The orbitozygomatic approach achieves better

Transcription

1 OPERATIVE NUANCES THE ORBITOZYGOMATIC APPROACH Wouter Ralph van Furth, M.D., Ph.D. Department of Neurosurgery, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands Anne Maria R. Agur, Ph.D. Division of Anatomy, Department of Surgery, Toronto, Ontario, Canada Nicholas Woolridge, B.M.C., B.F.A., B.Sc., M.Sc. Division of Biomedical Communications, Department of Surgery, Ontario, Canada OBJECTIVE: The orbitozygomatic approach is a modification and extension of the pterional craniotomy to gain a wider exposure of structures at a cranial base. To simplify the understanding and performance of the approach, we developed a teaching video that follows a systematic approach to the surgical anatomy and technique. METHODS: The authors have incorporated three-dimensional (3D) renderings into the descriptions of the surgical technique and contemporary computer animation is used to demonstrate surgical details and nuances of the procedure. RESULTS: A teaching video was compiled, and it was well received by neurosurgical residents in Europe and Canada. CONCLUSION: With mastery in the surgical laboratory and with guided supervision, the approach can be routinely applied without adding morbidity to a variety of pathologies such as aneurysms and tumors. KEY WORDS: Anatomy, Computer animation, Cranial base surgery, Orbitozygomatic approach, Surgical education, Surgical technique Neurosurgery 58[ONS Suppl 1]:ONS-103 ONS-107, 2005 DOI: /01.NEU C1 Michael D. Cusimano, M.D., Ph.D. Division of Neurosurgery, St. Michael s Hospital, Departments of Neurosurgery, Education, and Public Health, Toronto, Ontario, Canada Reprint requests: Wouter Ralph van Furth, M.D., Ph.D., University of Amsterdam, Academic Medical Center H2-209, PO Box 22660, 1100 DD Amsterdam, The Netherlands. W.R.vanFurth@amc.uva.nl Received, December 16, Accepted, April 27, The orbitozygomatic approach achieves better exposure of basal structures with less brain retraction than the frontotemporal approach for lesions of the cranial base. By extending the frontotemporal craniotomy with an orbitozygomatic osteotomy, the orbitozygomatic approach allows excellent exposure to lesions of the frontal, middle, and upper segment of the posterior fossa, infratemporal fossa, pterygopalatine fossa, petrous apex, and tentorial incisura. The orbitozygomatic osteotomy decreases working distances and opens a larger volume of access to the surgeon, thus allowing greater maneuverability of instruments while lessening brain retraction (3). Vascular and neoplastic lesions such as anterior communicating artery aneurysms and medial sphenoid wing meningiomas are common indications for the procedure (7, 9). We have routinely used the approach, similar to others, for basilar artery aneurysms, craniopharyngiomas, pituitary macroadenomas, chordomas, and meningiomas arising in the anterior, middle and petrous apex-posterior fossa region. For lesions involving the middle fossa, infratemporal region, and basilar tip, removal of the zygomatic arch removes the bulky temporalis muscle that limits exposure with the nonorbitozygomatic approaches that require more brain retraction than the orbitozygomatic approach. We ultimately tailor the extent of the osteotomy to the specifics of the pathology and the patient s anatomy. For lesions such as basilar artery termination aneurysms and Meckel s cave region tumors, we routinely use the full orbitozygomatic approach. With lesions that require minimal or no subtemporal exposure such as anterior communicating artery aneurysms, we only remove the orbital component of the orbitozygomatic osteotomy (9). This paper will focus on the full orbitozygomatic approach. We have used the approach routinely since 1992, and the senior author (MDC) has taught it to over 40 neurosurgeons. Despite a number of papers (2, 4 6, 8, 10) describing the approach in the literature, we are frequently impressed at how challenging the approach can be to learn, even for senior level residents and experienced surgeons familiar with the anatomy of the region. For this reason, we sought to incorporate contemporary three-dimensional animation, artist s drawings, cadaveric dissection, and surgical video footage into a video to facilitate learning of the orbitozygomatic approach (complete video can be seen at utoronto.ca:8080/ramgen/extra3/ozc/ozc- 1v.rm). The purpose of this paper is to describe the orbitozygomatic approach as we have performed it in over 250 cases, emphasizing nuances through the accompanying threedimensional animation that accompanies this paper. VOLUME 58 OPERATIVE 1 FEBRUARY 2006 ONS-103

