17 Medial Transcavernous Approach

The cavernous sinus is a venous dural sinus that is located in the cranial portion of the parasellar region and houses a number of neurovascular structures that are partially or totally immersed in venous blood. Due to the density of relevant structures, Parkinson and Dolenc defined this area as “anatomic jewel box.” ¹ From a topographic standpoint, the cavernous sinus can be considered boat-shaped (i.e., like a prism), with the keel oriented anteroinferiorly. ² Therefore, it has five walls: the anterior wall faces the sphenoid sinus and the superior orbital fissure, the posterior wall is adjacent to the posterior cranial fossa, the medial wall separates the venous sinus from the sellar region, the lateral wall neighbors the Meckel cave and the middle cranial fossa, and the roof is intimately related to the anterior clinoid process and the petroclinoid folds of the tentorium cerebri.

The paraclival and parasellar tracts of the internal carotid artery are located within the cavernous sinus along with the oculomotor, trochlear, ophthalmic, abducens, and maxillary nerves. In greater detail, only the internal carotid artery and the abducens nerve are actually free within the sinus, whereas the remaining structures are included within one or more of the above-mentioned walls. The cavernous portion of the internal carotid artery can be used to define four main compartments, which can be variably invaded by tumors of this area ³ : the inferior compartment lies between the anterior and inferior aspects of the parasellar carotid artery and the anterior wall of the cavernous sinus; the superior compartment is located between the superior face of the horizontal parasellar carotid artery and the roof of the cavernous sinus; the posterior compartment is enclosed between the paraclival tract of the internal carotid artery and the posterior wall of the cavernous sinus; the lateral compartment is situated between the cavernous carotid artery and the lateral wall of the cavernous sinus. Additionally, some other minor structures can be found in the cavernous sinus, namely, the sympathetic branch tended from the internal carotid artery to the abducens nerve, the meningohypophyseal and inferolateral trunks, and a complex system of dural ligaments, which only recently has been systematically described. ⁴

Given the dense network of critical structures, the cavernous sinus has been historically considered to be an unapproachable area when invaded by tumors. With the increasing experience, implementation, and refinement of hemostatic materials and neurophysiological monitoring, and evolution of anatomical knowledge of the cavernous sinus, its surgical clearance in well-selected cases is no longer considered a heresy. ⁵ – ⁷ Consistently with this trend, the morbidity of approaching the cavernous sinus in adequately selected cases has been widely resized. ⁸ Two main transnasal endoscopic approaches to the cavernous sinus can be identified with respect to the internal carotid artery: the medial transcavernous approach, which will be described in this chapter, and the lateral transcavernous approach, illustrated in Chapter 18. Both approaches pass through the anterior wall of the cavernous sinus, which is exposed underneath the carotid prominence and carotid sulcus. Further details on the borderline area between the lateral portion of the cavernous sinus and Meckel’s cave are reported in Chapter 21.

The medial transcavernous approach, which was first developed to treat sellar lesions extending to the cavernous sinus, is employed to manage the inferior compartment and to a lesser extent to reach the superior and posterior compartments. This approach has been mostly adopted for the treatment of nonfunctioning pituitary adenomas with resectable extension to the cavernous sinus. ^{9 , 10} Its role in the removal of functioning and/or nonresectable adenomas is more controversial due to the difficulty to fully control symptoms, although subtotal or partial reduction of tumor volume could facilitate adjuvant stereotactic radiotherapy or Gamma Knife radiosurgery. ¹¹ – ¹⁸ Meningiomas of the cavernous sinus pose more serious concerns due to the higher rate of complications following endoscopic resection. ¹⁹ Consequently, stereotactic radiotherapy or Gamma Knife radiosurgery, alone or following endoscopic subtotal resection, is emerging as a valuable alternative to aggressive surgery. ²⁰ Finally, a large number of nonadenomatous, nonmeningeal tumors (metastases, chordomas, chondrosarcomas, hemangiomas, lymphomas, craniopharyngiomas, schwannomas), and tumor-like lesions (sarcoidosis, fungal infection, thrombophlebitis complicating acute rhinosinusitis) of the cavernous sinus have been approached endoscopically to obtain a histological/microbiological diagnosis and/or to remove the lesion. ^{19 , 21} – ²³

Related posts:

1 Classification of Endoscopic Transnasal Approaches to the Skull Base and Adjacent Areas 9 Transsellar Approach 10 Transsellar Transdorsal Approach 15 Transpterygomaxillary Approach 18 Lateral Transcavernous Approach 21 The Suprapetrous (Meckel’s Cave) Approach

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