SCALP and Temporal Fascia in the Cranio-Orbito-Zygomatic Approach: Highlighting the Interfascial Dissection Plane

SCALP and Temporal Fascia in the Cranio-Orbito-Zygomatic Approach: Highlighting the Interfascial Dissection Plane | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article SCALP and Temporal Fascia in the Cranio-Orbito-Zygomatic Approach: Highlighting the Interfascial Dissection Plane Tufan Agah Kartum, Ayberk Karaman, Levent Aydın, Eren Soğuk, Revna Çetiner, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9396173/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract BACKGROUND : Cranio-orbito-zygomatic approach (COZA) requires adequate SCALP, fascia and muscle retraction to access the zygomatic arch, malar eminence (ME) and inferior orbital fissure (IOF), which endanger the facial nerve branches. Performing skull base reconstruction also demands a layer-by-layer understanding of the SCALP and fasciae. We aimed to examine the relationship between the SCALP layers, temporal fascia and facial nerve branches from a surgical viewpoint and highlight the optimal dissection plane during the COZA. METHOD : The SCALP and temporalis fascia layers were examined using COZA on 10 formalin-fixed cadavers (20 sides). Stepwise dissections analyzed the relationships between SCALP layers, temporoparietal fascia, deep temporal fascia (DTF) and facial nerve branches. In addition, facial dissections were conducted to examine the relationships between the facial nerve branches and the associated fasciae. RESULTS : The temporoparietal fascia was continuous with the galea superomedial to superior temporal line. Facial nerve branches coursed between the galea and the DTF. The DTF divided into superficial and deep layers; superficial layer continuous with the pericranium and extending anteriorly toward periorbita. Following the superficial layer of the DTF inferiorly ensured natural surgical interfascial dissection plane for facilitate to exposure of the ME. Deep layer of the DTF further divided into medial and lateral laminae with an interfascial fat pad between them. The lateral and medial laminae attached to the lateral and medial surfaces of the zygomatic arch, respectively, and merged at the superior margin. CONCLUSIONS : Recognizing the interfascial plane between the superficial and deep layers of the DTF and the deep interfascial fat pad, may improve surgical orientation and facilitate tissue retraction during exposure of the lateral orbital wall and ME in the COZA. deep temporal fascia facial nerve orbitozygomatic craniotomy SCALP temporoparietal fascia zygomatic arch Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. INTRODUCTION Fundamental surgical skills encompass a comprehensive knowledge of microsurgical anatomy and the ability to safely expose the targeted area by accurately identifying the correct plane of dissection.[6, 31] Concept of the ‘tissue plane’ emphasizes the importance of ‘creating’ a plane of dissection by entering the correct anatomical plane, allowing safe exposure of the surgical field while preserving functional nerves.[6, 7, 31] This principle becomes particularly critical in cranio-orbito-zygomatic approach (COZA), especially during elevation of the SCALP layers and temporalis fascia. COZA requires adequate SCALP and temporalis muscle retraction to access the zygomatic arch, malar eminence (ME) and inferior orbital fissure (IOF) prior to osteotomies, which endanger facial nerve branches.[2, 3, 12, 13, 18, 22, 27, 29, 34] Frontotemporal skin incisions pose unique difficulties due to complex anatomical relationships between the SCALP layers, temporalis fascia and relevant neurovascular structures. In addition, skull base reconstruction using galeal and pericranial flaps requires a precise understanding of continuity between these fascial layers.[24] Preservation of vascular supply and neural integrity is essential to prevent SCALP ischemia and temporalis muscle atrophy.[21] Interfascial and subfascial dissection techniques have been described to preserve facial nerve during pterional and orbitozygomatic craniotomies.[8, 32] Although these techniques are well established and widely practiced, variations in terminology and inconsistent descriptions of temporal fascial layering may create uncertainty during operative dissection. A clearer stepwise understanding of relationships between the SCALP layers, temporoparietal fascia (TPF), deep temporal fascia (DTF) and facial nerve branches—particularly at level of the superior temporal line (STL) and zygomatic arch—may facilitate a more reproducible surgical strategy. In this study, we examined the relationships between the SCALP layers, temporal fasciae and facial nerve branches from a surgical perspective. We aimed to provide a detailed microsurgical analysis of these layers during COZA to highlight the optimal fascia–muscle dissection plane that may assist safe exposure of the ME and lateral orbital wall while maintaining facial nerve integrity. 2. MATERIAL AND METHODS Ten formalin-fixed, silicone-injected cadaveric heads (20 sides) were examined to reveal relationships between layers of SCALP and temporalis muscle fasciae and neurovascular structures by performing COZA. In each specimen, frontotemporal skin incisions were made and a stepwise dissection was performed to expose SCALP layers, TPF, DTF, interfascial fat pad and their relationships to facial nerve branches, zygomatic arch, ME and STL. Facial dissections were also performed to examine the facial nerve branches. Dissections were performed under a Zeiss Surgical Microscope (Carl Zeiss AG, Oberkochen, Germany) at x 6 to x 40 magnification. Three-dimensional images of each step of dissection were obtained. 3. RESULTS Stepwise Frontotemporal Skin Incision based on the SCALP Layer Dissections: After frontotemporoparietal skin incision with head in 30-45 degrees rotation to contralateral side, the skin layer (S layer) was dissected from the connective tissue (C layer) just below it (Fig. 1a, 2a and 3a) . The branches of the superficial temporal artery (STA) were identified in C layer (Fig. 1a, 2a, 3a - b, and 4a - b) . Next, the C layer was elevated and the galea (A layer, aponeurosis) was revealed underneath the connective tissue (Fig. 1b, 2b, 3b and 4b) Lateral and inferior of the STL, galea was continuous with the TPF or the superficial temporal fascia (Fig. 1b - c, 2b, 3b and 4b) (Table 1) . STA was located in the TPF at the level of the tragus and its branches subsequently became superficial towards the connective tissue as they move medially (Fig. 1c, 2b - c, 3b and 4b) . As loose areolar tissue (L layer) formed a good dissection plane between the galea and pericranium, galea layer and loose areolar tissue were dissected together. TPF was then elevated anteroinferiorly from the underlying DTF, which was divided into two layers—superficial and deep—with the superficial layer continuous with the pericranium and extending anteriorly to form the periorbita (Fig. 1d, 2b, 3c - d and 4c) . The subgaleal (suprafacial) fat pad was identified between the TPF and DTF and the fronto-temporal branches of the facial nerve were encountered at this subgaleal level (Fig. 1e - f - g, 2c - d - e, 4c - d) (Table 2) . Noticeably, loose areolar tissue and subgaleal fat pad were at the same level (Fig. 1f, 2c - d - e, 4c - d) (Table 1) . At the level of the STL, the DTF was observed to split into superficial and deep layers (Fig. 1h - i - j - k - l, 2f, 3c - d - e - f, 4e - f) . Our dissections demonstrated that the pericranium (P layer, periosteum), located beneath the galea, continues as the superficial layer of DTF lateral and inferior to the STL (Fig. 1b and d, 2b, 3c and 4c) (Table 1) . The superficial layer of the DTF extended inferiorly over the zygomatic arch and ME without firm adhesion and maintained continuity with the periorbita anteriorly. This anatomical arrangement created a favorable surgical dissection plane that facilitated safe tissue separation and preservation of the facial nerve branches, clearly aiding osteotomies during COZA (Fig. 3e – f, 4g - h – i – j) . The deep layer of DTF was further composed of two laminae – lateral and medial –with an interfascial fat pad situated between them (Fig. 3g – h – i – j) (Tables 1 and 2) . The lateral and medial laminae attached to the lateral and medial surfaces of the zygomatic arch, respectively, and merged at the superior margin. Lateral lamina of the deep layer of the DTF adhered to lateral surface of the zygomatic arch and medial lamina adhered to the medial surface of the zygomatic arch. These two laminae typically merged at the superior edge of the zygomatic arch (Fig. 3g – h – i – j, 4k – l) . The reflection of interfascial fat pad was also visible on the surface of the deep layer of the DTF (Fig. 1k, 3f, 4f – g – h - i) . An important anatomical observation in our dissections was the presence of anastomotic branches of the facial nerve traversing the interfascial fat pad between the lateral and medial laminae (Fig. 1L). The final step of dissection involved removing deep layers of the DTF, which uncovered the subfascial fat pad lying between the temporalis muscle and the fascia (Fig. 1m – n, 3j, 4k - l) (Table 2) . After dissecting the temporalis muscle from the STL, the temporal pericranium was revealed between the muscle and calvarium (Fig. 1o – p, 2g - h) . Table 1. Continuity of the layers in the superior (medial) and inferior (lateral) to STL and the structures they contain Layer superior (medial) to STL Continuing Layer Inferior (lateral) to STL The Structures It Contains Galea Temporoparietal fascia (superficial temporal fascia) STA Loose areolar tissue Subgaleal fat pad (suprafacial fat pad) Temporal branches of the facial nerve Pericranium Deep temporal fascia (temporal fascia): It consists of two layers Superficial layer of deep temporal fascia: It continues with the periorbita Deep layer of deep temporal fascia : It consist of two layers and the interfascial fat pad is located between these two: Lateral lamina: Attaches to the lateral surface of the zygomatic arch Medial lamina: Attaches to the medial surface of the zygomatic arch Sensory anastomotic branches between the facial nerve and the trigeminal nerve Interfascial fat pad (STA: superficial temporal artery, STL: superior temporal line) Table 2. Localization of the three different fat pads and the structures they contain Fat Pad Localization The Structures It Contains Subgaleal (Suprafacial) Between temporoparietal fascia and superficial layer of the deep temporal fascia Temporal branches of the facial nerve Interfascial (Superficial) Between lateral and medial laminas of the deep layer of deep temporal fascia