Anatomic evaluation of endoscopic transnasal transorbital approach to the lateral orbital apex Bianca Kenyon, B.S., and Jastin L. Antisdel, M.D.
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ABSTRACT
Background: This anatomic study investigates the feasibility of an endoscopic transnasal transorbital approach to the lateral orbital apex. Methods: Five cadavers with no prior history of sinus surgery were studied bilaterally. Standard techniques and instrumentation for functional endoscopic sinus surgery were used to perform dissections and delineate anatomy of sinuses and orbits. Results: With resection of the inferior aspect of the lamina papyracea and the medial portion of the orbital floor, followed by incision of the periorbita along the inferomedial aspect of the orbit and removal of minimal orbital fat, a satisfactory view of the surgical field is achieved. The medial and inferior rectus muscles are dissected and retracted to allow visualization of the optic nerve. By dissecting inferior to the optic nerve and using 0 and 30° endoscopes, the lateral orbital apex could be accessed without damage to the optic nerve. Conclusion: In patients whose vision is irreparably damaged, one might consider an endoscopic approach to lesions of the lateral orbital apex. Approach in patients with intact vision should be handled with caution because of possible traction of the optic nerve. (Am J Rhinol Allergy 28, 82–85, 2014; doi: 10.2500/ajra.2014.28.4000)
A
ccess to the orbital apex has traditionally been limited to open approaches: including transconjunctival and transcranial approaches as well as medial or lateral orbitotomies. With the advent of functional endoscopic sinus surgery, transnasal endoscopic techniques are increasingly being used to gain access to a variety of anatomic structures of the anterior skull base, including the orbital apex. In 1997, Sethi and Lau were among the first to successfully perform biopsies of lesions of the orbital apex using an endoscopic approach.1 Since that time, the usefulness of the endoscopic approach has been substantiated in a number of cases.2–5 Endoscopic surgery has advantages over traditional open approaches in that it is minimally invasive, affording a better cosmetic result and posing less risk to the patient. This has expanded the use of endoscopic techniques for biopsy, decompression, debulking, and resection of various lesions of the orbital apex. One factor that determines the type of orbital apex approach used is the location of the lesion. Current literature suggests that endoscopic approaches are best for medial and inferior lesions of the orbital apex.1,3,4 Historically, an endoscopic approach to the lateral orbital apex has been avoided because of concerns of feasibility. Although anatomic studies have described techniques to the medial and inferior orbital apex,6 none have explored access to the lateral orbital apex. In this anatomic study, we examine the feasibility and technique of an endoscopic, transnasal approach to the lateral orbital apex.
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Five fresh adult cadaver heads were obtained. Sinonasal cavities were dissected bilaterally for a total of 10 orbital approaches. Exclusion criteria for the cadavers included prior history of sinus dissection and maxillofacial trauma. Zero and 30° rigid rod-lens endoscopes were connected to a light source via a fiber optic cable and to a camera for viewing purposes. Standard surgical positioning and instrumentation were used for the dissections. From the Department of Otolaryngology–Head and Neck Surgery, Saint Louis University, Saint Louis, Missouri Presented at the Combined Otolaryngology Spring Meeting, April 2012, San Diego, CA The authors have no conflicts of interest to declare pertaining to this article Address correspondence to Jastin Antisdel, M.D., Saint Louis University Hospital, Department of Otolaryngology, 3635 Vista Avenue, 6 FDT, Saint Louis, MO 63110 E-mail address: [email protected] Copyright © 2014, OceanSide Publications, Inc., U.S.A.
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Dissection began with medialization of the middle turbinate to expose the uncinate process and ethmoid bulla. The uncinate process was resected. A very large maxillary antrostomy was performed with resection in superior and posterior directions to identify the floor of the orbit. Next, total ethmoidectomy was performed from anterior to posterior direction. The skull base and lamina papyracea were skeletonized. The sphenoid ostium was identified and widely enlarged with removal of the sphenoid face laterally until flush with the lamina papyracea. The sphenoid sinus was then inspected with identification of landmarks; including the optic canal, carotid protuberance, and opticocarotid recess. Surgical opening of the sinuses exposes the medial wall of the orbit, including the lamina papyracea and optic canal. The lamina papyracea was then resected in a posterior to anterior direction, starting ⬃2 cm anterior to the sphenoid face. The medial portion of the orbital floor was then resected (can be taken as far laterally as the infraorbital nerve). Exposed periorbita was then incised horizontally from posterior to anterior along the inferomedial aspect of the orbit. Periorbital fat that extrudes from the opening was carefully removed. As the fat was removed, the medial and inferior rectus muscles were identified. The optic nerve was identified next through careful dissection. With gentle retraction of the medial and inferior rectus muscles, a corridor was opened inferior to the optic nerve. In the cadaver, this space can easily be followed to the bony wall of the lateral orbital apex.
