Fronto-orbital Temporal and Pterional Transcranial Approaches

The frontotemporal incisions and scalp flap elevation are designed according to the particular need for orbital access. A standard pterional incision (curvilinear, just anterior to the tragus to the midline apex of the anterior hairline) is usually adequate to access the superolateral orbit. However, to extend the access medially to the superior orbit or inferiorly/laterally, the incision should be at least a modified bicoronal one extending from the tragus on the side ipsilateral to the pathology to the contralateral superior temporal line or even to the contralateral tragus (Fig. 147-4). An imaginary line drawn between one end of the incision and the other should cross the orbital region of interest. The entire scalp flap should be elevated in a subperiosteal plane over the frontoparietal area and the superficial layer of the deep temporal fascia. We incise this fascia, which is continuous with the periosteum of the orbitozygomatic complex, by following an imaginary line from the superior orbital rim to the root of the zygoma. Elevation of the scalp/facial flap continues deep relative to this plane (i.e., subperiosteally) to protect the frontal branches of the facial nerve. Elevation with inferior retraction of the temporalis muscle exposes the lateral orbit. The muscle can easily be dissected from the underlying squamosal bone by starting the dissection at the root of the zygoma after making a posterior incision in the muscle and dissecting inferiorly to superiorly in the direction of the fascial attachments rather than against them as is traditionally done. This provides a much cleaner dissection and may help preserve some of the microvascular supply to the muscle, thus decreasing atrophy. If any part of the zygoma will be removed for access, the corresponding attachment (origin) of the masseter muscle is transected. Its fascia is incised and elevated from the muscle (parotid-masseteric fascia). Dissection of the muscle is then completed by electrocautery while using a malleable retractor to protect the temporalis muscle, which lies deep relative to the masseter.

FIGURE 147-4 Partial bicoronal skin flap for the fronto-orbital temporal transcranial approach with unilateral orbitotomy. A, Approximate skin incision overlying the craniotomy. B, Superior view of the tumor accessed via this approach, with both intracranial and orbital components. C, The subperiosteal dissection should be carried onto the orbit and around its rim to dissect the periorbita from the inner wall of the orbit. D, Superolateral view showing access to the frontal and temporal dura, as well as the superolateral orbit, with the supraorbital neurovascular bundle freed and retracted with the orbit. E, Orbitotomy cuts can be made with the craniotomy, but the posterior osteotomy can be performed in more controlled fashion if the two are done separately.

The subperiosteal dissection should be carried onto the orbit and around its rim to dissect the periorbita from the inner wall of the orbit. There is always periorbital adherence at the superolateral corner of the zygomaticofrontal suture. Dissecting all areas around the orbit at the same depth before deepening the dissection prevents inadvertent tears in the periorbita. The supraorbital neurovascular bundle should either be dissected from its notch or, if in a true foramen, be freed with diagonal osteotomies (inverted V) directed away from the nerve. This technique allows the nerve to be moved freely away from the orbital bone.

Next, a standard frontotemporal craniotomy is performed. The lateral bone of the greater wing of the sphenoid is then dissected free from the dura and removed with rongeurs and a high-speed drill until flush with the orbit. Bone removal should stop at the depth of the orbitomeningeal artery to prevent inadvertent injury to the contents of the superior orbital fissure. The orbitomeningeal artery is an important landmark marking the “tip of the iceberg,” with the superior orbital fissure lying beneath. At this point the frontal dura can be dissected free from the roof of the orbit so that the orbital bone is freed from dura on one side and periorbita on the other before performing the orbital osteotomies. We prefer to use a reciprocating saw for the orbital osteotomies while protecting the brain and orbit with malleable retractors (“brain ribbons”). The saw is inserted into the orbit and the cut is made from the orbit toward the frontal dura. The medial cut is usually at or just lateral to the supraorbital notch. The lateral cut is made by inserting the tip of the reciprocating saw into the inferior orbital fissure and completing an osteotomy from within the orbit at a level just above or through the zygomatic prominence, as needed. The final posterior osteotomy is completed with a small drill bit from the brain side while protecting the orbit with a ribbon. This cut is made from the posterior aspect of the medial osteotomy across the roof of the orbit, through the remaining sphenoid wing, and connected laterally to the lateral osteotomy in the inferior orbital fissure. These osteotomies should be extended as posterior as possible to prevent loss of orbital bone, which would require reconstruction to prevent enophthalmos. At this point the orbitozygomatic complex can be freed from any remaining soft tissue attachment and removed to provide access to the entire superolateral orbit, as well as the regional frontotemporal dura and related brain region, if needed (Fig. 147-5). It is important that the posterior portion of the superior orbit be removed adequately because this bone can prevent adequate dural retraction and defeat any advantage of the superior orbitotomy.

