The frontotemporal-orbitozygomatic (FTOz) approach was introduced in the early 1980s as an extension of the traditional pterional approach.1-4 In 1982, Jane et al1 first described the orbito-frontal variant of this approach and demonstrated its ability to achieve broad skull base access without significant brain retraction. Subsequently, Pellerin et al,2 Hakuba et al,3 and Al-Mefty4 reported their own experiences and versions of the approach, resulting in a broader application and widespread adoption in neurosurgery.
The indications for using the FTOz approach include selective vascular and neoplastic lesions of the anterior, middle, and central cranial fossae and the upper segment of the posterior cranial fossa. These lesions include suprasellar and parasellar tumors; lesions of the third ventricle, medial sphenoid wing and spheno-orbital meningiomas; lesions of the orbital apex, interpeduncular cistern, and upper paraclival regions; and anterior communicating artery and basilar-tip aneurysms.5,6 In this article, we discuss advantages and disadvantages of the FTOz approach and describe related important technical nuances and common pitfalls. We briefly discuss the 1-piece,7 2-piece,6 and 3-piece5 techniques. Our goal was to provide an up-to-date report of this time-tested surgical approach using original high-quality dissections, three-dimensional (3D) models, and 4K videos to serve as a reliable and practical educational resource for neurosurgery trainees and junior neurosurgeons. A case example is also provided to show the 1-piece orbitozygomatic approach.
Institutional review board/ethics committee approval and patient consent were neither required nor sought for this study.
PROS AND CONS OF THE FTOz APPROACH
The extended bone removal required for the FTOz approach (ie, removal of the superior and lateral orbital rims and the zygoma) enhances the surgical angle of attack and instrument maneuverability.8-12 A wide access to the skull base can be achieved using this approach, with minimal or no brain retraction needed. After the osteotomies are performed, the dura is typically tented inferiorly over a broad surgical base, which opens the subfrontal corridor widely and provides an expanded operative view of the anterior and middle cranial fossae. Alternatively, for lesions such as medial sphenoid wing meningiomas, the dura can be opened after an extradural anterior clinoidectomy along the frontotemporal dural fold parallel to the Sylvian fissure and toward the falciform ligament of the optic canal. This method provides direct and early access to the optic canal, distal dural ring, and roof of the cavernous sinus in an extradural fashion and allows merging intradural and extradural corridors.
The panoramic view reveals various trajectories toward important cerebral vasculature such as the carotid terminus, middle cerebral artery (M1), anterior cerebral artery (A1), anterior communicating artery, and basilar apex (see 3D Model 1).13 Aneurysms in these locations can be surgically clipped using this approach, which creates enough room to achieve both proximal and distal control. The FTOz approach also provides an expanded inferosuperior trajectory, which makes it a good surgical option for high-riding tumors that extend superiorly within the suprasellar or third ventricular spaces. In such cases, removing the superior orbital rim is particularly helpful when a high trajectory is needed.
Similarly, the zygomatic osteotomies allow for further inferior mobilization of the temporalis muscle for deeper trajectories into the middle and posterior cranial fossae, which helps address lesions located along the tentorial incisura and posterior to the oculomotor trigone while minimizing temporal lobe manipulation.9 When no such trajectory is needed, some authors have chosen a modified version of the FTOz approach that spares the zygomatic osteotomies and uses osteotomies of the superior and lateral orbital rims only.13,14 This conservative approach is adequate for most lesions of the anterior and middle cranial fossae. The FTOz approach also provides access to lesions of the posterior one-third of the orbit, such as intraorbital meningiomas and cavernous hemangiomas.
3D Model 1.
Frontotemporal-orbitozygomatic (FTOz) craniotomy. Shown is a panoramic view of the skull base and good exposure of important neural and cerebrovascular structures (https://www.neurosurgicalatlas.com/3d-models/orbitozygomatic-craniotomy). (With on from The Neurosurgical Atlas by Aaron Cohen-Gadol, MD.)
