Abstract
Background Transpterygoid approaches to the skull base require dissection of the sphenopalatine artery, potentially compromising the option to harvest an ipsilateral nasoseptal flap (NSF) for reconstruction. In cases where other reconstructive options are limited, it may be necessary to utilize a NSF ipsilateral to the transpterygoid approach. Here, we describe the technique of NSF pedicle preservation with reconstruction outcomes.
Methods This was a retrospective single-institution review of all expanded endonasal skull base cases utilizing a NSF ipsilateral to a transpterygoid approach. Reconstruction outcomes collected include intraoperative fluorescence with indocyanine green (ICG), postoperative magnetic resonance imaging (MRI) gadolinium enhancement, endoscopic assessment, and reconstruction-related complications.
Results Twenty-one cases were included in this study (mean age 51.0 ± 20.6 years, 61.9% female). Indications for NSF ipsilateral to the transpterygoid approach included: bilateral transpterygoid approach (52.4%), revision reconstruction (23.8%), or significant septal deviation (19.0%). Twelve of 14 (85.7%) flaps demonstrated intraoperative perfusion with ICG, 15 of 15 (100%) enhanced on postoperative MRI, and 21 of 21 (100%) flaps had a healthy, viable appearance on postoperative endoscopy. There were no instances of flap necrosis or postoperative cerebrospinal fluid leaks. Technical keys to optimize mobilization of the pedicle include wide decompression of the sphenopalatine foramen and release of neurovascular tethering points of the pterygopalatine fossa. These steps allow for wide skull base exposure with preservation of the sphenopalatine artery.
Conclusion With this technique, the transpterygoid approach can be performed in a manner that preserves the pedicle for an ipsilateral NSF and achieve an excellent reconstructive outcome.
Keywords: endoscopic skull base surgery, transpterygoid, nasoseptal flap, reconstruction, skull base reconstruction
Introduction
In endoscopic endonasal skull base surgery, a transpterygoid approach can be employed for access to lateral and inferior regions of the skull base, including the parasellar region, paraclival region, petrous apex, Meckel's cave, middle cranial fossa, and infratemporal fossa. This approach requires manipulation of the pterygopalatine fossa (PPF) contents and the sphenopalatine artery (SPA), which provides the vascular supply to the nasoseptal flap (NSF) on its respective side. Overly manipulating or sacrificing the SPA, as described in some transpterygoid techniques, can compromise the pedicle and preclude use of the NSF on that side. In some cases, however, it may be necessary to utilize a NSF ipsilateral to the transpterygoid approach.
Currently, there is limited data regarding reconstructive outcomes of ipsilateral NSFs from a transpterygoid approach, with existing series pertaining to encephalocele or cerebrospinal fluid (CSF) leak repair. 1 2 3 There are currently only case reports with limited flap outcome data from expanded endonasal skull base cases, where wider exposures and longer cases may impose additional risks and challenges to pedicle management. 4 Here, we report our reconstructive outcomes in expanded endonasal skull base cases that utilize ipsilateral NSFs during a transpterygoid technique with SPA preservation.
Methods
Patient Selection
This study protocol was approved by the Stanford University Institutional Review Board. We retrospectively reviewed all patients that underwent endoscopic endonasal skull base surgery at our institution from 2018 to 2023. Case logs were reviewed to assess candidates for study. Cases were included if they utilized a NSF ipsilateral to a transpterygoid approach. Patients of all ages and all skull base pathologies were included. Patients were included if data was available for at least one of three outcomes to assess reconstruction viability (intraoperative angiography, postoperative magnetic resonance imaging [MRI] with contrast, and/or postoperative nasal endoscopy).