Sensory anastomotic branches between the facial nerve and the trigeminal nerve Subfascial (Deep) Between deep lamina of the deep layer of deep temporal fascia and temporalis muscle Small anastomotic branches between the STA and the maxillary artery (STA: superficial temporal artery) SCALP Dissection in relation to the Facial Nerve: Following a preauricular incision extending to neck, skin and subcutaneous fat tissue were removed, exposing the galea, the TPF and superficial musculoaponeurotic system (SMAS). TPF and SMAS were at the same level (Fig. 5a – b) . Frontotemporal branches of the facial nerve traversed superficial to the zygomatic arch. Facial nerve branches coursed anterior and deep to the STA at the level of the zygomatic arch and coursed within the subgaleal fad pad above the arch to ascend anteriorly towards the orbicularis oculi and frontalis muscles (Fig. 5c – d – e – f, 6a – b- c) . Anastomotic sensory branches were revealed deep to the subgaleal fat pad (Fig. 6d) . The anterior and posterior deep temporal arteries and deep temporal nerves supply and innervate the temporalis muscle, respectively (Fig. 5g - h) . Preservation of Facial Nerve Branches: Interfascial and Subfascial Dissections: Interfascial Dissection : After frontotemporal skin incision, skin, C layer, galea and the TPF were dissected at the level of loose areolar tissue. The TPF and galea were dissected together and harvested as a vascularized pedicled TPF-galeal flap (Fig. 1a - j) . The pericranium was dissected over the calvarium separataly to obtain pericranial flap (Fig. 1i - m) . After an incision was made in the superficial layer of the DTF, this layer was elevated along with the subgaleal fat pad, preserving the facial nerve branches. When the superficial layer of the DTF was separated from its deep layer and followed inferiorly, zygomatic arch and the ME were reached. (Fig. 3d - e – f, 4f – g – h - i) . Subfascial Dissection : Frontotemporoparietal skin incision was performed to elevate skin and the C layer and galea and the TPF were then dissected together, revealing pericranium and the DTF (Fig. 3a – b – c –d) . The DTF and pericranium, can be elevated together and harvested for skull base reconstruction (Fig. 3a – b – c –d, 4f) . During the subfascial dissection technique, all layers of the DTF were incised down to the level of the temporalis muscle to preserve the facial nerve branches. An additional incision in the deep layer of the DTF was required to expose the zygomatic arch ( Fig. 4k – l ). 4. DISCUSSION Temporal pericranium, located on the calvarial surface of temporalis muscle, is a continuation of frontoparietal pericranium.[16, 17] Accordingly, frontoparietal pericranium can be considered continuous with three distinct layers inferolateral to the STL: the superficial and deep layers of the DTF and temporal pericranium (Fig. 1o –p, 2g - h) . Comparison of Dissection Techniques for Preservation of Facial Nerve Branches: Whether the TPF is truly continuous with the SMAS remains a matter of debate; nonetheless, the TPF follows the same anatomical plane as the SMAS above the zygomatic arch (Fig.5 and 6) .[1, 5, 14, 17, 19, 25] Frontotemporal branches of the facial nerve traverse the subgaleal fat pad and positioned deep in the TPF above the zygomatic arch; whereas below the arch, the nerve branches lie deep in the SMAS (Fig. 5 and 6) .[23] Injury to these branches may result in frontalis dysfunction..[8, 25, 32] Three distinct dissection techniques have been suggested for preserving the facial nerve branches during pterional craniotomy and COZA: submuscular method, interfascial technique and subfascial method[8, 32] Although the submuscular technique minimizes the risk of facial nerve injury, it is less optimal for COZA due to limited exposure of the zygomatic arch, the lateral orbital wall and ME up to the level of zygomaticofacial foramen.[8, 32] Consequently, interfascial and subfascial techniques are more commonly employed when adequate retraction are required.[8, 32] This study demonstrates that the DTF splits into superficial and deep layers at the level of the STL. Our dissections underscore the critical role of the superficial layer of DTF in preserving facial nerve branches during COZA, highlighting several key anatomical factors. The superficial layer of DTF extends inferiorly over the zygomatic arch without firm adhesion and maintains anterior continuity with the periorbita. Following the superficial layer of the DTF inferiorly allows consistent utilization of the natural dissection plane between the superficial and deep layers. This plane facilitates exposure of the ME and lateral orbital wall up to the level of zygomaticofacial foramen, as well as the IOF, and assists both lower and orbital osteotomies during COZA.[7, 27, 28] In addition, because frontoparietal pericranium is continuous with the superficial layer of the DTF, this layer may also serve as a vascularized pericranial flap when needed. These findings suggest that interfascial dissection, by following the superficial layer of the DTF inferiorly, utilizes a natural dissection plane that keeps the ME superficial to the plane of separation while preserving the facial nerve branches. Because the deep layer of the DTF adheres to the borders of the zygomatic arch, it must be dissected to achieve complete exposure of the arch in both interfascial and subfascial approaches. Although the facial nerve branches course more superficially within the subgaleal fat pad, anastomotic connections to the DTF require careful dissection along the lateral margin of the zygoma. (Fig. 4k – l) . In our dissections, the deep layer of DTF was further seperated into two laminae – lateral and medial –with an interfascial fat pad situated between them (Fig. 3g – h – i – j) . These two laminae typically merge at the superior edge of the zygomatic arch and reflection of the interfascial fat pad can be observed consistently. Anastomotic branches of the facial nerve were identified traversing this fat pad between these two laminae. Interfascial fat pad can also be helpful in maintaining the correct dissection plane. Unlike the subfascial dissection method, the interfascial dissection technique involves an additional incision into the deep layers of the DTF under direct vision, which minimizes the risk of injury to facial nerve branches. This is because the superficial layer of the DTF is separated from the deep layer at the level of the zygoma (Fig. 3 and 4) . Núñez et al . supported the reliability of the interfascial dissection technique by demonstrating that intraoperative stimulation of the trigeminofacial anastomotic branch – located between the layers of the DTF – elicited no motor response from the facial nerve, and that sacrificing this branch did not affect frontalis muscle function.[20] The subfascial dissection method inevitably requires an incision on the superior edge of the zygomatic arch – not only in the DTF, where the medial and lateral laminae merge – but also through the adherent, unseparated superficial layer of the DTF. This maneuver involves dissection through the adherent superficial layer of the DTF and may place the subgaleal and interfascial branches at potential risk. At the level of the zygomatic arch, facial nerve branches lie anterior to the STA (Fig. 5e – f - g) . Accordingly, fascia incisions made posterior to the STA at this level are unlikely to cause injury to the facial nerve.[15, 28] Campero et al . described “facial-zygomatic triangle”, as a landmark to preserve both the facial nerve and STA during dissection around the zygomatic arch.[4] Poblete et al . reported that facial nerve branches course within the subaponeurotic plane (loose areolar tissue) and recommended 'subpericranial–interfascial' or 'subpericranial–subfascial' dissection technique to reduce nerve injury . [7, 23] They also noted that galeal incisions within 4 cm of the lateral orbital rim may endanger the frontotemporal branches.[23] STL represents a key anatomical junction where the galea, pericranium, fasciae and muscle converge in the frontotemporal region. To separate the superficial and deep layers of the DTF, a DTF incision can be made inferolateral to the STL so that the interfascial surgical plane is effectively identified. Medial to STL, the pericranium and the superficial layer of DTF should be dissected as a single layer. Vascularized flaps and interfascial dissection Vascularized temporoparietal fascia flaps and pericranial flaps are commonly used for reconstruction and dural repair.[11, 30, 33] Elevating these layers, along with the layers that continue throughout the STL, allows for the creation of a larger flap. During this step, preservation of the arterial supply and the facial nerve branches that course between the layers is essential. Loose areolar tissue provides a good dissection plane for obtaining a pericranial flap.[1, 9, 10, 23, 26, 30] Pericranium could be elevated along with the continuation of the DTF to obtain a larger vascularized pericranial flap. To preserve the facial nerve branches in the subgaleal plane, an interfascial dissection of the DTF should be performed. Special emphasis should be placed on the superficial layer of the DTF, as elevating this layer together with the overlying skin, connective tissue, and galea–TPF is crucial for maintaining anatomical integrity and protecting subgaleal facial nerve branches.