30 Endoscopic Approach to the Cavernous Sinus Area: Surgical Technique
Abstract
With the development of endoscopic surgery, cavernous sinus tumors became accessible for surgical removal via transnasal transsphenoidal approach.
Due to the location, complexity of the anatomical composition, and the relationship with the surrounding structures, the cavernous sinus is the subject of numerous interdisciplinary studies involving neurosurgeons, neurologists, otolaryngologists, and ophthalmologists. In the operating room (OR) as well, collaboration of ear, nose, and throat (ENT) surgeons and neurosurgeons would be advisable.
This chapter presents the lateral transsphenoidal approach through the pterygopalatine fossa that allows access not only to the lateral recess of the sphenoid sinus, cavernous sinus, but also to the Meckel’s cavity, the medial part of the middle cranial fossa.
For successful endoscopic operations in the area of the cavernous sinus, sufficient high-quality endoscopic equipment and neurosurgical instruments must be at hand.
All stages of endoscopic transnasal transsphenoidal approach should be performed only with good visualization of the main anatomical landmarks and in a clean operating field. During extended laterosellar approach, we prefer the bi-nostil approach, which allows surgeons to comfortably use the four-hand technique, which allows them to work more safely and efficiently.
Another important component of successful surgery is adequate hemostasis. Therefore, it is useful to have all kinds of local hemostatic agents and a complete set of coagulation tweezers with different angled tips, allowing hemostasis in any deep surgical areas. In addition to conventional hemostasis methods, in our practice, we use an alternative technique of applying the fibrin-thrombin glue, which ensures high-precision results.
Keywords: skull base, cavernous sinus, transnasal approach, endoscopy
30.1 Introduction
Before the 1960s, surgical treatment of the cavernous sinus tumors was considered impossible. With the advent of microsurgery, resection of tumors of this location became quite frequent, Dolenc approach with resection of the anterior clinoid process being predominant.1 , 2 , 3 Dwight Parkinson was a pioneer in direct cavernous sinus surgery who inspired development of many approaches to improve the surgical outcomes in this area.4 Nevertheless, transcranial approaches to this area have been accompanied by oculomotor nerves injury in most cases. This is due to the fact that the oculomotor nerves are located on the lateral wall of the cavernous sinus, which is damaged during open access surgery.5 , 6 , 7
With the development of purely endoscopic surgery, cavernous sinus tumors have become accessible for the surgical removal via transnasal transsphenoidal approach.2 , 8
Extended lateral endoscopic approaches, including the resection of the cavernous sinus wall, allow removal of various tumors with laterosellar expansion from the cavernous sinus, despite the involvement of neurovascular structures into the tumor tissue.9 , 10 The advantage of the endoscopic access is that the medial wall of the cavernous sinus is first exposed,11 but not the lateral one as via open approach, and therefore the risk of oculomotor nerve damage is reduced.7 , 10
Due to the location, complexity of the anatomical composition, and interrelation with the surrounding structures, the cavernous sinus area has long been a subject of interest for numerous multidisciplinary studies involving neurosurgeons, neurologists, otolaryngologists, and ophthalmologists.
30.2 Technical Equipment and Surgical Supplies
It is essential to have sufficient high-quality endoscopy-related equipment and modern neurosurgical instrumentation at hand to ensure successful endoscopic operations in the area of the cavernous sinus (Fig. 30.1).
Taking into account the intricate anatomy of this region, the use of intraoperative neuronavigation is highly advisable, too, as it allows maintaining anatomical orientation during the surgical approach and tumor resection (Fig. 30.1).
For effective and safe resection of the lesions in the area of the cavernous sinus, it is necessary to have a full range of instruments: a microsurgical set (a microscalpel, microscissors), rigid endoscopes with different angles of view (0, 30, 45, and 70 degrees), mono- and bipolar coagulators, bone nippers, high-speed drills (cutting and diamond burrs), nasal tips for ultrasonic disintegrator, and standard instruments for endonasal access (Fig. 30.2).
Fig. 30.2 (a) A general view of the instruments necessary for carrying out a transnasal operation. (b) A set of high-speed burr tips, cutting and diamond burrs, and shaver tips for soft-tissue excision during endonasal access. (c) Microsurgical instruments for resection of the tumor. (d) A motor system with a shaver function and a drill. (e) A general view of various types of monopolar and bipolar coagulators and tips of bipolar tweezers with different angles for coagulation in hard-to-reach places. (f) Endoscopes with various angles of view.
It is useful to have a full set of coagulation tweezers with tips of different angles, allowing thermal hemostasis in any deep surgical sites ( Fig. 30.2e).
The use of cavitron ultrasonic surgical aspirator (CUSA) apparatus is very helpful during tumor removal (Fig. 30.3). Its operating principle is based on the cavitation destruction of living cells of various tissues, containing a large amount of liquid, by means of ultrasonic exposure with frequency above 20,000 Hz, carried out by direct mechanical contact of the vibrating metal rod with the target tissue surface.
Fig. 30.3A general view of cavitron ultrasonic surgical aspirator (a), a handpiece, and nasal tips for cavitation ultrasound aspirator, destroying both soft and bony structures (b).
30.3 Preoperative Preparation Stage
30.3.1 Setup of the Patient and the Surgeon
The adequate positioning of the patient may considerably contribute to the flow of the surgical procedure as well as to a positive patient outcome. In this type of surgery, a semi-sitting position of the patient is advantageous as it ensures less bleeding due to reduced venous pressure and increased venous outflow (Fig. 30.4).11
Fig. 30.4 (a) A general view of the operating room with an endoscopic column, a sterile table for the nurse, the patient in the semi-sitting position, and a pneumatic arm holding the endoscope inserted into the nasal cavity. (b) A pneumatic arm can hold the endoscope in any required position.
In order to facilitate the surgical process, it is good to use a pneumatic arm that easily moves and reliably locks the endoscope enabling the surgeons to freely manipulate the tools with four hands.
It is very important to control the intracranial pressure (ICP) during the main stage of the surgery. To that end, it is advisable to preoperatively install an external lumbar drainage system for managing the cerebrospinal fluid (CSF) outflow. Drainage of a small amount of CSF can prevent the sellar diaphragm from sagging into the surgical field in case of increased ICP, and thus allows for the thorough inspection of the surrounding anatomical structures and total removal of the tumor.
30.4 Surgical Technique
30.4.1 Stages of the Surgical Procedure
Endonasal Stage
The endonasal phase of the procedure involves the surgical access to the anterior wall of the main sinus.
During the expanded laterosellar access, we prefer a bi-nostil approach, which enables surgeons to use comfortably a four-hand technique.
All stages of endoscopic transnasal transsphenoidal approach should be performed only when the main anatomical landmarks are visualized well.12 , 13 , 14
The anatomical landmarks of the endonasal phase of the procedure include upper, middle, and inferior nasal concha, choana, nasal septum, and sphenoethmoidal recess (Fig. 30.5).
