Transorbital Approaches to the Sinuses, Skull Base, and Intracranial Space

In addition to having a number of options for approaching a target, we can also use two or more pathways at once to treat a lesion (multiportal technique). 4 Operating through a single pathway or paired adjacent pathways (e.g., through both nostrils) can lead to visual obstruction of the target by instruments, or a challenge in instrumenting the target because the endoscope may be in the way. Furthermore, blood and secretions can run down the instruments onto the endoscope, further obscuring visualization. By operating through two or more separated portals, these problems can be avoided with the additional benefits of adding more working room between instruments and hands and the additional perspective of another viewing angle ( ▶ Fig. 16.1).

Multiportal approach using precaruncular and transnasal pathways for optic nerve decompression.

Fig. 16.1 Multiportal approach using precaruncular and transnasal pathways for optic nerve decompression.

Endoscopic procedures involving the orbit involve two primary pathways: transorbital (using approaches through a transcutaneous or transconjunctival orbitotomy) and transnasal. Transorbital surgery can be further categorized to describe targets within the orbit (i.e., endoscopic orbital surgery), targets adjacent to the orbit (i.e., transorbital endoscopic surgery), and neurological targets adjacent to the orbit (i.e., transorbital neuroendoscopic surgery). Transorbital approaches are further categorized by the orbital quadrant that they address ( ▶ Fig. 16.2 and ▶ Fig. 16.3): superior (typically through a blepharoplasty incision); medial (transconjunctival, precaruncular, transcaruncular); inferior (transconjunctival inferior fornix), and lateral (retrocanthal or lateral blepharoplasty). This chapter will focus on transorbital rather than transnasal approaches to the orbit.

Trajectory of four quadrant approaches through the orbit.

Fig. 16.2 Trajectory of four quadrant approaches through the orbit.

Bony anatomy of the four quadrants of the orbit.

Fig. 16.3 Bony anatomy of the four quadrants of the orbit.

While these approaches are applicable and commonly used to address trauma of the orbit, optic nerve, brain, and adjacent structures, a discussion of transorbital endoscopic trauma surgery is beyond the scope of this chapter.

16.2 Patient Selection / Indications

Transorbital endoscopic approaches are indicated for targets within the orbit, or adjacent to the orbit in the paranasal sinuses, maxilla, infratemporal fossa, and adjacent anterior cranial fossa (ACF) and middle cranial fossa (MCF). The pathology must be amenable to an endoscopic or endoscopic-assisted approach. For tumors invading major vessels such as the internal carotid artery, an open craniotomy should be considered for proximal and distal vascular control in cases of malignant pathology. Transorbital approaches can be used alone or in multiportal combination with other endoscopic portals or as an assistive approach with traditional craniotomies.

Transorbital approaches are contraindicated in patients with recent trauma causing a ruptured globe or hyphema. These approaches should be used with caution for patients who have had intraocular surgery within the last 6 months, or a recent infectious or inflammatory condition of the orbit that has not fully resolved. 5

16.2.1 Superior Approach

The superior and lateral approaches are the workhorse approaches to the ACF and MCF. A combination of the two approaches gives wide access to the superior and lateral orbits to address lesions involving the anterior fossa, middle fossa, orbit, and structures abutting the superior orbital fissure (SOF) such as the cavernous sinus and Meckel’s cave. The superior approach on its own provides good access and visualization to manage orbital, frontal sinus, and ACF lesions. Opening the orbital roof in the floor of the frontal sinus gives access to lateral lesions that are difficult to access with an endoscopic Lothrop procedure, especially bony lesions such as osteomas and fibrous dysplasia. The superior approach is therefore useful during multiportal surgery or in conjunction with a transnasal approach for large lesions extending into the frontal sinus or ACF. The medial aspect of the contralateral frontal sinus and intersinus frontal cells can also be reached through this approach, allowing removal of the intersinus septum if desired. The orbital roof is very thin posterior to the frontal sinus and dura is easily exposed to manage ACF lesions or intracranial collections due to complicated sinusitis. The superior pathway gives wide access up to the orbital apex and SOF. Endoscopic visualization of the posterior/superior orbit is expedient and less disruptive than to a traditional open craniotomy where removal of the orbital roof is required to access posterosuperior orbital lesions. This access route allows neurosurgeons, ophthalmologists, and otolaryngologists to approach orbital lesions, creating an opportunity to close the management gap that exists with regard to orbital pathology. The authors have successfully removed orbital cavernous hemangiomas, neurofibromas, hydatid cysts, and meningoceles using the endoscope through the superior approach.