[32] TPF flaps are supplied by STA and dissection plane between connective tissue and galea is not always clearly defined. Excessive separation of C layer from S layer during flap elevation may compromise SCALP vascularity and increase the risk of necrosis. During TPF flap elevation, facial nerve located within subgaleal plane may also be at risk. Interfascial dissection along the superficial layer of discussthe DTF at the level of the subgaleal fat pad can help preserve these branches during TPF flap harvesting. Limitations Use of formalin-fixed specimens may alter tissue properties and ease of fascial separation compared with live surgical conditions. This study was descriptive in nature; no quantitative morphometric measurements were performed. No clinical series were included to correlate these anatomical findings with surgical outcomes. However, the step-by-step anatomical observations presented here can help guide the dissection process during COZA. 5. CONCLUSION The superficial layer of DTF extends inferiorly over the zygomatic arch and ME without firm adhesion and maintains anterior continuity with the periorbita. The plane between the superficial and deep layers of the DTF provides a practical interfascial dissection corridor that allows tissue separation while preserving the frontotemporal branches of the facial nerve during COZA. Recognition of this anatomical relationship may facilitate exposure of ME, lateral orbital wall and IOF and assist orbital osteotomies. Awareness of the interfascial fat pad between the deep layers of the DTF and their attachments along the zygoma may prove helpful during surgery. Abbreviations DTF: deep temporal fascia COZA: cranio-orbito-zygomatic approach IOF: inferior orbital fissure ME: malar eminence STA: superficial temporal artery STL: superior temporal line TPF: temporoparietal fascia Declarations Conflict of interest: The authors declare that they have no conflict of interest. Acknowledgments: The authors sincerely thank those who donated their bodies to science so that anatomical research could be performed. Conflict-of-interest disclosure: The authors declare no competing financial interests and no sources of funding and support, including any for equipment and medications. Funding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. AUTHOR CONTRIBUTIONS Conception and design : Tanriover, Kartum. Acquisition of data : Kartum, Karaman, Aydın, Soğuk, Çetiner, Karaçoban. Analysis and interpretation of data : Tanriover, Kartum, Karaçoban. Drafting the article : Kartum, Aydın. Critically revising the article : Tanriover, Kartum. Reviewed the submitted version of manuscript : Tanriover, Kartum. Approved the final version of the manuscript on behalf of all authors : Tanriover. Administrative/technical/material support: Tanriover, Kartum. Study supervision : Tanriover. References Abul-Hassan HS, von Drasek Ascher G, Acland RD (1986) Surgical anatomy and blood supply of the fascial layers of the temporal region. Plast Reconstr Surg 77(1):17–28 Al-Mefty O (1987) Supraorbital-pterional approach to skull base lesions. Neurosurgery 21(4):474–477 al-Mefty O, Anand VK (1990) Zygomatic approach to skull-base lesions. J Neurosurg 73(5):668–673 Campero A, Socolovsky M, Martins C, Yasuda A, Torino R, Rhoton AL (2008) Facial-zygomatic triangle: a relationship between the extracranial portion of facial nerve and the zygomatic arch. 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Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 11 May, 2026 Reviews received at journal 11 May, 2026 Reviews received at journal 24 Apr, 2026 Reviewers agreed at journal 17 Apr, 2026 Reviewers agreed at journal 15 Apr, 2026 Reviewers invited by journal 15 Apr, 2026 Editor assigned by journal 13 Apr, 2026 Submission checks completed at journal 13 Apr, 2026 First submitted to journal 12 Apr, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9396173","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":626632095,"identity":"2730151f-cbc4-446e-963f-688f011634e1","order_by":0,"name":"Tufan Agah Kartum","email":"","orcid":"","institution":"Istanbul University Cerrahpaşa","correspondingAuthor":false,"prefix":"","firstName":"Tufan","middleName":"Agah","lastName":"Kartum","suffix":""},{"id":626632096,"identity":"76f49fe2-66f3-44a0-9719-25918c961cf3","order_by":1,"name":"Ayberk Karaman","email":"","orcid":"","institution":"Istanbul University Cerrahpaşa","correspondingAuthor":false,"prefix":"","firstName":"Ayberk","middleName":"","lastName":"Karaman","suffix":""},{"id":626632098,"identity":"babf00c8-1862-4369-92b7-27449a798b7e","order_by":2,"name":"Levent Aydın","email":"","orcid":"","institution":"Istanbul University Cerrahpaşa","correspondingAuthor":false,"prefix":"","firstName":"Levent","middleName":"","lastName":"Aydın","suffix":""},{"id":626632099,"identity":"faf17e4f-9f93-4272-ad6c-74d3c39acdb0","order_by":3,"name":"Eren Soğuk","email":"","orcid":"","institution":"Istanbul University Cerrahpaşa","correspondingAuthor":false,"prefix":"","firstName":"Eren","middleName":"","lastName":"Soğuk","suffix":""},{"id":626632100,"identity":"6888e847-d812-43c7-b0e1-8f14badd0bbc","order_by":4,"name":"Revna Çetiner","email":"","orcid":"","institution":"Istanbul University Cerrahpaşa","correspondingAuthor":false,"prefix":"","firstName":"Revna","middleName":"","lastName":"Çetiner","suffix":""},{"id":626632101,"identity":"03d34ca2-29e6-4fef-8908-51cd8d2528af","order_by":5,"name":"Tuba Özge Karaçoban","email":"","orcid":"","institution":"Istanbul University Cerrahpaşa","correspondingAuthor":false,"prefix":"","firstName":"Tuba","middleName":"Özge","lastName":"Karaçoban","suffix":""},{"id":626632102,"identity":"f558e11d-ca7a-4d8f-ab5c-35d2a2bb85c0","order_by":6,"name":"Kardelen Akıncı","email":"","orcid":"","institution":"Istanbul University Cerrahpaşa","correspondingAuthor":false,"prefix":"","firstName":"Kardelen","middleName":"","lastName":"Akıncı","suffix":""},{"id":626632103,"identity":"371b96fe-a99f-4cfe-bb0e-0a9bbf75626d","order_by":7,"name":"Necmettin Tanriover","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAv0lEQVRIiWNgGAWjYNCCiv9yDAw8RCtnBuIzzMYkamFsY05sIFqLOfv5g58L2NjSNxw/e/DBBwY7Od0GAlose5KZpWfw8ORuOJOXbDiDIdnY7AABLQY3mBmkeSQkcjccyDGT5mE4kLiNCC3Mv3kMDNINzr8hXgubNE9CQoLBDaJtOZNsZs1z4IDhzBtvjA1nGBDjl+MHH9/m/XdAnu98juGDDxV2cgS1wIECWKUBscpBQL6BFNWjYBSMglEwogAAKkA+k+nTqv4AAAAASUVORK5CYII=","orcid":"","institution":"Istanbul University Cerrahpaşa","correspondingAuthor":true,"prefix":"","firstName":"Necmettin","middleName":"","lastName":"Tanriover","suffix":""}],"badges":[],"createdAt":"2026-04-12 18:18:44","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9396173/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9396173/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":107650737,"identity":"1e1f7303-be74-44ff-b1a4-6b5ec9e44435","added_by":"auto","created_at":"2026-04-23 15:02:15","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1388729,"visible":true,"origin":"","legend":"\u003cp\u003eLayer by layer SCALP dissection following frontoparietotemporal skin incision. \u003cstrong\u003e\u0026nbsp;a.\u003c/strong\u003eAfter a right-sided frontoparietotemporal skin incision with the head rotated 45 degrees to the contralateral side, the “S” layer was removed and the connective tissue and galea layer were exposed. The distal thin branches of the STA are located within the connective tissue. \u003cem\u003e(The inset shows the skin incision\u003c/em\u003e.\u003cem\u003e)\u003c/em\u003e \u003cstrong\u003eb.\u003c/strong\u003e The galea and temporoparietal fascia have been dissected together to expose the pericranium located deep to them. \u003cstrong\u003ec.\u003c/strong\u003e After removing the connective tissue, the galea and temporoparietal fascia have been exposed. The galea continues as the temporoparietal fascia inferior and lateral to the superior temporal line (STL). The main trunk of the STA and the proximal frontal and parietal branches are located within the temporoparietal fascia. \u003cstrong\u003ed.\u003c/strong\u003e By retracting the galea and temporoparietal fascia together anteriorly, the pericranium and deep temporal fascia have been revealed in a deeper layer. The pericranium continues as the deep temporal fascia inferor and lateral to the STL. The galea continues as the temporoparietal fascia inferior and lateral to the STL. \u003cem\u003e(Black dashed lines indicate STL.)\u003c/em\u003e \u003cstrong\u003ee.\u003c/strong\u003e Deep to the galea, the loose areolar tissue layer between the galea and the pericranium provides a good dissection plane between the galea and the pericranium. The galea and temporoparietal fascia have been retracted more anteriorly over the pericranium and deep temporal fascia, to disclose the subgaleal fat pad situated between the temporoparietal fascia and the deep temporal fascia. \u003cstrong\u003ef - g.\u003c/strong\u003e The subgaleal fat pad has been displayed between the temporoparietal fascia and the deep temporal fascia within the loose areolar tissue. The frontotemporal branches of the facial nerve are located within the subgaleal fat pad. \u003cstrong\u003eh – ı – j.\u003c/strong\u003e The deep temporal fascia – continuous with the pericranium – has been separated into two layers, superficial and deep, at the level of the STL. The temporalis muscle is located deep to the deep layer of the deep temporal fascia and attaches to the STL. The subgaleal fat pad is located between the temporoparietal fascia and the superficial layer of the deep temporal fascia. \u003cstrong\u003ek.\u003c/strong\u003e By retracting the superficial layer of the deep temporal fascia anteriorly, the reflexion of the interfascial fat pad located within the deep layer of deep temporal fascia was revealed. \u003cstrong\u003el. \u003c/strong\u003eThe anastomotic nerves lie within the interfascial fat pad deep to the superficial layer of deep temporal fascia. \u003cstrong\u003em.\u003c/strong\u003e Temporalis muscle has been exposed following the retraction of deep layer of the deep temporal fascia. \u003cstrong\u003en.\u003c/strong\u003eThe subfascial fat pad is located between the deep layer of the deep temporal fascia and the temporalis muscle. \u003cstrong\u003eo- p.\u003c/strong\u003eThe temporal pericranium has been exposed deep to the temporalis muscle. \u003cem\u003e(Br: branch, Fasc: fascia, Front: frontal, Musc: muscle, Par: parietal, Subfasc: Subfascial, STA: superficial temporal artery, STL: superior temporal line, Temp: temporal)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9396173/v1/bd32de82e884d061ed16438a.png"},{"id":107706583,"identity":"91f35c09-b76d-43e8-82eb-11e0ea2603cb","added_by":"auto","created_at":"2026-04-24 09:18:25","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1343457,"visible":true,"origin":"","legend":"\u003cp\u003eLayer by layer SCALP dissection after left-sided frontoparietotemporal skin incision. a. The S layer of SCALP was dissected and elevated, and the C layer was revealed. Branches originating from STA and occipital artery – the main arteries responsible for SCALP nutrition – and dense anastomoses between them are located the C layer. The galea layer is located deep in the C layer. \u003cem\u003e(The inset shows the skin incision line.)