Microsurgical evaluation of the pterional approach to aneurysms of the distal basilar circulation.

The microsurgical correlates the pterional approach to the distal basilar circulation were evaluated in 20 cases of posterior circulation aneurysms, 50 human cadaver dissections, and a variety of other intracranial surgical lesions. The pterional approach permitted successful clipping of the aneurysm in 13 of 15 basilar bifurcation aneurysms, 1 of 2 basilar-posterior cerebral aneurysms, and 2 of 3 basilar-superior cerebellar aneurysms. In each of the failed attempts via the pterional approach, the subtemporal route ultimately resulted in proper clip application. The interposition of the posterior clinoid process was the impediment to successful clipping in three of the four cases that could not be managed via the pterional approach. All 3 of these patients had a basilar bifurcation that was below the level of the posterior clinoid on angiography, whereas none of the remaining 17 aneurysm patients demonstrated a low-lying bifurcation. Posterior displacement of the basilar artery away from the posterior clinoid exceeded 1 cm in only 13% of our cases and was not an impediment to successful clipping of the aneurysm via the pterional route. We conclude that, when the anatomical situation is appropriate, the pterional approach offers the advantages of less brain retraction and better visualization of the parent arteries and important perforating branches when compared to the subtemporal approach.