FIGURE 147-5 Frontotemporal craniotomy and orbitotomy provide access to the entire superolateral orbit, as well as to the regional frontotemporal dura and related brain region.

This approach is ideal for tumors such as meningiomas with both intracranial and orbital components (see Fig. 147-3). If intracranial access is desired, after opening the frontotemporal dura, multiple retraction stitches can be applied across the internal surface of the dura to retract the orbit inferiorly. If the middle cranial fossa dura is involved or there is significant superior extension, the addition of zygomatic osteotomies can be advantageous. This allows more aggressive removal of subtemporal bone and access to the basal foramina and decreases brain retraction when addressing superiorly extending lesions by allowing a more inferior to superior angle of dissection. We prefer to remove the orbit and zygoma as one piece with a straight osteotomy through the main portion of the zygoma and a diagonal cut flush with its posterior attachment to the temporal bone (root of the zygoma). A variant of the approach just described is a “one-piece cranio-orbitozygomatic approach” wherein the craniotomy and orbitozygotomy are done as one piece; it is reported to potentially improve cosmetic outcomes. We have not found cosmesis to be an issue with the “two-piece” approach, however, because defects are easily reconstructed with titanium mesh and plates.

Depending on the location of the tumor within the optic canal, the roof of the canal may need to be thinned and then removed with a dissector or small curet. Continuous irrigation should be used to avoid thermal injury to the nerve from the diamond drill bit. The underlying dura should be left intact. The frontalis nerve is then identified under the periorbita, overlying the palpebral muscle. Intraorbital tumor can be identified by digital palpation, image guidance, or intraoperative ultrasonography. The periorbita is opened in an anterior-to-posterior direction, and dissection is performed through the periorbital fat. If tumor is located in the medial or superior intraconal space or is affecting the optic nerve, the annulus of Zinn should be opened medial to the levator and superior rectus muscles to prevent injury to the oculomotor nerve. These muscles can be retracted laterally for improved exposure. It can be difficult to preserve the trochlear nerve with this approach, but it should be attempted. Standard microsurgical techniques are used for tumor dissection and removal.

There are alternative “minimally invasive” approaches to this region, mostly useful for small tumors. Incisions such as the “eyebrow” incision and other similar variants provide access to the orbital roof and anterior fossa. Patients must be selected for these approaches carefully, and the cosmetic results from an incision in the eyebrow are variable.

Anterior Medial Micro-orbitotomy Approach

Tumors located anteriorly and medially in the orbit can be accessed by a medial micro-orbitotomy approach. Ophthalmic preparation of the orbit and surrounding area is performed, and a small eyelid retractor is put in place. A conjunctival peritomy is performed 90 degrees around the cornea (Fig. 147-7). The medial rectus muscle is isolated with a double-armed suture at its insertion site into the globe after relaxing conjunctival incisions are made superior and inferior to the muscle. The muscle is then freed from its intermuscular septa and check ligaments distally and severed from the insertion site. The lid retractor is removed and a medial orbital self-retaining retractor inserted. The retractor has an enucleation spoon that is placed medially on the globe for medial-to-lateral retraction (see Fig. 147-7). The orbital fat is dissected while viewed with the operating microscope, aided by more self-retaining retractors. Cottonoids or cotton-tipped applicators are used for retraction of orbital fat. Performing a lateral orbitotomy (as described previously) can provide even more room for lateral globe displacement while avoiding compression of the orbital contents.

