Salvage skull base reconstruction in the endoscopic era: Vastus lateralis free tissue transfer

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1 Received: 7 May 2017 Revised: 2 October 2017 Accepted: 10 January 2018 DOI: /hed CASE REPORT Salvage skull base reconstruction in the endoscopic era: Vastus lateralis free tissue transfer Stephen Y. Kang MD 1 Antoine Eskander MD 1 Ralph Abi Hachem MD 1 Enver Ozer MD 1 Theodoros N. Teknos MD 1 Matthew O. Old MD 1 Daniel M. Prevedello MD 2 Ricardo L. Carrau MD 1 1 Department of Otolaryngology - Head and Neck Surgery, The Ohio State University Wexner Medical Center, The James Cancer Hospital and Solove Research Institute, Columbus, Ohio 2 Department of Neurosurgery, The Ohio State Wexner Medical Center, The James Cancer Hospital and Solove Research Institute, Columbus, Ohio Correspondence Stephen Y. Kang, Starling-Loving Hall, 320 West 10th Avenue, Room B221, Columbus, OH Stephen.kang@osumc.edu Section Editor: Jonathan Irish, MD Abstract Background: When locoregional flaps fail to reconstruct the skull base, the microvascular surgeon faces several reconstructive challenges. We present our technique and results of salvage anterior skull base reconstruction utilizing the vastus lateralis free tissue transfer (VLFTT). Methods: Four patients with anterior skull base defects after previous locoregional flap failure underwent free tissue transfer reconstruction with VLFTT. Results: The success rate of free tissue transfer was 100%. Complete separation of the intracranial and sinonasal cavities was achieved in all patients; thus, resolving the cerebrospinal fluid (CSF) leakage in all patients. The VLFTT was inset through a minimally invasive approach utilizing an anterior maxillotomy via a gingivobuccal incision, an endoscopic medial maxillectomy, and endoscopic inset in all patients. No vein grafts were needed. Conclusion: This technique permits endoscopic endonasal inset and placement of reliable, well vascularized free tissue that may be utilized for complex, secondary reconstruction of the skull base. KEYWORDS endoscopic skull base, free flap, head and neck reconstruction, microvascular reconstruction, skull base reconstruction 1 INTRODUCTION Microvascular reconstruction of the anterior cranial base is well reported in the literature. 1 6 However, these published techniques describe the utilization of free tissue transfer in primary reconstruction of open (transcranial or transfacial) skull base surgery. The endoscopic era of skull base surgery continues to expand the ability to resect tumors through a minimally invasive endoscopic approach. As the techniques for expanded endonasal approaches have advanced, so have the development of local and regional flap reconstruction. The majority of skull base defects are successfully reconstructed with a combination of free grafts, local flaps, and regional flaps. 7 However, when locoregional flaps fail to reconstruct the skull base, the microvascular surgeon faces many reconstructive challenges. Patients that undergo loss of local and regional flaps often have undergone previous radiation treatment. Although traditional open approaches permitted wide access to reconstruct the skull base, modern skull base defects exist within a very narrow corridor, and there is often no direct access to the defect to perform the flap inset, Head & Neck.2018;40:E45 E52. wileyonlinelibrary.com/journal/hed VC 2018 Wiley Periodicals, Inc. E45

2 E46 KANG ET AL. FIGURE 1 A, Sublabial incision and anterior maxillotomy is performed to access the maxillary sinus while preserving the infraorbital nerve. Endoscopic medial maxillectomy is subsequently performed. The vastus lateralis can then be passed through the sublabial incision into the nasal cavity, and then endoscopic positioning of the flap is performed. B, Sagittal view showing inset of the vastus lateralis against the cranial base. The pedicle courses through the anterior maxillotomy through a tunnel in the buccal space, deep to the buccinator, to reach the recipient vessels in the neck (facial artery and vein) especially in the salvage secondary reconstructive setting. Finally, the choice of flap must have a pedicle length that allows reaching the recipient vessels in the neck in order to avoid vein grafting. 8 This article describes a novel technique, which was developed to address the challenges of secondary anterior skull base reconstruction in the endoscopic era of skull base surgery. This technique utilizes the vastus lateralis free tissue transfer (VLFTT) to provide robust separation of the sinonasal and intracranial cavities and cerebrospinal fluid (CSF) leak repair, and is inset through an endoscopic approach without the need for craniotomy. 2 CASE REPORTS 2.1 Case series design This retrospective case series included 4 patients with anterior skull base defects resulting in communication between the intracranial and sinonasal cavities. All patients underwent previous local and/or regional flap reconstruction of the skull base that failed, requiring a secondary reconstruction of the skull base with a VLFTT from July 2014 to November 2016 at The James Cancer Hospital and Solove Research Institute and The Ohio State University Wexner Medical Center. Mean follow-up was 11 months (range 5-21 months). Institutional review board approval and written informed consent were obtained. 