1	Endovascular Management of Posterior Circulation Aneurysms: Our Experience at Henry Ford Hospital. Shehanaz K Ellika, Horia Marin, Max Kole & William Sanders.
2	Table of contents Introduction Normal anatomy Classification of aneurysms Saccular aneurysm Nonsaccular aneurysm Distal aneurysm Techniques of endovascular management
3	Table of contents Eg of PICA aneurysm Eg of basilar tip aneursym Eg of aneurysm rupture Eg of coil unraveling Eg of coil extrusion Endovascular coiling Complications of endovascular coiling Complication of coiling: Aneurysm recanalization
4	Table of contents Eg of balloon assisted coiling Eg of stent assisted coiling in ruptured aneurysm Eg of stent assisted coiling in unruptured aneurysm Eg of Y stent assisted coiling Balloon assisted coiling Stent assisted coiling
5	Table of contents Eg of parent vessel occlusion in acute dissecting VA aneurysm Eg of parent vessel occlusion in PCA aneurysm Eg of vessel wall remodeling Parent vessel occlusion Vessel wall remodeling
6	Table of contents Eg of flow remodeling Eg of liquid embolization Flow remodeling Liquid embolization
7	Introduction Particularity of posterior circulation aneurysms: Difficult surgical exposure. Difficult dissection due to presence of acute SAH & adhesion of aneurysm to surrounding thrombus. Location near deep brainstem structures (cranial nerves & brainstem perforators). Difficulty in obtaining proximal control.
8	Normal anatomy of posterior circulation Vertebral artery Posterior inferior cerebellar artery Basilar artery Anterior inferior cerebellar artery Superior cerebellar artery Posterior cerebral artery Brainstem perforating vessels
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10	Classification of aneurysms Morphology Saccular Nonsaccular Distal Presentation Ruptured Unruptured Size Small (< 10 mm) Large (10 – 25 mm) Giant (> 25 mm)
11	Saccular aneurysms Typical “berry” aneurysm arising at vessel branching points. Has dome and neck. Treatment options include surgical clipping or endovascular coiling.
12	Nonsaccular aneurysms Presentation can be: Acute dissecting Chronic Fusiform Dolichoectatic Transitional Involves vessel wall circumferentially. Not related to vessel branching points.
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14	Non saccular aneurysms Symptoms due to mass effect, rupture or ischemia Poor natural history with near 50% mortality at 5 years* Limited treatment options including Deconstructive methods (vessel clipping or proximal occlusion) Reconstructive methods (stent placement, surgical bypass).
15	Distal aneurysms Distal aneurysms of the posterior circulation are uncommon (0.6% of all treated aneurysms). Their pathology, presentation, natural history, and clinical management are poorly understood. Most distal aneurysms involve the circumference of the parent vessel without an apparent neck. Treatment either surgical or endovascular is occlusion of the parent vessel.
16	Distal aneurysms Endovascular treatment Endovascular parent vessel occlusion is technically easy. Can be performed in the acute phase of hemorrhage in poor-grade patients Surgery Access to distal cerebellar aneurysms is challenging. Most patients are in poor clinical condition and are not good surgical candidates in the acute phase. Surgery often complicated by cranial nerve dysfunction.
17	Techniques of endovascular management Endovascular occlusion using coils (coiling) Balloon assisted coiling Stent assisted coiling Parent vessel occlusion Vessel wall remodeling Flow remodeling Liquid embolization
18	Techniques of endovascular management Endovascular occlusion using coils (coiling) Balloon assisted coiling Stent assisted coiling Parent vessel occlusion Vessel wall remodeling Flow remodeling Liquid embolization
19	Endovascular Coiling of Intracranial Aneurysms Timeline
20	Endovascular coiling Platinum coils are inserted into aneurysm & detached with complete embolization often requiring multiple coils.
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22	Pathophysiology of endovascular coiling Coil occlusion prevents blood flow into aneurysm. Thrombus formation within the coil mass stabilizes the aneurysm. Thrombus becomes organized and replaced by connective tissue. Neck of the aneurysm is covered by neointima resulting in long term healing.