Data Collection and Analysis
The following clinical data was collected from the electronic medical record: patient age, sex, pathology for index case, and revision status of the case. Operative reports were reviewed to assess approach, sidedness of approach, side of NSF, need for concurrent septoplasty, presence of CSF leak, and reconstruction method. Reconstructive outcomes were assessed using three metrics. Intraoperatively, fluorescence angiography was performed using intravenous indocyanine green (ICG) to assess perfusion. 5 A 12.5-mg dose of ICG is administered intravenously, followed by a 10-mL saline flush. ICG was then visualized using the IMAGE1 S 4U Rubina 4K NIR/ICG endoscope (Karl Storz SE & Co. KG, Tuttligen, Germany). For cases utilizing intraoperative fluorescence angiography, the presence or absence of intraoperative perfusion after the NSF inset was recorded. For cases where a postoperative MRI was performed, imaging was reviewed to assess for the presence of NSF enhancement with gadolinium contrast. All patients also went a nasal endoscopy between 2 and 6 weeks postoperatively to visually assess the viability of reconstruction. The findings of nasal endoscopy procedure were recorded. Complications related to the reconstruction were recorded, including persistent postoperative CSF leak or flap necrosis.
Surgical Technique
The complete technique is demonstrated in the online video by Chang and Patel. 6
The approach begins with a standard transsphenoidal exposure of the skull base. To initiate a transpterygoid approach, the maxillary sinus is opened widely, beginning with resection of the uncinate process followed by expansion to the posterior maxillary sinus wall. Often, a total ethmoidectomy can also be performed to provide additional lateral exposure of the skull base and lamina papyracea. The sphenopalatine foramen can then be identified just posterior to the crista ethmoidalis. The sphenopalatine foramen is then widened with a Kerrison Rongeur to expose the fascia surrounding the PPF contents ( Fig. 1 ). Wide expansion of the sphenopalatine foramen and removal of the palatine bone that serves as the posterior maxillary sinus wall are key to allow for broad decompression of the SPA. Often, the posterior maxillary sinus wall is removed laterally to the plane of the infraorbital nerve. Throughout the dissection around the SPA, careful removal of bony fragments is imperative to prevent inadvertent injury of the vascular pedicle.
Fig. 1.
Performing a wide maxillary antrostomy and removing the posterior sinus wall to expose the pterygopalatine fossa on the right side.
The mobilization of the PPF contents inferiorly and laterally can then begin through the release of key attachment points. The base of the superior turbinate is released with a through-cut instrument, disconnecting its mucosal attachment to the pedicle and enabling inferior displacement of the pedicle ( Fig. 2 ). This maneuver also allows for the preservation of the superior turbinate, as it can now be displaced laterally and superiorly out of the surgical view and corridor throughout the case. Exposure of the sphenoid rostrum bone is then performed by elevation of the pedicle inferiorly and laterally. As elevation continues laterally, the sphenoidal process of the palatine bone will then be encountered, and the palatosphenoidal artery just medial to this structure. The palatosphenoidal artery is then cauterized and divided to allow for lateral mobilization of the pedicle ( Fig. 3 ). Continued elevation laterally will reveal the vidian nerve and artery, which can be divided to allow for further mobilization of the pedicle laterally. With the pedicle mobilized out of the way, the pterygoid bone is removed via drilling to achieve the exposure necessary for tumor resection. This transpterygoid approach can be expanded to expose the entire lateral recess of the sphenoid sinus, cavernous sinus, Meckel's cave, petroclival region, and petrous apex.
Fig. 2.
Release of superior turbinate by removing the lateral lamellar attachment, allowing reflection of the superior turbinate superolaterally and inferior mobilization of the nasoseptal flap (NSF) pedicle.
Fig. 3.
Division of the palatosphenoidal artery and removal of the pterygoid wedge.
The NSF can be harvested prior to the tumor resection in standard fashion 7 or following resection from a rescue flap, 8 although in most transpterygoid cases, elevation at the beginning of the case allows for best protection of the mucosal surface. The nasal floor and lateral wall of the inferior meatus is often included as part of this NSF harvest, as the resection cavity following a combined transsphenoidal and transpterygoid approach can often require reconstruction of a larger surface area. The NSF is placed over the skull base defect ( Fig. 4 ) and bolstered with tissue sealant and absorbable packing material.
Fig. 4.
Final reconstruction of the nasoseptal flap from an ipsilateral transpterygoid approach, with flap perfusion confirmed using intravenous indocyanine green.
