Fig. 2.

Dural opening and intradural exposure in the LSO approach. ( A ) The dura is opened in a C-shaped fashion, exposing the frontal lobe, the Sylvian fissure and the superior temporal lobe. ( B ) With proximal dissection of the Sylvian fissure, the MCA and insula are subsequently exposed. ( C ) The ICA, optic nerve, and anterior clinoid process are exposed subfrontally with minimal retraction. ( D ) The contra- and ipsilateral optic nerves and A1 segments of the ACA are further exposed; the recurrent artery of Heubner can be seen branching off A1. ( E ) The ACoA and bilateral A2 are not well visualized in this approach due to obstruction by the gyrus rectus. The ipsilateral olfactory tract can be seen on the inferior surface of the frontal lobe. ( F ) Further intrasylvian dissection reveals the ipsilateral ICA and MCA bifurcation. ( G ) The pituitary stalk can be accessed via the window between the ipsilateral optic nerve and ICA. The PCoA and AChA perforators are seen branching off the supraclinoidal ICA. ( H ) Further lateral dissection with temporal lobe retraction can expose the oculomotor nerve. Abbreviations: ACA, anterior cerebral artery; ACoA, anterior communicating artery; AChA, anterior choroidal artery; ACP, anterior clinoid process; A1, A1 segment of the anterior cerebral artery; A2, A2 segment of the anterior cerebral artery; CN, cranial nerve; cont., contralateral; ICA, internal carotid artery; ipsi, ipsilateral; LSO, lateral supraorbital; MCA, middle cerebral artery; olf., olfactory; optic n., optic nerve; PCoA, posterior communicating artery; PCP., posterior clinoid process; pit., pituitary; rec. a., recurrent artery (of Heubner); temp, temporal.