Marco Ferrari, Marco Ravanelli, Francesco Belotti, Alberto Schreiber, Roberto Maroldi
The lateral compartment of the cavernous sinus is located between the cavernous portion of the internal carotid artery and the lateral wall of the cavernous sinus.1The mediolateral extension of sellar lesions invading the cavernous sinus is classified in four grades according to Micko et al2: grades 1 to 3 are defined in relation to three lines connecting the cross-sectional parasellar and intracranial internal carotid artery (grade 3 is further divided into 3A or 3B when the tumor grows cranially or caudally to the parasellar internal carotid artery, respectively). Namely, the medial tangent, the line through the cross-sectional centers, and the lateral tangent permit definition of the incremental medial-to-lateral extension of pituitary adenomas with parasellar growth. In grade 4, the parasellar tract of the internal carotid artery is encased by the tumor. Meningiomas of the parasellar area frequently involve the lateral compartment of the cavernous sinus by following the meningeal framework.3As a consequence of the lateral position of neural structures within the cavernous sinus, parasellar schwannomas tend to arise from the lateral compartment. Similarly, hemangiomas and epidermoid cysts frequently invade the lateral portion of the cavernous sinus.4–10Thus, both neurogenic and meningeal lesions of the parasellar area pose similar, if not greater, problems to grade 3 and 4 pituitary adenomas.
The lateral transcavernous approach passes laterally to the parasellar tract of the internal carotid artery, from the anterior wall to the roof and posterior wall of the cavernous sinus.11When far posterior extension to the interpeduncular/parapeduncular area is needed, the medial and lateral transcavernous sinus corridors can be merged and/or further extended posteriorly with the transdorsal or transoculomotor triangle approaches (see interdural hypophysiopexy, as shown in Chapter 10).12,13Given its wider lateral extension compared to the medial transcavernous approach, a superior transpterygoid approach can be helpful, though not strictly necessary, to adequately expose the inferolateral portion of cavernous sinus (see also Chapter 21). The lateral transcavernous approach crosses the trajectory of the nerves of the lateral wall of the cavernous sinus and Meckel’s cave, which are therefore exposed to the risk of being damaged. Considering the benign behavior of most diseases involving this area, there is general consensus that their management should be discussed by a multidisciplinary team and tailored on a case-by-case basis. The current trend consists of achieving the most complete resection while minimizing the risk of postoperative complications. In line with this philosophy, stereotactic radiotherapy or Gamma Knife radiosurgery should be kept in consideration to manage critical and/or residual extensions of the lesion rather than with aggressive surgery.
Fig. 18.1 Sagittal view of the cavernous sinus. This sagittal illustration shows the main structures of the lateral portion of the cavernous sinus.
This chapter illustrates in a step-by-step fashion the dissection of the lateral transcavernous approach, and provides several anatomical details on the vascularization of the lateral portion of the cavernous sinus. Interestingly, the identification of structures within the cavernous sinus will entail meticulous removal of fat tissue that can be variably found within the dural sinus, and especially nearby neurovascular structures.14,15Given their strict relationship, the lateral transcavernous approach and suprapetrous approach to Meckel’s cave share several anatomical details. Therefore, reading of Chapter 21 is strongly recommended before starting dissection of the lateral compartment of the cavernous sinus.
Fig. 18.2 Subtemporal lateral-to-medial view of the cavernous sinus. This cadaver picture shows with a lateral-to-medial epidural perspective the lateral portion of the left cavernous sinus. The mandibular nerve (V3) has been sectioned and displaced to properly expose the cavernous sinus. III, oculomotor nerve; IV, trochlear nerve; V1, ophthalmic nerve; V2, maxillary nerve; VI, abducens nerve; DPN, descending palatine nerve; ET, eustachian tube; GSPN, greater superficial petrosal nerve; ION, infraorbital nerve; peICA, petrous tract of the internal carotid artery; pICA, paraclival tract of the internal carotid artery; VN, vidian nerve. (Black arrowheads, sympathetic branch for the abducens nerve.)Fig. 18.3 Axial and sagittal MRI anatomy of the cavernous sinus. Axial (a) and sagittal (b) T1-weighted contrast-enhanced fat-saturated images passing through the cavernous sinus. The cavernous sinus is formed by four compartments: the inferior compartment (InCS) is located anterior and inferior to the paraclival (pICA) and parasellar tracts of the internal carotid artery (sICA). The superior compartment (SuCS) lies between the parasellar carotid artery and the roof of the cavernous sinus. The posterior compartment (PoCS) is located posterior to the internal