FIGURE 147-7 A, The medial micro-orbitotomy approach begins with a conjunctival peritomy that is performed 90 degrees around the cornea. B, Tumors located in the anterior and medial aspects of the orbit (arrow) can be accessed via this approach. C, The self-retaining retractor has an enucleation spoon that is placed medially on the globe for medial-to-lateral retraction to provide access to the tumor.

After tumor resection, the medial rectus muscle is reattached to the globe with 6-0 absorbable suture, and the conjunctiva is closed with “purse-string” sutures through the conjunctiva and limbus over the superior and inferior relaxing incisions. The morbidity associated with this approach is similar to that of extraocular muscle surgery. This approach is useful for anterior lesions but becomes progressively restrictive when extended posteriorly. For medial tumors it has become the authors’ practice to use an endonasal approach, which allows a more medial trajectory and thus provides more posterior orbital access while limiting the need for globe retraction.

Medial-Inferior Extraconal Approach

All endonasal approaches to the orbit have similar initial phases. After undergoing endotracheal intubation and induction of general anesthesia, the patient is placed in a three-point head fixation system in a neutral or slightly extended position. In addition, the head is turned 5 to 10 degrees toward the surgeons (to the patient’s right, in our practice). Image guidance is used in all cases. The patient’s midface is prepared with a povidone solution while avoiding contact with the cornea. If necessary, the periumbilical part of the abdomen is prepared for potential harvest of a free fat graft. All surgeries at our institution are performed by a team of two surgeons—one otolaryngologist, and one neurosurgeon—with an oculoplastic surgeon added for intraconal work.

A 0-degree endoscope is used for most of the operation. The sinus phase includes a complete uncinectomy, wide maxillary antrostomy, anterior and posterior ethmoidectomies, and sphenoidotomy to expose the medial and inferior orbital walls. The extent of this phase can be limited, depending on the access needed, to preserve olfaction. The sphenoid sinus is opened from the natural os and extended medially, laterally, and superiorly, as needed, for visualization of the bony landmarks overlying the ICA and optic nerve, the planum and sella (Fig. 147-8). Next, the lamina papyracea is removed in an anterior-to-posterior direction. At this point the periorbita, optic nerve, and carotid artery are well defined (Fig. 147-8). The key anatomic landmarks in this region are the lateral and medial opticocarotid recesses. The lateral opticocarotid recess represents the pneumatization of the optic strut and provides access to the superior orbital fissure. The medial opticocarotid recess is perhaps more critical because it represents the intersection of the optic nerve and ICA at the opticocarotid cistern. This can be valuable for identifying the nerve posteromedially and isolating the optic sheath, which can then be followed anteriorly into the orbit.

FIGURE 147-8 Endonasal endoscopic view after the initial sinus phases of exposure for an orbital approach, including the orbital apex (CP, carotid protuberance [parasellar]; LP, lamina papyracea; ON, optic nerve; Planum, planum sphenoidale; Sella, sella turcica). A, Endoscopic endonasal view in a cadaveric specimen. B, Intraoperative image guidance showing triplanar views with the pointer (P) at the orbital apex, just above the nerve in the event of traumatic optic nerve decompression. C, Intraoperative endoscopic endonasal view showing the drill being used for exposure of an orbital apex schwannoma.

For the medial-inferior extraconal technique, a single-nostril approach with preservation of the middle turbinate can often be used, especially when addressing smaller tumors. However, when dissection of the orbital apex or intraconal work is needed, a two-nostril approach provides more flexibility for dissection and manipulation of instruments. During a two-nostril approach, the middle turbinate ipsilateral to the pathology is removed, the posterior nasal septum is resected, and the sphenoid sinus rostrum is opened widely. This transforms the posterior sinonasal cavities into one single space for ease of dissection. It should be noted that if a two-nostril approach is planned and a nasoseptal flap²² is needed for reconstruction (recommended for intradural work and cases involving exposure of the carotid artery), this flap must be raised before transecting the posterior septum or the vascular pedicle will be lost.

