction. The patient sustained mild hemiparesis despite anticoagulation, volume expansion, and rehabilitation. In the long term, all patients showed good or excellent clinical outcome. Imaging Outcome Table 1 lists the imaging follow-up of all patients. Immediately after endovascular treatment, all aneurysms except one (Patient 6) were excluded from the circulation. Long-term follow-up in 12 patients showed a decrease in size or a disappearance of thrombosed aneurysms in 9 of them. One patient with a BA aneurysm (Patient 7) was treated by selective coiling in another institution. Magnetic resonance angiography at 6 months revealed recanalization, and subsequent bilateral vertebral occlusion was performed in our department. Imaging follow-up showed a recurrence of the aneurysm in the long term. In the other two patients (Patients 2 and 13), one thrombosed vertebral aneurysm and one thrombosed basilar aneurysm did not decrease in size during imaging follow-up. DISCUSSION This study shows that PAO seems safe and effective for the treatment of GVBAs. Worsening of symptoms, related to mass effect on the brainstem, may be observed after embolization. However, most patients showed good or excellent outcome and a decrease in size of the aneurysm in the long term. Pathophysiology of Giant Intracranial Aneurysms Giant aneurysms are defined as aneurysms greater than 25 mm in diameter (30) and represent 5% of all intracranial aneurysms. GVBAs are more frequent in male patients (1, 47), whereas anterior circulation giant aneurysms (mostly intra- 320 | VOLUME 55 | NUMBER 2 | AUGUST 2004 cavernous) carry the opposite female dominance. This was confirmed in the present series that included 10 men and 3 women. These aneurysms may be saccular, fusiform, or serpentine. The more common saccular aneurysms have a neck that separates the aneurysm from the parent artery, whereas fusiform aneurysms have circumferential arterial dilation without any ostium or neck. Therefore, there is a higher probability of perforating vessels arising from fusiform aneurysms (11). The serpentine aneurysm is a mostly thrombosed aneurysm with a tortuous and irregular vascular channel inside (26, 33). All of these aneurysms can present with mass effect (75% of cases), ischemia, or hemorrhage, but serpentine aneurysms are less likely to bleed (33). Neurosurgical and endovascular experience has shown that partially thrombotic or nonthrombotic giant aneurysms can be particularly susceptible to swelling (3, 16). The severity of aggravation after PAO is directly proportional to the size of the remnant lumen and to the clot that can result after aneurysm thrombosis (16). As giant aneurysms are considered to grow by recurrence of intramural hemorrhage of the aneurysm wall (23, 37, 45), they remain poor candidates for endosaccular embolization because of the documented growth potential of these lesions, even after complete thrombosis (2, 23). However, GVBAs have a poor natural history (36, 39, 41, 42, 44, 47) if left untreated, and all pathophysiological features must be taken into account to perform the best treatment for the patient. Treatment strategies are mostly influenced by the clinical presentation and the risk of SAH. Giant aneurysms that present with SAH are rare and generally not thrombosed. Aggressive therapeutic options should be proposed in this life-threatening situation, and the patient must be treated immediately to prevent a rebleeding. If PAO is planned, it should ideally be delayed after the vasospasm phase to avoid ischemic complications. Currently, a partial coiling can be performed at the acute phase to reduce risks of rebleeding and then PAO can be performed several days later. However, most giant aneurysms present with mass effect or ischemia of thromboembolic origin. In these patients, the aims of the treatment are to decrease mass effect and prevent thromboembolic events. Aspirin therapy may be administered while treatment options are discussed by the neurointerventional and neurosurgical teams. Tolerance for Occlusion Although balloon occlusion of the parent vessel is a safe treatment for giant aneurysms, patient outcome depends mainly on the tolerance to occlusion. Criteria for successful test occlusion are difficult to define for the vertebrobasilar territory. In the largest series of 201 deliberate vertebrobasilar artery surgical ligations, Steinberg et al. (51) used the tourniquet technique (39) in 50 awake patients when there was a concern about adequate collateral flow. Their study showed that the size of the posterior communicating arteries was a good predictor of tolerance to BA occlusion. Aymard et al. (1) performed an angiographic, clinical, and 133Xe-computed