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METHODS
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DISSECTION
RESULTS The bilateral dissections were performed successfully on each cadaver for a total of 10 dissections. In each case, the general dissection described previously was performed. A maxillary antrostomy was necessary for complete visualization of the junction of the medial orbital wall and the orbital floor. This helped guide further skeletonization of the lamina papyracea during ethmoidectomy and prevented any premature unguided penetration of the lamina papyracea. A wide sphenoidotomy was performed in all dissections to confirm the locations of the optic nerve and internal carotid artery, which can be identified by their overlying bony protuberances. In four of the dissections, optic nerve decompression was performed to evaluate its necessity. We found that this may not be indicated because it did not aid in the approach to the lateral orbital apex and may be omitted depending on the location and extent of the orbital apex lesion. In two of the dissections, the entire lamina papyracea was removed to expose the entire periorbita, but we found that this was not necessary to reach the lateral orbital apex. During the other eight dissections, a
January–February 2014, Vol. 28, No. 1
Delivered by Ingenta to: Economics Dept IP: 95.181.217.250 On: Tue, 28 Jun 2016 17:47:14 Copyright (c) Oceanside Publications, Inc. All rights reserved. For permission to copy go to https://www.oceansidepubl.com/permission.htm
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Figure 1. (A) Inferior view of the surgical field (left orbit). A probe is located within the maxillary sinus. The orbit floor is shown in which its medial aspect has been partially resected. This allows for easier access inferior to the optic nerve. (B) A probe is inserted inferior to the optic nerve (right orbit). The lateral orbital wall can be reached with curved instruments. (C) The inferior and medial rectus muscles have been retracted such that the interior of the orbit can more easily be visualized. An inferomedial corridor can be used to access the lateral orbital wall, which is in direct contact with the probe. IR, inferior rectus muscle; PO, periorbita; POF, periorbital fat; OF, orbit floor; MR, medial rectus muscle; LR, lateral rectus muscle; ON, optic nerve.
partial removal of the lamina papyracea was performed, leaving the superior half intact. A portion of the medial orbital floor was then removed. This gave sufficient room for entrance into the orbit from the inferomedial angle. The incision of the periorbita was performed starting near the bony optic canal and moving anteriorly along the inferomedial aspect of the orbit. This positioning allowed for direct access to the necessary structures for dissection. Moving from posterior to anterior allowed for removal of the extruding periorbital fat before it could block the view of the surgical field. Fat that was in direct view of the surgical field was removed, whereas fat found more anteriorly and superiorly was left in place because it did not obstruct the dissection. Careful dissection of the medial and inferior rectus muscles and identification of the optic nerve are vital and provided the corridor for access to the lateral orbit. A probe can be inserted between the inferior and medial rectus muscles and inferior to the optic nerve, while these structures are carefully retracted. The probe was seen in contact with the lateral orbital wall in each dissection (Fig. 1). As previously mentioned, standard sinus surgery instrumentation was used throughout the dissections. The 0° endoscope was ideal for most of the dissection, but on entering the orbit we found the 30° endoscope necessary for dissection as structures are placed laterally to the field of view.