2.2 Surgical technique Preparation of the recipient site After endoscopic debridement of the necrotic tissue from the failed reconstruction, preparation of the recipient site begins by creating access for the vastus lateralis flap to be inserted in the sinonasal cavity, inferior to the skull base defect (ie, onlay). First, a sublabial incision is made, and the anterior surface of the maxilla is exposed. Next, an anterior maxillotomy is performed. Bone surrounding the infraorbital nerve is removed in a U-shaped fashion (see Figure 1) and the infraorbital nerve is preserved within and out of its canal. The piriform aperture (ie, ascending process of the maxilla) is also preserved. Next, an endoscopic medial maxillectomy is performed in preparation for the free flap to be passed through the anterior maxillotomy and into the sinonasal cavity. Recipient vessels, typically the facial artery and facial vein, if available, are dissected through a submandibular incision. The marginal branch of the facial nerve is preserved and the vessels are typically ligated just inferior to the nerve, in order to maximize recipient vessel length. A tunnel is then

3 KANG ET AL. E47 FIGURE 2 The descending branch of the lateral circumflex femoral artery is identified entering the vastus lateralis. A Doppler probe is used to identify the intramuscular course of the artery (inset). A long, thin harvest of the vastus lateralis is performed, centered around the pedicle created through the buccal space, deep to the buccinator muscle, between the recipient vessels and the anterior maxillotomy (see Figure 1). 2.3 Flap harvest The VLFTT is a modification of the anterolateral thigh free tissue transfer. 9 A cutaneous paddle is not harvested in this technique. A line is drawn from the anterior superior iliac spine and the lateral patella to landmark the approximate location of the separation between the vastus lateralis and the rectus femoris muscles. An incision is made along this line through the skin and adipose tissue. Because a cutaneous paddle is not included, perforators in this region may be divided. The rectus femoris is identified and retracted medially, exposing the descending branch of the lateral femoral circumflex artery and the vastus lateralis. The pedicle is then identified at the entry point to the vastus lateralis. An acoustic Doppler sonography probe is used to identify the course of the pedicle as it passes through the vastus lateralis (see Figure 2). A narrow strip of vastus lateralis is then harvested around the course of the pedicle (see Figure 2). The descending branch of the lateral femoral circumflex artery is dissected until the branch to the rectus femoris is identified, to maximize the pedicle length. 2.4 Flap inset Once the vastus lateralis flap is disconnected, it is passed through the sublabial incision and anterior maxillotomy into the maxillary sinus and through the medial maxillectomy defect into the nasal cavity. Its passage and endonasal positioning is shepherded endoscopically, guiding the distal portion of the flap toward the posterior extent of the skull base defect. Most commonly, this involves pushing the distal aspect of the flap into the sphenoid sinus. A Freer elevator is then used to nudge the vastus lateralis medially and superiorly to obliterate the communication between the sinonasal and intracranial cavity. The muscle should be in immediate direct contact with the defect and overlap its periphery. A layer of absorbable, nonadherent material helps to separate the flap from the rest of the nasal packing (ie, expandable sponges). Nasal trumpets are then placed at the inferior aspect of the packing to further bolster the flap and to provide a nasal airway. Once the flap is in a good position, the pedicle is tunneled from the anterior maxillotomy, through the buccal space, deep to the buccinator, to reach the recipient vessels (see Figure 1). Positioning and bolstering of the flap is completed before microvascular anastomosis to achieve optimal positioning before the edema and enlargement of the muscle that occurs subsequent to its reperfusion, and to prevent tension or movement of the anastomosis after revascularization. The CSF diversion was not used. 2.5 Postoperative care Patients were admitted to the neurointensive care unit for 24 hours. Noncontrasted brain CT scans were performed immediately after surgery to ensure the absence of intracranial complications. A contrasted MRI was performed within 24 hours of surgery to confirm the oncologic resection (when appropriate) and evaluate the positioning of the flap. Nasal trumpets and nasal packing were left in place for 7 days. Nasal endoscopy and debridement was performed weekly in the postoperative period. 2.6 Outcome measures and results Outcome measures included flap survival, separation of sinonasal and intracranial cavities, resolution of meningitis, and/ or CSF leak, and major and minor complications.