tomography test occlusion. In other series, including those of www.neurosurgery-online.com TREATMENT AND FOLLOW-UP OF GIANT VERTEBROBASILAR ANEURYSMS Fox et al. (9) and Sluzewski et al. (47), only angiographic and clinical test occlusion were performed. However, none of these protocols predict delayed ischemic events with accuracy. In our department, before bilateral or unilateral dominant VA or BA occlusion, we perform angiographic and clinical test occlusion. For dominant VA occlusion, we focus on the clinical tolerance and on the delay between the venous phase of the cerebellar hemispheres. This protocol is based on the angiographic criteria for internal carotid artery occlusion, which are better defined in the literature (55). In the case of unilateral nondominant VA occlusion, we perform only a four-vessel angiography with an Allcock test (6, 39) because of the ability of the contralateral VA to supply blood to the BA. Of 13 patients treated for a GVBA, only 1 (Patient 3) developed a delayed ischemic infarction. This patient had a giant aneurysm of the VBJ and tolerated the test occlusion. The treatment has been performed under full heparinization, so the patient may have developed an occlusion of a perforating artery rather than a thromboembolic event. Endovascular Treatment and Alternative Options Previous publications on series of intracranial aneurysms treated by selective embolization with GDCs have included some GVBAs (8, 14, 32, 38, 53, 54, 56). All of these series reported relatively high rates of incomplete occlusion and recanalization in large and giant aneurysms. Furthermore, several authors have recently treated giant aneurysms with selective embolization (12, 35, 43) to preserve the parent vessel. Their series showed that endosaccular coiling is not appropriate because of the size of the aneurysm and the high frequency of thrombus in the aneurysmal sac, which can embolize during manipulation of microcatheters or coils. Giant aneurysms also exhibit a high frequency of regrowth of the sac after using GDCs as a result of coil compaction (12, 35, 43). Moreover, recently published series indicate that GDC coiling in giant aneurysms may aggravate symptoms of mass effect (32). The aims of nonselective treatment in patients with a GVBA are to eliminate mass effect, cure symptoms, and protect from SAH. Techniques for endovascular occlusion of the parent vessel depend mainly on aneurysm location. Aneurysms of the VA are treated by PAO performed distal to the PICA origin or at the C1 level if there is not sufficient space between the PICA and the BA. Ideally, the VA should be occluded by trapping the aneurysm (Fig. 1) to ensure mechanical obstruction to flow and to avoid reopening of the aneurysm. This can be achieved by using detachable balloons or coils. We used GDCs in our patients because this technique was judged safer and provided excellent morphological results in all patients. In the case of arterial occlusion at the C1 level, an anterograde flow is preserved within the BA through external carotid artery-VA anastomoses, but it may prevent aneurysm thrombosis. Aneurysms involving the VBJ or the BA must be treated by bilateral VA or lower BA occlusion (1, 47, 51). To our knowledge, no consensus or formal data are available in the literature about the staging of bilateral VA NEUROSURGERY occlusion and its timing. Aymard et al. (1) performed staged bilateral VA occlusion in their series, with good clinical and angiographic results in all cases. Sluzewski et al. (47) reported three deaths in six patients treated by direct bilateral VA occlusion. On the other hand, Steinberg et al. (51) reported two patients with giant VBJ aneurysms who experienced acute SAH shortly after occlusion of one VA. On the basis of these published data, we performed staged bilateral VA occlusion in three basilar artery aneurysms, bilateral VA-lower BA occlusion in a VBJ aneurysm (Fig. 2), and unilateral VA occlusion in the remaining nine aneurysms of the VA. In case of poor tolerance of test occlusion, different treatment options should be considered, including stenting, PAO after posterior fossa revascularization, and direct surgery. Several authors (31, 34, 40) have recently shown promising results in patients treated using intracranial stents—alone or in conjunction with coils or liquid polymer—for difficult cerebral aneurysms. Surgical approaches to the revascularization of the posterior fossa, allowing for subsequent safe PAO, have been reported (18, 20, 50, 57) and include superficial temporal artery-to-posterior cerebral artery or superior cerebellar artery bypass in the case of midbasilar lesions and PICA-to-PICA in situ bypass or occipital