Aneurysms of the posterior inferior cerebellar artery (PICA) are the second most common aneurysms of the posterior circulation (after basilar tip aneurysms). They generally arise at the junction of PICA and vertebral artery and are in close proximity to the lower cranial nerves (glossopharyngeal, vagus, spinal accessory, and hypoglossal).

The challenge in surgical treatment of PICA aneurysms is twofold: 1) exposing the aneurysm, which is often partially hidden in front of the medulla, and 2) working between the delicate fibers of lower cranial nerves to clip the aneurysm. This exposure requires a far lateral suboccipital craniectomy, which involves resection of occipital bone from foramen magnum to and into the occipital condyle, thus providing a surgical window lateral to the medulla.

Vertebral angiogram showing PICA aneurysm.

Post-operative CT revealing the extent of bone removal in far lateral suboccipital craniectomy.