4 E48 KANG ET AL. TABLE 1 Patient information and demographics Patient Age, years Etiology Prior surgery Prior reconstruction Prior treatment Defect Intracranial sinonasal separation achieved? Follow-up Status at last follow-up 1 55 T4N0 M0 (intergroup stage III) rhabdomyosarcoma Open and EEA Duragen, PCF, and TFL IC and CRT Cribriform and PS Yes 6 mo Well 2 24 Osteoblastoma 1. EEA 2. Open and EEA 1. NSF 2. PCF, TFL, and fat graft None Cribriform and PS Yes 10 mo Well 3 46 T4a N0 ethmoid SCC Open and EEA PCF and Allomax IC and CRT Cribriform and PS Yes 21 mo Well 4 65 Kadish C olfactory neuroblastoma EEA PCF, NSF, and fat graft XRT Cribriform and PS Yes 5 mo DOD Abbreviations: CRT, chemoradiotherapy; DOD, died of disease; EEA, expanded endonasal approach; IC, induction chemotherapy; NSF, nasal septum flap; PCF, pericranial flap; PS, planum sphenoidale; SCC, squamous cell carcinoma; TFL, tensor fascia lata; XRT, external radiotherapy. Demographic and patient information are summarized in Table 1. All 4 patients (100%) underwent extirpative skull base surgery for skull base neoplasms and were reconstructed at the time of surgery with local or regional flaps. Three patients (75%) had combined open and endoscopic endonasal surgery using an endoscopic endonasal approach to resect the nasal portion of the tumor and a bifrontal craniotomy to resect the intracranial portion, and 1 patient had an endoscopic endonasal resection. All 4 patients were initially reconstructed at the time of resection with local and regional flaps. One patient underwent a nasoseptal flap reconstruction during the primary tumor resection, followed by pericranial flap reconstruction after a secondary stage resection, whereas the other 3 patients underwent primary reconstruction with a pericranial flap and tensor fascia lata free grafts. Three patients (75%) received adjuvant treatment, including chemoradiation treatment in 2 patients (50%) and just radiation treatment in 1 patient (25%). All 4 patients (100%) had a delayed necrosis of the pericranial flap, necessitating a secondary free flap reconstruction of the skull base. The success rate of the VLFTT was 100%, achieving a complete separation of the intracranial and sinonasal cavities in all patients and resolving a CSF fistula in 2 of 2 patients. The vastus lateralis was able to survive transplantation into an infected wound in 2 patients, one with acute bacterial meningitis and another with an epidural abscess. One patient who underwent cranioendoscopic surgery had a postoperative intracranial infection; therefore, the craniotomy bone graft was removed to avoid persistent infection. A helmet was used postoperatively to protect the frontal lobe of the brain. A cranioplasty, with a customized titanium plate, was completed 6 months postoperatively, after corroborating that the infection had resolved. We encountered 3 major complications and 1 minor complication. One patient required a return to the operating room on postoperative day 8, after the nasal packing was removed, when increasing pneumocephalus was noted on the head CT. The VLFTT was noted to separate from the medial orbital wall/skull base and was managed with endoscopic debridement of the medial orbital wall mucosa and replacement of nasal packing for 1 additional week. One patient developed a neck hematoma on postoperative day 5 that required operative drainage. One patient developed a donor site infection on postoperative day 42 that required operative drainage. One patient developed a donor site seroma that was managed with needle aspiration. 2.7 Case 1 A 55-year-old man presented with a T4 N0 M0 rhabdomyosarcoma (alveolar type) of the sinonasal cavity with intracranial invasion involving the frontal lobe. He was treated with induction chemotherapy, receiving 5 cycles of vincristine, dactinomycin, and cytoxan. He had a partial response, with residual tumor in the anterior skull base involving the frontal convexity. He underwent a combined open craniofacial and endoscopic endonasal resection, achieving a gross total resection. The tumor was intradural in the anterior cranial fossa, and multilayer skull base reconstruction with acellular