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24	Endovascular coiling - Indication Unruptured aneurysm Primary prevention Treatment of mass effect Data regarding future hemorrhage risk is from ISUIA trial Ruptured aneurysm Treatment of rupture Secondary prevention Data regarding benefits of endovascular treatment is from ISAT trial
25	ISAT International Subarachnoid Trial Dependent or dead at 1 year Coiling = 23.7% Clipping = 30.6% Relative risk = 0.774, p=0.0019 Relative Risk Reduction = 22.6% Absolute Risk Reduction = 6.9% Landmark study of treatment of ruptured intracranial aneurysms Patients randomized to clip vs. coil Conclusion: Endovascular coil treatment is significantly more likely to result in survival free of disability 1 yr after SAH than neurosurgical treatment
26	ISUIA International Study of Unruptured Intracranial aneurysms 5 year cumulative rupture risk < 7mm (group 1) 2.5% < 7mm (group 2) 3.4% 7-12 mm 14.5% 13-24 mm 18.4% >25 mm 50% group 1: no previous hx of SAH group 2: Hx of SAH of another aneurysm * posterior circulation included Pcomm origin aneurysms Largest prospective natural history study examining rupture risk of asymptomatic unruptured aneurysms Conclusion: Rupture risk is substantially higher for larger aneurysms posterior circulation aneurysms *** patients with previous history of SAH
27	Coil properties Coil wire diameter (0.018,0.014,0.012,0.010 in) Coil length (1 mm – 35 mm) Spatial configuration (2D,3D,random shaped etc) Coil characteristics ( stretch resistance, flexibility and softness) Coating (bare platinum vs. coated coils)
28	Endovascular coils Coated coils Matrix (PGLA-coated coils Boston Scientific, Natick, Mass). HydroCoil (hydrogel-coated coils MicroVention,Aliso Viejo, Calif). Sapphire fibered coils (ev3, Irvine, Calif). Cerecyte (PGA-coated coils; Micrus, Sunnyvale, Calif). Bare platinum coils GDC (Boston Scientific) Cordis Micrus Microplex
29	Bare Platinum vs. Coated Coils Coated coils are meant to obtain a better and more durable aneurysm occlusion. Overall morbidity/mortality rates are comparable (2.9%–5.4%). To date, there is no prospective randomized trial to prove benefit in aneurysm occlusion, recanalization, retreatment or rupture/rerupture.
30	Endovascular coiling-complete occlusion 41 year old female presenting with headache, nausea and vomiting. Hunt and Hess grade of II. CT scan showed SAH.
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39	Endovascular coiling-complete occlusion 62 year old male with incidentally detected unruptured basilar tip aneurysm
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47	Complications of endovascular coiling 1) Aneurysm rupture Procedural perforation by microcatheter, microguidewire or coil 2) Thromboembolic complications Catheterization related: Clotting within guide catheter and or microcatheter Coil related: Coil migration/Coil dysfunction/Coil unraveling Coil mass effect Clot formation on coil mesh 3) Aneurysm recanalization
48	Complications of endovascular coiling 1) Aneurysm rupture Procedural perforation by microcatheter, microguidewire or coil 2) Thromboembolic complications Catheterization related: Clotting within guide catheter and or microcatheter Coil related: Coil migration/Coil dysfunction/Coil unraveling Coil mass effect Clot formation on coil mesh 3) Aneurysm recanalization
49	Aneurysm rupture Aneurysm rupture during coiling occurs in 2-5% of procedures. Mortality rate of 1%. Treatment consists of: Heparin reversal with protamine Rapid completion of aneurysm obliteration with coils Intracranial decompression via ventricular drainage or craniectomy
50	Aneurysm rupture Risk factors for aneurysm rupture during coiling: 1. Small aneurysm size 2. Ruptured aneurysms 3. Aneurysms associated with teats 4. Aneurysms located in anterior communicating artery region & posterior circulation 5. Temporary occlusion balloon used
51	Outcomes in aneurysm rupture Good outcome: Patients who had ventriculostomies in place or in whom it was emergently placed after rupture were found to have better outcomes. Shorter time to control rupture with good control of ICP and BP. Poor outcome: Patients presenting in poor neurological grade. Perforating agent was a microcatheter or coil, as opposed to microguidewire.