\u003c/em\u003e b. The C layer has been completely removed and the galea layer has been partially elevated to show the continuity of the galea layer and temporoparietal fascia lateral and inferior to the STL. STA runs into the galea and temporoparietal fascia. The loose areolar tissue is medial to the STL and situated deep in the galea. The subgaleal fat pad between the temporoparietal fascia and the temporal fascia has been exposed. c. Enlarged view. STA traverses along the temporoparietal fascia. d - e. Dissection of the temporoparietal fascia has been proceeded more anteriorly. The temporal branches of facial nerve are located within the subgaleal fat pad. Temporal branches of the facial nerve lie anterior and deep to the STA. f. The deep temporal fascia, which is the continuation of the pericranium medial to the STL, is separated into two layers: the superficial layer (superficial layer of the deep temporal fascia) and the deep layer (deep layer of the deep temporal fascia). g - h. The temporal pericranium is located deep to the temporalis muscle and lies over the calvarium. \u003cem\u003e(Fasc: fascia, FN: facial nerve, Front. Br: frontal branch, Loose Ar. T: loose areolar tissue, Musc: muscle, Par. Br: parietal branch, Pericr: pericranium, STA: superficial temporal artery, STL: superior temporal line, Temp: temporal)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9396173/v1/e40535b0c7c1356185877c34.png"},{"id":107650739,"identity":"9ebee5f1-8284-4331-8d19-b8b70692ca8a","added_by":"auto","created_at":"2026-04-23 15:02:15","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":845681,"visible":true,"origin":"","legend":"\u003cp\u003eAnatomical relationships between the deep temporal fascia layers, the zygomatic arch and interfascial fat pad. \u003cstrong\u003ea.\u003c/strong\u003e After a left-sided frontotemporoparietal skin incision, the skin has been elevated and the connective tissue has been exposed. \u003cem\u003e(The inset shows the skin incision.)\u003c/em\u003e \u003cstrong\u003eb.\u003c/strong\u003e Upon removal of the connective tissue, the temporoparietal fascia and its continuity – the galea – have been exposed. The main branches of the STA lie within the temporoparietal fascia. \u003cstrong\u003ec.\u003c/strong\u003e Following elevation of the temporofascial fascia and galea, the pericranium and the deep temporal fascia have been displayed. The deep temporal fascia is continuous with the pericranium superomedial to the superior temporal line. \u003cstrong\u003ed.\u003c/strong\u003e The temporofascial fascia has been elevated to expose the deep temporal fascia, which is separated into two layers—superficial and deep—with the superficial layer continuous with the pericranium and extending anteriorly to form the periorbita. \u003cstrong\u003ee - f.\u003c/strong\u003e The superficial layer of the deep temporal fascia has been dissected from its deep layer, exposing the zygomatic arch, malar eminence and lateral orbital rim. The deep layer of the deep temporal fascia attaches to these structures. The reflection of the interfascial fat pad is visible on the surface of the deep layer of the deep temporal fascia. The superficial layer of the deep temporal fascia extended inferiorly over the zygomatic arch and malar eminence without firm adhesion, which may clearly aid orbital osteotomies during cranio-orbito-zygomatic approach (COZA). \u003cstrong\u003eg – h – i.\u003c/strong\u003e The deep layer of the deep temporal fascia consisted of two laminae, lateral and medial. The lateral lamina adhered to the lateral surface of the zygomatic arch, and the medial lamina adhered to its medial surface. The medial lamina coursed over the temporalis muscle. The interfascial fat pad lie between the lateral and medial laminae at the level of the zygomatic arch. \u003cstrong\u003ej.\u003c/strong\u003e The lateral and medial laminae of the deep layer of the deep temporal fascia merged on the superior surface of the zygomatic arch. \u003cem\u003e(DTF: deep temporal fascia, Emin: eminence, Fasc: fascia,\u003c/em\u003e \u003cem\u003eFront. Br: frontal branch, Lat: lateral, Musc: muscle, Orb: orbital, Par. Br: parietal branch, Subfasc: subfascial, Temp: temporal, Zyg: zygomatic)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-9396173/v1/bf17b6262111142895647c2e.png"},{"id":107706009,"identity":"5c522444-ceb8-4ff7-b036-b3c1bf5c0680","added_by":"auto","created_at":"2026-04-24 09:17:08","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":946832,"visible":true,"origin":"","legend":"\u003cp\u003eAnatomical relationships between zygomatic arch and deep temporal fascia\u003cstrong\u003e a. \u003c/strong\u003eWith the head rotated to the contralateral side, a right-sided frontotemporal skin incision has been performed to expose the connective tissue and the distal branches of STA within it. \u003cem\u003e(The inset shows the skin incision\u003c/em\u003e.\u003cem\u003e)\u003c/em\u003e \u003cstrong\u003e\u0026nbsp;b. \u003c/strong\u003eAfter the removal of the connective tissue, the galea and its inferolateral continuation – the temporoparietal fascia – have been exposed. The proximal STA courses within the temporoparietal fascia and becomes superficial toward the connective tissue distally.\u003cstrong\u003e c. \u003c/strong\u003eBy removing the galea and temporoparietal fascia, the pericranium and the superficial layer of the deep temporal fascia have been exposed. The subgaleal fat pad is located between the temporoparietal fascia and the superficial layer of the deep temporal fascia.\u003cstrong\u003e d. \u003c/strong\u003eThe frontotemporal branches of the facial nerve are located within the subgaleal fat pad. \u003cstrong\u003ee – f – g - h.\u003c/strong\u003e The superficial layer of the deep temporal fascia together with the frontoparietal pericranium have been elevated to expose the deep layer of the deep temporal fascia. The reflection of the interfascial fat pad located in between the laminae of the deep layer of the deep temporal fascia can be appreciated. \u003cstrong\u003ei.\u003c/strong\u003e The superficial layer of the deep temporal fascia continued downward without adhering to the zygomatic arch and this layer was dissected from the deep layer of deep temporal fascia. \u003cstrong\u003ej.\u003c/strong\u003e After retracting the superficial layer of the deep temporal fascia downward, the deep layer was found to adhere to the lateral surfaces of the zygomatic arch, malar eminence, and lateral orbital rim. The superficial layer of the deep temporal fascia extended inferiorly over the zygomatic arch without firm adhesion and maintained continuity with the periorbita anteriorly, which may facilitate orbital osteotomies during cranio-orbito-zygomatic approach (COZA). \u003cstrong\u003ek.\u003c/strong\u003e Removal of the deep layer of the deep temporal fascia exposed the temporalis muscle and the subfascial fat pad situated between them. The deep layer adhered to the lateral and medial borders of the zygomatic arch and merged along its superior border. \u003cstrong\u003el.\u003c/strong\u003e The yellow dashed line indicates the location of the zygomatic arch. The subfascial fat pad is located deep to the zygomatic arch. Deep layer adhered to the lateral and medial borders of the zygomatic arch and merged along its superior border. \u003cem\u003e(Emin: eminence, Fasc: fascia, FN: facial nerve, Interfasc: interfascial, Pericr: pericranium, Subfasc: subfascial, Subgl: subgaleal, STA: superficial temporal artery, Temp: temporal)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-9396173/v1/e5cdab2e4802b8709e19add5.png"},{"id":107707494,"identity":"f26aec93-674c-4cf1-8c53-d80e76abca22","added_by":"auto","created_at":"2026-04-24 09:20:27","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1714197,"visible":true,"origin":"","legend":"\u003cp\u003eRight side superficial to deep facial dissection showing the relationship between the layers of the face, facial nerve branches, temporoparietal fascia and temporalis muscle. \u003cstrong\u003ea.\u003c/strong\u003e The inset demarcates the skin incision. The facial region is composed of four distinct layers: the skin, subcutaneous fatty tissue, the superficial musculoaponeurotic system (SMAS) and the parotid–masseteric fascia. Following removal of the skin and subcutaneous fat tissue, the galea has been exposed above the zygomatic arch. The frontalis muscle and the superficial temporal artery (STA) are located within the galea. Inferior to the STL, the temporoparietal fascia continuous with the galea. The SMAS has been revealed after removal of skin and subcutaneous tissue inferior to the zygomatic arch. The SMAS and the temporoparietal fascia lie at the same anatomical level. \u003cstrong\u003eb.\u003c/strong\u003e The SMAS is continuous with the superficial fascia of the parotid gland and the platysma in the neck. The SMAS and temporoparietal fascia are positioned at the same level. The frontalis muscle is located within the galea, whereas the orbicularis oculi and zygomaticus major muscles are situated within the superficial musculoaponeurotic system SMAS. \u003cstrong\u003ec.\u003c/strong\u003e After removing the SMAS along with the continuous superficial fascia of the parotid gland, the masseter muscle and the superficial layer of the parotid gland were exposed. After emerging from the stylomastoid foramen, the branches of the facial nerve course between the superficial and deep lobes of the parotid gland. The frontotemporal branches of the facial nerve course within the subgaleal fat pad and innervate the orbicularis oculi, frontalis and corrugator supercilii muscles. \u003cstrong\u003ed - e. \u003c/strong\u003eThe SMAS and the superficial layer of the parotid gland have been removed, exposing the masseter muscle, the deep layer of the parotid gland, and the facial nerve branches located laterally.After exiting the stylomastoid foramen, the facial nerve runs in between the superficial and deep layers of the parotid gland and divides into distinct branches: temporal, zygomatic, buccal, marginal mandibular, cervical. \u003cstrong\u003ef.\u003c/strong\u003e The SMAS and parotid gland have been removed. The facial nerve branches course superficially to the zygomatic arch, and at the level of the arch, they are positioned anteriorly and deep relative to the STA. While the STA is situated within the temporoparietal fascia, the facial nerve branches reside within the subgaleal fat pad. \u003cstrong\u003eg.\u003c/strong\u003e The mandible, zygomatic arch, malar eminence, and temporalis muscle have been exposed after removal of the SMAS, masseter muscle, temporoparietal fascia, deep temporal fascia, and fatty planes. The temporalis muscle extends between the coronoid process of the mandible and the STL. The frontotemporal facial nerve branches run over the zygomatic arch and lie anterior and deep to the STA at that level. \u003cstrong\u003eh.