Chapter 13 Cavernous Sinus Approach

10.1055/b-0037-143519

Chapter 13 Cavernous Sinus Approach

Ernesto Pasquini, Diego Mazzatenta, Matteo Zoli, Michael Ghirelli, Giorgio Frank

Introduction

The endoscopic endonasal approach (EEA) to cavernous sinus (CS) tumors is a safe and effective route for the treatment of tumors located in the medial and lateral compartments of the CS. This approach allows the surgeon to follow the extension of the tumor into the CS through a straightforward and completely extracranial route, and permits to tailor the approach for each specific case. At the beginning of the last decade, the main issues related to CS surgery were the high invasiveness and elevated morbidity rate of standard transcranial approaches.1–3 These factors led to a progressive abandoning of CS surgery in favor of radiosurgery.1–5 The renewing interest of the CS surgery started thanks to the works of Alfieri and Jho, who reconsidered the anatomy of the CS under the endoscopic endonasal perspective.6,7 The contribution of these and many other authors has permitted this approach to become widely adopted with satisfactory results in terms of tumor removal and complications rate.8–10 In recent years, the endonasal CS approach has proved to be a replicable technique with similar results in different surgical series.8–10 Thus, it represents a technique that can be learn, transmitted, and adopted with satisfaction by incoming generations of neurosurgeons after a proper endoscopic endonasal training. In this chapter, we will analyze the anatomic and surgical premises and the results of this approach.

13.1 Indications

The case selection is one of the most important features to maximize the potentiality of the EEA to CS and minimize the morbidity. There are two main parameters that must be kept in consideration: (1) the biologic features, in terms of tumor infiltration of vessels and nerves; and (2) the pattern of growth, in particular in relationship with the dural layers. Some tumors, for example, meningiomas, metastasis, or carcinomas, tend to infiltrate the walls of internal carotid artery (ICA) and the cranial nerves (CNs). Thus, for these cases the EEA can cause catastrophic consequences, such as ICA rupture or permanent CN palsies, as dissection between the tumor and the surrounding structures is not possible.9 It is noteworthy that for these cases, and especially for meningiomas, the risk of massive intra- or postoperative bleeding is represented by the occurrence of ICA rupture and/or by the injury of the hypertrophic tumor feeders from the intracavernous ICA, such as the meningohypophyseal trunk or the inferolateral artery.11 The latter makes this surgery particularly hazardous, as it is quite complex to identify the course of these vessels even with neuronavigation or intraoperative Doppler. For meningiomas or malignancies of the CS, some authors only recommend an endoscopic endonasal osteodural decompression as a palliative measure in cases of ophthalmoplegia. This technique consists in drilling the posterior wall of the sphenoid in the sella and parasellar area, followed by the opening of the dura layer to decompress the neural structures.12–14

A further parameter to be considered is the growth of the tumor. Some substantially extradural tumors, for instance, chondrosarcoma or chordomas, could, in their growth, compress and displace the CS without any invasion.15,16 In these cases, the EEA allows to approach the tumor through an extradural route, following the same extension of the tumor to the CS. Also in case of infiltration of the CS, for example, by a pituitary macroadenoma, this approach permits as well to follow the direction of growth of the tumor.17 When persistent trigeminal arteries (PTAs) involve only the medial or posterosuperior compartments of CS, displacing laterally the ICA, a midline transsphenoidal approach is enough to manage the entire extension of the tumor. Conversely, when the tumor involves the anteroinferior or lateral compartments, displacing medially the ICA, we consider an ethmoido-pterygoido-sphenoidal (EPS) corridor more appropriate. A third selection criterion that should be taken into account for the case selection is the tumor consistency. When the tumor is soft, its resection is clearly favored; conversely, a hard, fibrous consistency with a hemorrhagic aspect greatly increases the surgical complexity, hampering the tumor resection with a greater risk of vessel or nerve damage during the surgical maneuvers. Unfortunately, this crucial feature of the tumor, which is associated with better outcome, is still scarcely predictable before surgery. Until now, this selection criterion is purely theoretic;16,18–27 but in the future, neuroimaging exams, such as magnetic resonance elastography, would maybe ensure the consistency of the tumor preoperatively.27

13.2 Surgical Steps

Depending on the different types of tumor invasion, two different surgical approaches to CS can be adopted: the mid to line transsphenoidal and the EPS.