16.2.2 Lateral Approach

The lateral approach provides a wide surgical pathway to the lateral orbit, infratemporal fossa, MCF, greater and lesser wing of the sphenoid, and trigeminal ganglion/lateral cavernous sinus 6,​ 7 and lateral sphenoid sinus. 8 The most common pathology requiring the lateral transorbital route is sphenoid wing meningiomas. The lateral hyperostotic orbital wall can be managed through this approach, obviating the need to remove the orbital rim as with the traditional pterional approach ( ▶ Fig. 16.4). By removing the lateral orbital wall, temporalis muscle is exposed ( ▶ Fig. 16.5) and access can be obtained to the infratemporal fossa. Lesions such as angiofibromas or meningiomas extending to the superior infratemporal fossa can be addressed using the lateral pathway as an adjunct during multiportal surgery. After removing the greater wing of the sphenoid bone, a wide surgical pathway is created to the MCF and SOF to manage lesions in these areas. The lateral approach is useful when a two-wall orbital decompression is required in patients with thyroid orbitopathy and can be combined with an endoscopic medial decompression that can be performed either transnasally or through a precaruncular approach. Use of the endoscope allows for preservation of the orbital rim, and bone can be removed up to the inferior orbital fissure and SOF during a lateral decompression. Laterally located orbital lesions and the lateral rectus muscle can be accessed via this route. Manipulating the endoscope within an orbital cystic lesion or meningocele is useful since visualization of the posterior attachment of the lesion to vital structures can be appreciated within a cavity that is usually bloodless and free of herniating fat.

Lateral pathway showing bony hyperostosis in a sphenoid wing meningioma.

Fig. 16.4 Lateral pathway showing bony hyperostosis in a sphenoid wing meningioma.

Lateral approach showing pathway between temporalis muscle (arrow) and periorbita of the right eye.

Fig. 16.5 Lateral approach showing pathway between temporalis muscle (arrow) and periorbita of the right eye.

16.2.3 Medial Approach

The medial approach is used for a variety of pathology ranging from endoscopic ligation of the anterior, posterior, and accessory ethmoid arteries to the repair of complex cerebrospinal fluid (CSF) leaks, 9 treatment of orbital and frontoethmoidal mucoceles, orbital and optic nerve decompression, foreign body removal, and resection of tumors of the orbit, ACF, ethmoid and sphenoid sinuses. For tumors involving the ethmoid sinuses and interorbital ACF, we favor this approach due to its ability to provide surveillance of the orbital contents and dura for extent of tissue invasion before resection of the actual mass. Using multiportal technique for tumor resection, the procedure can begin with localization of critical neurovascular structures and then progress toward the sinonasal cavities. We believe this to be safer than working from the nose through tumor into the orbit and cranium. The contralateral precaruncular approach gives excellent access and a direct trajectory to the lateral aspect of a well-pneumatized sphenoid sinus for the repair of Sternberg canal defects and CSF leaks ( ▶ Fig. 16.6 and ▶ Fig. 16.7).

The Sternberg canal defect in lateral sphenoid sinus.

Fig. 16.6 The Sternberg canal defect in lateral sphenoid sinus.

Contralateral approach to lateral aspect of sphenoid sinus for the Sternberg canal defect repair.

Fig. 16.7 Contralateral approach to lateral aspect of sphenoid sinus for the Sternberg canal defect repair.

