|Year : 2021 | Volume
| Issue : 1 | Page : 3-8
Micro-catheter assisted coiling (MAC): A mid-path between simple and assisted coiling techniques in treating ruptured wide neck aneurysms and immediate post procedure outcomes
Vetrivel Muralidharan1, Mario Travali2, Tiziana Liliana Cavallaro3, Letizia Tomarchio3, Gabriele Corsale3, Federica Cosentino2, Marco Angelo Politi3, Concetto Cristaudo2
1 Department of Surgery, Panimalar Medical College Hospital and Research Institute, Chennai, Tamil Nadu, India
2 Department of Medical, Surgical Science and Advanced Technologies 'GF Ingrassia', University of Catania, Catania, CT, India
3 Department of Neuroradiology, Cannizzaro Hospital, Catania, Sicily, Italy
|Date of Submission||19-Jan-2021|
|Date of Decision||14-May-2021|
|Date of Acceptance||30-May-2021|
|Date of Web Publication||27-Aug-2021|
Dr. Concetto Cristaudo
Department of Medical, Surgical Science and Advanced Technologies 'GF Ingrassia', University of Catania, Catania, CT
Source of Support: None, Conflict of Interest: None
Background: Aneurysms with neck diameter >4 mm or dome to neck ratio <2 are wide-neck aneurysms. Balloons and stents are used to assist in coiling the wide-neck aneurysms, but these are associated with increased intra-procedure and peri-procedure risk in ruptured aneurysms. Microcatheter-assisted coiling (MAC) is an alternative salvage technique in these situations which is under reported.
Materials and Methods: We describe our experience in a cohort of 16 patients with ruptured wide neck aneurysm treated with MAC technique. Our primary objective of intervention in acute setting was to secure the aneurysm to prevent rebleed.
Results: Anterior communicating artery aneurysm was the most common (56.3%) followed by middle cerebral artery bifurcation aneurysm (18.8%), paraclinoid aneurysm (12.5%), posterior communicating artery aneurysm (6.3%) and basilar tip aneurysm (6.3%). Mean greatest dimension of dome and neck were 8.9 mm and 4.6 mm, respectively. Mean neck to dome ratio was 1.8. Fisher grade 3 and grade 4 subarachnoid haemorrhage (SAH) were observed in 56.3% and 43.7% patients, respectively. Immediate post-procedure digital subtraction angiography (DSA) showed Raymond Roy grade 1, grade 2 and grade 3 embolisation in 62.5%, 33.3% and 6.7% patients, respectively. No distal embolus, vessel occlusion, vessel perforation or aneurysm rupture was observed. Immediate post-procedure DSA showed good distal flow in all patients. Infarct was observed at 24 and 48 hours respectively, in two patients with Fisher Grade 3 SAH.
Conclusion: Ruptured wide neck aneurysms can be embolised with complete preservation of branching vessel and distal flow. Total occlusion can be achieved in 2/3rd of patients.
Keywords: Assisted coiling, dual microcatheter, ruptured aneurysm, wide-neck aneurysm
|How to cite this article:|
Muralidharan V, Travali M, Cavallaro TL, Tomarchio L, Corsale G, Cosentino F, Politi MA, Cristaudo C. Micro-catheter assisted coiling (MAC): A mid-path between simple and assisted coiling techniques in treating ruptured wide neck aneurysms and immediate post procedure outcomes. J Cerebrovasc Sci 2021;9:3-8
|How to cite this URL:|
Muralidharan V, Travali M, Cavallaro TL, Tomarchio L, Corsale G, Cosentino F, Politi MA, Cristaudo C. Micro-catheter assisted coiling (MAC): A mid-path between simple and assisted coiling techniques in treating ruptured wide neck aneurysms and immediate post procedure outcomes. J Cerebrovasc Sci [serial online] 2021 [cited 2021 Sep 18];9:3-8. Available from: http://www.jcvs.com/text.asp?2021/9/1/3/324817
| Introduction|| |
Aneurysms with neck diameter >4 mm or dome to neck ratio <2 are considered as wide-neck aneurysms., Endovascular treatment of these wide neck aneurysms is challenging and in presence of acute subarachnoid hemorrhage (SAH) deciding on a safe endovascular technique becomes arduous. Adjunctive devices such as balloon or stent are used as an aid to embolise these wide-neck aneurysms. However, increased rate of rupture of the parent artery, intimal injury and procedure related thromboembolic complications are observed with the usage of supportive devices like balloon while embolising ruptured aneurysms.,,,,
