Endoscopic Approaches to the Skull Base

A. B. Kassam, P. A. Gardner

• Publisher: S. Karger
• Year: 2012
• ISBN:
  9783805592116
• Topic: Medicine
• Subtopic: Neurosurgery

During the last decade the endoscopic endonasal approach (EEA) to the skull base has become a very powerful method to add to the array of neurosurgical technologies. This volume provides a broad overview of the role of transnasal approaches in a wide spectrum of skull base diseases. It starts with a historical perspective of the evolution from the microscope to the endoscope in endonasal surgery and then explores in depth the principles and techniques of the various methods. Discussed are topics based on anatomical boundaries: pituitary fossa to the suprasellar space to the cavernous sinus, clivus and the anterior cranial fossa. Access to the infratemporal and posterior fossae via both the endoscopic endonasal and the retrosigmoid approaches are reviewed. In addition, the critical topic of reconstruction following 'minimally invasive' skull base surgery and finally the learning curve and complications associated with the applications of these new and exciting approaches are discussed. This volume will provide the latest knowledge to help neurosurgeons, otolaryngologists, head and neck surgeons as well as craniofacial surgeons understand the applications and practice of this important technique.

Kassam AB, Gardner PA (eds): Endoscopic Approaches to the Skull Base.
Prog Neurol Surg. Basel, Karger, 2012, vol 26, pp 119-139

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Cavernous Sinus: Endoscopic Endonasal Approaches

Giorgio Frank^a · Ernesto Pasquini^b

^aCenter of Surgery for Pituitary Tumors, Department of Neuroscience, Bellaria Hospital, and ^bCenter of Endoscopic ENT Surgery, ENT Department Sant'Orsola-Malpighi Hospital, Bologna, Italy

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Abstract

The endoscopic transsphenoidal extended approach to the cavernous sinus is a recent but still evolving technique which may contribute to the management of cavernous sinus pathologies. As with other transsphenoidal extended approaches, it is direct and extracerebral having the advantage of being rapid and well-tolerated. Many variants exist (midline transsphenoidal endoscopic approach, ethmoid-pterygoid-sphenoidal endoscopic approach, trans-maxillo-pterygoid endoscopic approach) which should be tailored according to tumor extension in order to allow the best access to the compartments involved by the tumor. Clinical Material: Since 1998, we have performed 793 endoscopic transsphenoidal procedures, 141 (18%) of them for pathologies involving the cavernous sinus. In this chapter, we consider pituitary adenomas, chordomas and chondrosarcomas the most frequent groups (132 procedures). Pituitary adenomas invading the cavernous sinus (103 patients, 107 procedures) were the most representative group involving the superior portion of the cavernous sinus. Chordomas and chondrosarcomas (19 patients, 25 procedures) were the second group of tumors invading the cavernous sinus and affected mainly the inferior portion of the cavernous sinus. Results:The median hospital stay was 4 days for adenomas and 5 days for chordomas and chondrosarcomas. Radical tumor removal, according to postoperative MRI, was obtained in 53% of pituitary adenomas and in 44% of chordomas/chondrosarcomas. The biological cure of secreting adenomas, according to the modern remission-criteria, was obtained in 27% of the patients. A clinical improvement was observed in the great majority of patients; neurological symptoms (trigeminal neuralgia and ophthalmoplegia) responded to the release of tumoral compression. Major complications included 1 case of adjunctive oculomotor nerve palsy, 4 cases of delayed CSF leak, 1 case of hemorrhagic infarction of the residual tumor and one case of carotid artery injury. There was no perioperative mortality. Conclusion: Due to the different biological and morphological characteristics of tumors involving the cavernous sinus, a single surgical procedure of choice does not exist. Endoscopic endonasal surgery represents an adjunctive technique in the armamentarium of skull base surgeons. It is indicated in selected cases (intracavernous, soft tumors not invading the vessels and/or the nerves) and represents the most balanced technique as regards safety, tolerability and efficacy. Surgery still plays a central role in the treatment of cavernous sinus tumors; sometimes surgery alone is sufficient but, more frequently, multimodal therapy is required in which medical and radiation therapy contribute to controlling neoplastic disease.

Copyright © 2012 S. Karger AG, Basel

Cavernous sinus (CS) surgery represents a surgical challenge due to the anatomical complexity and high functional value of the structures contained in this ‘jewelry box’. Since the 1960s, surgical interest in this region has increased as has the anatomical knowledge of this region. Before then, it had been considered to be a large, intradural, trabeculated venous cavern, similar to other dural sinuses. This belief is due to Claudius Galen who dissected animals with parasellar carotid retia bathed in venous blood and then transposed his findings to human anatomy. Winslow [1] christened this structure the ‘cavernous sinus’, presumably thinking that it resembled the corpus cavernosum of the penis. When it was first entered deliberately in a case of long-standing arteriovenous fistula, the engorged and thickened arterialized veins were noted to be neither cavernous nor dural sinus but a plexus of veins [2]. Multiple surgical explorations, gross dissections and microscopic views led to the present belief: the lateral sellar compartment is extradural and the venous structures contained within consist of a variable plexus of thin-walled veins. This compartment continues along the clivus and basiocciput with the extradural space of the spine. Anteriorly, the compartment is continuous through the superior orbital fissure with a similar arrangement in the orbit. ‘Lateral sellar compartment’ is the name proposed to replace the old term ‘cavernous sinus’ which is inappropriate [3]. However, since all scientific texts today continue to call this compartment and the veins within it exclusively the cavernous sinus, we will continue to use this nomenclature due to its general acceptance, even if it is incorrect and misleading.