Results
Twenty-one cases were reviewed in this study ( Table 1 ). Patients had mean age of 51.0 ± 20.6 years (range 4–72). In 17 cases, a transpterygoid approach was performed to obtain lateral exposure for resection of tumors with cavernous sinus involvement and/or extension lateral to the internal carotid artery. In four cases, a transpterygoid approach was employed for access to tumor involving the foramen lacerum and petrous apex. There were three indications for utilization of a NSF ipsilateral to the transpterygoid approach. In 11 (52.4%) cases, a bilateral transpterygoid approach was required for tumor resection. Five (23.8%) cases were revision endoscopic skull base tumor resections and the NSF contralateral to the transpterygoid approach was not available or viable. In four (19.0%) cases, there was a significant septal deviation and/or spur preventing the harvest of a NSF contralateral to the transpterygoid approach. In 20 of 21 (95.2%) cases the NSFs were harvested upfront prior to resection, while 1 (4.8%) NSF was harvested from a rescue flap following tumor resection. Fifteen of 21 (71.4%) cases had intraoperative CSF leaks, of which 10 were low-flow leaks from the sella and 5 were high-flow leaks from the clival or suprasellar regions. Six of 21 (28.6%) cases did not have a CSF leak but a NSF was elected to be placed for coverage of the exposed internal carotid artery or attenuated arachnoid membrane.
Table 1. Patient characteristics and reconstruction outcomes.
| # | Age (y) | Sex | Pathology | Indication | NSF harvest timing | Intraoperative CSF leak | Length of follow-up (d) | Fluorescent on ICG angiography | MRI enhancement | Endoscopy appearance |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 4 | F | Clival chordoma | Bilateral transpterygoid | Upfront | High flow | 40 | N/A | Yes | Viable |
| 2 | 28 | F | Pituitary adenoma | Septal anatomy | Upfront | Low flow | 113 | No | Yes | Viable |
| 3 | 30 | M | Pituitary adenoma | Revision reconstruction | Upfront | None | 15 | Yes | Yes | Viable |
| 4 | 32 | F | Pituitary adenoma | Revision reconstruction | Upfront | Low flow | 8 | N/A | Yes | Viable |
| 5 | 33 | F | Pituitary adenoma | Bilateral transpterygoid | Upfront | Low flow | 47 | No | Yes | Viable |
| 6 | 33 | F | Clival chordoma | Bilateral transpterygoid | Upfront | High flow | 57 | Yes | Yes | Viable |
| 7 | 35 | M | Clival chordoma | Bilateral transpterygoid | Upfront | High flow | 78 | Yes | Yes | Viable |
| 8 | 41 | M | Pituitary adenoma | Bilateral transpterygoid | Upfront | Low flow | 21 | Yes | N/A | Viable |
| 9 | 42 | M | Pituitary adenoma | Bilateral transpterygoid | Upfront | Low flow | 43 | Yes | N/A | Viable |
| 10 | 45 | M | Atypical teratoid rhabdoid tumor | Revision reconstruction | Delayed | Low flow | 106 | Yes | Yes | Viable |
| 11 | 52 | F | Pituitary adenoma | Bilateral transpterygoid | Upfront | None | 43 | Yes | Yes | Viable |
| 12 | 60 | F | Pituitary adenoma | Revision reconstruction | Upfront | Low flow | 81 | Yes | N/A | Viable |
| 13 | 63 | M | Pituitary adenoma | Revision reconstruction | Upfront | None | 8 | N/A | Yes | Viable |
| 14 | 68 | F | Pituitary adenoma | Septal anatomy | Upfront | None | 47 | N/A | Yes | Viable |
| 15 | 70 | F | Pituitary adenoma | Bilateral transpterygoid | Upfront | None | 15 | Yes | Yes | Viable |
| 16 | 70 | F | Pituitary adenoma | Bilateral transpterygoid | Upfront | Low flow | 15 | Yes | N/A | Viable |
| 17 | 70 | M | Clival chordoma | Bilateral transpterygoid | Upfront | High flow | 15 | Yes | Yes | Viable |
| 18 | 71 | F | Pituitary adenoma | Septal anatomy | Upfront | Low flow | 25 | N/A | N/A | Viable |
| 19 | 71 | F | Meningioma | Septal anatomy | Upfront | High flow | 20 | Yes | Yes | Viable |
| 20 | 72 | M | Pituitary adenoma | Bilateral transpterygoid | Upfront | Low flow | 15 | N/A | Yes | Viable |
| 21 | 82 | F | Pituitary adenoma | Septal anatomy | Upfront | Low flow | 12 | Yes | N/A | Viable |
Abbreviations: CSF, cerebrospinal fluid; F, female; ICG, indocyanine green; M, male; MRI, magnetic resonance imaging; N/A, not available; NSF, nasoseptal flap.
