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Chapter 15

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15.1 Surgical Steps 156

Transorbital

Neuroendoscopic

Approach

15.2 Conclusion 162

Transorbital Neuroendoscopic Approach

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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.

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.

1–5

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

Lacrimal gland

Eisler fat pad

Lateral canthal

tendon

Lateral fat pad

Arcuate expansion

of lockwood ligament

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Central fat pad

Interpad septum

Nasal fat pad

Medial canthal tendon

Nasal fat pad

Inferior oblique m.

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

Transorbital Neuroendoscopic Approach

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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

Inferior fornix Inferior orbit MCF, foramen rotundum, pterygopalatine fossa, sella, parasella, orbital ﬂ oor/max sinus

Precaruncular Medial orbit Bilateral ACF, contralateral MCF, orbital apex, parasella, cavernous sinus, cavernous

Superior lid crease Superior orbit Orbital roof fracture, frontal sinus (posterior wall fracture with CSF), and anterior fossa

Abbreviations: ACF, anterior cranial fossa; CSF, cerebrospinal ﬂ uid; ITF, infratemporal fossa; MCF, middle cranial fossa.

fossa, lateral sphenoid sinus

carotids, optic ner ve, and central corridor

pathology

Lacrimal

gland

Lateral

canthus

Tro ch leaLevator muscle

Inferior oblique muscle

Fig. 15.2 The four quadrants of the orbit, right side, superﬁ cial 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 ﬂ oor

Medial canthus

Lacrimal sac

and the orbital roof.

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. 15.3 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.

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.

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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.

15.1.5 Globe Retraction

Due to mild laxity of the optic nerve, temporary retraction of the healthy globe up to 1 cm appears to be safe. It is important to check pupil size every 15 minutes throughout the case. When operating deeper in the orbit, behind the globe and near the apex, the pupil should be checked more frequently. If mydriasis or irregularity of the pupil develops, remove all instruments and allow the globe to rest until it returns to near baseline. If mydriasis persists, consider alternate causes such as topical anesthetic with epinephrine.

15.1.6 General Considerations for Transorbital Approaches

Regardless of specific approach, there are commonalities and anesthesia considerations important to each transorbital case.

With the patient asleep on the table, registration of the navigation system is performed and accuracy is confirmed. Using navigation instruments, final choice of approach portal and pathway is made by analyzing vector characteristics (length and volume of pathway, danger to adjacent critical neurovascular structures,

ability to instrument the surgical target) (Fig. 15.4). A temporary tarsorrhaphy is place on the contralateral eye lids that will allow the pupil to be checked. Cottonoids soaked in vasoconstrictor are placed intranasally as needed.

15.1.7 Access to the Lateral Orbit through a Lateral Retrocanthal Approach

This approach can be used to access the middle cranial fossa (MCF), infratemporal fossa, temporal lobe, lateral cavernous sinus, orbital apex, and lateral aspect of frontal fossa. The safety limits of bone removal area are superior optic fissure (superior), inferior optic fissure (inferior), optic strut (medial), and optic foramen. Foramen of optic nerve is medial, coplanar with the anterior and posterior ethmoid arteries, and separated by superior orbital fissure contents. For these reasons, the optic nerve should be at minimal risk during this procedure. LRC approach is used to avoid cutaneous incisions and incisions through the lateral canthal tendon (Fig. 15.5). The approach can be extended with a lateral canthotomy and cantholysis, but we find this extension is often not necessary.

Begin by checking both pupils and noting any asymmetry, and then place a lubricated corneal protector. Retract the eyelids lateral and palpate the lateral canthal tendon attachment to the medial aspect of the lateral orbital wall. Using 1% lidocaine with 1:100,000 epinephrine, inject approximately 1 mL immediately posterior to the lateral canthus. Using a 15 blade, incise the conjunctiva posterior to the canthal tendon. Carry this incision through the periosteum. Extend the incision superior and inferior along the orbital rim. As

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Fig. 15.4 Surgical approach analysis.

A lateral retrocanthal approach is planned to access meningocele in lateral sphenoid recess. The length of the pathway, structures traversed, and adjacent critical neurovascular anatomy are evaluated to determine the correct trajectory.