Intracranial stents are prothrombogenic and stent-assisted coiling (SAC) technique requires antiplatelet drug administration which kindles a controversy in presence of acute SAH and use of SAC in ruptured wide-neck aneurysms. SAC technique has been reported to achieve 63%–93% efficacy of complete occlusion with a compromise of 4.7%–17% thromboembolic events due to the procedure.,,,,, The prevalence of aspirin and clopidogrel resistance further complicates the situation in opting SAC to treat wide-neck ruptured aneurysms., Dual antiplatelet therapy and alternate platelet inhibitors like ticagrelor are used as a salvage, but increased rates of haemorrhagic complications in patients on dual antiplatelet therapy with 3.42 times odds of a radiographic haemorrhage further adds on to the constrain.,
Ruptured wide-neck aneurysms straddle the endovascular neurointerventionist between risks and benefits with limited technical options. Widening the armamentarium with an additional technique will help the Endovascular Neurointerventionist to handle these cases. We describe here microcatheter assisted coiling (MAC) technique to tackle the wide neck aneurysms with acute SAH. This technique has been used as a bail-out technique to treat wide-neck aneurysms, as a microcatheter protection technique by Lee et al. Here, we describe our experience with MAC to treat ruptured wide-neck aneurysms.
| Materials and Methods|| |
A retrospective chart review was done to identify patients with ruptured intracranial aneurysms treated at our centre from 2012 to April 2020. We identified 413 patients with ruptured aneurysms treated with endovascular coiling. Of all the 413 patients, 16 patients were treated using MAC technique. Computed tomography (CT) brain plain was done for all the patients as they presented with clinical features of acute SAH. CT angiography was performed for all the patients prior to digital subtraction angiography (DSA). DSA was done using Allura angiography unit (Philips Healthcare, Best, Netherland) till June 2019 and Azurion angiography unit, (Philips Healthcare, Best, Netherland) since July 2019. Three-dimensional reconstruction was done using inbuilt angiography software. Morphological characteristics of the aneurysm, size of the neck, height and width of the aneurysm were evaluated. Demographic details, Fisher grade, location of the aneurysm and dimensions are mentioned in [Table 1].
|Table 1: Demographic details, Fisher's grade, location of the aneurysm and dimensions|
Click here to view
Therapeutic intervention was performed in the same sitting for all the patients. Our primary objective of the intervention in acute setting was to secure the aneurysm to prevent rebleed. Our secondary objective was to achieve complete occlusion. All the patients treated using MAC had neck diameter >4 mm or dome to neck ratio <2. All the patients were evaluated for intra-procedure and immediate post-procedure (72 h) thrombosis\embolic event, vessel occlusion\perforation\rupture and aneurysmal rupture. Grade of embolisation was evaluated immediately after the procedure with Raymond-Roy grade. Patients with residual neck were planned for an elective stent deployment after 3 months.
Microcatheter assisted coiling technique
All the procedures were done under general anaesthesia. Right common femoral artery puncture was made using Seldinger technique with 19G needle and a 6 French (F) sheath was placed. Continuous heparin infusion (2500 units in 1 L normal saline) was flushed through the sheath using a pressurised bag. Additional bolus dose of 3000 units of heparin was administered after protecting the bleb of the aneurysm with first coil and 1000 units of heparin was repeated every hour if the procedure extended beyond 1 h.
In all the cases, two Excelsior SL-10, with inner diameter of 0.0165 in (Stryker. Inc.,) microcatheters were passed through a single 6F (>0.70 inch) guide catheter. One microcatheter was steam-shaped adapting the local microanatomical geometry of the aneurysm sac, neck and parent vessel to deploy the coils. Second microcatheter was used with/without shaping and positioned across the neck into the distal vessel or into a branch from the parent vessel with in-situ microguide wire. This second microcatheter acts as strut across the neck and prevents the prolapse of coil into the parent vessel or the distal branch. [Figure 1] shows a pictorial illustration of use of two microcatheters within a single guide catheter, with one microcatheter shaped adapting the local microanatomy and another positioned across the neck distally into the side branch. The use of MAC technique in anterior communicating artery with hypoplastic right A1 is illustrated in [Figure 2].
