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|Year : 2015 | Volume
| Issue : 5 | Page : 723-726
Reshaping the zygomatic complex: A “small step” in frontotemporal craniotomy and a “big leap” in exposure
Shashwat Mishra1, Arun K Srivastava2, Hitesh Kumar1, Bhawani S Sharma1
1 Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi, India
2 Department of Neurosurgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
|Date of Web Publication||6-Oct-2015|
Dr. Shashwat Mishra
Room No: 1, Sixth Floor, Neurosciences Centre, All India Institute of Medical Sciences, New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
Context: Pterional or fronto-temporal craniotomy, developed by Prof. M. G. Yasargil, is among the most familiar skull base surgery techniques. The cranio-orbito zygomatic (COZ) approach evolved to address the significant limitations of the pterional exposure in excising some parasellar lesions. Although extremely versatile, the COZ technique involves extensive dissection of the cranio-facial soft tissue and reconstruction towards the end of the procedure. The zygomatic reshaping is a minor modification of the pterional approach, which enhances the exposure possible through the classical approach and often circumvents the need for an orbito-zygomatic osteotomy.
Aims: To demonstrate the technique of reshaping of the zygomatic complex for an optimum surgical exposure and cosmetic results.
Materials and Methods: Between April 2013 and December 2014, 8 patients with various middle and anterior skull base lesions were operated using this technique. These patients form the clinical material for this study. The clinical details, radiological images and follow-up data of these patients were collected for this clinical series.
Results: No mortality or significant morbidity were noted in this series. The post-operative cosmetic results were also acceptable.
Conclusions: A quick and easy modification of the classical pterional approach through zygomatic reshaping has the potential to provide a significantly enhanced surgical exposure for parasellar lesions. Using this approach, it might be possible to avoid an extensive orbito-zygomatic osteotomy in suitable lesions.
Keywords: Modification; pterional; reshaping; zygomatic arch
|How to cite this article:|
Mishra S, Srivastava AK, Kumar H, Sharma BS. Reshaping the zygomatic complex: A “small step” in frontotemporal craniotomy and a “big leap” in exposure. Neurol India 2015;63:723-6
|How to cite this URL:|
Mishra S, Srivastava AK, Kumar H, Sharma BS. Reshaping the zygomatic complex: A “small step” in frontotemporal craniotomy and a “big leap” in exposure. Neurol India [serial online] 2015 [cited 2020 Feb 23];63:723-6. Available from: http://www.neurologyindia.com/text.asp?2015/63/5/723/166540
| » Introduction|| |
The sub-discipline of skull base surgery owes its origin to the tenacity of neurosurgeons devoted to preventing undue retraction on the brain surface. Ever since Prof. Yasargil developed the pterional craniotomy, which is probably the first and most popular technique of skull base surgery, innovative neurosurgeons have attempted to enlarge the fronto-temporal exposure through additional osteotomies. The most popular of these augmentative procedures is the orbitozygomatic osteotomy, introduced by Zabramski et al. Although immensely versatile in its application for parasellar pathologies, the formal cranio-orbitozygomatic exposure significantly increases operative time and needs elaborate and meticulous reconstruction during closure. The simpler technique of “reshaping the zygomatic complex,” which we describe in this paper, provides an excellent exposure and often avoids the need for a formal zygomatic osteotomy in situations where the latter is traditionally indicated.
After routine prepping and draping of the scalp, the fronto-temporal scalp flap is marked. The configuration of the flap may be adjusted according to the epicenter of the lesion. If the surgical plan involves exposure and drilling of the petrous apex, a significant posterior extension of the flap, skirting the pinna, is necessary. For optimum exposure following reflection of the scalp flap, it is advisable to ensure that the line joining the two ends of the scalp incision is within 1 cm of the key burr-hole point. A meticulous attempt is made to preserve the parietal branch of the superficial temporal artery. Subfascial dissection of the temporal fat pad protects the frontal branch of the facial nerve. The zygomatic complex is exposed subperiosteally in its entirety. The temporalis muscle attachment to the frontal process of the zygomatic bone is divided. The muscle attachment to the zygomatic arch is spared. Separation of the periorbita from the orbit at this stage is not required unless an orbital osteotomy is additionally planned.