2 VAN FURTH ET AL. PREOPERATIVE ASSESSMENT Particular attention to the patient s history of proptosis, visual disturbances such as decreased visual acuity and diplopia, trigeminal nerve symptoms, frontal or temporal lobe symptoms, and trismus is important to help in defining the extent of resection needed and in understanding the postoperative status and needs of the patient. For example, a patient with significant preoperative proptosis caused by a hyperostosing sphenoid wing meningioma would require extensive resection of the tumor-involved bone and a reconstruction tailored to the position of the patient s normal eye and to the patient s wishes. As in any procedure for lesions of the frontolateral skull base, a detailed assessment of all cranial nerves and frontal and temporal lobe functions preoperatively is essential. Imaging depends on the suspected pathology. Computerized tomography and magnetic resonance imaging are complimentary and routinely used. If the frontal sinus is extending lateral to the supraorbital notch or extends into the orbital roof, surgical planning must include measures to avoid postoperative cerebrospinal fluid leakage. Transgression of the lesion into the orbit, sinuses, through the middle fossa floor, or into the posterior fossa are important anatomic features to note preoperatively. An assessment of whether an intradural or purely extradural approach depends on both the presumed pathology and the anatomy of the lesion preoperatively. PROCEDURE Frontotemporal Craniotomy In the supine position, with the patient s head rigidly fixated, the head is rotated to the contralateral side, 10 to 20 degrees for primarily anterior lesions and more for more posterior lesions (Fig. 1). The zygomatic bone is positioned parallel to the floor to allow gravity to pull the frontal and temporal lobes gently away from the surgeon s access. The patient is padded appropriately and strapped in place to FIGURE 1. Patient positioning for orbitozygomatic approach, frontal view. allow movements of the operating table to optimize exposures and lessen retraction. The skin incision begins in a crease just inferior and anterior to the tragus (Fig. 1). For more inferiorly placed lesions such as those extending into the infratemporal fossa, the incision is carried to the level of the lobule. The incision is carried to the midline up to the hairline or rarely to the most superior frontalis muscle crease in the midline in patients with very high foreheads. The superficial layer of the temporalis fascia and the periosteum is carried up with the scalp flap. The periosteal blood supply is always preserved, making it available for paranasal sinus repair for the prevention of cerebrospinal fluid leakage. At the level of the fat pad over the temporalis muscle just posterior to the keyhole, we incise the superficial temporal fascia, elevate the fat pad, and carry the dissection anteriorly on the deep fascial plane to prevent injury to the frontal division of the temporal branch of the facial nerve. At the orbital rim, sharp dissection is often needed to elevate the periosteum fully. The dissection is carried along the orbital rim to the zygoma and then along the zygomatic arch to the temporal process and root of the zygomatic arch. This allows the scalp to be mobilized fully and not hinder exposure. If necessary, the dissection can be carried down onto the masseteric fascia to access lesions in the infratemporal of pterygopalatine fossae. If the supraorbital nerve is encountered in a foramen, small osteotomes are used to convert the foramen into a notch, thereby freeing the nerve and its accompanying vessels. Dissection of the periobita must be performed with utmost care; if it is kept intact, postoperative periorbital swelling is minimal. Before the maneuver, the anesthesiologist is informed in the event that the patient experiences a vagal response during the dissection. The periorbita is most adherent to the frontalzygomatic suture at the superolateral orbital margin where it ought to be dissected initially, often with a small scalpel or sharp elevator. Subsequently, the inferior-lateral and superior-medial aspect of the periobita are dissected to a depth of 2.5 to 3 cm. Cottonoids are then placed to protect the periobita. The temporalis muscle is fully mobilized starting from the posterior-inferior aspect just posterior to the zygomatic root and then carried anteriorly. The muscle is fully elevated from the temporalis fossa to under the zygomatic arch, and its soft tissue attachments to the arch are divided. We prefer to do a four-hole bone flap using the bridge technique in which the cuts between burr holes are left incomplete except for small 2 mm bridges of bone that are cracked free when the bone flap is elevated. The bridges act as a support for the bone flap when replaced and frequently obviate the need for any sort of implants for closure (1). The external cortex of the pterion is left in place to facilitate a cosmetic reconstruction. An extradural dissection is then performed along the frontal and temporal fossae, and the dura is protected with cottonoids. Self-retaining retractors are also used to protect the dura. The temporalis muscle is placed back and forth to be out of the way when performing the osteotomy. In the case of a recent subarachnoid hemorrhage and concomitant hydrocephalus, a ventriculostomy with release of cerebrospinal fluid is performed at this stage. ONS-104 VOLUME 58 OPERATIVE 1 FEBRUARY