|Figure 1: 'Step by step' pictorial illustration of microcatheter assisted coiling technique in embolising a ruptured, wide-neck, saccular right MCA bifurcation aneurysm (a-h). Left-oblique projection in DSA (a) and corresponding pictorial image (b) depict the location and shape of aneurysm with wide neck partially involving the superior division of MCA. First microcatheter (arrow head [c], blue [d]) adapts the local geometry of parent vessel and neck, with its tip in the sac. Second microcatheter (arrow [c], orange [d]) is placed distally across the neck of aneurysm in superior division of MCA. Second microcatheter (arrow [e], orange [f]) acts as a strut, supports and prevents the prolapse of coil into the superior division of MCA. (g-h) Complete embolisation of the aneurysm is seen. OA: Ophthalmic artery, ICA: Internal carotid artery, MCA: middle cerebral artery, DSA: Digital subtraction angiography|
Click here to view
|Figure 2: Microcatheter assisted coiling technique in embolising ruptured wide neck anterior communicating artery aneurysm with hypoplastic right A1 (a-d). The three-dimensional reconstruction image (a) shows a large wide neck anterior communicating artery aneurysm predominantly involving right A1–A2 angle. Working projection digital subtraction angiography (b) during embolisation shows coil prolapse into right A1–A2 angle (white arrowhead). Working projection plain radiograph (c) shows position of second microcatheter (proximal marker, white arrow; distal tip, white arrowhead) across the neck into right distal A2 with in-situ microguide wire, preventing the coil prolapse; proximal marker of first microcatheter delivering the coils is also seen (black arrowhead). (d) Complete embolisation of the aneurysm with patent parent vessels and distal flow seen|
Click here to view
| Results|| |
In our cohort, the mean age of presentation was 67.3 years (range, 45–80). Females were 13/16 (81.3%) and males were 3/16 (18.7%). Of all the sixteen patients who were treated with MAC technique, 9/16 (56.3%) were anterior communicating artery aneurysm, 3/16 (18.8%) were middle cerebral artery (MCA) bifurcation aneurysm, 2/16 (12.5%) were paraclinoid aneurysm, 1/16 (6.3%) was posterior communicating artery aneurysm and 1/16 (6.3%) was basilar tip aneurysm.
Aneurysm dimension and grade of subarachnoid haemorrhage
Mean greatest dimension of the aneurysm dome was 8.9 mm (range, 2.6–26). Mean neck dimension was 4.6 mm (range, 2.6–8). Mean neck to dome ratio was 1.8 (range, 0.7–5.7). Fisher grade 3 SAH was observed in 9/16 (56.3%) patients and Fisher grade 4 SAH was observed in 7/16 (43.7%) patients.
Grade of embolisation
Immediate post-procedure DSA showed Raymond Roy Grade 1 embolisation in 10/16 (62.5%) patients, Raymond Roy Grade 2 embolisation in 5/15 (33.3%) patients and Raymond Roy grade 3 embolisation in 1/15 (6.7%) patients.
No periprocedural complication like distal embolus or vessel occlusion or vessel perforation or rupture of aneurysm was observed. Immediate post-procedure DSA showed good distal flow in all the patients. Early post-procedural complication (<48 h) was observed in 1/16 (6.3%) patient, case no 14. This patient presented with Fisher grade 3 SAH [Figure 3]d due to a ruptured bilobed right side MCA bifurcation aneurysm. MAC technique was used to coil the superior sac and inferior sac was embolised by simple coiling technique. Immediate post-procedure DSA showed complete embolisation of both the sacs and well-preserved distal flow, as in [Figure 3]a,[Figure 3]b,[Figure 3]c. CT brain plain done 24 h post-procedure showed infarct involving the superior division of MCA, [Figure 3]e. Sixty months after the procedure the patient was independent for activities of daily living, mRS 2. DSA after 1 year showed no residual aneurysm.