Superior

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tarsus

Inferior

tarsus

Conjunctival incision

you extend the incision superior, retract the lacrimal gland medial to avoid injury. Use a periosteal elevator to lift the periosteum along the entire lateral wall from the inferior fissure to the orbital roof. Use a 0-degree 4-mm rigid telescope to improve visualization. Have an assistant provide gentle medial retraction of the orbital contents using a malleable retractor. Be mindful to check the pupils and alert the anesthesiologist that you are retracting the orbital contents. Be mindful of the zygomatico-orbital branch of the middle temporal artery; this can be divided after bipolar cauterization. Under image guidance, make craniotomy using ultrasonic bone aspirator to provide access to the pathology. The frontal fossa can be accessed with a craniotomy superior to the sphenofrontal suture, while craniotomy inferior to this suture will provide access to the anterior temporal lobe.

The soft tissue should be repositioned in anatomic position and corneal protector removed. Closure of the conjunctiva is not necessary. Reconstruction of the orbit is also not generally required. To reconstruct after lateral canthotomy and cantholysis, approximate the lateral canthal tendon with 5–0 permanent sutures. If the LRC approach was extended to or beyond a transconjunctival approach, several inverted 5–0 fast-absorbing gut sutures are placed to loosely approximate the conjunctival edges and the lower eyelid is extended superiorly to ensure that it is not tethered.

15.1.8 Access to the Inferior Orbit through a Transconjunctival Deep Fornix Approach

The transconjunctival IF approach provides access to the MCF, pterygopalatine fossa, foramen rotundum, sella, parasellar region, orbital floor for trauma, and maxillary sinus. The preseptal approach is used to prevent orbital fat from herniating into the surgical field and impeding endoscopic view. For extended approaches, the conjunctival incision can be extended medial and lateral to be continuous with the precaruncular and LRC incisions.

Start by checking the pupils and then place a lubricated corneal protector. Injected 1 mL of 1% lidocaine with 1:100,000 epinephrine in the submucosal plane along planned incision. Using needle tip monopolar cautery or a scalpel, make a conjunctival incision 2 mm inferior to tarsus (~6 mm inferior to eyelid margin). Tenotomy scissors are then used to dissect in the plane between

Transorbital Neuroendoscopic Approach

Fig. 15.5 Lateral retrocanthal approach. Conjunctival incision is made posterior to the insertion of the lateral canthal tendon, approximately 2 mm posterior to the lateral orbital rim. The incision should be made anterior to the lacrimal gland, and must avoid the structures of the upper eye lid.

Fig. 15.6 Transconjunctival lower eye lid approach to inferior orbital quadrant.

the orbicularis and orbital septum until the orbital rim is encountered. Similar to the upper eyelid, the orbital septum is difficult to recognize; therefore, the dissection plane is defined as just deep to the orbicularis oculi. To improve visualization, place a horizontal suture through the conjunctival flap and retract superiorly over the corneal protector (Fig. 15.6). Using needle-tipped monopolar cautery, incise the periosteum over the posterior aspect of the orbital rim and use a periosteal elevator or suction freer to gently lift the periosteum off the orbital floor. Use a 0-degree 4-mm rigid telescope and have an assistant gently retract the orbital contents with a malleable retractor. Always alert the anesthesiologist prior to retraction of the orbital contents. Continue elevation of periosteum under endoscopic guidance and be mindful to leave the infraorbital nerve down on the orbital floor. The fascial attached between the infraorbital nerve and the orbital contents can be severed. Perform orbitotomy based on preoperative planning and image guidance.

The orbital floor should be reconstructed with titanium orbital implant if a significant orbital volume defect is expected that could lead to diplopia and/or enophthalmos. If orbitotomy removed landmarks, reconstruction with

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Transorbital Neuroendoscopic Approach

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Fig. 15.7 Image-guided mirror image overlay as a reconstruction technique for orbital ﬂ oor defects with loss of anatomic landmarks.

mirror image overlay is recommended to duplicate precise preoperative anatomy (Fig. 15.7). The soft tissue is then replaced with anatomic position. The suture is removed from the conjunctival flap and corneal protector removed. It is not necessary to suture the conjunctival defect.

