Chapter 15 Transorbital Neuroendoscopic Approach

10.1055/b-0037-143521

Chapter 15 Transorbital Neuroendoscopic Approach

Kris Moe, Angelique M. Berens

Introduction

Transorbital approaches to the skull base continue to gain momentum as an alternative to extensive craniofacial resection. Patients benefit from transorbital approaches due to decreased intensive care unit and hospital stay. Avoiding extensive brain retraction decreases postoperative cerebral edema. Patients also experience less cosmetic disfigurement when compared with external approaches. The surgeon benefits from coplanar visualization and less impairment of view from instruments located in the direct visual plane of the endoscope. Although transorbital approaches can be used solo to reach the skull base, a multiportal approach combining a transorbital with a transnasal or transmaxillary approach often provides the most advantageous working distance between instruments with minimal obstruction of target visualization. Additional advantages of the multiportal approach include variation in working and endoscopy portals to improve perspective and access.1–5

When considering a transorbital approach, the only absolute contraindications are patients with a ruptured globe or hyphema. The following conditions warrant preoperative consultation with ophthalmology: intraocular surgery in last 6 months, active orbital infection, severe orbital inflammation or congestion, diminished corneal sensation (presents higher risk of postoperative complications), and/or pathology that creates mass effect.

If the surgeon is not familiar with orbital surgery, it is critical to study this anatomy in the cadaver laboratory, and consider assistance from a facial plastic or oculoplastic surgeon until adequate experience has been obtained.

15.1 Surgical Steps

15.1.1 Preoperative Planning and Image Guidance

Preoperative planning and image guidance for complex approaches to the skull base require multidisciplinary preoperative planning. Preoperative planning must consider critical neurovascular structures that may be encountered along the pathway to the target pathology and modify planning to decrease interaction with these structures. Open-source DICOM viewing software, such as 3D Slicer, or surgical navigation software allows for analysis of multiple possible pathways to the target. Once the surgical approach is planned, intraoperative navigation is essential to carry out the operative plan and determine location of craniotomy.

15.1.2 Approaches

There are four primary transorbital approaches to the middle and anterior cranial fossae: superior lid crease (SLC); precaruncular medial; inferior fornix (IF; transconjunctival); and lateral retrocanthal (LRC). The choice of approach is based on location of the target pathology ( Table 15.1 ) ( Fig. 15.1 ). The pathway chosen should be the shortest, most direct approach that allows adequate volume for instrumentation, and target visualization preferably within a single plane. The key soft-tissue structures to consider in the approach portals are illustrated in Figs. 15.2 and 15.3 . The transcutaneous SLC approach, identical to a blepharoplasty incision, accesses the orbit between the lacrimal gland and trochlea (the trochlea can be displaced in the subperiosteal plane if needed for extended inferomedial approach); the transconjunctival PC approach lies between the trochlea above and the origin of the medial oblique muscle inferiorly (like the trochlea, this can also be elevated subperiosteally as needed); the transconjunctival IF approach extends from the inferolateral orbit to the medial wall posterior to the lacrimal sac; and the LRC approach may be extended from the lacrimal gland to the orbit floor (the inferior and superior boarders can be extended as needed, the superior extension must avoid the lateral horn of the levator aponeurosis).

**Fig. 15.1** Superficial orbital anatomy. Note the medial and lateral canthal tendons, the primary support structures of the eye lids.

**Fig. 15.2** The four quadrants of the orbit, right side, superficial anatomy. The superior approach is directed between the lacrimal gland and the trochlea; the medial approach is centered between the trochlea and the inferior oblique muscle; the inferior approach is located between the origin of the inferior oblique muscle and the lateral wall of the orbit; the lateral approach focuses on the region between the orbital floor and the orbital roof.

**Fig. 15.3** The four quadrants of the orbit, right side, bone anatomy. Lines indicate approximate borders of access between the approaches; dissections may cross these divisions. 1, superior quadrant; 2, medial quadrant; 3, inferior quadrant; 4, lateral quadrant. Note that structures may lie within two potential approaches.

**Table 15.1 Summary of targets per approach**
	Approach	Targets
Lateral retrocanthal	Lateral orbit	MCF, ITF, temporal lobe, lateral cavernous sinus, orbital apex, lateral aspect of frontal fossa, lateral sphenoid sinus
Inferior fornix	Inferior orbit	MCF, foramen rotundum, pterygopalatine fossa, sella, parasella, orbital floor/max sinus
Precaruncular	Medial orbit	Bilateral ACF, contralateral MCF, orbital apex, parasella, cavernous sinus, cavernous carotids, optic nerve, and central corridor
Superior lid crease	Superior orbit	Orbital roof fracture, frontal sinus (posterior wall fracture with CSF), and anterior fossa pathology
Abbreviations: ACF, anterior cranial fossa; CSF, cerebrospinal fluid; ITF, infratemporal fossa; MCF, middle cranial fossa.

15.1.3 Instruments

Endoscope, malleable brain/orbit retractors, suction Freer elevator, long bipolar cautery, Westcott scissors, and endoscopic skull base instrumentation.
Choice of ultrasonic bone aspirator (Sonopet) or high-speed drill. A radiofrequency ablator (Coblator) is very helpful for removing mucosa from bone to identify precise bone anatomy and provide a site of adherence for reconstructive materials.

15.1.4 Anesthesia Considerations

Surgery within the orbit may trigger the oculocardiac reflex and lead to bradycardia, arrhythmia, or asystole. In the case of bradycardia, the surgeons should remove all instruments until normal sinus rhythm returns. Administration of antimuscarinic agents, such as atropine or glycopyrrolate, will decrease the incidence of bradycardia, arrhythmia, and asystole.

Only gold members can continue reading. Log In or Register to continue