High Cortical Subarachnoid Hemorrhage Associated with Treatment of Internal Carotid Artery Aneurysm using Flow Diverter Stent

Background— Isolated high convexity subarachnoid hemorrhage is a rare complication of flow diversion treatment.
We present two cases of ipsilateral focal sulcal subarachnoid hemorrhage not related to either aneurysm rupture or
arterial wire perforation following flow diverter placement with its probable hypothesis.
Case Description—
Case 1—An adult male presented with painful left oculomotor nerve palsy. Patient underwent balloon assisted
coiling for left anterior choroidal artery aneurysm. Angiography after six months showed recanalisation of
aneurysm. Pipeline flow diverter was deployed covering aneurysm. After fourteen hours he developed right
sided weakness. CT brain showed high convexity subarachnoid hemorrhage.
Case 2—An adult female presented with painful right abducent nerve palsy. Angiography showed dissecting
cavernous internal carotid artery aneurysm with right direct carotid cavernous fistula. Surpass flow diverter (4.5
X 20cm) was placed from distal cavernous into ascending limb of internal carotid artery along with multiple
detachable coils. Post procedure CT showed high convexity subarachnoid hemorrhage.
Conclusions— High convexity subarachnoid hemorrhage following flow diverter placement is a rare complication.
Sudden hemodynamic change / stress at the level of collateral conduits due to watershed shift, augmented systolic
flow and in certain instances impaired vasomotor reserve could have resulted in collateral rupture. Flow studies are
necessary to confirm our hypothesis