16.2.4 Inferior Approach

The inferior transorbital approach accesses the lower orbit through a transconjunctival deep fornix approach. This incision can be extended laterally into a lateral retrocanthal or canthotomy/cantholysis approach depending on access required. Similarly, the incision can be extended medially into a precaruncular approach. An isolated inferior approach is often used to treat pathology of the inferior orbital contents or the infraorbital nerve. In addition, this approach is used in multiportal technique with transnasal and transmaxillary approaches to treat extensive pathology of the maxilla such as juvenile nasopharyngeal angiofibroma (JNA). This technique allows instrumentation and visualization through separate portals, which improves the working space between instruments and moves instruments so they do not obstruct visualization of the pathology.

16.3 Diagnostic Workup

A multidisciplinary team is required when the transorbital route to orbital, sinonasal, or intracranial lesions is contemplated. Patients should be discussed at tumor board meetings with representatives from ophthalmology, neurosurgery, otolaryngology, and neuroradiology present. The best surgical route and trajectory should be planned using navigation software to compare transnasal, transorbital, transmaxillary, and open approaches alone or in combination. Multiportal or staged surgery may be required for large complex lesions involving multiple areas. An oncologist should provide input in the initial decision making for lesions that may require adjunctive radiotherapy or chemotherapy.

16.3.1 Physical Examination

Ophthalmological examination should be thorough since most patients requiring transorbital surgery have some visual loss, cranial nerve fallout, or proptosis. It is therefore imperative to accurately document ophthalmological findings such as visual acuity, visual fields, relative afferent pupillary defect, eye movements, degree of optic atrophy, and proptosis preoperatively. From an otolaryngologist’s perspective, it is necessary to evaluate the anatomical configuration and size of the sinuses abutting the orbit, depending on which pathway will be utilized. Sensation in the area of the supraorbital and infraorbital nerves should be tested. All cranial nerves, especially III, IV, V1, and VI, should be evaluated preoperatively because of the risk of tumor invasion through the SOF and because of the risk of traction injury that could occur during surgery. A full neurological examination is always needed for patients with any intracranial tumor component.

16.3.2 Laboratory and Radiological Evaluation

Blood tests would depend on patient factors such as age and comorbid diseases. For patients with proptosis, thyroid function tests should be done to exclude thyroid eye disease. Computed tomography (CT) of the orbits, sinuses, and brain, and magnetic resonance imaging (MRI) with and without contrast are required in all cases to delineate tumor extent and assess the degree of bony infiltration. CT and MRI scans should be obtained under navigation protocol. The use of navigation and preoperative surgical route and trajectory planning is important to choose the best approach with maximal exposure but minimal morbidity. Angiography and embolization may be required in some cases to assess and address any feeding vessels.

16.4 Surgical Anatomy

It is useful to consider the anatomy of the orbit in four quadrants, which is how we group surgical approaches in target-centered surgical planning. Each quadrant has primary approaches whose pathways transgress it, and unique anatomy to consider when planning a trajectory that involves the region ( ▶ Fig. 16.8).

Quadrant-centered approaches to the orbit. In the deep orbit, the lateral approach is separated from the superior and inferior approaches by the superior and inferior orbital fissures, respectively.

Fig. 16.8 Quadrant-centered approaches to the orbit. In the deep orbit, the lateral approach is separated from the superior and inferior approaches by the superior and inferior orbital fissures, respectively.