Pioneers of cavernous sinus surgery [2, 4, 5] used a craniotomic approach to penetrate the cavernous sinus through the narrow windows existing between the nerves on its superior and lateral walls; the main advantage of the transcranial approach is the safety given by the proximal and distal control of the internal carotid artery. After an enthusiastic phase with this type of surgery which lasted 20 years, its use has been steadily decreasing, partly due to the appearance of alternative non-surgical therapies such as radiosurgery and partly due to its high morbidity. In the 1980s, one of the most famous skull base neurosurgeons wrote about cavernous sinus surgery that the ‘very early enthusiasm will undoubtedly be tempered in time by the poor results and complications that will be encountered in some patients’ [5]. At present, the strategy for the management of cavernous sinus tumors is changing; the aim is to control the mass effect and not necessarily radically remove the tumor, achieving improvement of neuropathies and avoiding the risk of increasing neural damage [6]. Therefore, a multidisciplinary strategy is preferred in which surgery, radiation therapy and pharmacological therapy all contribute to obtaining the final result. The transcranial approach still remains the main surgical procedure for meningiomas, vascular malformations, or tumors with a major intradural component.

Currently, there is increasing interest in anterior extracranial approaches to the cavernous sinus for tumors growing within the cavernous sinus or those extending to it but having an extradural extracranial location.

The first anterior extracranial approach to the cavernous sinus was described by Laws et al. [7] in 1979 for the treatment of a carotid-cavernous fistula using a contralateral ethmoid-sphenoidal approach. Subsequently, several microscopic anterior approaches were proposed for the treatment of cavernous sinus pathologies: transsphenoethmoidal [8], transmaxillosphenoidal [9], transmaxillary [10] transmaxillary-transnasal [11] and, recently, an extended transsphenoidal approach with submucosal posterior ethmoidectomy [12]. The aim of these approaches is to overcome the strictly median exposure and the reduced peripheral vision characteristic of the transsphenoidal approach, creating a wider surgical channel in order to allow adequate exposure of the surgical field.

The emergence of the endoscope on the neurosurgical landscape [13] has introduced the possibility of wide peripheral and endocavitary vision through a limited surgical channel.

Detailed anatomical studies [14, 15] have shown the feasibility and the advantages of the endoscope in approaching the cavernous sinus. Three types of approaches, paraseptal, middle turbinectomy and middle meatal, have been described which are tailored according to the mediolateral extension of the tumor.

Regarding the endoscopic approach to the CS, the Bologna group has suggested a ‘far lateral’ approach, the etmoido-pterygo-sphenoidal approach, which is appropriate for tumors which also invade the lateral compartment of the cavernous sinus [16]. A further extreme lateral approach may be suggested, the transmaxillo-pterygoid approach, which is of value in tumors extending from the cavernous sinus through the foramen rotundum to the pterygo-maxillary fossa, or vice versa. Therefore, multiple endoscopic endonasal approaches are currently available and they should be selected according to the CS compartments which are involved by tumor.

Anatomical Remarks

The following paragraph is not intended to describe the anatomy of the cavernous sinus but simply to make some observations useful in understanding surgical strategy.

The cavernous sinuses are located near the center of the head on each side of the sella and body of the sphenoid bone. The cavernous sinuses have an oblique converging direction extending from the lower surface of the anterior clinoid process and from the posterior edge of the superior orbital fissure to the posterior clinoid process above the junction of the petrous apex with the body of the sphenoid bone. A cavernous sinus has four walls: lateral, medial, roof, posterior. The roof faces the basal cisterns, the lateral wall faces the temporal lobe, the medial wall faces the sella turcica, the pituitary gland and the sphenoid bone, and the posterior wall faces the posterior cranial fossa. The medial and lateral walls join inferiorly in a ‘keel-like’ formation at the level of the superior margin of the maxillary nerve. The medial wall may be divided into a superior part (sellar part) and into an inferior part (sphenoidal part or inferior wall) [17]. The cavernous sinus walls envelop the cavernous carotid segment and its branches: the sympathetic plexus, the IIIrd, IVth and VIth cranial nerves, the first trigeminal division and multiple venous structures.

The walls of the CS are composed of two layers: the external meningeal layer and the internal endosteal layer. Only the medial wall, in the sellar part and in the sphenoidal part or inferior wall, is formed by one layer. This layer is formed by the meningeal layer in the sellar part and by the endosteal layer in the sphenoidal part or inferior wall [17]. The intercavernous sinuses, connecting the two cavernous sinuses, are found between the two layers covering the anterior, posterior and inferior surfaces of the sella. The IIIrd, IVth and ophthalmic branch of the Vth cranial nerve are embedded in the reticularis membrane that forms the ...