Although the FTOz approach offers several advantages for select patients, it is not without limitations. The extra bone work needed to perform this approach requires the neurosurgeon to have a good understanding of the surgical anatomy and adequate practice in the neuroanatomy laboratory before operating on patients. The surgical steps should be performed carefully to ensure appropriate visualization of the relevant anatomy and controlled performance of the osteotomies. The FTOz approach places the orbital contents at risk of injury if the periorbita is not well protected while the orbital osteotomies are performed. It also confers a risk of injury to the optic nerve, especially if the thick and hyperostotic orbital roof is fractured in an uncontrolled fashion. This dangerous maneuver could also extend the fracture to involve the walls of the sphenoid and ethmoid sinuses, increasing the risk of cerebrospinal fluid leak. In addition, in patients with a laterally extending frontal sinus, the sinus is at risk of violation. It is important to review preoperative computed tomography images to understand the patient's bone and sinus anatomy. The supraorbital nerve is also at risk, and its injury can cause numbness in the adjacent area. In addition, this approach can leave cosmetic deformity related to inadequate or defective reconstruction of the orbitozygomatic bone and malar eminence.
The patient is positioned supine with the head rotated 15° to 60° to the contralateral side, depending on the anatomic region and pathology being addressed. The closer the pathology is to the midline, the less head rotation is needed. The neck is typically slightly extended to allow the frontal lobe to fall back with gravity. Lesions closer to the skull base require less head extension. The malar eminence is typically maintained at the highest point of the surgical field. After the head is fixed with a 3-point Mayfield clamp, the patient's body is strapped with thick tape to ensure stability in case intraoperative head rotation or flexion/extension is needed. In the following section, we describe the 1-piece FTOz approach and then discuss the 2-piece and 3-piece variants.
The incision is often started within 1 cm anterior to the tragus at the level of the zygomatic root, typically after a natural crease. It is then extended upward and curved forward, crossing the midline to terminate at the contralateral midpupillary line right behind the hairline (Figure 1A). As an option, a three-quarter or full coronal incision can be performed for lesions that require access to midline anterior structures (nasion, frontal sinus, falx, and sagittal sinus). The superficial temporal artery branches are ideally identified and preserved, but the frontal branch will often be encountered and sacrificed. Raney clips or selective bipolar coagulation are applied to the galeal edges to maintain hemostasis, and a no. 10 scalpel blade is used to transect the scalp flap off the cranium. The scalp flap is turned anteriorly along with the underlying pericranium using a broad periosteal elevator (Video 1). The superficial fat pad, which contains the frontalis branches of the facial nerve, is located approximately 2.5 to 3 cm posterior to the frontal process of the zygoma. The fat pad is reflected anteriorly using the interfascial technique (stays superficial to the temporalis fascia) or the subfascial technique (transects and dissects under the temporalis fascia; Figure 1B). The frontalis branches of the facial nerve reside in the superficial fascia of the fat pad and are normally preserved if mobilized anteriorly along with the fat pad. The interfascial technique is performed along natural dissection planes because it does not require any violation of the temporalis muscle fascia to expose the orbitozygomatic region.
FIGURE 1. One-piece frontotemporal-orbitozygomatic approach. A, The curved incision is started 1 cm anterior to the tragus (at the level of zygomatic root) and ends behind the hairline at the contralateral midpupillary line. The STA is preserved. B, The superficial fat pad is reflected anteriorly along with the frontalis branches of the facial nerve; subperiosteal dissection is performed to expose the superior orbital rim, frontozygomatic process, malar eminence, and zygomatic arch. C, The supraorbital nerve and vessels are mobilized anteriorly using gentle blunt dissection; exposure of both the frontal dura and periorbita (MacCarty keyhole) is shown. D, The temporalis muscle is reflected inferiorly, and a craniotome with a protective footplate is then used to connect the burr holes (sequential bone cuts 1-4 are labeled with black and white dashed lines). E, Drilling across the body of the zygoma (above the malar eminence) and the root of the zygoma is then performed (bone cuts 5 and 6 are labeled with white dashed lines; the previous bone cut 2 is shown with a black dashed line). F, The 1-piece bone flap is detached. (With permission from Juan Carlos Fernandez-Miranda, MD, and The Neurosurgical Atlas by Aaron Cohen-Gadol, MD.) STA, superficial temporal artery.