5 KANG ET AL. E49 FIGURE 3 Preoperative T1 coronal A, and sagittal B, MRI showing loss of the pericranial flap reconstruction and frontal lobe exposure, with mild pneumocephalus. Postoperative T1 coronal C, and sagittal D, MRI after reconstruction with the vastus lateralis free tissue transfer. In C, note the pedicle coursing through the vastus lateralis (yellow arrow). Complete coverage of the exposed brain is achieved with this free tissue transfer, inset from an endoscopic endonasal approach dermis for dural replacement (AlloMax; Bard Davol, Warwick, RI) collagen matrix (DuraGen; Integra Neuroscience, Plainsboro, NJ) and autogenous tensor fascia lata inlay grafting and an epidural pericranial flap. He underwent adjuvant chemoradiation to 60 Gy in 30 fractions with concurrent carboplatin. Four months after completion of chemoradiation, central necrosis of the skull base reconstruction was noted on nasal endoscopy. Endoscopic examination showed that the pericranial flap had full thickness ulceration and was not viable leading to an anterior cranial base defect involving the cribriform and planum sphenoidale. The reconstructed dural was exposed, but there was no CSF leak or pneumocephalus. Figure 3 shows the preoperative MRI with necrosis of the pericranial flap and sinonasal/intracranial communication. A secondary reconstruction was performed using the aforementioned technique for the VLFTT. The skull base was accessed through a right sublabial approach, anterior maxillotomy, and endoscopic medial maxillectomy. The left VLFTT was harvested (see Figure 2) and inset, placing the distal aspect of the vastus lateralis flap in the sphenoid sinus and displacing the muscle superiorly against the dura. This was bolstered with absorbable and nonabsorbable nasal packing and nasal trumpets. The pedicle was tunneled through the buccal space to reach the ipsilateral facial artery and vein and microvascular anastomosis was performed. Preoperative and postoperative imaging is shown in Figure 3. Postoperative nasal endoscopy showed mucosalization of the flap with complete separation of the intracranial and sinonasal cavities and minimal crusting. 2.8 Case 2 A 23-year-old woman presented with acute bilateral loss of vision. Imaging showed an expansile osseous cranial base lesion with bilateral optic nerve compression. She underwent emergency expanded endoscopic endonasal bilateral optic nerve decompression and subsequently underwent a combined open and endoscopic resection to obtain a gross total resection of the biopsy proven osteoblastoma. She was reconstructed with an inlay subdural collagen matrix graft (DuraGen; Integra Neuroscience), followed by a free autologous graft of the tensor fascia lata, and then by a pericranial flap, all in the epidural space. Her immediate postoperative course was uneventful. She presented 2 weeks later in acute distress, with fever, altered mental status, malodorous nasal

6 E50 KANG ET AL. FIGURE 4 A, Nasal endoscopy, 2 weeks after combined open and endonasal resection of anterior skull base osteoblastoma, with complete necrosis of the pericranial flap and tensor fascia lata graft. B, After debridement of the pericranial flap and tensor fascia lata graft, dura and frontal lobe were exposed with cerebrospinal fluid leak (CSF). C, Three weeks postoperatively after endoscopic inset of vastus lateralis free tissue transfer. White arrows indicate the vastus lateralis free tissue transfer. Exposed frontal lobe is completely covered and the CSF leak has resolved. Crusting was debrided, revealing the well vascularized muscle transplant. D, Endoscopic examination, 5 months postoperatively, shows complete separation of the intracranial and sinonasal cavities. The free tissue transfer has undergone mucosalization and exhibits minimal crusting drainage, and severe headaches. Endoscopic examination showed infection and necrosis of the pericranial flap, a CSF leak, and exposed dura (see Figure 4). The cranial base was endoscopically debrided and she was reconstructed with the VLFTT, as detailed above. After the reconstruction and broad-spectrum i.v. antibiotics, her headaches, altered mental status, and CSF leakage resolved. Her nasal packing was removed on postoperative day 7 and she continued to improve until postoperative day 9, when she developed headaches and mental status changes. Imaging showed increased pneumocephalus and inferior displacement of the free flap. She was taken back to the operating room where endoscopic examination showed a small flap dehiscence along the left medial orbital wall. The medial orbital wall mucosa was debrided, the flap was repositioned to cover the defect, and a bolster comprising absorbable and nonabsorbable packing and nasal trumpets was again placed for 7 days. This resulted in complete separation of the sinonasal/intracranial cavities, resolution of CSF leak, and resolution of her headaches and altered mental status. Postoperative photographs are shown in Figure 4. 