For the former, the first target of the surgeon should be the identification of the sphenoid ostium. The tail of the superior turbinate points to the sphenoidal ostium as an arrow, and it is the more useful landmark in the nasal stage ( Figs. 13.1 and 13.2 ). For such approach, in case of normal pneumatization of the sinus, a complete sphenoidotomy is enough to identify the landmarks on the posterior wall of the sphenoid sinus and to identify the sellar bulge, the ICA protuberances, and the optic nerves ( Figs. 13.1–13.3 ). In case of conchal or presallar variant of the sphenoidal sinus, the adoption of neuronavigation and intraoperative Doppler is mandatory to identify the course of the carotid artery, while drilling off the bone to expose the sella and parasellar region.

**Fig. 13.1** Midline transnasal approach. The lateral dislocation of the middle and the upper turbinate permits identification of the natural ostium of the sphenoid sinus **(a,b)**. The opening of the sphenoidal sinus starts with the enlargement of the natural ostium, with a Kerrison or with a Stammberger punch **(c)**. All the intersinusal septa that reduce the vision and limit the maneuverability in front of the sella should be removed **(d)**.

**Fig. 13.2** Frontal view of the posterior wall of the sphenoidal sinus: the optic protuberance, the optic recess, the parasellar carotid protuberance, the tuberculum sellae, the planum, the sella, the paraclival carotid protuberance, and the clival indentation are visible **(a)**. The opening of the sellar floor should be as wide as possible from one cavernous sinus to the other and from the superior to the inferior intercavernous sinuses (four blue lines) **(b–d)**. Landmarks: parasellar (C5) and paraclival (C3) protuberance of internal carotid artery (ICA), superior intercavernous sinus, lateral opticocarotid recess (OCR).

**Fig. 13.3** The intercavernous sinus is resected, and dura resection is extended to the diaphragma sellae. The surgical route gives a straight access to the region of the chiasm, the suprasellar cistern, and the pituitary stalk. The zoomed image shows the incidental finding of an anterior communicating artery aneurysm at the dissection. A1–A2, first and second segment of anterior cerebral artery; C6, intradural portion of internal carotid artery; CNII, optic nerve; Sup hyp. art, superior hypophyseal artery.

The CS region is represented by the quadrangular space limited by the optic nerve superiorly, a horizontal line passing at the level of the vidian nerve inferiorly, the sellar bulge medially, and the junction between petrosal and cavernous ICA laterally ( Fig. 13.2 ). This anatomic exposure allows dissecting the entire extension of the CS both medially and laterally to the ICA. However, it is disadvantageous to work laterally to vessel, because it imposes an angled trajectory to the surgeon. To expand this approach laterally, it is necessary to expose and partially remove the upper part of pterygoid plates. This maneuver requires the resection of the middle turbinate and the exposure of the uncinate process and the bulla ethmoidalis ( Fig. 13.4 ). By removing these structures, the natural ostium of maxillary sinus is usually visible. The tail of the middle turbinate permits locating the sphenopalatine foramen. When this landmark is identified, it is possible to enlarge the sphenopalatine foramen on the vertical process of the palatine bone, which is the posteromedial border of maxillary sinus. After its removal, the upper part of pterygoid plates is exposed ( Fig. 13.5 ). The EPS ends when the medial and superior aspects of these processes are removed and the ethmoid is completely resected. This permits to clearly identify from a more lateral perspective all anatomic landmarks from the pterygoid canal with the vidian nerve to the opticocarotid recess, exposing frontally the entire region of CS ( Fig. 13.6 ). Opening the dura medially or laterally toward the ICA, the medial or lateral compartment of CS can be accessed ( Figs. 13.7–13.12 ). The course of the ICA can be verified by the auxilium of neuronavigation and intraoperative Doppler to avoid the damage this vessel ( Fig. 13.13 ).

**Fig. 13.4** **(a)** Uncinectomy. **(b)** Opening of the ethmoidal bulla. The opening of the bulla should be performed inferomedially to stay away from the risky areas; lamina papyracea, ethmoidal roof, and ethmoidal artery. The medial portion of the posterior wall of the maxillary sinus could be resected to expose the posterior wall of maxillary antrum and the vertical process of palatine bone. **(c)** Exposure of second portion of ground lamella of middle turbinate. **(d)** Final vision after sphenoethmoidectomy. Aeth a., anterior ethmoidal artery; B. eth, bulla ethmoidalis; Fs.o., frontal sinus ostium; LP, lamina papyracea; Max. o., maxillary ostium; MT, middle turbinate; Peth a., posterior ethmoidal artery; UP, uncinate process.