|Figure 3: Complication in case no. 14 after microcatheter assisted coiling technique in embolisation of right middle cerebral artery bifurcation ruptured bilobed aneurysm (a-e). Immediate post-procedure digital subtraction angiography during arterial (a) and late capillary phases (b) show preserved distal flow and complete embolisation of superior sac (arrow head) and inferior sac (white arrow). Computed tomography brain at admission (c) shows modified Fisher Grade 3 subarachnoid hemorrhage (black arrow). Computed tomography brain done 24 h post-procedure (d) shows infarct involving the superior division of right middle cerebral artery territory. At 6 months follow-up, early arterial phase digital subtraction angiography (e) shows no evidence of residual aneurysm|
Click here to view
In one patient (case no 8), vasospasm was observed 48 h after the procedure leading to malignant MCA territory infarct requiring decompressive craniectomy. This patient presented with Fisher grade 3 SAH due to a ruptured giant right paraclinoid aneurysm. In the first sitting, the aneurysm was secured with MAC technique to achieve Raymond Roy grade 3 embolization. Later, underwent simple coiling of the residual sac in the second sitting after 2 weeks of decompressive craniectomy and a stent was deployed in the third sitting after 3 weeks. The patient remained hemiplegic and dependent for activities of daily living, mRS 4 at 3 months follow-up.
| Discussion|| |
Strategising and opting a safe endovascular interventional technique to treat ruptured wide neck aneurysms is an immense challenge balancing the risk and benefits. In our experience, use of MAC technique aided us to achieve safe embolisation of ruptured wide-neck aneurysms. In our cohort, anterior communicating artery aneurysms were the majority followed by MCA bifurcation aneurysms. Furthermore, in various other anatomical locations like paraclinoid ICA and basilar tip adapting MAC technique aided us to safely embolise the ruptured aneurysm with coils. Distal flow was maintained in all the cases with complete preservation of distal branch in cases where a part of aneurysm neck was incorporated into the distal branch.
Instability of coils within the sac and tendency to prolapse into the parent vessel makes embolisation of the wide neck aneurysms difficult. Balloon or stent is used as an adjuvant device to embolise wide-neck aneurysms.,,, But in presence of acute bleed use of these devices increase the rate of rupture of parent artery, intimal injury and procedure-related thromboembolic complications while embolising the aneurysm.,,,,,,,
High dependency on operator experience, need of antiplatelet medications in acute bleed complicates the use of stent in treating the ruptured wide-neck aneurysms. Taylor et al. in a series of 42 consecutive patients with ruptured aneurysms treated using SAC, reported intraprocedural stent thrombosis of about 29%. Acute infarcts and clinically significant ischemic strokes have been reported from 12.5% to 60% in ruptured aneurysm treated with SAC., If the aneurysm cannot be coiled after stent deployment, the patient will be forced to remain on antiplatelet medications with an unsecured aneurysm. The use of antiplatelets in SAC also exposes the patient to increased risk of haemorrhage with additional surgical procedures like ventriculostomy. Lee et al., in their series of microcatheter protection technique to treat wide neck aneurysms reported 82.4% of their patients were pretreated with clopidogrel as their cohort included both ruptured and unruptured aneurysms. In our experience use of MAC technique eliminates the exposure to these risks as there is no inherent need for antiplatelet therapy.
Endovascular intervention of ruptured aneurysms has a higher risk of thromboembolic events and perforation compared to the unruptured aneurysms.,, Symptomatic ischemic events in balloon-assisted coiling (BAC) has been reported from 10% to 17%.,,,, Acknowledging the relatively higher risk of complications in ruptured aneurysms, we obliged to keep safety in priority besides efficacy to achieve complete embolization using MAC technique. Although two of our patients had ischaemic event, one requiring decompressive craniectomy for a malignant MCA infarct and another patient with infarct involving superior division of MCA territory, both had Fisher 3 SAH with severe vasospasm. In both the cases, immediate post-procedure DSA showed well-perfused distal territories. The Association of severe vasospasm with thick SAH and Fisher grade 3 is well established.,, Ischaemic events in our series were related to thick SAH rather to the procedure as there was good distal flow in the post-procedure DSA.
Shapiro et al. in their review of analysing the safety and efficacy of BAC reported total occlusion of aneurysm in 73% of all cases including both ruptured and unruptured with a thromboembolic complication of about 8% and aneurysmal perforation of 1.7% in ruptured aneurysms. In our experience, using MAC technique we could achieve Raymond Roy grade 1 occlusion in 63% of patients which is comparable to 60% reported by Lee et al. Although Lee et al., reported a 2.7% coil protrusion and 14.6% thromboembolic complication, none of our patients had periprocedural aneurysmal perforation or thromboembolic events directly related to the procedure. This difference could be attributed to our more conservative approach of aiming to secure the aneurysm in acute ruptured period achieving Raymond Roy grade 2. Even with this conservative approach, we were able to achieve remarkable occlusion in 94% of our patients, Raymond Roy grade 1 in 63% and Raymond Roy grade 2 in 31%. Need for repeat intervention was required only in 6% of our cohort. Pierot et al. in a prospective multicentric trial of 1088 patients observed anterior communicating artery location as a risk factor for intraoperative rupture. In our series, 56% of patients were anterior communicating artery and we achieved RR grade 1 occlusion in 66.7% and RR grade 2 in 33.3%. In our experience, we did not observe any complication in this subset of patients.