DISCUSSION
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Endoscopic transnasal approaches to the orbital apex have increased in popularity because of anatomic studies that confirmed their value.6,7 Many of these studies show that endoscopic transnasal approaches to the medial and inferior orbital apex are feasible and safe with minimal neurovascular retraction. However, these studies do not explore further access to the lateral orbital apex via an endoscopic transnasal approach. Currently, this region is accessed using open approaches such as lateral orbitotomies, which have the disadvantage of leaving a facial scar.8–10 This anatomic study determined the feasibility of an approach to the lateral orbital apex and is necessary to gain an understanding of the clinically relevant anatomy, which can be used to guide future surgical approaches. Previous literature postulates that endoscopic transnasal approaches to the lateral orbital apex are not feasible because of concern for damage to the optic nerve with irreparable loss of vision. The current study results show that in cadavers, with retraction of the medial and inferior rectus muscles combined with minimal removal of orbital fat, an access corridor is created that allows visualization of the lateral orbital wall. Negligible retraction of the cadaveric optic nerve yielded an even wider corridor to the lateral orbital apex. In patients with no vision, this traction would be acceptable. In patients with vision it is unclear if minimal traction is safe. As is seen in Fig. 1 C, using a very inferior approach allows the optic nerve to remain out of the path of dissection. Gently retracting the optic nerve supe-
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riorly even slightly can increase the field of vision tremendously. This could be performed with a “cotton tip applicator,” minimizing trauma to the optic nerve. In addition, this instrument can be used to dissect the fat around the optic nerve and move it out of the field of view. The position and course of the ophthalmic artery should be kept in mind when performing intraorbital dissection. As the artery emerges from the optic canal, it is positioned superolateral to the optic nerve. The artery then crosses over or under the optic nerve as it heads medially. It is estimated that the ophthalmic artery travels over the optic nerve 85% of the time.11 Thus, with an endoscopic approach from the inferomedial direction, the ophthalmic artery is protected by the optic nerve. When the ophthalmic artery courses under the optic nerve, careful dissection is necessary and there may be need to abort the approach. The branches of the ophthalmic artery may pose a challenge during endoscopic surgery. The lacrimal artery courses along the superior aspect of the lateral rectus muscle and will not be encountered during the inferomedial approach. As the ophthalmic artery turns medially and crosses over the optic nerve, it gives off posterior ciliary arteries. The inferior approach also prevents damage to these arteries, but it is important to remember that these will be inferior to the optic nerve in 15% of cases. The muscular branches of the ophthalmic artery supply the extraocular muscles and risk being damaged during intraorbital dissection. Some studies indicate that the anterior and posterior ethmoidal arteries can be damaged using an endoscopic transnasal approach.6 These arteries course in the superior aspect of the ethmoid sinuses. Complete resection of the superior ethmoids is not necessary for the inferomedial approach, thus decreasing the likelihood of injury to these arteries. The ciliary ganglion is another structure that may be encountered during intraorbital dissection of lateral orbital apex lesions. It is located around 10 mm anterior to the medial portion of the superior orbital fissure between the lateral rectus muscle and the optic nerve. It lies around 3 mm from the optic nerve and 10 mm from the lateral rectus muscle.12 From the ciliary ganglion emerge the short ciliary nerves, which run anteriorly near the optic nerve to insert into the globe. Damage to the ciliary ganglion or the short ciliary nerves can lead to a mydriatic or tonic pupil. The inferomedial approach to the lateral orbital apex will protect the ciliary ganglion from damage because it is located superiorly and laterally to the optic nerve and would not be visualized during dissection. Care must be taken when dissecting close to the optic nerve, because short ciliary nerves are difficult to find within the orbital fat. There may be some concern regarding the innervation of the extraocular muscles of the orbit. The lateral rectus, superior rectus, and superior oblique muscles will not be manipulated during the inferomedial approach. The medial rectus muscle is innervated by fibers from the inferior division of the oculomotor nerve. These travel under
American Journal of Rhinology & Allergy
Delivered by Ingenta to: Economics Dept IP: 95.181.217.250 On: Tue, 28 Jun 2016 17:47:14 Copyright (c) Oceanside Publications, Inc. All rights reserved. For permission to copy go to https://www.oceansidepubl.com/permission.htm
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the optic nerve to insert on the medial aspect of the middle third of the muscle.13 The inferior rectus muscle is also innervated by fibers from the inferior division. These course and insert on the superior surface of the inferior rectus muscle. Finally, the inferior division courses in the inferolateral direction to innervate the inferior oblique muscle. Damages to the medial rectus fibers are most likely avoided using an inferomedial approach to the lateral apex. However, it is possible that damage to the inferior rectus and inferior oblique muscle innervation may occur if dissection is not performed carefully. Finally, it is also important to note that direct damage to the muscles during retraction can cause postoperative eye movement disturbances. One may use transseptal sutures placed around the medial rectus muscle to medialize it and ensure its protection.14 Of note, retraction of these muscles and dissection of these areas is routinely safely performed in ophthalmic surgery. The amount of bone and fat that is resected with an inferomedial approach is minimal and approximates what would be necessary during medial orbitotomy and approach of medial orbital apex lesions. We found that total ethmoidectomy is not necessary. The superior half of the lamina papyracea, as well as most of the periorbital fat, are conserved. The inferomedial approach allows less fat to be removed while still preserving a good field of view. Therefore, the volume of the orbit can be maintained. However, it should still be noted that the risk of enophthalmos will inherently be greater when using this approach. The most important determinant for feasibility and safety lies in the exact position and extent of the lesion. The MRI image in Fig. 2 depicts a lateral orbital apex lesion in the left orbit. Such a lesion can be safely reached with an inferomedial corridor approach because of its lateral and slightly inferior location. However, lesions that are placed more superiorly may not be candidates for the approach described in this study, because injury to the optic nerve or ophthalmic artery is likely. The inferomedial approach should therefore be limited to lesions that are located in the lateral orbital apex with
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Figure 2. A magnetic resonance imaging (MRI) picture depicting an orbital apex lesion is shown that could be approached using the inferomedial corridor. The star in the image marks the location of the lesion in the left orbit. The optic nerve can be seen medial to the lesion.