artery-to-PICA bypass for VA aneurysms. A direct surgical approach may result from adjunctive techniques, including hypothermic circulatory arrest (46, 49) and endaneurysmal microendarterectomy (22). Various surgical series of GVBAs have reported good outcomes: Steinberg et al. (51) reported 75% successful long-term outcomes in the largest published series, whereas Drake et al. (7) reported 67% long-term good outcomes in 60 patients. In both series (7, 51), patients with a giant VBJ aneurysm made an excellent or good outcome in 60 and 74% of the cases, respectively. Finally, all of these surgical and endovascular techniques may be combined in a complementary way for the treatment of complex giant aneurysms (15). Clinical Outcome PAO is an accepted method for the treatment of giant aneurysms, which is associated with a low procedure-related complication rate (1, 5, 6, 9, 19, 29, 51). Cerebral infarct represents the most frequent complication after VA/BA occlusion. This is related to a thromboembolic event or perforating artery occlusion rather than a decreased blood flow in the occluded vessel (9, 10). This demonstrates that systemic anticoagulation is required during the embolization procedure. Because GVBAs are uncommon and are treated by using different techniques, few studies have assessed the complication rate for nonselective occlusion. Moreover, reports on bilateral VA balloon occlusion are either anecdotal or submerged in larger series of patients including other territories and treatment modalities. Steinberg et al. (51), in a series of 201 patients (consisting of 87% giant aneurysms) treated by surgical VA and/or BA occlusion, reported a successful long-term outcome in 75% of the cases. In a report of 21 patients (1) with predominantly GVBAs treated by PAO, only one death and VOLUME 55 | NUMBER 2 | AUGUST 2004 | 321 LUBICZ ET AL. one transient ischemic attack were related to the procedure. Among seven patients with a vertebrobasilar aneurysm treated by unilateral or bilateral VA occlusion reported by Fox et al. (9), one patient developed a reversible ischemic neurological deficit. Sluzewski et al. (47) reported six GVBAs treated by bilateral VA balloon occlusion: three patients died from recurrent hemorrhage and delayed brainstem ischemia, and three patients showed good clinical outcome. In our study, long-term clinical follow-up in 12 patients revealed good or excellent outcome, confirming the relative safety of VA/BA occlusion: there was one permanent deficit and one procedure-related death. One patient (Patient 3) with a VBJ aneurysm developed a stroke 1 day after treatment, which resulted in mild hemiparesis. One patient (Patient 6) with a vertebral aneurysm treated by parent vessel occlusion with coils placed proximal to the aneurysm died from a rebleeding. This phenomenon has been previously described as the “water-hammer effect” (27). Aneurysms of the VA and the BA are located in a vulnerable region, in continuity with the cerebral circulation, and thus exposed to the pulsatile blood flow within the BA. This “water-hammer effect” prevents aneurysm thrombosis unless obstruction to flow is done by trapping of the aneurysm. The other vertebral aneurysms were subsequently treated that way. Imaging Outcome Endovascular treatment leads to complete thrombosis of the aneurysm in most patients (1, 5, 6, 9, 19, 29, 51). In our series, all aneurysms except one thrombosed. In one patient (Patient 6) with a vertebral aneurysm treated by occlusion of the vessel without trapping of the aneurysm, the “water-hammer effect” of the BA prevented complete thrombosis. Imaging follow-up in 9 of 12 patients showed a reduction in the size of the aneurysm with a persistent thrombosis (Figs. 1 and 2). One 65-year-old man (Patient 7) exhibited regrowth of a BA aneurysm that had been treated by selective embolization in another institution. Magnetic resonance angiography at 6 months showed recanalization, and conventional angiography was performed to assess precisely the indication of a complementary treatment. Bilateral VA occlusion was performed in our department, but the aneurysm did not completely thrombose in the long-term course. This patient has been followed up by magnetic resonance angiography, and no further treatment is planned. In one patient (Patient 2) with a vertebral aneurysm treated by trapping with coils, complete exclusion from the circulation was demonstrated on posttreatment angiography. However, imaging follow-up at 48 months showed no reduction of the mass effect on the brainstem. The third patient (Patient 13) had a lower-third BA aneurysm treated by bilateral VA occlusion. Imaging follow-up revealed complete aneurysm thrombosis without