MAC technique has multiple advantages over BAC or SAC. Manoeuvring microcatheter is simpler than handling a stent or a balloon, especially in presence of acute rupture. Use of 6F guiding catheter is universal and no additional arterial puncture is required in MAC technique. Physical properties of the delivery microcatheter with in situ 0.014-inch microguide wire provide sufficient force to resist prolapse of the coils by acting as a strut. MAC is technically a midpath between simple coiling and BAC. Lee et al. emphasised the use of standalone microcatheter attributing the material composition of the microcatheter. But with our experience, we insist on using the microcatheter with a microguide wire to achieve a stronger resistance force. This might be the reason that we could leverage MAC even in paraclinoid aneurysms. Using large profile device will be difficult in cases with small tortuous side branch vessel from the neck of aneurysm. MAC can be also adapted with less technical demand in these situations.
| Conclusion|| |
MAC is a mid-path between simple coiling and assisted coiling techniques with ease of maneuverability. Wide neck ruptured aneurysms can be safely embolised with complete preservation of branching vessel and distal flow, provided less aggressive motive to achieve RR grade 2 embolisation to prevent rebleed is practiced. Post-procedure vasospasm should be watched out in patients with Fisher grade 3 SAH. Total occlusion of the aneurysm can be achieved in 2/3rd of patients.
Small sample size and retrospective study design has limited us to follow-up, analysis in long term regarding the recanalisation rates, and need for a second procedure.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Debrun GM, Aletich VA, Kehrli P, Misra M, Ausman JI, Charbel F. Selection of cerebral aneurysms for treatment using Guglielmi detachable coils: The preliminary University of Illinois at Chicago experience. Neurosurgery 1998;43:1281-7.
Zubillaga AF, Guglielmi G, Viñuela F, Duckwiler GR. Endovascular occlusion of intracranial aneurysms with electrically detachable coils: Correlation of aneurysm neck size and treatment results. Am J Neuroradiol 1994;15:815.
Zhao B, Yin R, Lanzino G, Kallmes DF, Cloft HJ, Brinjikji W. Endovascular coiling of wide-neck and wide-neck bifurcation aneurysms: A systematic review and meta-analysis. AJNR Am J Neuroradiol 2016;37:1700-5.
Akpek S, Arat A, Morsi H, Klucznick RP, Strother CM, Mawad ME. Self-expandable stent-assisted coiling of wide-necked intracranial aneurysms: A single-center experience. AJNR Am J Neuroradiol 2005;26:1223-31.
Ho MJ, Göricke SL, Mummel P, Mönninghoff C, Wrede K, Wanke I. Stent-assisted treatment of ruptured intracranial aneurysms in the acute phase: A single center experience. eNeurologicalSci 2018;10:31-6.
Alurkar A, Karanam LS, Nayak S, Oak S. Stent-assisted coiling in ruptured wide-necked aneurysms: A single-center analysis. Surg Neurol Int 2012;3:131.
] [Full text]
Pierot L, Barbe C, Nguyen HA, Herbreteau D, Gauvrit JY, Januel AC, et al
. Intraoperative complications of endovascular treatment of intracranial aneurysms with coiling or balloon-assisted coiling in a prospective multicenter cohort of 1088 participants: Analysis of recanalization after endovascular treatment of intracranial aneurysm (ARETA) study. Radiology 2020;295:381-9.
Sluzewski M, Rooij WJ Van, Beute GN, Nijssen PC. Balloon-assisted coil embolization of intracranial aneurysms: Incidence, complications, and angiography results. J Neurosurg 2006;105:396-9.
Taylor RA, Callison RC, Martin CO, Hayakawa M, Chaloupka JC. Acutely ruptured intracranial saccular aneurysms treated with stent assisted coiling: Complications and outcomes in 42 consecutive patients. J Neurointerv Surg 2010;2:23-30.