If a tumor such as a tuberculum or planum meningioma has extension along the medial optic nerve, the entire tumor can be addressed endonasally with a transplanum approach combined with orbital apex decompression and tumor resection from the canal. It is common with these tumors for the optic/orbital extension to be medial to the optic nerve because their origin is medial. Traditional transcranial approaches require transection of the falciform ligament and retraction of or blind dissection behind an often already tenuous ipsilateral optic nerve. This carries a well-documented risk of vision loss. Such retraction is obviated with an endonasal approach, and early series using this approach show potential for improved outcomes.^23–30

This approach is commonly used for sinonasal carcinomas that involve the orbit, meningiomas (both intradural and extradural), and juvenile nasal angiofibromas. In addition, this is in essence the approach that has the most established record for an endonasal approach to orbital pathology inasmuch as it has been used for orbital decompression for thyroid disease and trauma. We have also applied it in cases of fibrous dysplasia and as an adjuvant for complete optic nerve decompression before resection of lateral tumors.

Transmaxillary Extraconal Approach

The transmaxillary extraconal approach involves a sinonasal exposure similar to that described for the inferior-medial extraconal approach. In addition, a medial maxillectomy is extended anteriorly, and a portion of the piriform aperture and anterior maxillary sinus wall is removed. This allows more lateral extension inferiorly. The pterygopalatine fossa may be dissected and the branches of the trigeminal nerve identified to avoid inadvertent injury. Once identified, V2 can be traced back to the foramen rotundum and the infraorbital nerve followed into the infraorbital foramen. This provides immediate access to the inferior rectus and orbital contents above. It is very important to preserve the ophthalmic branch (V1) of the trigeminal nerve during the dissection because the vidian nerve is likely to be damaged during the trans–pterygopalatine fossa approach, especially if the vidian canal is used as a guide to the petrous ICA.³¹ The decreased lacrimation associated with sacrifice of the vidian artery combined with an insensate cornea has the potential for significant corneal morbidity.

As with any laterally extended endonasal approach, the carotid arteries or their branches, or both, come into play. To prevent inadvertent injury or hemorrhage, it is critical that one understand the location and relationships of the ICA in the infratemporal/parapharyngeal fossae as it enters the skull base, the horizontal petrous ICA, and the external carotid branches, such as the internal maxillary artery. The transmaxillary extraconal approach is one of the most advanced endonasal approaches, and we recommend reserving such approaches for experienced surgical teams.

Frequently, this approach is used for tumors that involve the middle fossa or Meckel’s cave and extend to compress the cone, such as meningiomas, juvenile nasal angiofibromas, or schwannomas that have extended into the infratemporal fossa, pterygopalatine fossa, or maxillary sinus.

Medial Intraconal Approach

The medial intraconal approach overcomes the limitation of posterior intraconal access associated with the anterior medial micro-orbitotomy approach discussed earlier. The key anatomic difference between intraconal and extraconal orbital tumors is the boundaries of the extraocular muscles. For medial/inferior and posterior intraconal lesions, the dissection corridor lies between the medial and inferior rectus muscles. Once the periorbita is incised, the surgeon has access to the orbital contents. Extraconal fat is excised with bipolar cautery, and the rectus muscles are identified. One problem is that the soft tissues of the orbit are all freely mobile and compressible, which makes it difficult to enter and dissect in the intraconal space.

Adding an oculoplastic surgeon to the EEA team has allowed us to develop a technique that includes retraction of the rectus muscle for intraconal access. From an external approach, the medial and inferior rectus muscles are identified at their insertion on the globe and controlled with vessel loops (Fig. 147-9). This allows passive movement of the muscles, which aids in endoscopic identification of them. It also allows retraction of the muscles, which widens the space between them and makes them easier to dissect (Fig. 147-10). Once this intraconal corridor is developed, the tumor can be identified and removed with limited bipolar cauterization and extensive sharp dissection (Fig. 147-11). A cotton-tipped applicator held by one surgeon provides excellent retraction of orbital fat. Again, standard microsurgical techniques are applied. Internal tumor debulking becomes even more important because the tumor mass itself can obscure visualization of the dissection margins. It is helpful to have one surgeon retract the mass inferiorly and medially while the other uses bimanual dissection to clear the lateral tumor margin. It is critical that the same microsurgical techniques used for open approaches be strictly adhered to when operating endonasally. Because the optic nerve is almost always lateral and superior to the tumor, once the lateral margin is cleared, the nerve is out of the field of dissection. As the dissection approaches the orbital apex, special care must be taken to avoid injury to the ophthalmic and central retinal arteries, which assume a medial trajectory with respect to the optic nerve within the orbit. The remaining soft tissue tumor attachments can be cut and the tumor removed en bloc.