size reduction. More remarkable in our series is the complete disappearance of a 60-mmdiameter VBJ aneurysm in a 15-year-old boy (Patient 3) after lower BA and bilateral VA occlusion (Fig. 2G). This illustrates the remarkable capacity of remodeling and sometimes spon- 322 | VOLUME 55 | NUMBER 2 | AUGUST 2004 taneous cure reported in children with giant aneurysms (4, 52). CONCLUSIONS Despite major advances in microneurosurgical techniques and endovascular options for managing patients with GVBAs, PAO remains a safe and effective treatment. A temporary clinical worsening related to mass effect on the brainstem may occur after treatment. However, symptom resolution as well as aneurysm thrombosis and disappearance of mass effect are observed in the long term in most patients. This treatment can be carried out with minimal morbidity and mortality using clinical and angiographic monitoring. REFERENCES 1. 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Van Rooij WJ, Sluzewski M, Metz NH, Nijssen PC, Wijnalda D, Rinkel GJ, Tulleken CA: Carotid balloon occlusion for large and giant aneurysms: Evaluation of a new test occlusion protocol. Neurosurgery 47:116–121, 2000. 56. Viñuela F, Duckwiler G, Mawad M: Guglielmi detachable coil embolization of acute intracranial aneurysm: Perioperative anatomical and clinical outcome in 403 patients. J Neurosurg 86:475–482, 1997. 57. Wakui K, Kobayashi S, Takemae T, Kamijoh Y, Nagashima H, Muraoka S: Giant thrombosed vertebral artery aneurysm managed with extracranialintracranial bypass surgery and aneurysmectomy: Case report. J Neurosurg 77:624–627, 1992. COMMENTS T he authors report 13 cases of giant vertebrobasilar (VB) aneurysm. This well-studied series shows the complexity of the disease and the potential artificial regrouping of lesions VOLUME 55 | NUMBER 2 | AUGUST 2004 | 323 LUBICZ ET AL. on the basis of size. It is unlikely that in this particular disease group, the pediatric population, the nonthrombosed acutely dissected aneurysm or chronic repeated dissections in adults carry the same natural history, requiring the same therapeutic management. These complex cases and the present article illustrate the necessary adjustment of the therapeutic strategy to the individual situation with regard to the disease but also to the anatomy for the purpose of anticipated collateral circulation: the external carotid to vertebral artery (VA), the anterior spinal axis, the cerebellar pontine angle anteroinferior cerebellar artery–posteroinferior cerebellar artery connections, and all the possible flow reversal in the basilar trunk. The type of VB junction (VBJ), the posteroinferior cerebellar artery, and the origin of the anterior spinal artery from the distal VA before fusion in most cases allow prediction of the brainstem tolerance to the VA occlusion. Surgical high-flow anastomoses must not be forgotten when insufficient collateralization is persistent. In general, various mass effects (or even water hammer effect?) should testify to the fact that whatever is mechanical is transdurally transformed into biological signals, and even if the mass seems anatomically significant enough to deform the cerebral structures, the ischemic changes noted clinically or only on magnetic resonance imaging may reflect disturbed interstitial water circulation and angiogenesis in relation to signal secondary to the chronic dissection at the adventitial level from the vasa vasorum. Finally, the clinical significance of subarachnoid hemorrhage (SAH) in these aneurysms may also vary from the partially thrombosed to the fully patent lumen. Therefore, some of these aneurysms may still be active after being completely disconnected from the patent vessel lumen after complete occlusion of the aneurysm sac on angiography. Pierre Lasjaunias Interventional Neuroradiologist Paris, France T he optimum treatment strategy for giant VB aneurysms, i.e., direct surgical management, endovascular trapping, flow reversal by proximal parent artery occlusion, parent artery occlusion in conjunction with posterior fossa revascularization, or stenting, must be determined on an individual basis; e.g., double-antiplatelet treatment after stenting in the acute post-SAH period can complicate shunting of hydrocephalus, and proximal artery occlusion in the acute post-SAH period is often dangerous because of compromised collateral circulation. The present series demonstrates that giant VB aneurysms can be managed effectively by endovascular trapping of the lesion. Endovascular treatment consisted of aneurysmal trapping in nine patients and proximal parent artery occlusion in four patients. The authors observed treatment-related clinical improvement in eight