1. Treatment of distal dissecting postero-inferior cerebellar
artery aneurysms with Onyx liquid embolic agent
Ajit S. Puri1 MD, Francesco Massari1 MD PhD, Peter Kan2 MD, J.D. Lozano1 MD, Samuel Y. Hou3 MD PhD, Anna Luisa Kuhn1 MD,
Mary Howk1 MS, Mary Perras1 NP, Christopher Brooks1 PA, Matthew J. Gounis1 PhD, Ajay K. Wakhloo1 MD PhD
1- Division of Neuroimaging and Intervention, Department of Radiology and New England Center for Stroke Research,
University of Massachusetts, Worcester, MA, USA
2-Department of Neurosurgery, University of South Florida College of Medicine, Tampa, FL, USA
3- Stroke and Neurovascular center of Central California, Santa Barbara, CA, USA

2. Disclosures
F. Massari, J.D Lozano, S.Y. Hou, Anna Luisa Kuhn, Mary Howk, Mary Perras, Christopher Brooks No disclosures A.S. Puri, Consultant: Codman and Covidien Research grant from Stryker Peter Kan Consultant: Stryker, Covidien, MicroVention M.J. Gounis Grants/Research Support: NIH, Philips Healthcare, Covidien/eV3 Neurovascular, Codman Neurovascular, Stryker Neurovascular, Wyss Institute, Tay Sachs Foundation Consultant: fee-per-hour consultation, Stryker Neurovascular A.K. Wakhloo Consulting for Stryker Research grants from Philips Medical Speakers Bureau: Harvard Postgraduate Course and Miami Baptist Vascular Institute

3. Purpose
Dissecting aneurysms of the distal segments of the PICA are an extremely rare entity, accounting for only 0.5% to 0.7 % of all intracranial aneurysms.
Treatment of these aneurysms is challenging both with surgical and endovascular approach.
We present our preliminary data regarding Onyx embolization agent utilization in the treatment of these aneurysms with proximal parent artery preservation.

4. Purpose Described treatment approaches: - observation only ?
- vessel sacrifice and surgical by-pass
- endovascular aneurysm coiling
- endovascular parent artery sacrifice (coils or glue)
 Complications included: - (re-) hemorrhage
- aneurysm growth
- brainstem perforator occlusion

5. Materials and Methods
A total of 7 consecutive ruptured peripheral postero-inferior cerebellar aneurysms were treated, in 7 patients, with superselective injection of Onyx.
Lister et al. PICA anatomical classification:
lateral medullary segment (1)
tonsillomedullary segment (1)
telovelotonsillary segment (5)
The technical feasibility, procedure-related complications, angiographic results, follow-up diagnostic imaging, and clinical outcome were reviewed.

6. Dissecting PICA Aneurysms Series1 2 5 6 7 3 4

7. Illustrative Case 1 A B C D E F
Ruptured dissecting left PICA aneurysm. A, NCCT axial image, demonstrating an extensive amount of SAH primarily involving the left cerebellomedullary cistern. Digital subtraction angiography (B frontal and C lateral views) shows the dissecting aneurysm involving the tonsillomedullary and telovelotonsillary segments of the PICA (red arrows). D, 3-dimensional view shows the aneurysm. E, Endovascular trapping with Onyx 34 of the ruptured dissecting left PICA aneurysm. F, Postoperative control angiogram shows a complete occlusion of the diseased segments and aneurysm with preserved patency of the anterior and lateral medullary segments of the left PICA.

8. Illustrative Case 2 A B C D E F
Ruptured dissecting right PICA aneurysm. A, NCCT right parasagittal image, demonstrating an extensive amount of SAH primarily involving the right cerebellomedullary cistern and forth ventricle. B, Digital subtraction angiography (lateral view) shows the dissecting aneurysm involving the telovelotonsillar segment of the PICA (red arrow). C, 3-dimensional view shows the aneurysm irregular morphology (red arrow). D, Microcatheter contrast injection within the aneurysm, demonstrating a long segment of distal right PICA involved by disease. E, Endovascular trapping with Onyx 34 of the ruptured dissecting right PICA aneurysm. F, Postoperative control angiogram shows a complete occlusion of the diseased segments and aneurysm with preserved patency of the anterior and lateral medullary segments of the right PICA.

9. Illustrative Case 3 A B C D E F
Ruptured dissecting left PICA aneurysm. A, NCCT axial image, demonstrating an extensive amount of SAH in the subtentorial cisterns, more prominent involving the left cerebellomedullary cistern. B, Digital subtraction angiography (lateral view) shows the dissecting aneurysm involving the telovelotonsillar segment of the PICA (red arrows). C, 3-dimensional view shows the aneurysm irregular morphology (red arrows). D, Microcatheter contrast injection within the aneurysm, demonstrating a long segment of distal left PICA involved by disease. E, Endovascular trapping with Onyx 18 of the ruptured dissecting left PICA aneurysm. F, Postoperative control angiogram demonstrating a complete occlusion of the diseased segments and aneurysm with preserved patency of the anterior and lateral medullary segments of the left PICA.

10. Results
Endovascular treatment was successful in all cases, with complete aneurysm occlusion and proximal parent artery preservation at final post-procedural angiogram follow-up.
No treatment-related complications were noted.
One patient with poor pre-procedural clinical condition died during hospital stay, due to sequelae of extensive subarachonid (SAH) and intraventricular hemorrhage (IVH).
No rebleeding or recanalization were observed during the follow-up.
Two patients had moderate to severe residual disability, instead favorable outcomes, with no or mild disability, were observed in four of the surviving patients.

11. Conclusion
Angiographic, diagnostic imaging, and clinical results of our series indicate that dissecting distal postero-inferior cerebellar aneurysms treatment with Onyx liquid embolic agent, with parent artery preservation, is an effective option with low morbidity and mortality rate, in those cases in which aneurysmal sac treatment is not suitable neither with surgical clipping nor with endovascular coiling.

12. Conclusion Advantages include: - minimal aneurysm manipulation
- preservation of brainstem perforator arteries
- reduction in recurrence rates
Larger studies with long-term follow-up are required to validate the results

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