\u003c/strong\u003e The mandible and zygomatic arch have been removed, the temporalis muscle retracted superolaterally to expose the infratemporal fossa. The anterior and posterior deep temporal arteries, originating from the maxillary artery in the infratemporal fossa, supply the temporalis muscle from its medial side. The deep temporal nerves, originating from the anterior division of the mandibular nerve, innervate the temporalis muscle. \u003cem\u003e(A: artery, Ant: anterior, Br: branch, Buc: buccal, Cerv: cervical, Fasc: fascia, FN: facial nerve, Front: frontal, Gl: gland, Lay: layer, Lat: lateral, M: muscle, MA: maxillary artery, Maj: major, Mand: mandibular, Marg: marginal, N: nerve, Par: parietal, Ocl: oculi, Orb: orbicularis, Pericr: pericranium, Post: posterior, Ptery: pterygoid, SMAS: superficial musculoaponeurotic system, Superfic: superficial, STA: superficial temporal artery, STL: superior temporal line, Temp: temporal, Zyg: zygomatic)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-9396173/v1/cadc9ffc076e0a3e62de7052.png"},{"id":107650741,"identity":"201fb6b3-3370-4457-930e-de50f3709b9b","added_by":"auto","created_at":"2026-04-23 15:02:16","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1677663,"visible":true,"origin":"","legend":"\u003cp\u003eSuperficial to deep facial dissection following a preauricular skin incision to display the course of the frontotemporal branches of the facial nerve. \u003cstrong\u003ea - b.\u003c/strong\u003e After the skin and connective tissue were removed, the galea and its continuation, the temporoparietal fascia, were clearly exposed. By removal of the subgaleal fat pad, the course of the zygomatic arch and frontotemporal branches of the facial nerve have been revealed. The frontotemporal branches of the facial nerve pass towards the frontalis muscle and orbicularis oculi muscles. The frontalis and orbicularis oculi muscles were identified at the level of the galea. The STA course along the temporoparietal fascia. At the level of the zygomatic arch, the facial nerve branches are located anterior to the STA. The auriculotemporal nerve lies posterior to the frontotemporal branches of facial nerve. \u003cstrong\u003ec. \u003c/strong\u003eThe frontotemporal branches of the facial nerve course towards the orbicularis oculi and frontalis muscles. \u003cstrong\u003ed.\u003c/strong\u003eAfter the orbicularis oculi muscle was elevated along with the superficial layer of DTF, the anastomotic nerves are located at the level of deep layer of DTF have been exposed. \u003cem\u003e(Aurtemp: auriculotemporal, DTF: deep temporal fascia, Fasc: fascia, Fr: frontal, FN: temporal branch of facial nerve, M: muscle, N: nerve, Orb: orbicularis, Par: parietal STA: superficial temporal artery)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-9396173/v1/ddcbc07b3130c6ffbfd7f264.png"},{"id":107709287,"identity":"47d91664-99f6-4042-8f0b-26f1d381a404","added_by":"auto","created_at":"2026-04-24 09:35:21","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":9758231,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9396173/v1/8f907218-f55e-4acd-897e-ff8b3927f128.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"SCALP and Temporal Fascia in the Cranio-Orbito-Zygomatic Approach: Highlighting the Interfascial Dissection Plane","fulltext":[{"header":"1. INTRODUCTION","content":"\u003cp\u003eFundamental surgical skills encompass a comprehensive knowledge of microsurgical anatomy and the ability to safely expose the targeted area by accurately identifying the correct plane of dissection.[6, 31] Concept of the \u0026lsquo;tissue plane\u0026rsquo; emphasizes the importance of \u0026lsquo;creating\u0026rsquo; a plane of dissection by entering the correct anatomical plane, allowing safe exposure of the surgical field while preserving functional nerves.[6, 7, 31]\u0026nbsp;This principle becomes particularly critical in cranio-orbito-zygomatic approach (COZA), especially during elevation of the SCALP layers and temporalis fascia.\u003c/p\u003e\n\u003cp\u003eCOZA requires adequate SCALP and temporalis muscle retraction to access the zygomatic arch, malar eminence (ME) and inferior orbital fissure (IOF) prior to osteotomies, which endanger facial nerve branches.[2, 3, 12, 13, 18, 22, 27, 29, 34]\u0026nbsp;Frontotemporal skin incisions pose unique difficulties due to complex anatomical relationships between the SCALP layers, temporalis fascia and relevant neurovascular structures.\u0026nbsp;In addition, skull base reconstruction using galeal and pericranial flaps requires a precise understanding of continuity between these fascial layers.[24]\u0026nbsp;Preservation of vascular supply and neural integrity is essential to prevent SCALP ischemia and temporalis muscle atrophy.[21]\u003c/p\u003e\n\u003cp\u003eInterfascial and subfascial dissection techniques have been described to preserve facial nerve during pterional and orbitozygomatic craniotomies.[8, 32] Although these techniques are well established and widely practiced, variations in terminology and inconsistent descriptions of temporal fascial layering may create uncertainty during operative dissection. A clearer stepwise understanding of relationships between the SCALP layers, temporoparietal fascia (TPF), deep temporal fascia (DTF) and facial nerve branches\u0026mdash;particularly at level of the superior temporal line (STL) and zygomatic arch\u0026mdash;may facilitate a more reproducible surgical strategy.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;In this study, we examined the relationships between the SCALP layers, temporal fasciae and facial nerve branches from a surgical perspective. We aimed to provide a detailed microsurgical analysis of these layers during COZA to highlight the optimal fascia\u0026ndash;muscle dissection plane that may assist safe exposure of the ME and lateral orbital wall while maintaining facial nerve integrity.\u003c/p\u003e"},{"header":"2.\tMATERIAL AND METHODS","content":"\u003cp\u003eTen formalin-fixed, silicone-injected cadaveric heads (20 sides) were examined to reveal relationships between layers of SCALP and temporalis muscle fasciae and neurovascular structures by performing COZA. In each specimen, frontotemporal skin incisions were made and a stepwise dissection was performed to expose SCALP layers, TPF, DTF, interfascial fat pad and their relationships to facial nerve branches, zygomatic arch, ME and STL. Facial dissections were also performed to examine the facial nerve branches.\u003c/p\u003e\n\u003cp\u003eDissections were performed under a Zeiss Surgical Microscope (Carl Zeiss AG, Oberkochen, Germany) at x 6 to x 40 magnification. Three-dimensional images of each step of dissection were obtained.\u003c/p\u003e"},{"header":"3.\tRESULTS","content":"\u003cp\u003e\u003cstrong\u003e\u003cem\u003eStepwise Frontotemporal Skin Incision based on\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003ethe SCALP Layer Dissections:\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAfter frontotemporoparietal skin incision with head in 30-45 degrees rotation to contralateral side, the skin layer (S layer) was dissected from the connective tissue (C layer) just below it \u003cem\u003e(Fig. 1a, 2a and 3a)\u003c/em\u003e. The branches of the superficial temporal artery (STA) were identified in C layer \u003cem\u003e(Fig.\u003c/em\u003e \u003cem\u003e1a, 2a, 3a - b, and 4a - b)\u003c/em\u003e. Next, the C layer was elevated and the galea (A layer, aponeurosis) was revealed underneath the connective tissue \u003cem\u003e(Fig. 1b, 2b, 3b and 4b)\u003c/em\u003e Lateral and inferior of the STL, galea was continuous with the TPF or the superficial temporal fascia \u003cem\u003e(Fig. 1b - c, 2b, 3b and\u003c/em\u003e \u003cem\u003e4b) (Table 1)\u003c/em\u003e. STA was located in the TPF at the level of the tragus and its branches subsequently became superficial towards the connective tissue as they move medially \u003cem\u003e(Fig. 1c, 2b - c, 3b and 4b)\u003c/em\u003e. \u0026nbsp;As loose areolar tissue (L layer) formed a good dissection plane between the galea and pericranium, galea layer and loose areolar tissue were dissected together.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTPF was then elevated anteroinferiorly from the underlying DTF, which was divided into two layers\u0026mdash;superficial and deep\u0026mdash;with the superficial layer continuous with the pericranium and extending anteriorly to form the periorbita \u003cem\u003e(Fig. 1d, 2b, 3c - d and 4c)\u003c/em\u003e. The subgaleal (suprafacial) fat pad was identified between the TPF and DTF and the fronto-temporal branches of the facial nerve were encountered at this subgaleal level \u003cem\u003e(Fig. 1e - f - g, 2c - d - e, 4c - d) (Table 2)\u003c/em\u003e. Noticeably, loose areolar tissue and subgaleal fat pad were at the same level \u003cem\u003e(Fig. 1f, 2c - d - e, 4c - d) (Table 1)\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003eAt the level of the STL, the DTF was observed to split into superficial and deep layers \u003cem\u003e(Fig. 1h - i - j - k - l, 2f, 3c - d - e - f, 4e - f)\u003c/em\u003e. Our dissections demonstrated that the pericranium (P layer, periosteum), located beneath the galea, continues as the superficial layer of DTF lateral and inferior to the STL \u003cem\u003e(Fig. 1b and d, 2b, 3c and 4c)\u003c/em\u003e \u003cem\u003e(Table 1)\u003c/em\u003e. The superficial layer of the DTF extended inferiorly over the zygomatic arch and ME without firm adhesion and maintained continuity with the periorbita anteriorly. This anatomical arrangement created a favorable surgical dissection plane that facilitated safe tissue separation and preservation of the facial nerve branches, clearly aiding osteotomies during COZA \u003cem\u003e(Fig. 3e \u0026ndash; f, 4g - h \u0026ndash; i \u0026ndash; j)\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003eThe deep layer of DTF was further composed of two laminae \u0026ndash; lateral and medial \u0026ndash;with an interfascial fat pad situated between them \u003cem\u003e(Fig. 3g \u0026ndash; h \u0026ndash; i \u0026ndash; j) (Tables 1 and 2)\u003c/em\u003e. The lateral and medial laminae attached to the lateral and medial surfaces of the zygomatic arch, respectively, and merged at the superior margin. Lateral lamina of the deep layer of the DTF adhered to lateral surface of the zygomatic arch and medial lamina adhered to the medial surface of the zygomatic arch. These two laminae typically merged at the superior edge of the zygomatic arch \u003cem\u003e(Fig. 3g \u0026ndash; h \u0026ndash; i \u0026ndash; j, 4k \u0026ndash; l)\u003c/em\u003e. The reflection of interfascial fat pad was also visible on the surface of the deep layer of the DTF \u003cem\u003e(Fig. 1k, 3f, 4f \u0026ndash; g \u0026ndash; h - i)\u003c/em\u003e. An important anatomical observation in our dissections was the presence of anastomotic branches of the facial nerve traversing the interfascial fat pad between the lateral and medial laminae (Fig. 1L).