After anterior reflection of the fat pad, subperiosteal dissection is performed anteriorly to expose the superior orbital rim and frontozygomatic process. The supraorbital nerve and vessels are mobilized anteriorly using gentle blunt dissection or, if needed, by drilling around the supraorbital notch to detach them anteriorly with a small rim of bone (Figure 1C). The periorbita is then freed from the lateral orbital rim using blunt dissection in the form of gentle sweeping movements between the supraorbital notch and the inferior orbital fissure. The temporalis muscle is then either totally detached or incised along the superior temporal line; a myofascial cuff is left for reattachment during closure. The muscle incision continues posteriorly and inferiorly parallel to or beyond the skin incision line. A periosteal elevator is used to reflect the temporalis muscle inferiorly toward the zygoma while the use of excessive monopolar coagulation is avoided (Figure 1C). Preservation of the deep periosteal fascia of the temporalis muscle is important for preventing muscle atrophy.
Burr holes are typically created at the MacCarty keyhole15 and in the inferior temporal region (above the root of the zygoma) and posterior temporal region (inferior to the superior temporal line). It is important to accurately locate the MacCarty keyhole15 to enable exposure of both the frontal dura and the periorbita (typically located 7 mm superior and 3 to 5 mm posterior to the frontozygomatic suture; Figure 1C). This step is essential when performing osteotomies along the roof of the orbit.
After creating the burr holes, the dura is detached off the inner table of the skull using a No. 3 Penfield dissector to prevent injury to the dura and the underlying brain parenchyma and cortical veins. A craniotome with a protective footplate is then used to connect the inferior squamous temporal and superior temporal line burr holes (Figure 1D). The craniotomy is then extended superiorly and curved anteriorly toward the orbital rim just lateral to the supraorbital nerve and notch. Then, a high-speed drill with an M8 drill bit (or straight side-cutting B1 drill bit) is used to connect the inferior temporal burr hole with the frontal portion of the keyhole across the sphenoid wing (3D Model 2). Then, a blunt dissector is used to protect the periorbita because the high-speed drill with an M8 drill bit is again used to remove the lateral wall of the orbit and expose the periorbita from the keyhole to the inferior orbital fissure. Using the 1-piece technique, the neurosurgeon does not have the advantage of visualizing the cut along the orbital roof from within the anterior cranial fossa. It is therefore imperative to protect the orbital contents while performing this step. Cottonoid strips can always be used to protect the frontal and periorbital dura while an osteotome is used to fracture the orbital roof in a lateral-to-medial direction. When the orbital roof is thicker, the M8 can be used to drill between the frontal dura and periorbita in a lateral-to-medial direction, with direct visualization from the orbital side. Next, a B1 drill bit or a reciprocating saw can be used to drill across the body of the zygoma (approximately 1 cm anterior to the zygomatic angle and just posterior to the zygomaticofacial foramen) and connect this cut with the previous cut that was created along the lateral orbital wall and inferior orbital fissure (Figure 1E). The final cut is made across the posterior root of the zygoma, allowing detachment of the 1-piece bone flap (Figure 1F). This bone flap elevation should be performed carefully in a medial-to-lateral direction to avoid orbital or frontal lobe injury while the orbital roof is mobilized. Video 2 shows a case example of the 1-piece orbitozygomatic approach addressing an intraorbital mass.
3D Model 2.
Outline of frontotemporal-orbitozygomatic (FTOz) approach osteotomies (https://www.neurosurgicalatlas.com/3d-models/orbitozygomatic-outline-of-osteotomy). (With on from The Neurosurgical Atlas by Aaron Cohen-Gadol, MD.)