The zygomatic notch is then deepened by drilling off the portion of the zygomatic complex as depicted in [Figure 1]. The deep periosteum of the zygomatic arch along with the attachment of temporalis muscle may be preserved and may theoretically allow for even reformation of the zygomatic process. This “reshaping” of the zygomatic complex, actually allows a greater inferior retraction of the temporalis muscle considerably increasing the exposure anterior and inferior to the temporal dura.
|Figure 1: (a) Cadaveric representation of the standard left pterional craniotomy; (b) zygomatic exposure and deepening of the zygomatic notch; (c) shaded portion indicates the zygomatic bone removed in this modification; (d) additional exposure of the temporal base (shaded area) following the zygomatic modification|
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The zygomatic “tubercle” [Figure 2]a, a small protuberance of the bone adjacent to the frontozygomatic suture is shaved off till it is flush with the lateral orbital wall. The temporalis muscle is then elevated subperiosteally leaving a thin fascial cuff near the superficial temporal line for reattachment during closure. A retrograde dissection technique using a sharp periosteal elevator, described by Oikawa et al., is employed to preserve the vascularity and innervation of the temporalis muscle. We conscientiously avoid using the Bovie cautery during this step. To utilize the advantage of the exposure properly, it is important that the retraction of the temporalis muscle is strong and low profile. We have found the sutures and rubber bands hooked to the Leyla bar most suitable for this purpose [Figure 2]c.
|Figure 2: Case 4) (a) Intraoperative exposure and drilling of zygomatic notch; (b) postoperative NCCT showing the extent of zygomatic notching; (c) the scheme of temporalis muscle retraction with rubber bands (representative); (d and e) pre- and postoperative contrast image showing total excision|
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The sphenoid ridge is then drilled off to eggshell thickness over the periorbita. This shell is then fractured and periorbita is separated from thinned shell of the bone. The bone is finally removed, unroofing the superior orbital fissure. The orbitotemporal periosteal dural fold is divided after coagulation of the meningo-orbital artery, which guides the surgeon easily to the anatomical dissection plane between the lamina propria and lateral wall of the cavernous sinus. The temporal dura can then be peeled off the lateral wall of the cavernous sinus exposing the clinoid process and facilitating its removal by the traditionally described techniques where needed.
The flattening of the zygomatic arch prior to retraction of the temporalis muscle provides improved access to the temporal base. The middle meningeal artery can be divided after coagulation and the dura propria overlying the posterior cavernous sinus peeled off to reveal the petrous rhomboid. Thus, an anterior petrosectomy is also possible through the same exposure without the need for a zygomatic osteotomy; the craniotomy must be appropriately situated, however, so that zygomatic root is adequately exposed.
The closure is fairly straightforward. To avoid an unsightly depression in the region of the drilled sphenoid ridge, we routinely fill the void in this region with the bone fragments and bone dust carefully collected while fashioning the craniotomy. At least our short term experience with the cosmetic outcome indicates this to be a low cost alternative to the more expensive reconstructive methods.
The described surgical technique was employed in 8 skull base lesions over a period of 14 months (April 2013 to December 2014). The surgical experience with this technique is summarized in [Table 1]. There was no surgical mortality in our series. [Table 2] describes the different variations of this approach.
|Table 2: Possible variations of the basic technique (fronto-temporal craniotomy + zygomatic reshaping)|
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| » Discussion|| |
The concept of minimizing brain handling through aggressive removal of skull base marked one of the most path-breaking advancements in cranial microsurgery. However, the pendulum has swung back from the era of extensive skull base exposures and there is a renewed emphasis on minimalism in skull base surgery. Tedious reconstructions, cerebrospinal fluid fistulae and poor cosmesis are among the frequently recognized complications of very extensive skull base exposures. The fronto-temporal approach developed and popularized by Yasargil et al., continues to be recognized as a workhorse for lesions of the anterior and middle cranial base. However, a realization of its limitations prompted several workers to develop various modifications of the standard pterional exposure. The popular technique of orbitozygomatic osteotomy evolved from the pioneering efforts of Pellerin et al., Hakuba et al., and Zabramski et al. When compared to the standard pterional craniotomy, it promised significantly improved exposure of parasellar lesions especially located at the basilar artery bifurcation, the upper clival and the suprasellar regions. However, the surgical steps for this osteotomy involve extensive soft-tissue dissection and cumbersome reconstruction following the completion of the surgical procedure. The aggressive mobilization of the temporalis muscle necessary to make the osteotomy cuts often results in its cosmetically noticeable atrophy. In addition, the interruption of the attachment of the masseter to the zygomatic arch often results in prolonged masticatory difficulties after surgery.