**Fig. 13.5** Combination of transnasal and transethmoidal approaches. The resection of middle **(a, b)** and superior turbinate **(c, d)** gives a full peripheral view of the sellar and parasellar region and improves the maneuverability of surgical instruments in the region. The vertical portion of the insertion of the middle and superior turbinate is usually kept in place to avoid frontal recess stenosis and damage of olfactory fibers. Aeth. a, anterior ethmoidal artery; ICA, internal carotid artery; LP, lamina papyracea; MT, middle turbinate; Oa, opthalmic artery; OC, optic canal; SphS, sphenoid sinus; ST, superior turbinate.

**Fig. 13.6** Transpterygoid access. The drill-out of upper portion of pterygoid process (PTproc) gives a lateral enlarging of the surgical field with the exposure of the lateral recess of sphenoid sinus and the region of CS from the lacerous portion of ICA to the OCr **(a, b)**. The CS region has a quadrilateral shape, located between the opticocarotid recess and the paraclival carotid protuberance medially, and the orbital apex and the trigeminal nerve protuberance laterally **(c, d)**. The pterygoid canal on the floor of the sphenoid sinus is a useful landmark because it indicates the junction between the horizontal petrosal part of the carotid artery and the ascending paraclival segment of the vessel and, therefore, it is a guide to the inferior portion of the cavernous sinus. C5, parasellar internal carotid artery; ICA, internal carotid artery; OC, optic canal; OCr, optic carotid recess; Opht. a., ophthalmic artery; P.eth a., posterior ethmoidal artery; SphS, sphenoid sinus.

**Fig. 13.7** Opening of the cavernous sinus. To avoid damage of ICA and nerves in specimen, the opening and removal of periosteal layer should be performed in a medial to lateral direction starting from the pituitary gland. After the dural removal, it is possible to expose all the intracavernous sinus segment of ICA, the VI CN, and the meningohypophyseal artery. C3, paraclival; C4, infrasellar; C5, parasellar of ICA; Men hyp a., meningohypophyseal artery.

**Fig. 13.8** Arteries of the cavernous sinus. Two major arterial branches derive from the ICA in the cavernous sinus: the inferolateral trunk (ILT) and the meningohypophyseal trunk (MHT). The former is identifiable throughout gentle medial retraction of ICA **(a)**. The ILT divides where the sympathetic fibers arising from the ICA join the VI cranial nerve. At that level, the ILT gives origin to the proximal superior branch, which runs posteriorly along the inferior aspect of the trochlear nerve, and supplies the proximal portions of the oculomotor, trochlear, and ophthalmic nerves. A second branch is represented by the artery to the superior orbital fissure, which courses in the apex of the anteromedial triangle of the cavernous sinus between the first two trigeminal nerves. From this point, its branches and the main portion continue toward the superior orbital fissure entering it, providing along its course small feeders to distal portion of the III, IV, VI, and V1 cranial nerves. ILT ends with two terminal branches, one to foramen rotundum and one to foramen ovale, respectively, which provide the supply to distal portion of V2 and V3 **(b)**. The MHT trunk can be identified following backward the inferior hypophyseal artery (IHA), located in the medial compartment of CS. This trunk originates three branches: the IHA, the tentorial artery, also known as Bernasconi–Cassinari artery, and the dorsal meningeal artery. Bernasconi–Cassinari artery supplies the proximal and middle portion of the third nerve and the fourth nerve along the cavernous sinus lateral wall and tentorial edge.

**Fig. 13.9** Exposure of lateral compartment of cavernous sinus. The involvement of lateral compartment of CS can be due to tumors extending in this compartment. To analyze this region in dissection, it is necessary to displace medially the ICA after the removal of periosteal layer. It is important to pay attention to the VI CN that run free in the CS close to the lateral wall of ICA. The others CN (III, IV, V1, and V2) are embedded between the periosteal and dural layers of lateral wall of CS. C3, paraclival; C4, infrasellar; C5, parasellar; C6, intracranial segments of internal carotid artery; Sup orb fiss, superior orbital fissure.