Of 14 cases that utilized intraoperative ICG fluorescence angiography, 12 (85.7%) flaps demonstrated perfusion. A postoperative MRI was obtained in 15 cases, at a mean of 37.6 days following surgery (range 1–131 days). All 15 (100%) flaps demonstrated enhancement with gadolinium contrast. On nasal endoscopic exam, which was performed and followed for a mean of 40.6 days (range 8–113 days) postoperatively, 21 of 21 (100%) flaps had a healthy, viable appearance. There were no instances of flap necrosis or postoperative CSF leaks.
Discussion
The NSF ipsilateral to the transpterygoid approach offers an important reconstructive option in endoscopic skull base surgery, particularly in cases where other reconstruction alternatives are limited. In revision cases, the contralateral NSF may be nonviable or compromised from previous surgery. Septal anatomy, such as a prominent spur causing mucosal attenuation, may necessitate the use of a specific side for the NSF. For extensive skull base tumors, a bilateral transpterygoid approach may be warranted along with a NSF for reconstruction. 4 Preservation of the SPA during a transpterygoid maintains the ipsilateral NSF as a reconstruction method prior to other salvage options such as the lateral nasal wall flap, tunneled temporoparietal fascia flap, or microvascular free flap.
The first three cases utilizing a NSF ipsilateral to a transpterygoid approach were reported in 2014. 4 In this initial description, the authors emphasized the importance of decompression of the sphenopalatine foramen and mobilization of the vascular pedicle through the release of PPF attachment points. Several small series of ipsilateral NSFs from a transpterygoid approach have been published, with largely successful reconstruction outcomes, though the existing reports are limited to repairs of encephaloceles and CSF leaks in the sphenoid sinus. 1 2 3 9 10 11
Our study builds on the existing body of literature by validating the use of NSFs from an ipsilateral transpterygoid approach in expanded endonasal approaches for more extensive tumors of the skull base. The technique shown here demonstrates that the strategies from prior descriptions are also key to achieving successful reconstruction outcomes in expanded endonasal cases: wide decompression of the sphenopalatine foramen and PPF contents, and release of the key neurovascular attachment points of the PPF. Additionally, in expanded endonasal cases where the field of resection is in close proximity to the NSF pedicle, the use of drills with nonrotating shafts will minimize the risk of inadvertent injury to the pedicle. Consideration should also be given to include the nasal floor and lateral wall of the inferior meatus as an extension of the NSF harvest, as the defect from cases with wider lateral extension can often be larger than cases limited to the sella.
This technique can be employed in transpterygoid approaches even when the need for a NSF is not expected. Preservation of the pedicle via a rescue flap 8 during the transpterygoid approach would keep it as a salvage reconstruction option if the resection were to cause an unexpected CSF leak during the same case, if the patients were to develop flap-related complication (i.e., necrosis of the contralateral NSF), or if a future tumor recurrence necessitated a revision surgery and revision reconstruction.
Our study also provides new data regarding intraoperative and postoperative assessments of flap perfusion. While 85% flaps demonstrated intraoperative perfusion as measured by ICG fluorescence, 100% of flaps demonstrated perfusion as measured by gadolinium contrast on MRI, and 100% demonstrated viability on postoperative endoscopy. While further research is needed to delineate the exact relationship between ICG fluorescence and flap viability, it is also possible that this discrepancy between intraoperative and postoperative measurements of perfusion may be indicative of a temporary or subclinical compromise of perfusion with increased dissection around the flap pedicle.
There are several limitations to this study. This study was retrospective in nature, which may increase the heterogeneity in which data was captured in the medical record. Additionally, there was variability in the methodology of assessing flap viability both intraoperatively (i.e., camera distance for visualizing ICG fluorescence) and postoperatively (i.e., timing of MRI, timing of postoperative endoscopy). The size of study cohort is relatively small; however, this study still represents the largest series to date reported in the literature regarding ipsilateral NSFs from a transpterygoid approach. Future prospective studies are warranted to validate and refine indications for this reconstructive technique.