3 ORBITOZYGOMATIC APPROACH ORBITOZYGOMATIC OSTEOTOMY (see video at web site) Five separate sequential bone cuts are required to free the orbit and zygomatic arch. We begin anteriorly and medially and progress laterally and posteriorly, although the order is not particularly crucial. Before making our cuts, we plan and mark them, and then pilot holes are made for placement of miniplates to optimize reconstruction of the osteotomy. Alternatively, this can be performed at the time of reconstruction. One assistant then retracts the cottonoids in the orbit just sufficient to observe the placement of the micro-reciprocating saw, while the surgeon operates the saw. If the pathology does not require exposure anteromedially (e.g., cribriform, posterior ethmoid, sphenoid region), the first cut is made just lateral to the supraorbital notch. If more medial exposure is necessary, consideration to more medial cuts or a bilateral orbital osteotomy is made. The first cut (Fig. 2A) extends directly posteriorly, approximately 2.5 cm from the inner table of the skull. The surgeon stands directly at the head of the patient, cutting toward her/himself. As the cut extends posteriorly, the surgeon s hand is carried anteriorly, thereby carrying the blade into a vertical direction so as to minimize the amount of frontal retraction necessary. The second cut (Fig. 2B) carries on from the posterior end of the first cut and extends from a medial to a lateral direction along the posterior orbital roof to just lateral to the most lateral extent of the superior orbital fissure. To make this cut, the surgeon changes position to stand to the side of the patient s pathology, facing medially. Holding the micro-reciprocating saw in a position parallel to the floor, with protection along the frontal lobe and periobita, the surgeon cuts from a medial to lateral direction, taking the saw deeper laterally to get through the thicker bone of the superolateral orbit. The cut is carried down the lateral orbit to approximately half way to the inferior orbital fissure, just within the anterior temporal fossa. The third osteotomy cut (Fig. 2C) is performed from the same standing position, although the surgeon rotates her/his own body so as to face the inferior orbital fissure as seen from the pterygopalatine fossa in the depths of the temporal fossa. The inferior orbital fissure is not visible from this point of view but is easy to identify by palpating the inferior orbital fissure with a small dissector while the assistant viewing from the orbital side confirms the location. With the blade of the saw within the inferior temporal fossa and with protection along the temporal dura, the cut is made from an inferior to a superoposterior direction to come close although not necessarily into the second cut. The fourth cut requires slight reorientation of the surgeon so as to face medially toward the patient s nose and the inferolateral periobita and to be able to see the inferior orbital fissure from the orbital side. The periorbita and temporalis muscle are protected with the temporalis muscle swung back toward the exposed dura. Placing the saw blade along the lateral orbital margin superficial to the inferior orbital fissure, the surgeon FIGURE 2. Bone cuts for orbitozygomatic osteotomies. A, first cut: through medial orbital rim and roof. B, second cut: through roof and lateral wall of the orbit. C, third cut: extends to inferior orbital fissure. D, fourth cut (part one): from inferior orbital fissure through anterior aspect of the zygomatic bone above the zygomaticofacial foramen. E, fourth cut (part two): through posterior aspect of zygomatic bone. F, fifth cut: through root of zygomatic process of temporal bone. G, orbitozygomatic bone piece removed. H, reconstruction of orbitozygomatic complex. Orbitozygomatic complex has been fixated with titanium microplates. cuts from a superficial to a deeper direction, elevating the hand holding the saw so as to progressively tilt the saw blade perpendicular to the floor and have the tip of the blade in the inferior orbital fissure on the orbital side. The cut is then carried posteriorly through the zygomatic bone, coming more superficially as the orbit is exited so as to only cut the bone and not the underlying temporalis muscle (Fig. 2D). The blade is removed at the midway point of the zygomatic bone and is repositioned at the posterior edge of the zygoma for the posterior part of this cut. This is done to create a slight V shape in VOLUME 58 OPERATIVE 1 FEBRUARY 2006 ONS-105