**Fig. 13.10** Nerves in the cavernous sinus. After pituitary resection, the course of the nerves of the CS is full exposed **(a)**. The III CN originates from the midbrain and runs in the interpeduncular cisterns. It crosses the basilar artery, passing between the posterior communicating artery and the superior cerebellar artery **(b)**. Then, it enters in the lateral wall of CS, where it courses directed toward the superior orbital fissure. The VI CN is coming from the dorsal surface of brainstem at the junction between the mesencephalon and the pons. It courses along the free margin of the tentorium and enters in the lateral wall of CS inferiorly to the III CN. The VI CN exiting from the Dorello′s canal comes into the CS, where it courses free within the sinus. With a 30-degree scope, the V CN coming from the pons and directed toward the Meckel′s cave is also visible. C3, paraclival; C4, infrasellar; C5, parasellar.

**Fig. 13.11** Superior orbital fissure, foramen rotundum, and ovale. At the superior orbital fissure, the III, IV, VI, and V1 are entering in the orbit from the CS **(a)**. Indeed, III CN at this level divides in two divisions; the inferior is directed to the inferior rectus and inferior oblique. Similarly, the superior division of the III CN, which provides the innervations of the medial and superior rectus, passes in the superior orbital fissure in the Zinn′s annulus. At the superior orbital fissure, V1 divides in its three divisions (frontal, nasociliar, and lacrimal). The frontal nerve passes through the superior orbital fissure courses on the *levator palpebrae* muscle, where it divides in the supratrochlear and supraorbital nerve. The lacrimal nerve passes above the lateral rectus muscle to innervate the lacrimal gland. The nasociliar nerve, which is the only branch of V1 passing through the Zinn′s annulus, divides in the nasal nerve, which gives origin to the anterior and posterior ethmoidal nerves and the ciliar nerve. The trochlear nerve passes medially and above the *levator palpebrae* directed toward the superior oblique muscle. The VI CN passes in the superior orbital fissure below the ophthalmic nerve to enter in the lateral rectus muscle. From the gasserian ganglion, the other two branches of trigeminal nerve arise. V2 is directed toward the foramen rotundum, to enter into the pterygopalatine fossa, while V3 enters in the foramen ovale to pass into the infratemporal fossa **(b)**. Internal carotid artery C2, intratemporal; C3, paraclival; C4, infrasellar; C5, parasellar Fiss; Sup. orb. fiss, superior orbital fissure.

**Fig. 13.12** Relationship with supradiaphragmatic structures. By opening the optic nerve sheet and the upper ring of ICA, it is possible to localize the ophthalmic artery (Ophth A) that runs back to follow the optic nerve into the optic canal to the orbit cavity, the superior hypophyseal artery (Sup hypo a), pituitary stalk, and chiasm. C3, paraclival; C4, infrasellar.

**Fig. 13.13** **(a–d)** Transpterygoid approach landmark and navigation system. The neuronavigation system is a very useful device to better recognize the ICA position during the bone removal and dura opening, mainly in not complete pneumatized sphenoid sinuses. After the opening of anterior wall of sphenoid sinus and the removal of the all intersinusal septae, all landmarks are visible for the cavernous sinus area: the optic canal (OC)—upper limit; pituitary gland—medial limit; orbit apex—antero-superior-lateral limit, foramen rotundum—antero-inferior-lateral limit; the pterygoid canal, where the vidian nerve runs—medial limit. The pterygoid canal (vidian nerve) is a very useful landmark to localize the genu between the paraclival and petrous segment of ICA. OCr, optic carotid recess.

The tumor removal can be performed with the microsurgical two-hand technique. Dissection of the tumor from the surrounding dural structures and normal pituitary gland is made in a progressive central debulking manner with suction or curettes. In this phase, we prefer to keep the endoscope fixed on a holder. The portion of the tumor invading the medial compartment is resected, following its extension and using the same opening in the medial wall of CS that the tumor created to invade the compartment ( Fig. 13.14 ). In case of involvement of the posterosuperior compartment of CS, the resection is extended to this portion following the tumor growth through the intracavernous carotid loop. At the end of the tumor removal, venous bleeding is usually not significant and can easily be controlled with hemostatic absorbable material. Afterward, the inspection of the surgical field with 30- and 45-degree- angled endoscopes permits the detection and removal of neoplastic residues ( Fig. 13.14 ). The dura can be opened also laterally to the ICA, after its identification with technological devices, to access lateral compartments of CS ( Fig. 13.15 ). The tumor removal technique in this region is not dissimilar to the previous one. Also in this case, bleeding from CS is usually not significant and can be controlled with hemostatic absorbable material. The surgical defect can be closed using absorbable material, whereas in the case of a cerebrospinal fluid (CSF) leak we usually repair using free graft with fat and/or mucoperiosteum taken from the middle turbinate or nasoseptal flap.