patients, whereas aneurysmal mass effect was increased in three patients, brainstem infarction occurred in one patient, and another patient suffered a fatal 324 | VOLUME 55 | NUMBER 2 | AUGUST 2004 aneurysmal rehemorrhage. Long-term follow-up disclosed marked aneurysm shrinkage in nine patients. In contrast to microsurgery or stenting, the technique described by the authors is deconstructive in nature and relies heavily on sufficient collateral flow. Therefore, posterior circulation vascular anatomy and clinical presentation, i.e., hemorrhagic versus nonhemorrhagic cases, are of equal importance in considering the optimal treatment option. Andreas Gruber Vienna, Austria Bernd Richling Salzburg, Austria L ubicz et al. described their experience in the treatment of 13 patients with giant VB aneurysms treated by parent vessel occlusion. In their population, 9 patients presented with mass effect and 4 patients presented with SAH. The authors performed temporary balloon occlusion with and without neurological monitoring using either clinical criteria or angiographic criteria with simultaneous venous phase filling in the parenchyma distal to the occluded vessel, demonstrating adequate collateral supply. Endovascular treatment provided clinical improvements in 8 patients, or 61%; however, 30% had significant morbidity, and 1 patient died as a result of an incompletely treated aneurysm from rehemorrhage. As the authors indicated, the major problem is not hypoperfusion in the postoperative period but rather primarily one of thromboembolism. There is no question that these lesions are treacherous once they become symptomatic, with 80% of patients being dead or disabled within 5 years without intervention. Giant aneurysms in this location present a formidable surgical dilemma and certainly can be treated with vessel occlusion with or without bypass as needed; however, parent vessel occlusion continues to be an excellent option, as the author’s series illustrates. There is no question that coverage stents, as they become applicable and navigable in the intracranial circulation, will make endovascular occlusion with parent vessel preservation an option. As microsurgical and endovascular techniques improve, the management of these formidable foes will become possible with lower morbidity. Robert H. Rosenwasser Philadelphia, Pennsylvania T his is a nice article describing the endovascular treatment and long-term follow-up of 13 consecutive patients with giant VB aneurysms. Six patients presented with gait disturbance secondary to mass effect, 3 with headache or neck pain, and 3 with SAH. The giant aneurysm involved one VA in 9 patients, the VBJ in 1 patient, and the basilar artery (BA) in 3 patients. Nine of the 10 VA aneurysms were treated with parent VA occlusion and trapping of the aneurysm using Guglielmi detachable coiling, and 1 was treated by parent vessel occlusion proximal to the aneurysm. The patient with the VBJ aneurysm underwent bilateral VA and lower BA www.neurosurgery-online.com TREATMENT AND FOLLOW-UP OF GIANT VERTEBROBASILAR ANEURYSMS occlusion. In the 3 patients with giant BA aneurysms (1 BA apex, 2 BA trunk), bilateral VA occlusions were performed, staging the occlusion by 2 to 12 weeks between sessions. Twelve of the 13 aneurysms were excluded from the circulation, and 9 of the thrombosed aneurysms showed a decrease in size on magnetic resonance angiography in long-term follow-up (12–48 mo; mean, 28 mo). Two of these 12 thrombosed aneurysms remained unchanged in size, but 1 BA aneurysm showed a regrowth after bilateral VA occlusion. Longterm clinical outcome was excellent in 8 patients and good in 4 patients. The 1 patient with a ruptured giant VA aneurysm who was treated with parent vessel coil occlusion proximal to the aneurysm (but not trapping) demonstrated only partial aneurysm thrombosis, and this patient rebled and died the next day. One patient (with a VBJ aneurysm) experienced a new brainstem infarction 1 day after treatment and continued to have a mild hemiparesis in long-term follow-up. In a report of 201 patients with predominantly giant posterior circulation aneurysms, treatment by occlusion of the parent vessel (surgically in 193 patients, endovascularly in 8 patients) resulted in excellent clinical outcome in 68%, but with 24% mortality (3). One VA was occluded in 24% of the patients. In the other patients, the BA or both VAs were occluded, resulting in flow reversal in the posterior circulation. Patient clinical outcome varied according to the patient’s condition on admission and the site of the aneurysm. The best results were achieved in patients with better preoperative grade, younger age (40 yr or less), and those with