52	Aneurysm rupture during coiling 69 year old female who presented with sudden loss of consciousness. O/E: Hunt & Hess grade 4. She was referred for endovascular coiling 24 hrs after initial rupture.
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69	Follow up Post endovascular coiling, patient was admitted to neurosurgical ICU for three weeks where she gradually improved neurologically and was discharged to rehabilitation.
70	Complications of endovascular coiling 1) Aneurysm rupture Procedural perforation by microcatheter, microguidewire or coil 2) Thromboembolic complications Catheterization related: Clotting within guide catheter and or microcatheter Coil related: Coil migration/Coil dysfunction/Coil unraveling Coil mass effect Clot formation on coil mesh 3) Aneurysm recanalization
71	Thromboembolic complications Estimated incidence is 3 -10%. Mortality of 1.9% & morbidity of 2.8%. Risk factors: Use of balloon remodeling technique Aneurysm size >10 mm Ruptured aneurysms
72	Thromboembolic complications Mechanism: Mechanical effects of guidewire & catheter on endothelium. Inherent thrombogenicities of catheters and wires. Electrothrombosis at time of coil detachment.
73	Management of thromboembolic complications Ruptured aneurysms Unruptured aneurysms Mechanical thrombectomy Pharmacological thrombolysis t-PA,Urokinase Glycoprotein IIb-IIIa inhibitors
74	Abciximab Glycoprotein IIb/IIIa inhibitor. Is a relatively safe and effective way of disrupting hyperacute thrombi without provoking hemorrhage from the aneurysm. Can be administered either intra-arterially or intravenously.
75	Complications of endovascular coiling 1) Aneurysm rupture Procedural perforation by microcatheter, microguidewire or coil 2) Thromboembolic complications Catheterization related: Clotting within guide catheter and or microcatheter Coil related: Coil dysfunction/Coil unraveling Coil mass effect Clot formation on coil mesh 3) Aneurysm recanalization
76	Coil related complications & management Coil dysfunction/unraveling Retrieval with endovascular snare Stent stabilization against the vessel wall Dual guidewire technique Coil extrusion Stent Coil mass effect on parent vessel Balloon or stent
77	Dual guidewire technique
78	Coil unraveling Occurs in <2% of coilings. If loose end of coil positioned in aortic arch, ICA or VA, high risk of coil herniating downstream & causing thrombosis and distal vessel occlusion. If loose end of fractured coil positioned in aorta downstream of supra-aortic vessels, it rarely causes vessel occlusion.
79	Coil unraveling 50 year old female presenting with SAH, Hunt and Hess grade III. Patient was referred for endovascular coiling of basilar tip aneurysm.
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90	Follow-up Patient was in critical condition in ICU for 2 weeks. Discharged to rehabilitation.
91	Coil extrusion Coil extrusion occurs in ~2.5% of aneurysm coilings. Complications: Thromboembolic phenomena including parent vessel occlusion. Management: Stent placement across the aneurysm neck to reposition the coil and restore the lumen of parent vessel.
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93	Coil extrusion 44 year old male presenting with SAH. Hunt and Hess grade II.
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102	Complications of endovascular coiling 1) Aneurysm rupture Procedural perforation by microcatheter, microguidewire or coil 2) Thromboembolic complications Catheterization related: Clotting within guide catheter and or microcatheter Coil related: Coil migration/Coil dysfunction/Coil unraveling Coil mass effect Clot formation on coil mesh 3) Aneurysm recanalization
103	Aneurysm recanalization Rate of aneurysm recanalization is proportional to size of coiled aneurysm. Small (< 10 mm) 15% Large (10-25 mm) 30% Giant (> 25 mm) >50% Degree of aneurysm occlusion is the strongest determinant for recanalization and rupture. Retreatment rate varies tremendously in literature depending on the type of coils and use of assist device ranging between 2-18%. Rebleeding rate for a coiled ruptured aneurysms 0.11%.