4 VAN FURTH ET AL. the cut to facilitate a cosmetic reconstruction (Fig. 2E). Protection of orbital contents by the assistant is no longer needed. This cut is kept above the zygomaticofacial foramen to avoid entry into a high-riding maxillary sinus. The fifth cut is performed with the surgeon at the same position; the temporalis muscle is mobilized anteriorly (Fig. 2F). The cut is taken obliquely through the most posterior aspect of the origin of the zygomatic process of the temporal bone, the socalled zygomatic root, at approximately a 30 degree angle. If the petrous carotid artery requires exposure, this cut can be modified to include the glenoid fossa and allow downward displacement or division of the mandibular condyle. With the five bone cuts performed, the orbitozygomatic bone piece can now be freed up by tapping the bone free with a 5 to 6 mm osteotome. Any remaining attachments of the temporalis and masseter muscles are cut from the zygomatic arch and the orbitozygomatic bone piece removed as one piece (Fig. 2G). The temporalis muscle is further reflected inferiorly, exposing more of the middle fossa floor. Additional bone removal can now be performed to give access to subtemporal structures. Any extradural dissection can then proceed. The superior orbital fissure is regularly opened with other bony or extradural dissection being dictated by the pathology. Reconstruction Reconstruction is planned simultaneously with the opening. In our experience, the cosmetic result with the orbitozygomatic approach is equal to, or better, than that with the standard pterional approach, which demands that the pterion and orbital ridges being drilled. Three titanium miniplates are used routinely for the osteotomy reconstruction (Fig. 2H) and can be positioned before the bone cuts. One is placed medially across the first cut, another is placed at the zygomatic bone cuts, and the final plate is at the zygomatic root. Constant irrigation with cold saline while the holes are being placed prevents later screw failure caused by thermal injury to bone. The craniotomy is repositioned with the bridge technique, and often heavy, nonabsorbable suture is all that is needed for fixation. Alternatively, if the bridge technique is not used, the craniotomy can be closed with sutures, plates, or specifically designed buttons with or without supplementation by synthetic bone cements. The temporalis muscle is repositioned in its anatomic position and secured with nonabsorbable sutures through the dura tag-up holes (1). The interfascial opening performed initially is resutured and the scalp closed in two layers. Postoperative Care Postoperative care is the same as with any other frontotemporal craniotomy if the periorbita has not been opened. If the periorbital fat is seen during the procedure, there can be marked periorbital edema and conjunctival edema, which begins on the second postoperative day. In such a case, it is essential that the conjunctiva and cornea be well lubricated and kept moist. Chemotic conjunctiva that is not kept well lubricated can scar permanently. Symptomatic relief of pain is achieved with ice packs or cold compresses applied over the area. Ptosis may persist for several weeks but routinely recovers fully. We have only had 2 patients in more than 250 that have noticed a mild ptosis persisting more than 6 months postoperatively and requested an eyelid tuck procedure by our plastic surgery colleague. Patients are routinely advised to exercise opening and moving their jaw from side to side to minimize temporomandibular pain. Variations of Orbitozygomatic Approach If the pathology is primarily located anteriorly, we modify the approach to only remove the orbit and to leave the zygomatic arch intact (9). If, however, the lesion extends into the middle fossa, particularly along the floor or medially, we will use the full approach. Some authors advocate only performing the zygomatic osteotomy for lesions isolated to the middle or infratemporal fossa. However, in our experience, this can be limiting, and in those cases, we tend to include a more lateral orbital osteotomy to get ideal access and remove the zygomatic bone completely. This allows full displacement of the temporalis muscle away from the surgical corridor. A good alternative technique with a similar generous approach is to leave the orbitozygomatic bone piece connected to the bone flap at the level of the zygomatic process of the frontal bone. Certainly, in younger patients, this approach can be safely performed. The cuts through the orbital roof and lateral wall (cut 2 and part of cut 1) have to be performed with a small osteotome, instead of a micro reciprocating saw, because two-sided visual inspection is impossible. This technique tends to remove less orbital roof with the osteotomy, and for those initially learning the technique, it may be more difficult to assimilate. CONCLUSIONS Although complex, the orbitozygomatic approach consists of a logical sequence of five bone cuts in addition to a standard frontotemporal craniotomy. Once mastered, the approach can be used to great advantage for a wide range of pathology affecting the cranial base. It minimizes brain retraction and allows greater surgeon maneuverability in a larger volume of access at a shorter working distance. Attention to reconstruction means that the approach also optimizes patient outcome with excellent cosmetic results. REFERENCES 1. Cusimano MD, Suhardja AS: Craniotomy revisited: Techniques for improved access and reconstruction. Can J Neurol Sci 27:44 48, Delashaw JB Jr, Tedeschi H, Rhoton AL Jr: Modified supraorbital craniotomy: Technical note. Neurosurgery 30: , Gonzalez LF, Crawford NR, Horgan MA, Deshmukh P, Zabramski JM, Spetzler RF: Working area and angle of attack in three cranial base approaches: Pterional, orbitozygomatic, and maxillary extension of the orbitozygomatic approach. Neurosurgery 50: , Hakuba A, Liu S, Nishimura S: The orbitozygomatic infratemporal approach: A new surgical technique. Surg Neurol 26: , ONS-106 VOLUME 58 OPERATIVE 1 FEBRUARY