the VA aneurysms, who were all treated by unilateral VA occlusion (5 with trapping), resulting in complete aneurysm thrombosis in 89% of VA aneurysms. The size of the posterior communicating artery proved to be a good predictor of tolerance to BA occlusion. Successful aneurysm thrombosis was achieved in 78% of patients. In general, the closer the proximal arterial occlusion to the aneurysm site, the more likely it was that complete thrombosis occurred. Of the group of patients with incompletely thrombosed aneurysms, 67% developed early or late neurological deterioration from SAH, progressive brainstem compression, or brainstem stroke, with 86% of complications proving to be fatal. Our group recently published our results on endovascular parent vessel occlusion for fusiform or dissecting aneurysms of the VBJ (2). This article evaluated the perioperative (within 30 days) and follow-up outcomes for patients treated with permanent occlusion of the VA for VB, fusiform, and dissecting aneurysms. We had 13 consecutive patients. Two groups were defined for the study. Group 1 patients underwent parent vessel occlusion to achieve complete thrombosis of the offending aneurysm. Group 2 patients underwent parent vessel occlusion to reduce flow to the aneurysm when complete thrombosis was not desirable. Modified Rankin scores were obtained at presentation and at longterm follow-up with a mean period of 22 months. We found that all Group 1 aneurysms were thrombosed on immediate follow-up angiograms. Statistically significant improvements in outcome score were achieved in all Group 1 patients (P ⫽ 0.026). All Group 2 patients had complete occlusion of the VA, NEUROSURGERY but continued filling of the fusiform aneurysm was still observed from the patent contralateral VA. Four patients in Group 2 died during the follow-up period. Two of these deaths were attributable to the aneurysms. Of the remaining three patients, two experienced clinical worsening and one remained stable. We concluded that in this series, parent vessel occlusion for chronic fusiform and acute dissecting aneurysms of the VB system is a useful therapeutic endovascular technique. Long-term outcome suggests that patients with aneurysms involving only one VA in which complete thrombosis can be achieved have better clinical outcome than those who have aneurysms involving the BA or both VAs in which complete thrombosis cannot be achieved by use of parent vessel occlusion. The authors in this present article were a bit more aggressive at trying to reduce flow to the aneurysm involving the VBJ and the BA, analogous to our Group 2 patients, in that they performed bilateral VA occlusion. They had four patients in this group, compared with seven patients in ours, and they achieved excellent outcomes in three patients and good outcome in one patient. Our patients in this category were treated by unilateral VA occlusion only, and this group did worse on subsequent follow-up. There are several reasons why this difference exists. First, possibly because of the difference in endovascular treatment method with better reduction of flow to the aneurysm, the authors were able to obtain aneurysmal thrombosis and subsequent size reduction. Second, our patients were significantly older and had more comorbidities than the authors’ patients. The mean age in our patients was 64 years, compared with a mean of 47.9 years in their overall group, and in their group with bilateral VA or basilar occlusion, the mean age was 40 years. Third, our patients had worse clinical status at presentation, with 9 of 13 patients having SAH and 4 of 13 patients having mass effect. In the present article, only 4 of 13 patients presented with SAH. Surprisingly, we subsequently treated a patient with a previously unruptured giant VA aneurysm using endovascular VA occlusion but not trapping and were dismayed when this patient suffered a fatal aneurysmal hemorrhage from recanalization of the completely thrombosed aneurysm because of retrograde flow from the contralateral VA (1). Although this study does not contain completely novel data, it certainly emphasizes important points regarding deliberate endovascular parent vessel occlusion for treating giant VB aneurysms. It is clear that parent vessel occlusion by endovascular methods is a safe and effective treatment for many difficult-to-treat giant VB artery aneurysms. Although a temporary clinical worsening may occur related to mass effect on the brainstem after treatment, long-term follow-up shows a progressive decrease in mass effect and persistent thrombosis in accordance with excellent clinical outcome. Trapping of the aneurysm, if possible, is preferable to proximal artery occlusion