CONTRALATERAL APPROACHES TO BILATERAL CEREBRAL ANEURYSMS - A MICROSURGICAL ANATOMICAL STUDY

In patients with bilateral supratentorial aneurysms, surgical clipping of all aneurysms via a unilateral approach would obviate the need for a second operation. The authors conducted a microsurgical study in hu man cadaver heads to examine the contralateral exposure for four commo n aneurysm sites in the anterior circulation: the ophthalmic artery (O A) origin, the posterior communicating artery (PCoA) origin, the inter nal carotid artery (ICA) termination, and the middle cerebral artery ( MCA) bifurcation. Frontotemporal craniotomies were performed in 16 cad avers to evaluate the corridor for exposure of these sites from the co ntralateral side. Morphometric data, including lengths and diameters o f major arterial segments and optic nerves, were documented for anatom ical cell-elation. In this study, the contralateral OA origin was succ essfully exposed in 62% of specimens, the PCoA origin in 50%, the ICA bifurcation in 100%, and the MCA bifurcation in 62%. Exposure of the O A origin and, in some cases, the PCoA, required incision of the falcif orm ligament and mobilization of the contralateral optic nerve. Exposu re of the MCA bifurcation was dependent on the length of the M-1 segme nt, with successful exposure only when this segment was shorter than 1 4 mm. Implications for the contralateral approach to aneurysms at thes e sites are discussed and the microsurgical corridors for exposure are described. For correlation with the anatomical study, a brief clinica l review of patients with bilateral supratentorial aneurysms treated a t The Johns Hopkins Hospital between 1992 and 1995 is presented. Guide lines for the contralateral approach to aneurysms are discussed with r eference to the anatomical study and the clinical review.