\u003c/p\u003e\n\u003cp\u003eThe final step of dissection involved removing deep layers of the DTF, which uncovered the subfascial fat pad lying between the temporalis muscle and the fascia \u003cem\u003e(Fig. 1m \u0026ndash; n, 3j, 4k - l) (Table 2)\u003c/em\u003e. After dissecting the temporalis muscle from the STL, the temporal pericranium was revealed between the muscle and calvarium \u003cem\u003e(Fig. 1o \u0026ndash; p, 2g - h)\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eTable 1.\u003c/em\u003e\u003c/strong\u003e Continuity of the layers in the superior (medial) and inferior (lateral) to STL and the structures they contain\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"642\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 31.3084%;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eLayer superior (medial) to STL\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 40.6542%;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eContinuing Layer Inferior (lateral) to STL\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.0374%;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eThe Structures It Contains\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 31.3084%;\"\u003e\n \u003cp\u003eGalea\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 40.6542%;\"\u003e\n \u003cp\u003eTemporoparietal fascia (superficial temporal fascia)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.0374%;\"\u003e\n \u003cp\u003eSTA\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 31.3084%;\"\u003e\n \u003cp\u003eLoose areolar tissue\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 40.6542%;\"\u003e\n \u003cp\u003eSubgaleal fat pad (suprafacial fat pad)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.0374%;\"\u003e\n \u003cp\u003eTemporal branches of the facial nerve\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 31.3084%;\"\u003e\n \u003cp\u003ePericranium\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 40.6542%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eDeep temporal fascia (temporal fascia):\u003c/strong\u003e It consists of two layers\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eSuperficial layer of deep temporal fascia:\u0026nbsp;\u003c/em\u003e\u003c/strong\u003eIt continues with the periorbita\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eDeep layer of deep temporal fascia\u003c/em\u003e:\u003c/strong\u003e It consist of two layers and the interfascial fat pad is located between these two:\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e\u003cu\u003eLateral lamina:\u003c/u\u003e\u003c/em\u003e\u003c/strong\u003e Attaches to the lateral surface of the zygomatic arch\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e\u003cu\u003eMedial lamina:\u003c/u\u003e\u003c/em\u003e\u003c/strong\u003e Attaches to the medial surface of the zygomatic arch\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28.0374%;\"\u003e\n \u003cp\u003eSensory anastomotic branches between the facial nerve and the trigeminal nerve\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eInterfascial fat pad\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cem\u003e(STA: superficial temporal artery, STL: superior temporal line)\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eTable 2.\u003c/em\u003e\u003c/strong\u003e Localization of the three different fat pads and the structures they contain\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 33.3333%;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eFat Pad\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 33.3333%;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eLocalization\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 33.3333%;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eThe Structures It Contains\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 33.3333%;\"\u003e\n \u003cp\u003eSubgaleal (Suprafacial)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 33.3333%;\"\u003e\n \u003cp\u003eBetween temporoparietal fascia and superficial layer of the deep temporal fascia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 33.3333%;\"\u003e\n \u003cp\u003eTemporal branches of the facial nerve\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 33.3333%;\"\u003e\n \u003cp\u003eInterfascial (Superficial)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 33.3333%;\"\u003e\n \u003cp\u003eBetween lateral and medial laminas of the deep layer of deep temporal fascia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 33.3333%;\"\u003e\n \u003cp\u003eSensory anastomotic branches between the facial nerve and the trigeminal nerve\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 33.3333%;\"\u003e\n \u003cp\u003eSubfascial (Deep)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 33.3333%;\"\u003e\n \u003cp\u003eBetween deep lamina of the deep layer of deep temporal fascia and temporalis muscle\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 33.3333%;\"\u003e\n \u003cp\u003eSmall anastomotic branches between the STA and the maxillary artery\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cem\u003e(STA: superficial temporal artery)\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eSCALP Dissection in relation to the Facial Nerve:\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFollowing a preauricular incision extending to neck, skin and subcutaneous fat tissue were removed, exposing the galea, the TPF and superficial musculoaponeurotic system (SMAS). TPF and SMAS were at the same level \u003cem\u003e(Fig. 5a \u0026ndash; b)\u003c/em\u003e. Frontotemporal branches of the facial nerve traversed superficial to the zygomatic arch. Facial nerve branches coursed anterior and deep to the STA at the level of the zygomatic arch and coursed within the subgaleal fad pad above the arch to ascend anteriorly towards the orbicularis oculi and frontalis muscles \u003cem\u003e(Fig. 5c \u0026ndash; d \u0026ndash; e \u0026ndash; f, 6a \u0026ndash; b- c)\u003c/em\u003e. Anastomotic sensory branches were revealed deep to the subgaleal fat pad \u003cem\u003e(Fig. 6d)\u003c/em\u003e. The anterior and posterior deep temporal arteries and deep temporal nerves supply and innervate the temporalis muscle, respectively \u003cem\u003e(Fig. 5g - h)\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003ePreservation of Facial Nerve Branches: Interfascial and Subfascial Dissections:\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eInterfascial Dissection\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e:\u0026nbsp;\u003c/strong\u003eAfter frontotemporal skin incision, skin, C layer, galea and the TPF were dissected at the level of loose areolar tissue. The TPF and galea were dissected together and harvested as a vascularized pedicled TPF-galeal flap \u003cem\u003e(Fig. 1a - j)\u003c/em\u003e. The pericranium was dissected over the calvarium separataly to obtain pericranial flap \u003cem\u003e(Fig. 1i - m)\u003c/em\u003e. After an incision was made in the superficial layer of the DTF, this layer was elevated along with the subgaleal fat pad, preserving the facial nerve branches. When the superficial layer of the DTF was separated from its deep layer and followed inferiorly, zygomatic arch and the ME were reached. \u003cem\u003e(Fig. 3d - e \u0026ndash; f, 4f \u0026ndash; g \u0026ndash; h - i)\u003c/em\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eSubfascial Dissection\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e:\u0026nbsp;\u003c/strong\u003eFrontotemporoparietal skin incision was performed to elevate skin and the C layer\u003cem\u003e\u0026nbsp;\u003c/em\u003eand galea and the TPF were then dissected together, revealing pericranium and the DTF \u003cem\u003e(Fig. 3a \u0026ndash; b \u0026ndash; c \u0026ndash;d)\u003c/em\u003e. The DTF and pericranium, can be elevated together and harvested for skull base reconstruction \u003cem\u003e(Fig. 3a \u0026ndash; b \u0026ndash; c \u0026ndash;d, 4f)\u003c/em\u003e. \u0026nbsp;During the subfascial dissection technique, all layers of the DTF were incised down to the level of the temporalis muscle to preserve the facial nerve branches. An additional incision in the deep layer of the DTF was required to expose the zygomatic arch (\u003cem\u003eFig. 4k \u0026ndash; l\u003c/em\u003e).\u003c/p\u003e"},{"header":"4.\tDISCUSSION","content":"\u003cp\u003eTemporal pericranium, located on the calvarial surface of temporalis muscle, is a continuation of frontoparietal pericranium.[16, 17] Accordingly, frontoparietal pericranium can be considered continuous with three distinct layers inferolateral to the STL: the superficial and deep layers of the DTF and temporal pericranium \u003cem\u003e(Fig. 1o \u0026ndash;p, 2g - h)\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eComparison of Dissection Techniques for Preservation of Facial Nerve Branches:\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWhether the TPF is truly continuous with the SMAS remains a matter of debate; nonetheless, the TPF follows the same anatomical plane as the SMAS above the zygomatic arch\u0026nbsp;\u003cem\u003e(Fig.5 and 6)\u003c/em\u003e.[1, 5, 14, 17, 19, 25] Frontotemporal branches of the facial nerve traverse the subgaleal fat pad and positioned deep in the TPF above the zygomatic arch; whereas below the arch, the nerve branches lie\u0026nbsp;deep in the SMAS \u003cem\u003e(Fig. 5 and 6)\u003c/em\u003e.[23]\u0026nbsp;Injury to these branches may result in frontalis dysfunction..[8, 25, 32]\u003c/p\u003e\n\u003cp\u003eThree distinct dissection techniques have been suggested for preserving the facial nerve branches during pterional craniotomy and COZA: submuscular method, interfascial technique and subfascial method[8, 32] Although the submuscular technique minimizes the risk of facial nerve injury, it is less optimal for COZA due to limited exposure of the zygomatic arch, the lateral orbital wall and ME up to the level of zygomaticofacial foramen.[8, 32]\u0026nbsp;Consequently, interfascial and subfascial techniques are more commonly employed when adequate retraction are required.[8, 32]\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis study demonstrates that the DTF splits into superficial and deep layers at the level of the STL. Our dissections underscore the critical role of the superficial layer of DTF in preserving facial nerve branches during COZA, highlighting several key anatomical factors. The superficial layer of DTF extends inferiorly over the zygomatic arch without firm adhesion and maintains anterior continuity with the periorbita. Following the superficial layer of the DTF inferiorly allows consistent utilization of the natural dissection plane between the superficial and deep layers. This plane facilitates exposure of the ME and lateral orbital wall up to the level of zygomaticofacial foramen, as well as the IOF, and assists both lower and orbital osteotomies during COZA.