5 ORBITOZYGOMATIC APPROACH 5. Hayashi N, Hirashima Y, Kurimoto M, Asahi T, Tomita T, Endo S: One-piece pedunculated frontotemporal orbitozygomatic craniotomy by creation of a subperiosteal tunnel beneath the temporal muscle: Technical note. Neurosurgery 51: , McDermott MW, Durity FA, Rootman J, Woodhurst WB: Combined frontotemporal-orbitozygomatic approach for tumors of the sphenoid wing and orbit. Neurosurgery 26: , Riina HA, Lemole GM Jr, Spetzler RF: Anterior communicating artery aneurysms. Neurosurgery 51: , Shigeno T, Tanaka J, Atsuchi M: Orbitozygomatic approach by transposition of temporalis muscle and one-piece osteotomy. Surg Neurol 52:81 83, Sindou M, Emery E, Acevedo G, Ben David U: Respective indications for orbital rim, zygomatic arch and orbito-zygomatic osteotomies in the surgical approach to central skull base lesions. Critical, retrospective review in 146 cases. Acta Neurochir (Wien) 143: , Zabramski JM, Kiris T, Sankhla SK, Cabiol J, Spetzler RF: Orbitozygomatic craniotomy. Technical note. J Neurosurg 89: , Acknowledgments The video clip for this paper is a short compilation of a teaching video that was financially supported, in the form of an unrestricted educational grant, by W. Lorenz Surgical, Medtronic, Codman, Ivy Medical Limited, Canada Microsurgical Limited, Carl Zeiss Canada Limited, TMG Medical Sales Incorporated. In a multimedia fashion, van Furth et al. present the nuances of the two-piece orbitozygomatic approach. We agree that this particular approach requires understanding the local anatomy to make the cuts in a rational fashion and to be able to loosen the osteotomies. We also agree that the surgical approach must be tailored to the location of the pathology. For lesions involving the middle fossa, infratemporal region, and basilar tip, the zygomatic arch must be cut and the bulky temporal muscle that limits exposure must be eliminated to decrease retraction over the brain. During the treatment of anterior circulation aneurysms, removing the orbital roof and lateral wall is enough to obtain adequate exposure medially to access the anterior communicating artery and laterally to access the middle cerebral artery. Zabramski et al. (1) published or report that detailed a sequence of six cuts that allows this approach to be performed in a logical and understandable way. This article provides no new knowledge of the local anatomy or areas of exposure through this approach. However, it nicely correlates a cadaveric dissection and a three-dimensional animation, creating a tool that will be very useful for neurosurgical trainees. L. Fernando Gonzalez Robert F. Spetzler Phoenix, Arizona COMMENTS Van Furth et al. have presented a concise, well-illustrated description of the orbitozygomatic approach for intracranial micro-neurosurgery. The utility of this approach for aneurysm surgery is still somewhat controversial. I have reserved this approach only for the complex basilar apex aneurysms or those that are located high above the dorsum. I do not feel that it is necessary for anterior circulation aneurysms. This morbidity of this approach is minimal, but many patients report increased postoperative pain, ptosis of the eyelid, and periorbital edema along with conjunctival edema. Because most of these issues are completely reversible, the techniques do not need to be avoided. However the added trauma of the exposure should be utilized only in cases where the extra exposure is necessary. Robert A. Solomon New York, New York 1. Zabramski JM, Kiris T, Sankhla SK, Cabiol J, Spetzler RF: Orbitozygomatic craniotomy. Technical note. J Neurosurg 89: , The technique of orbitozygomatic osteotomy is now well known to cranium base and vascular neurosurgeons. It has wide applications to tumors of the middle cranial fossa, and upper clivus, aneurysms of the upper basilar artery, temporal AV malformations, and other lesions of the basal temporal lobe. In addition to the technique described here by the authors, a more extensive method is removing the zygoma along with the condylar fossa, and then plating it back at the end of the operation. This technique is useful when a more extensive exposure of the petrous ICA and the extradural clival area is needed. Some surgeons have described and use the technique of removing the cranial bone and the orbitozygomatic piece together. However, I find this method more cumbersome and less safe for the patient. Laligam N. Sekhar Seattle, Washington VOLUME 58 OPERATIVE 1 FEBRUARY 2006 ONS-107