inferior extension. Preoperative planning using imaging studies and intraoperative image guidance are crucial for patient safety in these approaches. Total resection of a lesion using this approach could only feasibly be performed if imaging shows that the lesion is small and if no superior extension is present. If superior extension is present, a biopsy or partial resection could be performed as long as inferior extension is present. Intraoperative image guidance will allow the surgeon to have concrete information as to the necessary approach to be used during the procedure, as well as give the surgeon the option to abort if it is deemed to be unsafe. Although this study highlights an approach that could be used in reaching lesions of the lateral orbital apex, there are still some limitations to consider. Cadavaric studies approximate the surgical environment but can not entirely predict what the results will show in a live patient. Therefore, the next step would be to safely attempt the inferomedial approach in a patient with a lesion in the lateral/inferior orbital apex. Individual surgeon judgment will help guide what can safely be attempted. The ideal patient would be one in whom the optic nerve of the affected eye is already irreparably damaged. Another limitation in this study is that it is hard to gauge the degree of manipulation of the optic nerve necessary for total access to a lateral orbital apex lesion and whether that manipulation will lead to any adverse effects (as seen in Fig. 1 B). Future studies could be performed to determine whether a particular location and size of a lateral apex lesion visualized on preoperative imaging correlates with easier access to the lateral orbital apex.
CONCLUSION Endoscopic transnasal approaches to the lateral orbital apex have not previously been attempted. In this anatomic study, we determined that an inferomedial approach could be used in accessing lesions of the lateral orbital apex. However, the positions of various structures including the optic nerve, ophthalmic artery, and ciliary
January–February 2014, Vol. 28, No. 1
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6.
ganglion pose a safety concern, because injury to these structures can lead to complications. In patients with irreparably damaged vision in the affected eye, the inferomedial approach may be considered if the extent and location of the lateral orbital apex lesion is favorable. Perioperative imaging and surgeon judgment may help in identifying such lesions. Additional studies will be needed to assess safety of this approach in those patients with intact vision.
7.
8.
9.
REFERENCES 1. 2.
3.
4. 5.
Sethi DS, and Lau DP. Endoscopic management of orbital apex lesions. Am J Rhinol 11:449–455, 1997. Kingdom TT, and Delgaudio JM. Endoscopic approach to lesions of the sphenoid sinus, orbital apex, and clivus. Am J Otolaryngol 24: 317–322, 2003. Karaki M, Kobayashi R, and Mori N. Removal of an orbital apex hemangioma using an endoscopic transethmoidal approach: Technical note. Neurosurgery 59(suppl 1):159–160, 2006. Tsirbas A, Kazim M, and Close L. Endoscopic approach to orbital apex lesions. Ophthal Plast Reconstr Surg 21:271–275, 2005. Murchison AP, Rosen MR, Evans JJ, and Bilyk JR. Posterior nasal septectomy in endoscopic orbital apex surgery. Ophthal Plast Reconstr Surg 25:458–463, 2009.
10. 11. 12.
13. 14.
Abuzayed B, Tanriover N, Gazioglu N, et al. Endoscopic endonasal approach to the orbital apex and medial orbital wall: Anatomic study and clinical applications. J Craniofac Surg 20:1594–1600, 2009. Abed SF, Shams P, Shen S, et al. A cadaveric study of the morphometric and geometric relationships of the orbital apex. Orbit 30:72–66, 2011. (Epub February 3, 2011.) Carta F, Siccardi D, Cossu M, et al. Removal of tumours of the orbital apex via a postero-lateral orbitotomy. J Neurosurg Sci 42:185–188, 1998. Goldberg RA, Shorr N, Arnold AC, and Garcia GH. Deep transorbital approach to the apex and cavernous sinus. Ophthal Plast Reconstr Surg 14:336–341, 1998. Du¨z B, Secer HI, and Gonul E. Endoscopic approaches to the orbit: A cadaveric study. Minim Invasive Neurosurg 52:107–113, 2009. Hayreh SS, and Dass R. The ophthalmic artery. II: Intra-orbital course. Br J Ophthalmol 46:165–185, 1962. Izci Y, and Gonul E. The microsurgical anatomy of the ciliary ganglion and its clinical importance in orbital traumas: An anatomic study. Minim Invasive Neurosurg 49:156–160, 2006. Erdogmus S, Govsa F, and Celik S. Innervation features of the extraocular muscles. J Craniofac Surg 18:1439–1446, 2007. Tomazic PV, Stammberger H, Habermann W, et al. Intraoperative medialization of medial rectus muscle as a new endoscopic technique for approaching intraconal lesions. Am J Rhinol Allergy 25:363–367, 2011. e
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Erratum
In the article The potential role of hyaluronic acid in postoperative radiofrequency surgery for chronic inferior turbinate hypertrophy Am J Rhinol Allergy 27:234 –236, 2013; doi: 10.2500/ajra.2013.27.3869, the author line was incorrect. It should appear as Manuele Casale, M.D.,1 Giacomo Ciglia, M.D.,1 Valeria Frari, M.D.,1 Antonino Incammisa, M.D.,1 Francesco Mazzola, M.S.,1 Peter Baptista, M.D.,2 Ranko Mladina, M.D.,3 and Fabrizio Salvinelli, M.D.1
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The authors regret the error.