Lodi YM, Latorre JG, El-Zammar Z, Swarnkar A, Deshaies E, Fessler RD. Stent assisted coiling of the ruptured wide necked intracranial aneurysm. J Neurointerv Surg 2012;4:281-6.
Golshani K, Ferrel A, Lessne M, Shah P, Chowdhary A, Choulakian A, et al
. Stent-assisted coil emboilization of ruptured intracranial aneurysms: A retrospective multicenter review. Surg Neurol Int 2012;3:84.
] [Full text]
Maree AO, Fitzgerald DJ. Variable platelet response to aspirin and clopidogrel in atherothrombotic disease. Circulation 2007;115:2196-207.
Sofi F, Marcucci R, Gori AM, Giusti B, Abbate R, Gensini GF. Clopidogrel non-responsiveness and risk of cardiovascular morbidity. An updated meta-analysis. Thromb Haemost 2010;103:841-8.
Qureshi AI, Jahngir MU, Qualls K, Akinci Y, Lobanova I, Liaqat J, et al
. The effect of ticagrelor on platelet reactivity in patients with clopidogrel resistance undergoing neuroendovascular procedures. J Neuroimaging 2020;30:327-34.
Kung DK, Policeni BA, Capuano AW, Rossen JD, Jabbour PM, Torner JC, et al
. Risk of ventriculostomy-related hemorrhage in patients with acutely ruptured aneurysms treated using stent-assisted coiling. J Neurosurg 2011;114:1021-7.
Lee JY, Seo JH, Cho YD, Kang HS, Han MH. Endovascular treatment of wide-neck intracranial aneurysms using a microcatheter protective technique: Results and outcomes in 75 aneurysms. Am J Neuroradiol 2011;32:917-22.
Soeda A, Sakai N, Murao K, Sakai H, Ihara K, Yamada N, et al
. Thromboembolic events associated with Guglielmi detachable coil embolization with use of diffusion-weighted MR imaging. Part II. Detection of the microemboli proximal to cerebral aneurysm. AJNR Am J Neuroradiol 2003;24:2035-8.
Pierot L, Cognard C, Anxionnat R, Ricolfi F. Remodeling technique for endovascular treatment of ruptured intracranial aneurysms had a higher rate of adequate postoperative occlusion than did conventional coil embolization with comparable safety. Radiology 2011;258:546-53.
Park HK, Horowitz M, Jungreis C, Genevro J, Koebbe C, Levy E, et al
. Periprocedural morbidity and mortality associated with endovascular treatment of intracranial aneurysms. AJNR Am J Neuroradiol 2005;26:506-14.
Benitez RP, Silva MT, Klem J, Veznedaroglu E, Rosenwasser RH. Endovascular occlusion of wide-necked aneurysms with a new intracranial microstent (Neuroform) and detachable coils. Neurosurgery 2004;54:1359-67; discussion 1368.
Fiorella D, Albuquerque FC, Deshmukh VR, McDougall CG. Usefulness of the Neuroform stent for the treatment of cerebral aneurysms: Results at initial (3-6-mo) follow-up. Neurosurgery 2005;56:1191-2.
Tummala RP, Chu RM, Madison MT, Myers M, Tubman D, Nussbaum ES. Outcomes after aneurysm rupture during endovascular coil embolization. Neurosurgery 2001;49:1057-9.
Cai K, Zhang Y, Shen L, Ni Y, Ji Q. Comparison of stent-assisted coiling and balloon-assisted coiling in the treatment of ruptured wide-necked intracranial aneurysms in the acute period. World Neurosurg 2016;96:316-21.
Friedman JA, Goerss SJ, Meyer FB, Piepgras DG, Pichelmann MA, McIver JI, et al
. Volumetric quantification of Fisher Grade 3 aneurysmal subarachnoid hemorrhage: A novel approach to predict symptomatic vasospasm on admission computerized tomography scans. J Neurosurg 2002;97:401-7.
Rabb CH, Tang G, Chin LS, Giannotta SL. A statistical analysis of factors related to symptomatic cerebral vasospasm. Acta Neurochir (Wien) 1994;127:27-31.
Claire C, Gerard A, Francis G, Thierry C, Xavier D, Serge B, et al
. Multivariate analysis of predictors of cerebral vasospasm occurrence after aneurysmal subarachnoid hemorrhage. Stroke 1999;30:1402-8.
[Figure 1], [Figure 2], [Figure 3]