3 DISCUSSION The primary goal of anterior cranial base reconstruction is to separate the intracranial and extracranial compartments, achieving a watertight seal to prevent CSF leaks. 3,10 This may be achieved via different combinations of free grafts, local flaps, regional flaps, and free tissue transfers. 7 Microvascular reconstruction of the skull base has been well reported in the literature, 1,3,4,6,7 and a myriad of donor sites have been described to achieve successful skull base reconstruction, although the rectus and radial forearm donor sites are most commonly cited. 11 However, flap inset requires direct access to the skull base defect through open skull base approaches. 1,3 As such, microvascular reconstruction has largely been reported for primary reconstruction of skull base defects after open skull base surgery. Evolution of the expanded endonasal technique has permitted endoscopic resection of skull base tumors through a minimally invasive approach. 12 In parallel with minimally invasive extirpative techniques, surgeons have developed minimally invasive reconstructive techniques. Local flap

7 KANG ET AL. E51 techniques, such as the nasoseptal flap, have been developed 13,14 and refined 15 in order to achieve the goals of skull base reconstruction with high rates of success. Endoscopic techniques for harvest of the pericranial flap have also been developed. 16 Although local flaps, regional flaps, and free grafts have a high rate of success, 11 if these methods fail, limited options currently exist. In cases of local and/or regional flap failure where no other local or regional flap reconstructive options exist, the authors perform free tissue transfer. However, the reconstructive surgeon faces many challenges during salvage secondary skull base reconstruction. This patient population is a selected, high-risk population in which traditional reconstructive measures have failed. These are often heavily irradiated and/or infected recipient sites. Often, these are narrow defects in a tight corridor with very limited access to the defect. Furthermore, these skull base defects are often distant from nearby recipient vessels. The ideal flap for these salvage reconstructive settings would be a narrow, pliable flap that could be packed and conformed into a narrow corridor that could be inset endoscopically via the sinonasal corridor; thus, avoiding an open skull base approach and craniotomy to expose the defect, especially in the case of a salvage secondary reconstructive surgery. The ideal flap would also have a long pedicle to reach recipient vessels in the neck without the need for vein grafts. The technique described in this article was developed to address the challenges of large defects presenting after failure of traditional skull base reconstructive methods using locoregional flaps. The primary advantage of this technique is that it permits inset of the flap through a sublabial maxillotomy approach, and the flap placement is achieved endoscopically, without the need for a craniotomy to access the defect. The flap is narrow, flexible, and able to be compressed into a narrow corridor. A long strip of vastus lateralis can be harvested as long as the pedicle is included, and our series included up to 26 cm of vastus lateralis harvested with an additional 8 cm of pedicle length. Thus, vein grafts are not needed for this technique. Finally, the harvest of the myofascial flap is relatively simple as one does not need to worry about cutaneous perforators, and a 2-team approach can be utilized. Several important technical points exist that we have learned with increased experience with this technique. First, it is imperative that a large anterior maxillotomy and medial maxillectomy be performed, so that the flap can easily be tunneled, tension free, into the sinonasal cavity. Second, all sinonasal mucosa along the skull base and medial orbits must be debrided so that the muscle flap can adhere to these areas; thus, supporting its own weight and resist the brain and CSF pulsations and pressure. Meticulous placement of the flap, so that the muscle completely obliterates the space between the sinonasal cavity and intracranial cavities, is critical. The flap must be adequately bolstered with absorbable and nonabsorbable nasal packing followed by nasal trumpets. Finally, the