alone, and incomplete thrombosis can result in worsening mass effect or aneurysmal hemorrhage with disastrous neurological consequences. Younger patients tolerate bilateral VA or BA occlusion better than elderly patients, and more aggres- VOLUME 55 | NUMBER 2 | AUGUST 2004 | 325 LUBICZ ET AL. sive treatment options should be entertained in younger patients with giant VB aneurysms, aiming for complete aneurysm thrombosis. We hope that, with advances in techniques such as covered stenting or stent-assisted coiling, reconstructive endovascular methods will continue to improve the outcome for patients harboring these challenging aneurysms that are currently relegated to deconstructive approaches. Huy M. Do Interventional Neuroradiologist Gary K. Steinberg Stanford, California 1. Chang SD, Marks MP, Steinberg GK: Recanalization and rupture of a giant vertebral artery aneurysm after Hunerian ligation: Case report. Neurosurgery 44:1117–1121, 1999. 2. Leibowitz R, Do HM, Marcellus ML, Chang SD, Steinberg GK, Marks MP: Parent vessel occlusion for vertebrobasilar fusiform and dissecting aneurysms. AJNR Am J Neuroradiol 24:902–907, 2003. 3. Steinberg GK, Drake CG, Peerless SJ: Deliberate basilar or vertebral artery occlusion in the treatment of intracranial aneurysms: Immediate results and long-term outcome in 201 patients. J Neurosurg 79:161–173, 1993. T he authors report a series of 13 patients with giant VB artery aneurysms treated with endovascular parent vessel occlusion. Giant aneurysms in this location are very difficult to treat, and parent vessel occlusion in the posterior circulation can be hazardous. In this series, careful patient selection and management strategy led to “good” or “excellent” clinical outcomes in 12 of 13 patients at a mean follow-up of 28 months. Sacrifice of the dominant VA was undertaken after balloon test occlusion showed angiographic and clinical evidence of adequate collateral flow. Aneurysm size was reduced in 10 patients. This article reminds neurosurgeons that parent vessel occlusion can be performed safely in some giant VB artery aneurysms. Another useful message from this article is that the patient’s condition may worsen for a period of time after parent vessel occlusion and then improve. This transient neurological deterioration is likely to be a result of brain edema secondary to thrombosis of the aneurysm and not occlusion of brainstem perforators. Thus, measures to reduce brain edema and continued optimism are appropriate when a patient’s condition declines immediately after parent vessel occlusion. Despite the encouraging clinical outcomes, however, the radiographic outcomes in this series are disappointing. Magnetic resonance imaging was obtained in follow-up, rather than angiograms. Conventional angiography would permit more precise assessment of aneurysm and parent vessel anatomy, particularly in regions adjacent to platinum coils. More importantly, follow-up magnetic resonance imaging in this series showed disappearance of only one aneurysm; the remaining aneurysms were either unchanged or “reduced” in size, or in one patient, recanalized. Definitive treatment of intracranial aneurysms consists of occlusion of the aneurysm. Although partial thrombosis and reduction in size of a giant aneurysm may reduce the mass effect and ameliorate the patient’s symptoms after treatment in the short term, partial treatment leaves the potential for growth and rupture in the long term. One wonders whether further intervention in these patient would lead to complete occlusion of the aneurysms. Additional endovascular options for more complete treatment of the aneurysms are 1) stenting of the parent vessel to reduce flow into the aneurysm before parent vessel sacrifice and 2) sacrifice of the contralateral VA. An additional surgical approach is to occlude the distal VA with a clip if the length of the vessel between the posteroinferior cerebellar artery and the BA is too short for coil occlusion. Mark R. Harrigan L. Nelson Hopkins Buffalo, New York Congress of Neurological Surgeons/American Association of Neurological Surgeons Joint Section Chairmen Cerebrovascular Surgery: Warren R. Selman, Cleveland, Ohio Disorders of the Spine and Peripheral Nerves: Gerald E. Rodts, Jr., Atlanta, Georgia History of Neurological Surgery: Michael Schulder, Newark, New Jersey Neurotrauma and Critical Care: Donald W. Marion, Boston, Massachusetts Pain: Oren Sagher, Ann Arbor, Michigan Pediatric Neurological Surgery: Andrew D. Parent, Jackson, Mississippi Stereotactic and Functional Neurosurgery: G. Rees Cosgrove, Boston, Massachusetts Tumors: Raymond Sawaya, Houston, Texas 326 | VOLUME 55 | NUMBER 2 | AUGUST 2004 www.neurosurgery-online.com