Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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April 9, 2020
Dissecting Aneurysm of the Main Arterial Feeder of a Vermian AVM
- Background:
- Aneurysms associated with AVM are not rare and can be a source of subarachnoid hemorrhage. In the usual situation, aneurysms are located on a patent feeding artery of the AVM.
- In this case, the aneurysm was associated with occlusion of the right SCA that was the main feeder of the AVM as shown by the MRI performed 10 years earlier.
- The association between aneurysm and arterial occlusion suggested the diagnosis of a dissecting aneurysm. Dissecting aneurysms associated with AVM are rare, and only 1 case has been reported.
- Clinical Presentation:
- Intracranial arterial dissections usually present with sudden onset of severe headache. Complications may be hemorrhagic or ischemic.
- At a chronic stage, some dissections can evolve into large fusiform aneurysms, which may exert mass effect over the adjacent structures.
- Key Diagnostic Features:
- Tapered occlusion of the artery
- Pseudoaneurysm distal to an arterial bifurcation
- Contrast stasis in the affected artery
- High-flow AV shunt lesion fed by the artery
- MR BB VWI techniques can reveal high T1 signal within the vessel wall if there is methaemoglobin, or extrinsic wall thickening, with luminal narrowing and high T2 signal in the acute phase. In this case, MRI was not performed due to the clinical status of the patient.
- Differential Diagnoses:
- Feeding artery flow–induced aneurysms: They usually arise in bifurcation sites (as sacular aneurysms usually do) and do not have associated vessel occlusion or delayed washout.
- Perinidal aneurysm: Located close to the nidus or within the nidus; typically presents with parenchymal hematoma that may be associated with SAH
- Treatment:
- Endovascular treatment of the dissecting aneurysm with liquid embolic agent or coiling occlusion of the parent vessel
- Stenting of intracranial dissections has been proposed, but in this case, it was not considered due to the size of the vessel, concomitant occlusion, and associated AVM.
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