104	Techniques of endovascular management Endovascular occlusion using coils (coiling) Balloon assisted coiling Stent assisted coiling Parent vessel occlusion Vessel wall remodeling Flow remodeling Liquid embolization
105	Balloon assisted coiling Indications Ruptured/Unruptured wide necked aneurysms.
106	Technique First described by Moret et al in 1997. Small balloon occlusion microcatheter positioned across aneurysm neck and second microcatheter is placed within the aneurysmal sac. Balloon is temporarily inflated during coil deployment to protect parent artery lumen. 10% failure rate. Morbidity & mortality rate between 1-5%.
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108	Balloon assisted coiling Balloon serves two purposes Stabilizes microcatheter in aneurysm during coil delivery. Forces coil to assume 3D shape of aneurysm without impinging on parent vessel.
109	Balloon assisted coiling Advantages No hardware left behind (no antiplatelets to be given) Disadvantages Injury to vessel/Rupture Coil migration after deflation of balloon
110	Complications of balloon assisted coiling Thromboembolic phenomena Balloon promotes stasis & can lead to platelet aggregation & thrombus formation. Balloon in the vascular system can be a nidus for thrombus formation. Aneurysm rupture Vasospasm
111	Balloon assisted coiling 46 year old male with history of SAH & ruptured 5 mm diameter basilar tip aneurysm which was treated with coiling. Follow up angiography at 5 yrs shows recanalization at neck of aneurysm. Pt was referred for elective endovascular retreatment.
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118	Techniques of endovascular management Endovascular occlusion using coils (coiling) Balloon assisted coiling Stent assisted coiling Parent vessel occlusion Vessel wall remodeling Flow remodeling Liquid embolization
119	Stent assisted coiling Indications: Unruptured wide necked aneurysm.
120	Stent assisted coiling First described by Higashida in 1997. Stent acts as a scaffold across aneurysm neck, keeping coils inside aneurysm. Slows intra-aneurysmal flow velocity. Change in flow pattern with restoration of laminar flow. Simultaneous use of a stent & coil has additive effect in aneurysm occlusion.
121	Techniques of stent assisted coiling Placement of microcatheter in aneurysm & jailing with stent. Advantages: Stable & easier access to aneurysm Disadvantages Requires larger guiding catheter or bilateral access Deployment of stent across neck of aneurysm & accessing aneurysm through interstices of the stent. Advantage: Lower profile/single access to vessel Can be done as a staged procedure Disadvantage: Possible displacement of stent Difficult access into aneurysm
122	Deployment of stent across neck of aneurysm & accessing aneurysm through interstices of the stent.
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128	Stents Neuroform(Boston Scientific) Self-expanding nickel-titanium alloy stent Open-cell mesh design. High degree of elasticity and thermal memory Enterprise (Cordis) Self expanding nitinol stent Closed cell design. Distal ends flare out
129	Complications Acute in-stent thrombosis/Thromboembolic complications. Dislodgement or misplacement of stent. Delayed in-stent stenosis due to neointimal hyperplasia. Coil prolapse through interstices.
130	Stent assisted coiling of ruptured aneurysms Stent placement commits patient to antiplatelet therapy. Benefit of stent assisted coiling needs to be weighed against risk of intracranial hemorrhage in case of: Ventriculostomy placement Conversion to craniotomy for clipping or hematoma evacuation Aneurysm rerupture An alternative option is initial partial incomplete coiling (“securing the dome”) in the acute setting with a staged stent assisted coiling after stabilizing the patient
131	Stent assisted coiling in ruptured aneurysms 43 year-old female presenting with 4 days of severe headache. Hunt and Hess grade I. Patient was referred for possible coiling.
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140	Stent assisted coiling in unruptured PICA aneurysm 55 year old female presenting with headaches. Incidental PICA aneurysm was identified on CT angiography. Patient was referred for elective endovascular treatment.