The superior quadrant is centered between the lacrimal gland and the trochlea of the superior oblique muscle. The superior approach follows the orbital septum to the orbital rim, dissecting deep to the orbicularis oculi muscle. Deep to the septum is the preaponeurotic fat, which provides a buffer zone to protect the levator aponeurosis and muscle during the dissection. At the superior orbital rim, the supraorbital and supratrochlear neurovascular pedicles are identified and preserved, and the plane between the periosteum and the orbital bone is entered ( ▶ Fig. 16.9). The dissection in the superior orbit is bounded medially by the ethmoid neurovascular bundles at the junction of the ACF with the lamina papyracea. These foramina can be followed posteriorly in a plane posteriorly to the optic nerve, which is the medial boundary of the apical component of this quadrant. The lateral boundary of the apical component is the SOF, through which cranial nerves pass within a periosteal envelope as noted in ▶ Fig. 16.10. Thus, the apex of the dissection is centered between the optic nerve medially and the superior fissure laterally. The extensions of periosteum around these structures function as a landmark and protective layer during dissection.

Supraorbital and supratrochlear neurovascular pedicles within superior quadrant.

Fig. 16.9 Supraorbital and supratrochlear neurovascular pedicles within superior quadrant.

Superior orbital fissure as viewed through superior quadrant approach.

Fig. 16.10 Superior orbital fissure as viewed through superior quadrant approach.

The medial quadrant is bound by the trochlea of the superior oblique superiorly, and the inferior oblique inferiorly (these structures are not typically exposed during the approach). The entrance to this quadrant is created between the caruncle and the medial canthus. The superior and inferior lacrimal canaliculi run through the tarsus between the anterior and posterior limbs of the medial canthal tendon to the lacrimal sac. These structures course superficial to the plane of dissection. The dissection follows the deep side of the posterior limb of the medial canthal tendon back to its insertion on the posterior lacrimal crest, where the subperiosteal dissection plane is opened and entered. The lamina papyracea then forms the medial boundary of the dissection, the periosteum is the lateral structure, the junction of the lamina and the ACF (containing the ethmoid arteries as above) is the superior margin, and inferiorly the dissection proceeds to the junction of the lamina and the orbital floor. The critical structure of this quadrant is the optic nerve, which courses superomedially to enter the optic canal at the superior posterior aspect of the medial wall of the orbit. Navigation is recommended when dissecting toward the optic nerve, and the tighter curvature of the lamina will be noted as the dissection proceeds toward the posterior ethmoid artery and finally the optic canal. Removal of the posterior lamina will allow dissection to continue on the medial aspect of the optic canal within the sphenoid sinus.

The structures of the inferior quadrant are located between the attachment of the inferior oblique muscle medially and the junction of the floor and lateral wall laterally. The anatomy is analogous to the superior quadrant, with the lower lid retractors functioning similarly to the levator muscle. The approach is more direct, however, transecting the lid retractors when incising onto the inferior orbital rim. The plane between the periosteum and orbital floor is entered at the orbital rim. As dissection continues posteriorly, care is taken to identify the infraorbital nerve, which typically passes within a canal located within or inferior to the orbital floor, entering the orbit toward the apex as it traverses the posterior aspect of the inferior fissure to enter foramen rotundum. Laterally, the posterior dissection is contained by the inferior fissure. Unlike the superior fissure, however, the inferior fissure contains predominately fibrovascular tissue that can be transected without functional loss if extended access to or from the lateral orbital compartment is desired. The medial border of the dissection is the lamina papyracea. At the apex of the quadrant, the posterior aspect of the inferior fissure is encountered, and the periosteal attachment to this structure can be followed medially where it lies inferior to the optic nerve at the superior medial aspect of the posterior orbit.

The lateral quadrant of the orbit lies between the lacrimal gland superiorly and the junction of the lateral wall with the orbital floor medially. It is accessed through a transconjunctival lateral retrocanthal approach with or without a canthotomy/cantholysis, or a lateral extension of an upper blepharoplasty incision. The lateral canthal tendon inserts on the medial aspect of the lateral orbital wall 1 mm posterior to the rim, just below the frontozygomatic suture. If this structure is disturbed, it must be reconstructed at the end of the procedure to prevent lid dystopia. Once the subperiosteal plane is entered deep to the orbital rim, dissection continues posteriorly bounded by the orbital roof above and the inferior fissure below. As noted, the latter structure can be transected as needed for exposure. Dissecting deeper within the orbit, the pathway narrows as the superior and inferior fissures converge posteriorly. These structures, when preserved, prevent damage to the optic nerve medially. The bone of the lateral orbit divides the orbital contents from the infratemporal fossa and temporalis muscle anteriorly, thickening into the greater wing of the sphenoid posteriorly behind which lies the MCF and temporal lobe dura.

