*4.3.1 Anterior view from the petrous rhomboid corridor*

The petrous rhomboid area provides a large bone corridor to the petrous and clivus lesion. The endoscopic assistance offers a deep exposure of the middle to lower clivus, epipharyngeal space, and bilateral condylar regions (**Figure 5**). Advancing the petrous rhomboid corridor toward the petrosal apex allows us to drill the bone beneath the Gasserian ganglion. The IPS can be seen where it joins the cavernous sinus. And the ICA is seen rising from the neck just below the GSPN and joining the cavernous sinus. Laterally and anteriorly, the posterior wall of the retropharyngeal mucosa is seen behind the ICA. Care must be taken during exposing the essential structure around the cavernous sinus. Continuing to follow the bony corridor and proceeding with the removal of bone from the clivus, it reaches the mid-clivus until lower clivus. At this time, when the petrous rhomboid and V2-V3 corridor are combined, the posterior aspect of the sphenoid sinus can be reached. Posteroinferiorly, at the level of the mid and lower clivus, it follows to posterior wall of epipharynx. The ability of the V2-V3corridor to provide light assistance and an enlarged working space allows for extra resection of the pterygoid or sphenoid sinus tumor.

#### **Figure 5.**

*An endoscopic image and schema and cadaveric dissection image of the anterior view from the anterior petrosal approach. A. an anterior view through the petrous rhomboid corridor after removing the petrous apex and upper clival bone. The ICA goes into the cavernous sinus. The superior and inferior petrosal sinus emerge from the cavernous sinus. B. Below the mandibular nerve (V3), a large cavity can be obtained after removing the petrous apex.*

*Surgical Approach to the Cavernous Sinus and Middle Cranial, Pterygoid Fossa DOI: http://dx.doi.org/10.5772/intechopen.104956*

#### **Figure 6.**

*Posterior view through the petrous rhomboid. A, B. schematic drawing showing a posterior view onto the medial part of the jugular foramen through the petrous rhomboid. C. Endoscopic view, in a posterior trajectory, through the petrous rhomboid. The inferior petrosal sinus, which connects to the medial wall of the jugular bulb, is visualized below the cochlea. D. the horizontal segment of the ICA was skeletonized and followed posteriorly to the vertical segment of the ICA, close to the JB. E. the IPS was cut, exposing the medial wall of the jugular foramen. The jugular tubercle is located between the jugular foramen and hypoglossal canal. Under the hypoglossal canal, the condyle and foramen magnum can be accessed. The dura mater of the posterior fossa was opened. The cranial nerves VII, VIII, IX, X, XI, XII, and vertebral artery can be identified in the intradural space.*