doi: 10.2500/ajra.2014.28.3102
American Journal of Rhinology & Allergy
Delivered by Ingenta to: Economics Dept IP: 95.181.217.250 On: Tue, 28 Jun 2016 17:47:14 Copyright (c) Oceanside Publications, Inc. All rights reserved. For permission to copy go to https://www.oceansidepubl.com/permission.htm
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ABSTRACT
Background: This anatomic study investigates the feasibility of an endoscopic transnasal transorbital approach to the lateral orbital apex. Methods: Five cadavers with no prior history of sinus surgery were studied bilaterally. Standard techniques and instrumentation for functional endoscopic sinus surgery were used to perform dissections and delineate anatomy of sinuses and orbits. Results: With resection of the inferior aspect of the lamina papyracea and the medial portion of the orbital floor, followed by incision of the periorbita along the inferomedial aspect of the orbit and removal of minimal orbital fat, a satisfactory view of the surgical field is achieved. The medial and inferior rectus muscles are dissected and retracted to allow visualization of the optic nerve. By dissecting inferior to the optic nerve and using 0 and 30° endoscopes, the lateral orbital apex could be accessed without damage to the optic nerve. Conclusion: In patients whose vision is irreparably damaged, one might consider an endoscopic approach to lesions of the lateral orbital apex. Approach in patients with intact vision should be handled with caution because of possible traction of the optic nerve. (Am J Rhinol Allergy 28, 82–85, 2014; doi: 10.2500/ajra.2014.28.4000)
A
ccess to the orbital apex has traditionally been limited to open approaches: including transconjunctival and transcranial approaches as well as medial or lateral orbitotomies. With the advent of functional endoscopic sinus surgery, transnasal endoscopic techniques are increasingly being used to gain access to a variety of anatomic structures of the anterior skull base, including the orbital apex. In 1997, Sethi and Lau were among the first to successfully perform biopsies of lesions of the orbital apex using an endoscopic approach.1 Since that time, the usefulness of the endoscopic approach has been substantiated in a number of cases.2–5 Endoscopic surgery has advantages over traditional open approaches in that it is minimally invasive, affording a better cosmetic result and posing less risk to the patient. This has expanded the use of endoscopic techniques for biopsy, decompression, debulking, and resection of various lesions of the orbital apex. One factor that determines the type of orbital apex approach used is the location of the lesion. Current literature suggests that endoscopic approaches are best for medial and inferior lesions of the orbital apex.1,3,4 Historically, an endoscopic approach to the lateral orbital apex has been avoided because of concerns of feasibility. Although anatomic studies have described techniques to the medial and inferior orbital apex,6 none have explored access to the lateral orbital apex. In this anatomic study, we examine the feasibility and technique of an endoscopic, transnasal approach to the lateral orbital apex.
O D
Five fresh adult cadaver heads were obtained. Sinonasal cavities were dissected bilaterally for a total of 10 orbital approaches. Exclusion criteria for the cadavers included prior history of sinus dissection and maxillofacial trauma. Zero and 30° rigid rod-lens endoscopes were connected to a light source via a fiber optic cable and to a camera for viewing purposes. Standard surgical positioning and instrumentation were used for the dissections. From the Department of Otolaryngology–Head and Neck Surgery, Saint Louis University, Saint Louis, Missouri Presented at the Combined Otolaryngology Spring Meeting, April 2012, San Diego, CA The authors have no conflicts of interest to declare pertaining to this article Address correspondence to Jastin Antisdel, M.D., Saint Louis University Hospital, Department of Otolaryngology, 3635 Vista Avenue, 6 FDT, Saint Louis, MO 63110 E-mail address: [email protected] Copyright © 2014, OceanSide Publications, Inc., U.S.A.