16.5 Surgical Technique

16.5.1 Anesthesia and Preparation

The anesthesia and preparation is the same in all four approaches. The position of the head may differ according to the approach used and eye to be operated on. We do not recommend pinning the head, but instead use a horseshoe headrest so that the position of the head can be manipulated intraoperatively. The authors prefer total intravenous anesthesia (TIVA) to obtain normotensive anesthesia with a low heart rate. Patients are intubated using a south-facing ray tube secured to the left corner of the mouth to keep the area in front of the nose and eye clear for instrument and endoscope manipulation for a right-handed surgeon standing on the right of the patient. The head of the patient will need to be positioned according to the target area and the approach to be used. Pin fixation may be required in some instances, but being able to manipulate head position during surgery can be beneficial, especially during multiportal surgery. To access the frontal sinus and the anterior aspect of the ACF just posterior to the frontal sinus, the head often needs to be in extension (or 15 degrees of retroflexion) to achieve the optimum endoscope position and trajectory. During the initial part of the surgery, the surgeon creating the surgical pathway holds the endoscope and manages the powered instrumentation. The surgical team may differ from unit to unit and consist of a combination of otolaryngologist, neurosurgeon, or ophthalmologist working in synchrony. Two assistants are usually required to support the main surgeon unless specialized retractors and multifunctional instruments are used. A single hand holding one instrument that can perform three functions, for example, a drill that has irrigation and suction capabilities, can replace three hands with one less assistant needed. For the neurosurgical or intracranial part of the procedure, surgery is similar to transsphenoidal pituitary surgery, with the otolaryngologist manipulating the endoscope and managing the surgical field in order for the neurosurgeon to work bimanually.

16.5.2 General Approach

The surgical approach is chosen by the target location, as indicated in the discussion earlier. The appropriate approach is typically that corresponding to the quadrant that is primarily involved by the pathology; at times two transorbital approaches will be used synchronously (e.g., medial and inferior approaches) or transorbital and transnasal approaches may be combined in a multiportal technique 4,​ 10,​ 11 to improve manipulation and visualization. We have found that preoperative computer planning and analysis can be of significant benefit in planning these procedures. 12 As seen in ▶ Fig. 16.11, multiple approaches to each target should be considered. In this example of an undifferentiated carcinoma invading the orbit, maxilla, and nasal cavity, inferior and medial transorbital approaches are used at the beginning of the case to ascertain adherence of the tumor to intraorbital structures, and to dissect through normal tissues to the interorbital skull base. Before excision of tumor, the dura is inspected and determination of intracranial tumor extent, if any, is made. Once the involvement of adjacent structures has been definitively determined, resection of the tumor begins. Dissection proceeds outward from critical structures—from the orbital contents toward the sinuses and nasal cavity and from the dura inferiorly into the nasal cavity. The transnasal approach is used later for subsequent excision of the intranasal component. By beginning with transorbital dissection, safety of the orbital contents and brain can be assured without dissecting through tumor, moving outward from delicate structures into less critical regions. Accessing these structures from a transnasal approach requires dissection through tumor, which may be risky, particularly when the border between tumor and critical structures is obscured. Preoperative computer-aided surgical planning will help the surgeon determine the optimal number and placement of surgical portals, as well as the proper approach vectors and pathways to ensure successful completion of the surgical goal.

Preoperative planning and trajectory analysis.

Fig. 16.11 Preoperative planning and trajectory analysis.

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Feb 25, 2020 | Posted by in OTOLARYNGOLOGY | Comments Off on Transorbital Approaches to the Sinuses, Skull Base, and Intracranial Space

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