[7, 27, 28] In addition, because frontoparietal pericranium is continuous with the superficial layer of the DTF, this layer may also serve as a vascularized pericranial flap when needed. These findings suggest that interfascial dissection, by following the superficial layer of the DTF inferiorly, utilizes a natural dissection plane that keeps the ME superficial to the plane of separation while preserving the facial nerve branches.\u003c/p\u003e\n\u003cp\u003eBecause the deep layer of the DTF adheres to the borders of the zygomatic arch, it must be dissected to achieve complete exposure of the arch in both interfascial and subfascial approaches. Although the facial nerve branches course more superficially within the subgaleal fat pad, anastomotic connections to the DTF require careful dissection along the lateral margin of the zygoma.\u003cem\u003e\u0026nbsp;(Fig. 4k \u0026ndash; l)\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003eIn our dissections, the deep layer of DTF was further seperated into two laminae \u0026ndash; lateral and medial \u0026ndash;with an interfascial fat pad situated between them\u0026nbsp;\u003cem\u003e(Fig. 3g \u0026ndash; h \u0026ndash; i \u0026ndash; j)\u003c/em\u003e. These two laminae typically merge at the superior edge of the zygomatic arch and reflection of the interfascial fat pad can be observed consistently. Anastomotic branches of the facial nerve were identified traversing this fat pad between these two laminae. Interfascial fat pad can also be helpful in maintaining the correct dissection plane. Unlike the subfascial dissection method, the interfascial dissection technique involves an additional incision into the deep layers of the DTF under direct vision, which minimizes the risk of injury to facial nerve branches. This is because the superficial layer of the DTF is separated from the deep layer at the level of the zygoma\u0026nbsp;\u003cem\u003e(Fig. 3 and 4)\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003eN\u0026uacute;\u0026ntilde;ez \u003cem\u003eet al\u003c/em\u003e. supported the reliability of the interfascial dissection technique by demonstrating that intraoperative stimulation of the trigeminofacial anastomotic branch \u0026ndash; located between the layers of the DTF \u0026ndash; elicited no motor response from the facial nerve, and that sacrificing this branch did not affect frontalis muscle function.[20]\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe subfascial dissection method inevitably requires an incision on the superior edge of the zygomatic arch \u0026ndash; not only in the DTF, where the medial and lateral laminae merge \u0026ndash; but also through the adherent, unseparated superficial layer of the DTF.\u0026nbsp;This maneuver involves dissection through the adherent superficial layer of the DTF and may place the subgaleal and interfascial branches at potential risk.\u003c/p\u003e\n\u003cp\u003eAt the level of the zygomatic arch, facial nerve branches lie anterior to the STA \u003cem\u003e(Fig. 5e \u0026ndash; f - g)\u003c/em\u003e. Accordingly, fascia incisions made posterior to the STA at this level are unlikely to cause injury to the facial nerve.[15, 28] Campero \u003cem\u003eet al\u003c/em\u003e. described \u0026ldquo;facial-zygomatic triangle\u0026rdquo;, as a landmark to preserve both the facial nerve and STA during dissection around the zygomatic arch.[4] Poblete \u003cem\u003eet al\u003c/em\u003e. reported that facial nerve branches course within the subaponeurotic plane (loose areolar tissue) and recommended \u0026apos;subpericranial\u0026ndash;interfascial\u0026apos; or \u0026apos;subpericranial\u0026ndash;subfascial\u0026apos; dissection technique to reduce nerve injury\u003csup\u003e.\u003c/sup\u003e[7, 23]\u0026nbsp;They also noted that galeal incisions within 4 cm of the lateral orbital rim may endanger the frontotemporal branches.[23]\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSTL represents a key anatomical junction where the galea, pericranium, fasciae and muscle converge in the frontotemporal region.\u0026nbsp;To separate the superficial and deep layers of the DTF, a DTF incision can be made inferolateral to the STL so that the interfascial surgical plane is effectively identified. Medial to STL, the pericranium and the superficial layer of DTF should be dissected as a single layer.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eVascularized flaps and interfascial dissection\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eVascularized temporoparietal fascia flaps and pericranial flaps are commonly used for reconstruction and dural repair.[11, 30, 33] Elevating these layers, along with the layers that continue throughout the STL, allows for the creation of a larger flap.\u0026nbsp;During this step, preservation of the arterial supply and the facial nerve branches that course between the layers is essential.\u0026nbsp;Loose areolar tissue provides a good dissection plane for obtaining a pericranial flap.[1, 9, 10, 23, 26, 30] Pericranium could be elevated along with the continuation of the DTF to obtain a larger vascularized pericranial flap. To preserve the facial nerve branches in the subgaleal plane, an interfascial dissection of the DTF should be performed. Special emphasis should be placed on the superficial layer of the DTF, as elevating this layer together with the overlying skin, connective tissue, and galea\u0026ndash;TPF is crucial for maintaining anatomical integrity and protecting subgaleal facial nerve branches.[32]\u003c/p\u003e\n\u003cp\u003eTPF flaps are supplied by STA and dissection plane between connective tissue and galea is not always clearly defined. Excessive separation of C layer from S layer during flap elevation may compromise SCALP vascularity and increase the risk of necrosis. During TPF flap elevation, facial nerve located within subgaleal plane may also be at risk. Interfascial dissection along the superficial layer of discussthe DTF at the level of the subgaleal fat pad can help preserve these branches during TPF flap harvesting.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eLimitations\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eUse of formalin-fixed specimens may alter tissue properties and ease of fascial separation compared with live surgical conditions. This study was descriptive in nature; no quantitative morphometric measurements were performed. No clinical series were included to correlate these anatomical findings with surgical outcomes. However, the step-by-step anatomical observations presented here can help guide the dissection process during COZA.\u003c/p\u003e"},{"header":"5. CONCLUSION","content":"\u003cp\u003eThe superficial layer of DTF extends inferiorly over the zygomatic arch and ME without firm adhesion and maintains anterior continuity with the periorbita. The plane between the superficial and deep layers of the DTF provides a practical interfascial dissection corridor that allows tissue separation while preserving the frontotemporal branches of the facial nerve during COZA. Recognition of this anatomical relationship may facilitate exposure of ME, lateral orbital wall and IOF and assist orbital osteotomies. Awareness of the interfascial fat pad between the deep layers of the DTF and their attachments along the zygoma may prove helpful during surgery.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eDTF: deep temporal fascia\u003c/p\u003e\n\u003cp\u003eCOZA: cranio-orbito-zygomatic approach\u003c/p\u003e\n\u003cp\u003eIOF: inferior orbital fissure\u003c/p\u003e\n\u003cp\u003eME: malar eminence\u003c/p\u003e\n\u003cp\u003eSTA: superficial temporal artery\u003c/p\u003e\n\u003cp\u003eSTL: superior temporal line\u003c/p\u003e\n\u003cp\u003eTPF: temporoparietal fascia\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eConflict of interest:\u0026nbsp;\u003c/strong\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eAcknowledgments:\u003c/strong\u003e The authors sincerely thank those who donated their bodies to science so that anatomical research could be performed.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict-of-interest disclosure:\u003c/strong\u003e The authors declare no competing financial interests and no sources of funding and support, including any for equipment and medications.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u0026nbsp;\u003c/strong\u003eThis research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAUTHOR CONTRIBUTIONS\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eConception and design\u003c/em\u003e: Tanriover, Kartum. \u003cem\u003eAcquisition of data\u003c/em\u003e: Kartum, Karaman, Aydın, Soğuk, \u0026Ccedil;etiner, Kara\u0026ccedil;oban. \u003cem\u003eAnalysis and interpretation of data\u003c/em\u003e: Tanriover, Kartum, Kara\u0026ccedil;oban. \u003cem\u003eDrafting the article\u003c/em\u003e: Kartum, Aydın. \u003cem\u003eCritically revising the article\u003c/em\u003e: Tanriover, Kartum. \u003cem\u003eReviewed the submitted version of manuscript\u003c/em\u003e: Tanriover, Kartum. \u003cem\u003eApproved the final version of the manuscript on behalf of all authors\u003c/em\u003e: Tanriover. Administrative/technical/material support: Tanriover, Kartum. \u003cem\u003eStudy supervision\u003c/em\u003e: Tanriover.