Even a cursory examination of the anatomical origin and insertion of the temporalis muscle suggests that the zygomatic arch and the notch limit its surgically relevant inferior mobilization. If this obstruction could be removed, an improved exposure of the middle cranial base and pretemporal region is possible. Although a complete osteotomy is most effective, in our experience, even a minor “reshaping” of the zygomatic complex is able to significantly enhance exposure in this region to the point where a formal zygomatic osteotomy could be avoided in most cases.
The temporalis muscle originates from the temporal fossa and traverses medial to the zygomatic arch toward its insertion on the coronoid process of the mandible in the infratemporal fossa. The bulk of the muscle stem is in proximity to the zygomatic notch which is the focal point for the “remodeling.”
This approach has been well described by Krisht and Kadri for the surgical clipping of basilar bifurcation aneurysms, but its wider application has been infrequently described in the contemporary literature. Our own cadaveric dissections have revealed that this strategic addition to the pterional exposure, when coupled with a dissection of the cavernous sinus and drilling of the temporal base, can easily provide access to the anterior infratemporal fossa and the terminal ramifications of the internal maxillary artery. However, these observations need to be substantiated in more specimens before generalizations can be made.
| » Conclusions|| |
Zygomatic notching, allowing improved retraction of the temporalis muscle, is a useful technique, serves as an adjunct to the regular pterional approach and permits the surgeon to expand his exposure. Though by no means a replacement of the formal cranio-orbitozygomatic exposure, it can be a useful compromise between the more aggressive osteotomies and the limitation of surgical exposure with the classical pterional craniotomy.
| » References|| |
Zabramski JM, Kiris T, Sankhla SK, Cabiol J, Spetzler RF. Orbitozygomatic craniotomy. Technical note. J Neurosurg 1998;89:336-41.
Krayenbühl N, Isolan GR, Hafez A, Yasargil MG. The relationship of the fronto-temporal branches of the facial nerve to the fascias of the temporal region: A literature review applied to practical anatomical dissection. Neurosurg Rev 2007;30:8-15.
Oikawa S, Mizuno M, Muraoka S, Kobayashi S. Retrograde dissection of the temporalis muscle preventing muscle atrophy for pterional craniotomy. Technical note. J Neurosurg 1996;84:297-9.
Froelich SC, Aziz KM, Levine NB, Theodosopoulos PV, van Loveren HR, Keller JT. Refinement of the extradural anterior clinoidectomy: Surgical anatomy of the orbitotemporal periosteal fold. Neurosurgery 2007;61 5 Suppl 2:179-85.
Dolenc VV, Pregelj R, Kocijancic I. Evolution from the classical pterional to the contemporary approach to the central skull base. In: Rogers L, Dolenc VV, editors. Cavernous Sinus Developments and Future Perspectives. New York [etc.]: Springer-Wien; 2009. p. 61-74.
Choudhry OJ, Christiano LD, Arnaout O, Adel JG, Liu JK. Reconstruction of pterional defects after frontotemporal and orbitozygomatic craniotomy using Medpor Titan implant: Cosmetic results in 98 patients. Clin Neurol Neurosurg 2013;115:1716-20.
Pellerin P, Lesoin F, Dhellemmes P, Donazzan M, Jomin M. Usefulness of the orbitofrontomalar approach associated with bone reconstruction for frontotemporosphenoid meningiomas. Neurosurgery 1984;15:715-8.
Hakuba A, Tanaka K, Suzuki T, Nishimura S. A combined orbitozygomatic infratemporal epidural and subdural approach for lesions involving the entire cavernous sinus. J Neurosurg 1989;71:699-704.
Krisht AF, Kadri PA. Surgical clipping of complex basilar apex aneurysms: A strategy for successful outcome using the pretemporal transzygomatic transcavernous approach. Neurosurgery 2005;56 2 Suppl: 261-73.
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]
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