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149	Variations in stent assisted coiling “Y” configuration basilar to bilateral posterior cerebral artery (PCA) dual stent technique for coil embolization of wide-necked basilar tip aneurysms. Cross-over technique: Stents through the PComm across the basilar apex for wide-necked basilar aneurysms. “Waffle-cone” technique: Distal end of stent placed directly into the apex of a termination aneurysm and coiling is done through sidewall of the stent.
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151	Y stenting of basilar tip aneurysm 44 year old male with incidental basilar tip aneurysm which was treated with coiling. Patient presented 4yrs later with progressive recanalization of the base of the aneurysm. Example of Y stenting for regrowth of aneurysm neck, complicated with stent migration during placement of the second stent and early stent thrombosis treated with abciximab.
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158	Techniques of endovascular management Endovascular occlusion using coils (coiling) Balloon assisted coiling Stent assisted coiling Parent vessel occlusion Vessel wall remodeling Flow remodeling Liquid embolization
159	Parent vessel occlusion Described initially in cavernous internal carotid artery aneurysm. Aneurysm treated by occluding parent vessel across aneurysm neck. Possible only if no significant side-branches are arising from the occlusion segment and if collateral circulation supplies the distal territory.
160	Parent vessel occlusion In vertebrobasilar circulation, parent vessel occlusion best suitable for VA providing: Contralateral VA or PComm are supplying BA PICA & anterior spinal artery are preserved
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162	Parent vessel occlusion 43 year old male presenting with severe headache while mountain climbing. Neurological examination was negative for focal deficit.
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174	Parent vessel occlusion after balloon test occlusion 38 years old male presenting with long history of headache.
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183	Follow up Patient was asymptomatic and fully functional on 3 month clinical follow up.
184	Techniques of endovascular management Endovascular occlusion using coils (coiling) Balloon assisted coiling Stent assisted coiling Parent vessel occlusion Vessel wall remodeling Flow remodeling Liquid embolization
185	Vessel wall remodeling Indications Ruptured or unruptured fusiform aneurysms. Used when vessel cannot be sacrificed because of absent collaterals or presence of brainstem perforating vessels.
186	Principle Reconstruction of vessel lumen using scaffold of endovascular stent(s). The aneurysm can be further treated using coil embolization. Intravascular stent bridges the inflow and outflow and holds coils in place within the aneurysm.
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188	Vessel wall remodeling 42 year old presenting with severe headaches.
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202	Techniques of endovascular management Endovascular occlusion using coils (coiling) Balloon assisted coiling Stent assisted coiling Parent vessel occlusion Vessel remodeling Flow remodeling Liquid embolization
203	Flow remodeling Indications: Transitional aneurysm of BA and VA not suitable for other interventional techniques.
204	Principle Flow remodeling used when the aneurysm cannot be excluded from the circulation. There is redirection of arterial inflow patterns in the aneurysm in order to alter vascular hemodynamics and to prevent further growth of aneurysm. Redirection of arterial flow caused alteration in wall shear stress in the aneurysm.
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206	Flow remodeling 51 year old male presenting with worsening headaches.
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214	"Patient experienced PICA territory stroke" Patient experienced PICA territory stroke, 48 hours after coil occlusion of the left VA.
215	Follow up Following the PICA territory stroke, patient developed altered level of consiousness related to edema and brainstem herniation. Family refused surgical decompression and patient expired.
216	Techniques of endovascular management Endovascular occlusion using coils (coiling) Balloon assisted coiling Stent assisted coiling Parent vessel occlusion Vessel wall remodeling Flow remodeling Liquid embolization
217	Liquid embolization 80 year-old male presenting with history of intraventricular hemorrhage with posterior fossa arteriovenous malformation for selective embolization of a prenidal flow-related aneurysm on the right PICA.
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222	Conclusion Endovascular treatment is proved to be a safe and effective therapeutic alternative to surgical treatment in patients with ruptured or unruptured posterior circulation aneurysms.