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAbul-Hassan HS, von Drasek Ascher G, Acland RD (1986) Surgical anatomy and blood supply of the fascial layers of the temporal region. Plast Reconstr Surg 77(1):17\u0026ndash;28\u003c/li\u003e\n\u003cli\u003eAl-Mefty O (1987) Supraorbital-pterional approach to skull base lesions. Neurosurgery 21(4):474\u0026ndash;477\u003c/li\u003e\n\u003cli\u003eal-Mefty O, Anand VK (1990) Zygomatic approach to skull-base lesions. J Neurosurg 73(5):668\u0026ndash;673\u003c/li\u003e\n\u003cli\u003eCampero A, Socolovsky M, Martins C, Yasuda A, Torino R, Rhoton AL (2008) Facial-zygomatic triangle: a relationship between the extracranial portion of facial nerve and the zygomatic arch. Acta Neurochir (Wien) 150(3):273\u0026ndash;8; discussion 278\u003c/li\u003e\n\u003cli\u003eCampiglio GL, Candiani P (1997) Anatomical study on the temporal fascial layers and their relationships with the facial nerve. Aesthetic Plast Surg 21(2):69\u0026ndash;74\u003c/li\u003e\n\u003cli\u003eCarlson GW (1993) Surgical anatomy of the neck. Surg Clin North Am 73(4):837\u0026ndash;852\u003c/li\u003e\n\u003cli\u003eCornish P (2021) The Tissue Plane. Top Reg Anesth. doi: 10.5772/intechopen.99533\u003c/li\u003e\n\u003cli\u003eCoscarella E, Vishteh AG, Spetzler RF, Seoane E, Zabramski JM (2000) Subfascial and submuscular methods of temporal muscle dissection and their relationship to the frontal branch of the facial nerve. Technical note. J Neurosurg 92(5):877\u0026ndash;880\u003c/li\u003e\n\u003cli\u003eDavidge KM, van Furth WR, Agur A, Cusimano M (2010) Naming the soft tissue layers of the temporoparietal region: unifying anatomic terminology across surgical disciplines. Neurosurgery 67(3 Suppl Operative):ons120-9; discussion ons129-30\u003c/li\u003e\n\u003cli\u003eDonath A, Sindwani R (2006) Frontal sinus cranialization using the pericranial flap: an added layer of protection. Laryngoscope 116(9):1585\u0026ndash;1588\u003c/li\u003e\n\u003cli\u003eFerrari M, Vural A, Schreiber A, et al (2019) Side-Door Temporoparietal Fascia Flap: A Novel Strategy for Anterior Skull Base Reconstruction. World Neurosurg 126:e360\u0026ndash;e370\u003c/li\u003e\n\u003cli\u003eFigueiredo EG, Deshmukh P, Nakaji P, Shu EBS, Crawford N, Spetzler RF, Preul MC (2012) An anatomical analysis of the mini-modified orbitozygomatic and supra-orbital approaches. J Clin Neurosci Off J Neurosurg Soc Australas 19(11):1545\u0026ndash;1550\u003c/li\u003e\n\u003cli\u003eFreilinger G, Gruber H, Happak W, Pechmann U (1987) Surgical anatomy of the mimic muscle system and the facial nerve: importance for reconstructive and aesthetic surgery. Plast Reconstr Surg 80(5):686\u0026ndash;690\u003c/li\u003e\n\u003cli\u003eGhassemi A, Prescher A, Riediger D, Axer H (2003) Anatomy of the SMAS revisited. Aesthetic Plast Surg 27(4):258\u0026ndash;264\u003c/li\u003e\n\u003cli\u003eKawashima M, Rhoton ALJ, Tanriover N, Ulm AJ, Yasuda A, Fujii K (2005) Microsurgical anatomy of cerebral revascularization. Part I: anterior circulation. J Neurosurg 102(1):116\u0026ndash;131\u003c/li\u003e\n\u003cli\u003eKirolles S, Haikal FA, Saadeh FA, Abul-Hassan H, el-Bakaury AR (1992) Fascial layers of the scalp. A study of 48 cadaveric dissections. Surg Radiol Anat 14(4):331\u0026ndash;333\u003c/li\u003e\n\u003cli\u003eKrayenb\u0026uuml;hl N, Isolan GR, Hafez A, Yaşargil MG (2007) 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 30(1):8\u0026ndash;15; discussion 15\u003c/li\u003e\n\u003cli\u003eLemole GMJ, Henn JS, Zabramski JM, Spetzler RF (2003) Modifications to the orbitozygomatic approach. Technical note. J Neurosurg 99(5):924\u0026ndash;930\u003c/li\u003e\n\u003cli\u003eMitz V, Peyronie M (1976) The superficial musculo-aponeurotic system (SMAS) in the parotid and cheek area. Plast Reconstr Surg 58(1):80\u0026ndash;88\u003c/li\u003e\n\u003cli\u003eNunez MA, Mohyeldin A, Marotta DA, Vigo V, Asmaro K, Xu Y, Cohen-Gadol AA, Fernandez-Miranda JC (2023) Reappraisal of the anatomy of the frontotemporal branches of the facial nerve. J Neurosurg 139(4):1160\u0026ndash;1168\u003c/li\u003e\n\u003cli\u003eOikawa S, Mizuno M, Muraoka S, Kobayashi S (1996) Retrograde dissection of the temporalis muscle preventing muscle atrophy for pterional craniotomy. Technical note. J Neurosurg 84(2):297\u0026ndash;299\u003c/li\u003e\n\u003cli\u003ePitanguy I, Ramos AS (1966) The frontal branch of the facial nerve: the importance of its variations in face lifting. Plast Reconstr Surg 38(4):352\u0026ndash;356\u003c/li\u003e\n\u003cli\u003ePoblete T, Jiang X, Komune N, Matsushima K, Rhoton ALJ (2015) Preservation of the nerves to the frontalis muscle during pterional craniotomy. J Neurosurg 122(6):1274\u0026ndash;1282\u003c/li\u003e\n\u003cli\u003eSafavi-Abbasi S, Komune N, Archer JB, et al (2016) Surgical anatomy and utility of pedicled vascularized tissue flaps for multilayered repair of skull base defects. J Neurosurg 125(2):419\u0026ndash;430\u003c/li\u003e\n\u003cli\u003eStrandring S (ed) (2016) Head and Neck. Gray\u0026rsquo;s Anat. Anat. Basis Clin. Pract., 41st ed. Elsevier, London, pp 534\u0026ndash;555\u003c/li\u003e\n\u003cli\u003eTakumi I, Akimoto M, Hironaka K, Adachi K, Kon T, Matsumori T, Tanaka Y, Morita A (2018) Pedicle Galeo-pericranial Flap Augmentation in Salvage Frontotemporal Cranioplasty: Additional \u0026ldquo;Neurosurgeon-friendly\u0026rdquo; Reconstruction Technique of Aesthetic Neurosurgery in Superficial Temporal Artery Branch Compromised Host. Neurol Med Chir (Tokyo) 58(8):350\u0026ndash;355\u003c/li\u003e\n\u003cli\u003eTanriover N, Ulm AJ, Rhoton ALJ, Kawashima M, Yoshioka N, Lewis SB (2006) One-piece versus two-piece orbitozygomatic craniotomy: quantitative and qualitative considerations. Neurosurgery 58(4 Suppl 2):ONS-229-37; discussion ONS-237\u003c/li\u003e\n\u003cli\u003eTayebi Meybodi A, Lawton MT, Yousef S, S\u0026aacute;nchez JJG, Benet A (2017) Preserving the Facial Nerve During Orbitozygomatic Craniotomy: Surgical Anatomy Assessment and Stepwise Illustration. World Neurosurg 105:359\u0026ndash;368\u003c/li\u003e\n\u003cli\u003eTellioğlu AT, Tekdemir I, Erdemli EA, T\u0026uuml;ccar E, Ulusoy G (2000) Temporoparietal fascia: an anatomic and histologic reinvestigation with new potential clinical applications. Plast Reconstr Surg 105(1):40\u0026ndash;45\u003c/li\u003e\n\u003cli\u003eVinciguerra A, Taboni S, Bettini P, et al (2025) Surgical Anatomy of the Scalp: Technical Hints for Harvesting the Temporoparietal Fascial and Pericranial Flap. Head Neck 47(9):2603\u0026ndash;2610\u003c/li\u003e\n\u003cli\u003eWhalan C (2006) Tissue planes: traction and counter-traction. Assist. Surg. Oper. A Pract. Guid. Cambridge University Press, pp 51\u0026ndash;53\u003c/li\u003e\n\u003cli\u003eYaşargil MG, Reichman M V, Kubik S (1987) Preservation of the frontotemporal branch of the facial nerve using the interfascial temporalis flap for pterional craniotomy. Technical article. J Neurosurg 67(3):463\u0026ndash;466\u003c/li\u003e\n\u003cli\u003eYoshioka N, Rhoton ALJ (2005) Vascular anatomy of the anteriorly based pericranial flap. Neurosurgery 57(1 Suppl):11\u0026ndash;16\u003c/li\u003e\n\u003cli\u003eZabramski JM, Kiriş T, Sankhla SK, Cabiol J, Spetzler RF (1998) Orbitozygomatic craniotomy. Technical note. J Neurosurg 89(2):336\u0026ndash;341\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"acta-neurochirurgica","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"anch","sideBox":"Learn more about [Acta Neurochirurgica](http://link.springer.com/journal/701)","snPcode":"701","submissionUrl":"https://submission.springernature.com/new-submission/701/3","title":"Acta Neurochirurgica","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"deep temporal fascia, facial nerve, orbitozygomatic craniotomy, SCALP, temporoparietal fascia, zygomatic arch","lastPublishedDoi":"10.21203/rs.3.rs-9396173/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9396173/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBACKGROUND\u003c/strong\u003e: Cranio-orbito-zygomatic approach (COZA) requires adequate SCALP, fascia and muscle retraction to access the zygomatic arch, malar eminence (ME) and inferior orbital fissure (IOF), which endanger the facial nerve branches. Performing skull base reconstruction also demands a layer-by-layer understanding of the SCALP and fasciae. We aimed to examine the relationship between the SCALP layers, temporal fascia and facial nerve branches from a surgical viewpoint and highlight the optimal dissection plane during the COZA.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMETHOD\u003c/strong\u003e: The SCALP and temporalis fascia layers were examined using COZA on 10 formalin-fixed cadavers (20 sides). Stepwise dissections analyzed the relationships between SCALP layers, temporoparietal fascia, deep temporal fascia (DTF) and facial nerve branches. In addition, facial dissections were conducted to examine the relationships between the facial nerve branches and the associated fasciae.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRESULTS\u003c/strong\u003e: The temporoparietal fascia was continuous with the galea superomedial to superior temporal line. Facial nerve branches coursed between the galea and the DTF. The DTF divided into superficial and deep layers; superficial layer continuous with the pericranium and extending anteriorly toward periorbita. Following the superficial layer of the DTF inferiorly ensured natural surgical interfascial dissection plane for facilitate to exposure of the ME. Deep layer of the DTF further divided into medial and lateral laminae with an interfascial fat pad between them. The lateral and medial laminae attached to the lateral and medial surfaces of the zygomatic arch, respectively, and merged at the superior margin.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCONCLUSIONS\u003c/strong\u003e: Recognizing the interfascial plane between the superficial and deep layers of the DTF and the deep interfascial fat pad, may improve surgical orientation and facilitate tissue retraction during exposure of the lateral orbital wall and ME in the COZA.\u003c/p\u003e","manuscriptTitle":"SCALP and Temporal Fascia in the Cranio-Orbito-Zygomatic Approach: Highlighting the Interfascial Dissection Plane","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-23 15:02:11","doi":"10.21203/rs.3.rs-9396173/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-05-11T08:44:33+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-11T08:08:47+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-24T11:10:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"260204934497971373352638683456690047856","date":"2026-04-17T06:43:21+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"191705756966408900439150525564122183573","date":"2026-04-15T16:14:23+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-15T11:58:54+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-13T22:46:41+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-04-13T22:45:42+00:00","index":"","fulltext":""},{"type":"submitted","content":"Acta Neurochirurgica","date":"2026-04-12T17:55:11+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"acta-neurochirurgica","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"anch","sideBox":"Learn more about [Acta Neurochirurgica](http://link.springer.com/journal/701)","snPcode":"701","submissionUrl":"https://submission.springernature.com/new-submission/701/3","title":"Acta Neurochirurgica","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"d2dde819-2323-4db2-9b25-4ff0af3031ec","owner":[],"postedDate":"April 23rd, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Revision requested","date":"2026-05-11T08:44:33+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-11T08:08:47+00:00","index":13,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-19T08:38:30+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-23 15:02:11","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9396173","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9396173","identity":"rs-9396173","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}