[Surgery of vertebral artery aneurysm at the origin of posterior inferior cerebellar artery--with special reference to operative technics in cases with difficulty in direct operation].

Twenty-two patients with posterior inferior cerebellar artery (PICA) aneurysms were treated in our department from 1965 to 1982. Except for six cases with peripheral PICA aneurysms, all aneurysm were located on the vertebral artery at the origin of PICA (VA-PICA aneurysm). Direct approach to the aneurysm was carried out in 11 cases out of 16 with VA-PICA aneurysm. We encountered difficulties in access to the aneurysm in 5 cases (case 2,4,6,13,15) and in clipping procedures in 4 cases (cases 6, 7, 10, 15). Surgical procedures through either bilateral (case 2,4) or unilateral suboccipital craniotomy included exploration in 1 case; wrapping in 1, proximal vertebral artery clipping in 3 and neck clipping in 6. These difficulties encountered during operation were evaluated in relation to angiographical findings. The aneurysms located between 0 to 5 mm from the midline or more than 21 mm from the lateral point of the foramen magnum could be reached with difficulty through unilateral suboccipital craniotomy (Figure 3,4). The aneurysms with the dome directed posteriorly had to be treated carefully because of their possible adhesion to or invagination into the medullar oblongata. The aneurysms with the dome directed medially were difficult to be clipped because they existed on the opposite side of the vertebral artery. Although all aneurysms overlying the lower third of the clivus, even on the midline, can be exposed through unilateral suboccipital craniotomy, great care should be taken especially to the aneurysms located in high position, with the dome directed medially or posteriorly, and with the distal vertebral artery running medially.(ABSTRACT TRUNCATED AT 250 WORDS)