15.1.9 Access to the Medial Orbit through a Precaruncular Approach

Access to the medial orbit can be used to approach pathology in the following areas: bilateral anterior cranial fossa, contralateral MCF, orbital apex, sella, parasellar region, cavernous sinus, cavernous carotids, optic nerve, and the central corridor. When planning orbitotomy or craniotomy, it is important to remember the level of the skull base/cribriform plate, represented by the plane of the anterior ethmoid artery, posterior ethmoid artery, and optic nerve. The precaruncular approached is used instead of the transcaruncular approach to avoid damage to the lacrimal system. The conjunctival incision can extend lateral into the deep fornix for increased exposure.

Check both pupils. With lubricated corneal protector in place, inject 1 mL of 1% lidocaine with 1:100,000 epinephrine medial to the canthus and medial to the caruncle. For the less experienced surgeon, place lacrimal probes to prevent inadvertent transection. Incise the conjunctiva between the caruncle and skin with Westcott scissors. Carry the conjunctival incision superior and inferior along the superior and inferior limbs of the posterior limb of the medial canthal tendon (Fig. 15.8). Dissect medially along the posterior limb of the medial canthal tendon to the posterior lacrimal crest. Incise the periosteum immediate posterior to the posterior lacrimal crest. Lift the periosteum off the medial orbital wall (lamina papyracea) with periosteal elevator. Notify the

anesthesiologist prior to retraction on the globe. Have an assistant gently retract the orbital contents lateral with a malleable retractor and continue dissection in the subperiosteal plane under endoscopic guidance. The anterior and posterior ethmoid arteries enter the ethmoid sinus at the level of the skull base. When encountered, it can be ligated with bipolar cautery or vascular clips (Fig. 15.9). More often than not, a middle ethmoid artery will be present. Continue posterior dissection until visualization of the optic nerve at the most posterior aspect of the medial orbit. If the procedure does not involve the optic nerve, leave a vertical strut of bone anterior to the nerve for protection. Perform orbitotomy and/or craniotomy based on preoperative planning with the use of periosteal elevator and ultrasonic bone aspirator as needed.

The orbital defect need only be repair if a large disturbance in orbital volume is expected that would lead to enophthalmos or diplopia. If orbital reconstruction is required, mirror image overlay may be helpful if landmarks have largely been removed. The lacrimal probes and corneal protectors are removed and the soft tissue is approximated to anatomic position. The conjunctiva is then approximated, but generally does not require suture closure. If the caruncle is displaced due to edema, closure with a 6–0 fast gut can be sued between the apex of the caruncle and the medial eyelid.

15.1.10 Access to the Superior Orbit through Superior Lid Crease Approach

Pathology of the frontal sinus, supraorbital anterior cranial fossa, frontal lobe, olfactory region, and orbital

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Transorbital Neuroendoscopic Approach

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Lacrimal probe

Conjunctival incision

Caruncle

Incision for canthal tightening

Incision for orbital floor extension

Fig. 15.8 (a, b) Precaruncular approach to medial orbit—incision and dissection.

Lacrimal canal

Anterior limb medial canthal tendon Edge of skin

Lacrimal sac

Anterior Lacrunak crest

Posterior limb medial canthal tendon (Horner muscle

-inferior limb)

Fig. 15.9 Precaruncular approach to right medial orbit with malleable retractor, section Freer elevator, and endoscope in place. Inset: Transorbital ligation of ethmoid artery with surgical clip (can also be done by bipolar cautery).

roof factures can all be easily reached through the superior orbit using a blepharoplasty-type incision. Boundaries of bone removal extend from superior orbital fissure to orbital apex and the level of the ethmoid arteries.