authors leave the packing in for 7 days and wet the packing before removing it so that it does not adhere to the vastus lateralis flap. The primary disadvantage of this flap is near complete nasal obstruction in the immediate postoperative period due to the presence of the free tissue transfer and nasal packing. However, over time, this myofascial free tissue transfer undergoes gradual muscle atrophy. Interestingly, the flap undergoes mucosalization in the first 2 months, resulting in a thin, vascularized, and mucosalized free tissue transfer (see Figure 4). Single case reports exist of using the anterolateral thigh free flap for skull base reconstruction 17,18 but this is the first case to use a narrow myofascial flap that is inserted and inset endoscopically, without a cutaneous paddle. Although local and regional flap reconstruction success rates are high, skull base surgeons will occasionally face flap loss, in which limited reconstructive options exist. Our technique of VLFTT with an endoscopic inset through an anterior maxillotomy represents a safe, reliable, and minimally invasive method of salvage skull base reconstruction. ORCID Stephen Y. Kang MD 6149 Antoine Eskander MD 1393 REFERENCES [1] Califano J, Cordeiro PG, Disa JJ, et al. Anterior cranial base reconstruction using free tissue transfer: changing trends. Head Neck. 2003;25(2): [2] Chang DW, Robb GL. Microvascular reconstruction of the skull base. Semin Surg Oncol. 2000;19(3): [3] Chepeha DB, Wang SJ, Marentette LJ, Thompson BG, Prince ME, Teknos TN. Radial forearm free tissue transfer reduces complications in salvage skull base surgery. Otolaryngol Head Neck Surg. 2004;131(6): [4] Chiu ES, Kraus D, Bui DT, et al. Anterior and middle cranial fossa skull base reconstruction using microvascular free tissue techniques: surgical complications and functional outcomes. Ann Plast Surg. 2008;60(5): [5] Neligan PC, Mulholland S, Irish J, et al. Flap selection in cranial base reconstruction. Plast Reconstr Surg. 1996;98(7): ; discussion [6] Teknos TN, Smith JC, Day TA, Netterville JL, Burkey BB. Microvascular free tissue transfer in reconstructing skull base defects: lessons learned. Laryngoscope. 2002;112(10): [7] Hachem RA, Elkhatib A, Beer-Furlan A, Prevedello D, Carrau R. Reconstructive techniques in skull base surgery after resection

8 E52 KANG ET AL. of malignant lesions: a wide array of choices. Curr Opin Otolaryngol Head Neck Surg. 2016;24(2): [8] Suominen S, Asko-Seljavaara S. Free flap failures. Microsurgery. 1995;16(6): [9] Wong CH, Wei FC. Anterolateral thigh flap. Head Neck. 2010; 32(4): [10] Moyer JS, Chepeha DB, Teknos TN. Contemporary skull base reconstruction. Curr Opin Otolaryngol Head Neck Surg. 2004; 12(4): [11] Reyes C, Mason E, Solares CA. Panorama of reconstruction of skull base defects: from traditional open to endonasal endoscopic approaches, from free grafts to microvascular flaps. Int Arch Otorhinolaryngol. 2014;18(Suppl 2):S179-S186. [12] Prevedello DM, Kassam AB, Snyderman C, et al. Endoscopic cranial base surgery: ready for prime time? Clin Neurosurg. 2007;54: [13] Hadad G, Bassagasteguy L, Carrau RL, et al. A novel reconstructive technique after endoscopic expanded endonasal approaches: vascular pedicle nasoseptal flap. Laryngoscope. 2006;116(10): [14] Kassam AB, Thomas A, Carrau RL, et al. Endoscopic reconstruction of the cranial base using a pedicled nasoseptal flap. Neurosurgery. 2008;63(1 Suppl 1):ONS44-ONS52; discussion ONS52-ONS53. [15] Otto BA, Bowe SN, Carrau RL, Prevedello DM, Ditzel Filho LF, de Lara D. Transsphenoidal approach with nasoseptal flap pedicle transposition: modified rescue flap technique. Laryngoscope. 2013;123(12): [16] Zanation AM, Snyderman CH, Carrau RL, Kassam AB, Gardner PA, Prevedello DM. Minimally invasive endoscopic pericranial flap: a new method for endonasal skull base reconstruction. Laryngoscope. 2009;119(1): [17] Iida H. The advantage of the anterolateral thigh flap for reconstruction of the anterior skull base defect in recurrent cases. Plast Reconstr Surg. 2003;112(2): [18] Lo KC, Jeng CH, Lin HC, Hsieh CH, Chen CL. A free composite de-epithelialized anterolateral thigh and the vastus lateralis muscle flap for the reconstruction of a large defect of the anterior skull base: a case report. Microsurgery. 2011;31(7): How to cite this article: Kang SY, Eskander A, Hachem RA, et al. Salvage skull base reconstruction in the endoscopic era: Vastus lateralis free tissue transfer. Head & Neck. 2018;40:E45 E /hed.25094