carotid artery and anterior to the posterior wall of the cavernous sinus. The lateral compartment, which is shown in ▶Fig. 18.4, lies between the internal carotid artery and the lateral wall of the cavernous sinus. III, oculomotor nerve; AHyp, adenohypophysis; iICA, intracranial tract of the internal carotid artery; MCP, middle clinoid process; NHyp, neurohypophysis; ON, optic nerve; OpA, ophthalmic artery; pcICA, paraclinoid tract of the internal carotid artery.Fig. 18.4 (a–i) Coronal MRI anatomy of the cavernous sinus. The panel includes six CISS (constructive interference in steady state) MRI (left and right columns) and three T1-weighted contrast-enhanced fat-saturated images (central column) passing through the anterior (upper row), middle (middle row), and posterior portions of the cavernous sinus (lower row). The lateral compartment of the cavernous sinus (LaCS) is located laterally to the virtual plane (white dotted line) tangent to the lateral surface of the paraclival (pICA) and parasellar tracts of the internal carotid artery (sICA). The superior compartment (SuCS) lies between the plane passing through the superior aspect of the parasellar carotid artery (white dashed line) and the roof of the cavernous sinus and the anterior clinoid process (ACP). The lateral compartment houses several cranial nerves, namely, the oculomotor nerve (III), which runs in a borderline position close to the superior compartment, the trochlear (IV), abducens (VI), ophthalmic (V1), and maxillary nerves (V2). Moreover, the lateral compartment is adjacent to Meckel’s cave (MeC). V3, mandibular nerve; A1, precommunicating tract of the anterior cerebral artery; AHyp, adenohypophysis; ASIS, anterosuperior cavernous sinus; CSMW, medial wall of the cavernous sinus; DoS, dorsum sellae; ICLi, interclinoid ligament; iICA, intracranial tract of the internal carotid artery; MCA, middle cerebral artery; OCh, optic chiasm; ON, optic nerve; OT, optic tract; peICA, petrous tract of the internal carotid artery; PLLi, petrolingual ligament; PSt, pituitary stalk; VC, vidian canal.Fig. 18.5 Sagittal and parasagittal MRI of the oculomotor, trochlear, and abducens nerves. The panel includes one sagittal (a) and two parasagittal (b, c) CISS (constructive interference in steady state) MRI depicting the anatomy of the oculomotor (III), trochlear (IV), and abducens nerves (VI). The oculomotor nerve arises from the mesencephalon and passes between the precommunicating tract of the posterior cerebral artery (P1) and the superior cerebellar artery (SCA). Then, it reaches the cavernous sinus (CS) by piercing the posterior half of its roof. Finally, it runs within the lateral wall of the cavernous sinus while coursing adjacently to the inferior aspect of the anterior clinoid process (ACP). The trochlear nerve reaches the cavernous sinus below the oculomotor nerve, passing through the anterior insertion of the tentorium. The abducens nerve arises from the bulbopontine sulcus and runs within the median prepontine cistern (MPCis). Thereafter, it enters the basilar plexus (BaP) and reaches Dorello’s canal (between the two white bars), which is formed by the petroclival junction and the superior petrous apex (SuPA) inferiorly and the petroclinoid (or Gruber’s) ligament (PCLi) superiorly. The abducens nerve runs inside the cavernous sinus through Dorello’s canal, where it sharply acquires a more horizontal trajectory compared to the previous tracts. APMe, anterior pontine membrane; CPr, carotid prominence; iICA, intracranial tract of the internal carotid artery; LiM, Liliequist’s membrane; LOCR, lateral optic–carotid recess; ON, optic nerve; pcICA, paraclinoid tract of the internal carotid artery; pICA, paraclival tract of the internal carotid artery; sICA, parasellar tract of the internal carotid artery.
Endoscopic Dissection
Nasal Phase
Paraseptal sphenoidotomy.
Transrostral sphenoidotomy.
Expanded transrostral sphenoidotomy.
Vertical uncinectomy.
Horizontal uncinectomy.
Anterior ethmoidectomy.
Posterior ethmoidectomy.
Transethmoidal sphenoidotomy.
Middle and superior turbinectomy.
Type A endoscopic medial maxillectomy.
Facultative: Type B–D endoscopic medial maxillectomy.
Skull Base Phase
Facultative: Transsellar approach.
Facultative: Transcavernous (medial) approach.
Facultative: Transclival (midclivus) approach.
Facultative: Optic and orbital decompression.
Facultative: Superior transpterygoid approach.
Step 1: Removal of the carotid prominence and lateral wall of the sphenoid sinus.
Step 2: Removal of the optic strut.
Step 3: Removal of the carotid sulcus and partial removal of the midclivus.
Step 4: Removal of the lingual process.
Step 5: Incision of the anterior wall of the cavernous sinus.
Step 6: Medialization of the sellar portion of the internal carotid artery.
Step 7: Dissection of the lateral compartment of the cavernous sinus.
Step 8: Section of the inferolateral trunk.
Step 9: Dissection of the posterior compartment of the cavernous sinus.
Step 10: Dissection of the inferior compartment of the cavernous sinus.
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