We report 2 cases of thrombosed giant aneurysm of peripheral posterior inferior cerebellar artery (PICA) with progressive neurological deterioration due to brain stem and cerebellar compression. The patients underwent aneurysm trapping and revascularization by means of anastomosis between the distal PICA and the occipital artery (OA). In Case 1, which presented with tetraparalysis and lower cranial nerve signs and symptoms, a thrombosed giant aneurysm (4×3 cm) arising from the lateral medullary segment of PICA was treated by clip occlusion of the vertebral artery at 2 points, proximal and distal to PICA origin hidden by the aneurysmal dome, and clipping of PICA distal to the aneurysm. Thus, the aneurysm was trapped, and the PICA territory was revascularized by anastomosis between OA and the distal segment of PICA. In Case 2, which presented with hemiparesis and lateral medullary syndrome, a serpentine aneurysm (2.5×2.5 cm) arising from the lateral medullary segment of PICA was trapped, and the distal PICA was revascularized by anastomosis with OA. Thrombectomy was not done in either case. Both patients showed a very good recovery.
The procedure of choice in aneurysm surgery is the isolation of aneurysm from blood flow with preservation of the parent artery. Trapping of aneurysm with revascularization by bypass is the second-best choice in aneurysms in which direct neck clipping is impossible. Aneurysmal thrombectomy is not necessary as is shown in our cases. It should be avoided in deep and narrow operative fields where the hidden lower cranial nerves or the brain stem can be inadvertently damaged by the maneuver.
Trapping and bypass is the alternative when direct neck clipping or intravascular treatment is not feasible.