To protect the corneal, a tarsorrhaphy suture should be placed at the level of the lateral limbus with 6–0 nylon and ocular lubricant generously applied. Check both pupils. An incision is made through skin and orbicularis oculi muscle in the SLC (similar to standard blepharoplasty). Retract the musculocutaneous flap superiorly while dissecting in a preseptal plane. The orbital septum is often difficult to identify. The proper dissection plane can be found by dissecting just deep to the orbicularis oculi muscle. The medial and lateral boundaries of the soft tissue dissection are the trochlea and lacrimal gland, respectively (Fig. 15.10). It is critical to avoid dissection into the fat pad deep to orbital septum (preaponeurotic fat), as this can lead to damage to the levator aponeurosis

and result in ptosis. One must also be cognizant of the location of the supratrochlear and supraorbital neurovascular bundles and preserve them when approaching the orbital rim. The periosteum is incised at the inferior border of the superior orbital rim and freed periosteal elevator under endoscopic guidance with 0-degree 4-mm rigid telescope. Have an assistant provide gentle inferior retraction of orbital contents with a malleable retractor. Ensure the anesthesiologist is aware prior to orbital retraction. The subperiosteal dissection can extend medial to improved exposure; meanwhile, be mindful to bipolar and divide anterior and posterior ethmoid arteries when encountered. Craniectomy is then performed according to preoperative planning with a combination of ultrasonic bone aspirator and periosteal elevator.

After reconstruction of skull base defect, the soft tissue is returned to anatomic position and the incision is closed with simple running 6–0 nylon. Tarsorrhaphy suture is removed at the end of the case.

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Periosteum

Orbicularis oculi

muscle

Orbital septum

Tendon of levator palpebrae superioris muscle

Superior

conjunctival fornix

Conjunctiva

Tar s us

Levator palpebrae superioris muscle

Tarsal gland

Superior tarsal muscle (smooth muscle)

Fig. 15.10 Coronal anatomy of upper eye lid. Dotted line demonstrates pathway superﬁ cial to orbital septum, which is followed superiorly to its attachment at the superior orbital rim where the superior orbit is entered.

15.2 Conclusion

• Transorbital approaches allow for improved access to

many skull base targets. Addition of a transorbital portal to standard transnasal approach greatly increases the working space, allowing for more comfortable instrumentation.

• In a study looking at 107 patients who underwent

transorbital approaches for skull base pathology, there were no adverse visual outcomes.

• Safe use of transorbital portals requires the surgeon to

check the pupils every 15 to 30 minutes throughout the case and to perform forced ductions at the end of the case to ensure there is no extraocular muscle entrapment.

• Minimally disruptive transorbital approaches to the

skull base and cranial pathology decreases intensive care unit and hospital stay for patients.

• Patients also have improved cosmetic outcome from

decrease incisions and dissection of craniofacial soft tissue. At the same time, surgeons must adapt to increasingly complex cases.

• To continue to provide optimal care for our patients, it

is important that technology related to intraoperative navigation and preoperative planning evolves with the surgical techniques.

References

1. Moe KS, Bergeron CM, Ellenbogen RG. Transorbital neuroendoscopic surgery. Neurosurgery 2010;67(3)ons:16–28

2. Ciporen JN, Moe KS, Lopez S, et. al. Multiportal endoscopic approaches to the central skull base: A cadaveric study. World Neurosurg. 2010 Jun;73(6):705–712

3. Balakrishnan K, Moe KS. Applications and outcomes of orbital and transorbital endoscopic surgery. Otolaryngology–Head and Neck Surgery, 2011;144(5):815–820

4. Ellenbogen RG, Moe KS. Transorbital neuroendoscopic approaches to the anterior cranial fossa. In Snyderman C, Gardner P, eds. Skull base surgery. Philadelphia, PA: Wolters Kluwer; 2015:151–164

5. Moe KS, Ellenbogen RG. Transorbital neuroendoscopic approaches to the middle cranial fossa. In Snyderman C, Gardner P, eds. Skull base surgery. Philadelphia, PA: Wolters Kluwer; 2015:343–356

6. Moe KS, Linder T. The lateral transorbital canthopexy for correction and prevention of ectropion: report of a procedure, grading system, and outcome study. Arch Facial Plast Surg 2000;2(1):9–15

7. Moe KS, Kao C-H. Precaruncular medial canthopexy. Arch Facial Plast Surg 2005;7(4):244–250

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