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Dissection began with medialization of the middle turbinate to expose the uncinate process and ethmoid bulla. The uncinate process was resected. A very large maxillary antrostomy was performed with resection in superior and posterior directions to identify the floor of the orbit. Next, total ethmoidectomy was performed from anterior to posterior direction. The skull base and lamina papyracea were skeletonized. The sphenoid ostium was identified and widely enlarged with removal of the sphenoid face laterally until flush with the lamina papyracea. The sphenoid sinus was then inspected with identification of landmarks; including the optic canal, carotid protuberance, and opticocarotid recess. Surgical opening of the sinuses exposes the medial wall of the orbit, including the lamina papyracea and optic canal. The lamina papyracea was then resected in a posterior to anterior direction, starting ⬃2 cm anterior to the sphenoid face. The medial portion of the orbital floor was then resected (can be taken as far laterally as the infraorbital nerve). Exposed periorbita was then incised horizontally from posterior to anterior along the inferomedial aspect of the orbit. Periorbital fat that extrudes from the opening was carefully removed. As the fat was removed, the medial and inferior rectus muscles were identified. The optic nerve was identified next through careful dissection. With gentle retraction of the medial and inferior rectus muscles, a corridor was opened inferior to the optic nerve. In the cadaver, this space can easily be followed to the bony wall of the lateral orbital apex.
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METHODS
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DISSECTION
RESULTS The bilateral dissections were performed successfully on each cadaver for a total of 10 dissections. In each case, the general dissection described previously was performed. A maxillary antrostomy was necessary for complete visualization of the junction of the medial orbital wall and the orbital floor. This helped guide further skeletonization of the lamina papyracea during ethmoidectomy and prevented any premature unguided penetration of the lamina papyracea. A wide sphenoidotomy was performed in all dissections to confirm the locations of the optic nerve and internal carotid artery, which can be identified by their overlying bony protuberances. In four of the dissections, optic nerve decompression was performed to evaluate its necessity. We found that this may not be indicated because it did not aid in the approach to the lateral orbital apex and may be omitted depending on the location and extent of the orbital apex lesion. In two of the dissections, the entire lamina papyracea was removed to expose the entire periorbita, but we found that this was not necessary to reach the lateral orbital apex. During the other eight dissections, a
January–February 2014, Vol. 28, No. 1
Delivered by Ingenta to: Economics Dept IP: 95.181.217.250 On: Tue, 28 Jun 2016 17:47:14 Copyright (c) Oceanside Publications, Inc. All rights reserved. For permission to copy go to https://www.oceansidepubl.com/permission.htm
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Figure 1. (A) Inferior view of the surgical field (left orbit). A probe is located within the maxillary sinus. The orbit floor is shown in which its medial aspect has been partially resected. This allows for easier access inferior to the optic nerve. (B) A probe is inserted inferior to the optic nerve (right orbit). The lateral orbital wall can be reached with curved instruments. (C) The inferior and medial rectus muscles have been retracted such that the interior of the orbit can more easily be visualized. An inferomedial corridor can be used to access the lateral orbital wall, which is in direct contact with the probe. IR, inferior rectus muscle; PO, periorbita; POF, periorbital fat; OF, orbit floor; MR, medial rectus muscle; LR, lateral rectus muscle; ON, optic nerve.
partial removal of the lamina papyracea was performed, leaving the superior half intact. A portion of the medial orbital floor was then removed. This gave sufficient room for entrance into the orbit from the inferomedial angle. The incision of the periorbita was performed starting near the bony optic canal and moving anteriorly along the inferomedial aspect of the orbit. This positioning allowed for direct access to the necessary structures for dissection. Moving from posterior to anterior allowed for removal of the extruding periorbital fat before it could block the view of the surgical field. Fat that was in direct view of the surgical field was removed, whereas fat found more anteriorly and superiorly was left in place because it did not obstruct the dissection. Careful dissection of the medial and inferior rectus muscles and identification of the optic nerve are vital and provided the corridor for access to the lateral orbit. A probe can be inserted between the inferior and medial rectus muscles and inferior to the optic nerve, while these structures are carefully retracted. The probe was seen in contact with the lateral orbital wall in each dissection (Fig. 1). As previously mentioned, standard sinus surgery instrumentation was used throughout the dissections. The 0° endoscope was ideal for most of the dissection, but on entering the orbit we found the 30° endoscope necessary for dissection as structures are placed laterally to the field of view.