FIGURE 147-9 Illustration of the technique used to gain endonasal access to medial intraconal tumors. The medial rectus muscle (MRM) and inferior rectus muscle (IRM) are looped externally, and these loops are used to retract the muscles, thereby providing an intraconal window.

FIGURE 147-10 Intraoperative endoscopic endonasal view of the left medial rectus (MR) and inferior rectus (IR) muscles after the periorbita has been partially resected. A glimpse of the tumor is seen between the two muscles.

FIGURE 147-11 Intraoperative endoscopic endonasal view of the left medial orbit with retraction applied to the medial rectus (MR) and inferior rectus (IR) muscles via external vessel loops. Spreading the muscles with this retraction provides a medial window for tumor resection.

Other variations for controlling the rectus muscles include detaching the medial rectus muscle from the globe, tagging it with a long silk suture, and passing the suture from within the orbit into the nose. This opens the medial orbit like a book, with the medial rectus pedicled posteriorly on the annulus of Zinn. After resection of the tumor, the rectus muscle is replaced and sutured back onto the globe. We have also placed a vessel loop endoscopically around the posterior medial rectus muscle and then around the contralateral septum. This allows medial retraction of the muscle, which further opens the corridor into the intraconal space.

Reconstruction can consist of the application of fibrin glue, acellular dermis, abdominal free fat graft, mucosal grafts, or (in most cases) a nasoseptal flap. Given the extensive dissection required for intraconal tumors and the possibility of rectus muscle scarring in the sinus with resultant diplopia, we often reconstruct the medial orbital wall with a pedicled nasoseptal mucoperichondrial flap.²² This flap is raised at the beginning of the procedure and pedicled on the posterior nasoseptal artery. It is placed in the nasopharynx during resection of the orbital tumor. Once the tumor is removed, the rectus muscle vessel loops are released, and extraocular movements are tested. The rectus muscles are placed back into their native positions, and orbital fat is pulled over them to prevent scarring. When a septal flap is used, it is placed over the defect, and Surgicel and a fibrin sealant are used to hold it in position during initial healing. No packing is used because of the potential for increasing intraocular pressure by putting pressure on a large orbital defect. We have not had a problem with enophthalmos when using the nasal septal flap for endonasal reconstruction of large medial orbital defects, and we believe that this flap recapitulates the periorbital fascia nicely.

The medial intraconal approach can be used for any intraconal tumor that arises medial or inferior to the optic nerve, including nerve sheath meningiomas, extraocular nerve schwannomas, hemangiomas, and metastases. A slight modification of the approach can provide a limited degree of superior medial access. By completely removing the lamina papyracea and retracting the orbital contents laterally (after adequate optic canal decompression is achieved), the medial and superior roof of the orbit can be drilled (supramedial orbitotomy). The periorbita is opened, and access above the medial rectus and beneath the superior oblique can be gained. This access is limited by the position of the ophthalmic artery, as discussed previously.

General Principles for Endonasal Resection of Orbital Tumors

Several key anatomic principles should be followed for safe resection of orbital tumors via an endonasal approach. First, the optic nerve forms the lateral boundary for resection within the orbit. This makes tumors located superior or lateral to the nerve contraindicated for an endonasal approach. These tumors should be approached with standard open lateral techniques. In addition, as mentioned, the ophthalmic artery is a key superolateral limiting structure for intraorbital dissection. Second, dissection should generally be below the ethmoidal foramina. Dissection above this plane puts the ethmoidal arteries at risk within the orbit. Inadvertent injury to these vessels could result in postoperative retrobulbar hemorrhage and loss of vision. Third, the extraocular muscles should be respected. Dissection should occur between these muscles and not through them unless they are directly involved and intentionally sacrificed. Finally, appropriate use of computed tomography or magnetic resonance imaging guidance allows us to follow these anatomic principles with better precision.