The 2-piece FTOz approach follows the same steps as the 1-piece approach but involves a standard initial pterional bone flap removal followed by osteotomies to remove the orbitozygomatic bone separately. This 2-step technique provides not only better visualization of the orbital roof from the anterior cranial fossa but also significantly more incorporation of the orbital roof bone into the orbitozygomatic bone flap (Figure 2A). After removing the pterional bone flap, removal of the orbitozygomatic bone flap is initiated by performing an osteotomy with the B1 drill bit or a reciprocating saw that crosses the superior orbital rim, just at or lateral to the supraorbital notch. Next, gentle extradural elevation of the frontal lobe dura provides extensive exposure of the orbital roof. The M8 bit can be used to drill posteriorly halfway across the orbital roof and then gently curve in front of the orbital apex and toward the lateral orbital wall to end up at the inferior orbital fissure (Figure 2B). This part of the craniotomy is typically performed before opening the dura to avoid drilling while the brain surface is exposed. Next, an osteotomy across the malar eminence is performed and connected to the inferior orbital fissure, similar to the 1-piece procedure (Video 3). Finally, an osteotomy across the root of the zygoma is performed, and the orbitozygomatic bone flap is removed gently (Figure 2C).
The 3-piece FTOz approach uses a similar technique but splits the orbitozygomatic bone flap into 2 pieces, avoiding an osteotomy along the body of the zygoma (Figure 3). The first 2 osteotomies are made across the root of the zygoma and at the most anterior aspect of the zygomatic arch leading to the removal or detachment of the first bone piece (Video 4). To gain full advantage of the 3-piece variant, the zygomatic piece is left attached to the masseter muscle inferiorly while still allowing further inferior mobilization of the temporalis muscle.
Then, a pterional bone flap is turned, and the second bone piece is removed. The next osteotomies are similar to those performed in the 2-piece approach, as previously discussed, and similarly allows for extensive preservation of the orbital roof.
A preoperative evaluation of the bone anatomy is crucial for avoiding underestimation of bony tumor involvement or hyperostosis. Similarly, understanding the anatomy of the frontal sinus is key to avoiding an unplanned and unnecessary frontal sinus breach. Understanding of the anatomy of the frontalis branches of the facial nerve is also important for preventing avoidable frontalis palsy. Making the cut far anteriorly over the superficial fat pad leads to nerve fiber transection and subsequent postoperative deficit. Inaccurate placement of the MacCarty keyhole can be disorienting because for a 1-piece orbitozygomatic craniotomy, exposure of both frontal dura and periorbita is necessary for performing the osteotomies.
Lack of knowledge of keyhole anatomy could lead the surgeon to wander into the orbit and disrupt the periorbita, which results in significant postoperative periorbital edema and bruising. For similar reasons, it is important to protect the orbital contents while performing the lateral orbital wall osteotomy. This procedure can be performed using blunt dissection with or without placement of cottonoid strips. Exposure of periorbital fat should be avoided as much as possible, although exposure of a small amount of fat can be safely coagulated using bipolar cautery. Blind fracture of the orbital bone should be avoided while removing the orbital roof. Such a fracture could extend posteriorly into the optic canal, causing ipsilateral optic nerve injury, or the fracture could extend to the ethmoid or sphenoid sinuses, risking an avoidable cerebrospinal fluid leak. Caution must be entertained when cutting the root of the zygoma to avoid violation of the temporomandibular joint. A good reconstruction plan is extremely important and plays a vital role in the performance of a successful FTOz approach.14
It is important for neurosurgeons to be familiar with the 3 variants described here. The 1-piece FTOz approach provides a clear benefit in simplifying reconstruction; however, it is more time-consuming, technically challenging, and can require orbital roof reconstruction. The 2-piece and 3-piece variants are technically simpler and allow for better preservation of the orbital roof, which is important for preventing pulsatile enophthalmos; however, the reconstruction is more time-consuming. The 3-piece approach better preserves the masseter muscle attachments, requiring less exposure of the zygomatic body without affecting the enhanced exposure. The neurosurgeon should tailor the FTOz variant to the pathology in question, the surgeon's expertise, and the patient's anatomy. Although these extensive skull base approaches can cause postoperative soft tissue swelling and discomfort, they carry the advantage of minimizing brain tissue manipulation.
The authors sincerely appreciate the support of the Stead Family Endowed Chair in creation of this work.
This study did not receive any funding or financial support.
The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
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