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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December 1, 2014
Giant Serpentine Aneurysm
- Giant serpentine aneursyms are uncommon (< 0.1%), fusiform, partially thrombosed aneurysms with a separate outflow tract to normal distal cerebral vessels and, possibly, they result from repeated dissection of an intrinsic abnormal vessel wall with intramural hemorrhages.
- Fifty percent occur in the MCA, 18% in the PCA, 15% in the vertebral artery or vertebrobasilar junction, 13% in the ICA, and 3% in the ACA.
- Clinical Presentation: Mostly related to mass effect and, less frequently, to distal ischemia by distal emboli or flow impairment. Common symptoms include headache, nausea/vomiting, hemiparesis, dysphasia/aphasia, and seizure.
- Key Diagnostic Features:
- CT: Well-circumscribed extra-axial heterogeneous mass lesion with surrounding edema, occasionally with thin peripheral rim calcifications. Intense homogeneous enhancement of the serpiginous vascular lumen and peripheral rim enhancement of the aneurysm wall.
- MRI: Heterogeneous hyeprintense signal on T1W, heterogeneous signal on T2W, perilesional a central or excentric irregular flow void on spin-echo sequences representing the patent arterial lumen. No consistent pattern for contrast-enhancement.
- Angiography: A partially thrombosed sac greater than 25 mm in diameter, with a tortuous centra or excentrical vascular channel following a wavy and sinusoidal course. There, long segmental involvement with a separate inflow and outflow zones differentiates them from saccular aneurysms.
- DDx: Cerebral arteriovenous fistula. Normal arteries on both sides are the diagnostic clue, in contrast to AVFs, where the dilated vascular pouch has a venous origin.
- Rx:
- Surgical bypass with obliteration and endovascular occlusion are the main treatment options.
- Reconstructive techniques with flow diverter stents have been used, but with higher rates of in-stent thrombosis.
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