DISCUSSION
O D
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O N
Endoscopic transnasal approaches to the orbital apex have increased in popularity because of anatomic studies that confirmed their value.6,7 Many of these studies show that endoscopic transnasal approaches to the medial and inferior orbital apex are feasible and safe with minimal neurovascular retraction. However, these studies do not explore further access to the lateral orbital apex via an endoscopic transnasal approach. Currently, this region is accessed using open approaches such as lateral orbitotomies, which have the disadvantage of leaving a facial scar.8–10 This anatomic study determined the feasibility of an approach to the lateral orbital apex and is necessary to gain an understanding of the clinically relevant anatomy, which can be used to guide future surgical approaches. Previous literature postulates that endoscopic transnasal approaches to the lateral orbital apex are not feasible because of concern for damage to the optic nerve with irreparable loss of vision. The current study results show that in cadavers, with retraction of the medial and inferior rectus muscles combined with minimal removal of orbital fat, an access corridor is created that allows visualization of the lateral orbital wall. Negligible retraction of the cadaveric optic nerve yielded an even wider corridor to the lateral orbital apex. In patients with no vision, this traction would be acceptable. In patients with vision it is unclear if minimal traction is safe. As is seen in Fig. 1 C, using a very inferior approach allows the optic nerve to remain out of the path of dissection. Gently retracting the optic nerve supe-
O C
riorly even slightly can increase the field of vision tremendously. This could be performed with a “cotton tip applicator,” minimizing trauma to the optic nerve. In addition, this instrument can be used to dissect the fat around the optic nerve and move it out of the field of view. The position and course of the ophthalmic artery should be kept in mind when performing intraorbital dissection. As the artery emerges from the optic canal, it is positioned superolateral to the optic nerve. The artery then crosses over or under the optic nerve as it heads medially. It is estimated that the ophthalmic artery travels over the optic nerve 85% of the time.11 Thus, with an endoscopic approach from the inferomedial direction, the ophthalmic artery is protected by the optic nerve. When the ophthalmic artery courses under the optic nerve, careful dissection is necessary and there may be need to abort the approach. The branches of the ophthalmic artery may pose a challenge during endoscopic surgery. The lacrimal artery courses along the superior aspect of the lateral rectus muscle and will not be encountered during the inferomedial approach. As the ophthalmic artery turns medially and crosses over the optic nerve, it gives off posterior ciliary arteries. The inferior approach also prevents damage to these arteries, but it is important to remember that these will be inferior to the optic nerve in 15% of cases. The muscular branches of the ophthalmic artery supply the extraocular muscles and risk being damaged during intraorbital dissection. Some studies indicate that the anterior and posterior ethmoidal arteries can be damaged using an endoscopic transnasal approach.6 These arteries course in the superior aspect of the ethmoid sinuses. Complete resection of the superior ethmoids is not necessary for the inferomedial approach, thus decreasing the likelihood of injury to these arteries. The ciliary ganglion is another structure that may be encountered during intraorbital dissection of lateral orbital apex lesions. It is located around 10 mm anterior to the medial portion of the superior orbital fissure between the lateral rectus muscle and the optic nerve. It lies around 3 mm from the optic nerve and 10 mm from the lateral rectus muscle.12 From the ciliary ganglion emerge the short ciliary nerves, which run anteriorly near the optic nerve to insert into the globe. Damage to the ciliary ganglion or the short ciliary nerves can lead to a mydriatic or tonic pupil. The inferomedial approach to the lateral orbital apex will protect the ciliary ganglion from damage because it is located superiorly and laterally to the optic nerve and would not be visualized during dissection. Care must be taken when dissecting close to the optic nerve, because short ciliary nerves are difficult to find within the orbital fat. There may be some concern regarding the innervation of the extraocular muscles of the orbit. The lateral rectus, superior rectus, and superior oblique muscles will not be manipulated during the inferomedial approach. The medial rectus muscle is innervated by fibers from the inferior division of the oculomotor nerve. These travel under
American Journal of Rhinology & Allergy
Delivered by Ingenta to: Economics Dept IP: 95.181.217.250 On: Tue, 28 Jun 2016 17:47:14 Copyright (c) Oceanside Publications, Inc. All rights reserved. For permission to copy go to https://www.oceansidepubl.com/permission.htm
