Relationship of the Paraclival and Parasellar Internal Carotid Artery With the Cavernous Sinus and Meckel’s Cave. A, 0-degree view after a left-sided hemisellaectomy and transmaxillary/transpterygoid approach have been performed, and the lateral recess of the sinus has been opened. The lateral opticocarotid recess, maxillary strut, lingular process, and upper edge of the petroclival fissure have been identified. The vidian nerve can be followed posteriorly from the pterygopalatine ganglion to the lateral aspect of the foramen lacerum where the petrous ICA transitions to the paraclival segment. The ICA sock has been partially removed. The V2 can be identified inferior to the maxillary recess. B, 45-degree view lateral to medial on the left side. The periosteal dura overlying the paraclival and parasellar ICA, the cavernous sinus, and Meckel’s cave have been removed, and the sympathetic plexus has been identified. C–E, stepwise advancement of a 45-degree endoscope lateral to the left paraclival ICA. C, The lingular process of the sphenoid sinus has been identified lateral to the proximal aspect of the paraclival ICA. The gasserian ganglion has been retracted laterally. D, The lingular process of the sphenoid sinus (asterisk), petrous apex (arrowhead), petrolingual ligament (arrow), and trigeminal impression are identified. Superior to the petrolingual ligament and immediately lateral to the paraclival ICA is the anteroinferior compartment of the cavernous sinus. The proximal aspect of the cavernous segment of the abducens nerve runs almost horizontally lateral to the transition of the paraclival to parasellar ICA in the cavernous sinus. Distal to the level where the nerve crosses the transition from paraclival to parasellar ICA, it rises obliquely (at an ~30-degree angle) toward the superior orbital fissure (SOF). This subsegment of the nerve is termed distal cavernous. Immediately lateral to the lower aspect of the cavernous sinus is the upper third of Meckel’s cave and the gasserian ganglion. The V1 nerve courses lateral to the abducens nerve in the lower part of the sinus; both structures are lateral to the parasellar ICA. The V2 nerve is located outside the cavernous sinus. Lateral and postero- and inferolateral to the petrolingual ligament are the lower two-thirds of Meckel’s cave. E, More posteriorly, at the transition from the paraclival to the parasellar ICA, the abducens nerve is seen passing below Gruber’s ligament (asterisk) as it enters the cavernous sinus. The proximal cavernous subsegment of the nerve runs almost horizontally along the same trajectory of the gulfar subsegment. The trigeminal nerve is seen more laterally as it enters Meckel’s cave. F, The petroclival fissure has been drilled, the petrous apex is shown (asterisk), and the vertical aspect of the inferior petrosal sinus has been exposed and opened. The bone overlying the inferolateral aspect of the sellar floor as well as the clival recess has been drilled as in A. The cisternal segments of the fourth, fifth, and sixth nerves are identified. (Images courtesy of AL Rhoton, Jr.)