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the optic nerve to insert on the medial aspect of the middle third of the muscle.13 The inferior rectus muscle is also innervated by fibers from the inferior division. These course and insert on the superior surface of the inferior rectus muscle. Finally, the inferior division courses in the inferolateral direction to innervate the inferior oblique muscle. Damages to the medial rectus fibers are most likely avoided using an inferomedial approach to the lateral apex. However, it is possible that damage to the inferior rectus and inferior oblique muscle innervation may occur if dissection is not performed carefully. Finally, it is also important to note that direct damage to the muscles during retraction can cause postoperative eye movement disturbances. One may use transseptal sutures placed around the medial rectus muscle to medialize it and ensure its protection.14 Of note, retraction of these muscles and dissection of these areas is routinely safely performed in ophthalmic surgery. The amount of bone and fat that is resected with an inferomedial approach is minimal and approximates what would be necessary during medial orbitotomy and approach of medial orbital apex lesions. We found that total ethmoidectomy is not necessary. The superior half of the lamina papyracea, as well as most of the periorbital fat, are conserved. The inferomedial approach allows less fat to be removed while still preserving a good field of view. Therefore, the volume of the orbit can be maintained. However, it should still be noted that the risk of enophthalmos will inherently be greater when using this approach. The most important determinant for feasibility and safety lies in the exact position and extent of the lesion. The MRI image in Fig. 2 depicts a lateral orbital apex lesion in the left orbit. Such a lesion can be safely reached with an inferomedial corridor approach because of its lateral and slightly inferior location. However, lesions that are placed more superiorly may not be candidates for the approach described in this study, because injury to the optic nerve or ophthalmic artery is likely. The inferomedial approach should therefore be limited to lesions that are located in the lateral orbital apex with
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Figure 2. A magnetic resonance imaging (MRI) picture depicting an orbital apex lesion is shown that could be approached using the inferomedial corridor. The star in the image marks the location of the lesion in the left orbit. The optic nerve can be seen medial to the lesion.
inferior extension. Preoperative planning using imaging studies and intraoperative image guidance are crucial for patient safety in these approaches. Total resection of a lesion using this approach could only feasibly be performed if imaging shows that the lesion is small and if no superior extension is present. If superior extension is present, a biopsy or partial resection could be performed as long as inferior extension is present. Intraoperative image guidance will allow the surgeon to have concrete information as to the necessary approach to be used during the procedure, as well as give the surgeon the option to abort if it is deemed to be unsafe. Although this study highlights an approach that could be used in reaching lesions of the lateral orbital apex, there are still some limitations to consider. Cadavaric studies approximate the surgical environment but can not entirely predict what the results will show in a live patient. Therefore, the next step would be to safely attempt the inferomedial approach in a patient with a lesion in the lateral/inferior orbital apex. Individual surgeon judgment will help guide what can safely be attempted. The ideal patient would be one in whom the optic nerve of the affected eye is already irreparably damaged. Another limitation in this study is that it is hard to gauge the degree of manipulation of the optic nerve necessary for total access to a lateral orbital apex lesion and whether that manipulation will lead to any adverse effects (as seen in Fig. 1 B). Future studies could be performed to determine whether a particular location and size of a lateral apex lesion visualized on preoperative imaging correlates with easier access to the lateral orbital apex.
CONCLUSION Endoscopic transnasal approaches to the lateral orbital apex have not previously been attempted. In this anatomic study, we determined that an inferomedial approach could be used in accessing lesions of the lateral orbital apex. However, the positions of various structures including the optic nerve, ophthalmic artery, and ciliary
January–February 2014, Vol. 28, No. 1
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ganglion pose a safety concern, because injury to these structures can lead to complications. In patients with irreparably damaged vision in the affected eye, the inferomedial approach may be considered if the extent and location of the lateral orbital apex lesion is favorable. Perioperative imaging and surgeon judgment may help in identifying such lesions. Additional studies will be needed to assess safety of this approach in those patients with intact vision.
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Erratum
In the article The potential role of hyaluronic acid in postoperative radiofrequency surgery for chronic inferior turbinate hypertrophy Am J Rhinol Allergy 27:234 –236, 2013; doi: 10.2500/ajra.2013.27.3869, the author line was incorrect. It should appear as Manuele Casale, M.D.,1 Giacomo Ciglia, M.D.,1 Valeria Frari, M.D.,1 Antonino Incammisa, M.D.,1 Francesco Mazzola, M.S.,1 Peter Baptista, M.D.,2 Ranko Mladina, M.D.,3 and Fabrizio Salvinelli, M.D.1
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The authors regret the error.
doi: 10.2500/ajra.2014.28.3102
American Journal of Rhinology & Allergy
Delivered by Ingenta to: Economics Dept IP: 95.181.217.250 On: Tue, 28 Jun 2016 17:47:14 Copyright (c) Oceanside Publications, Inc. All rights reserved. For permission to copy go to https://www.oceansidepubl.com/permission.htm
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