Conclusion
In expanded endonasal skull base surgery, the transpterygoid approach can be performed with preservation of the SPA for an ipsilateral NSF, with excellent reconstructive outcomes.
Funding Statement
Funding This article received funding from Stanford University Departments of Otolaryngology and Neurosurgery.
Footnotes
Conflict of Interest K.A. is a consultant in SPIWAY. J.N. is a consultant at Medtronic, Olympus, Cook Medical, Hydravascular LLC. P.H. is a consultant at Sanofi, GSK. Z.P. is also a consultant at Medtronic, ConsumerMedical, Mediflix, Ethicon J&J; Advisory Board – Optinose, Regeneron/Sanofi, Dianosic; Equity – Olfera Theraputics. The rest of the authors have nothing to disclose.
References
- 1.Anania P, Ceraudo M, Prior A et al. Ipsilateral nasoseptal flap pedicle for transpterygoid approach: technical note. Iran J Otorhinolaryngol. 2021;33(119):361–367. doi: 10.22038/IJORL.2021.54687.2866. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Bartier S, Verillaud B, Guichard J P, Kania R, Camous D, Herman P. Anatomo-radiological study supporting the use of ipsilateral nasoseptal flap for the transpterygoid management of temporo-sphenoidal meningoceles. A review of 21 cases. Eur Ann Otorhinolaryngol Head Neck Dis. 2020;137(01):37–42. doi: 10.1016/j.anorl.2019.10.006. [DOI] [PubMed] [Google Scholar]
- 3.Sreenath S B, Tang D M, Ting J Y et al. Modified transpterygoid approach to sphenoid meningoencephaloceles: a shorter run for a longer slide. Laryngoscope. 2021;131(10):2224–2230. doi: 10.1002/lary.29672. [DOI] [PubMed] [Google Scholar]
- 4.Pinheiro-Neto C D, Paluzzi A, Fernandez-Miranda J C et al. Extended dissection of the septal flap pedicle for ipsilateral endoscopic transpterygoid approaches. Laryngoscope. 2014;124(02):391–396. doi: 10.1002/lary.24256. [DOI] [PubMed] [Google Scholar]
- 5.Kerr E E, Jamshidi A, Carrau R L et al. Indocyanine green fluorescence to evaluate nasoseptal flap viability in endoscopic endonasal cranial base surgery. J Neurol Surg B Skull Base. 2017;78(05):408–412. doi: 10.1055/s-0037-1602777. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Chang M T, Patel Z M.Use of ipsilateral nasoseptal flap for skull base reconstruction after a transpterygoid approachYoutube;2023. Accessed December 29, 2023 at:https://youtu.be/JIxMGVKEB6g
- 7.Hadad G, Bassagasteguy L, Carrau R L et al. A novel reconstructive technique after endoscopic expanded endonasal approaches: vascular pedicle nasoseptal flap. Laryngoscope. 2006;116(10):1882–1886. doi: 10.1097/01.mlg.0000234933.37779.e4. [DOI] [PubMed] [Google Scholar]
- 8.Rivera-Serrano C M, Snyderman C H, Gardner P et al. Nasoseptal “rescue” flap: a novel modification of the nasoseptal flap technique for pituitary surgery. Laryngoscope. 2011;121(05):990–993. doi: 10.1002/lary.21419. [DOI] [PubMed] [Google Scholar]
- 9.Schmidt R F, Choudhry O J, Raviv J et al. Surgical nuances for the endoscopic endonasal transpterygoid approach to lateral sphenoid sinus encephaloceles. Neurosurg Focus. 2012;32(06):E5. doi: 10.3171/2012.3.FOCUS1267. [DOI] [PubMed] [Google Scholar]
- 10.Ulu M O, Aydin S, Kayhan A et al. Surgical management of sphenoid sinus lateral recess cerebrospinal fluid leaks: a single neurosurgical center analysis of endoscopic endonasal minimal transpterygoid approach. World Neurosurg. 2018;118:e473–e482. doi: 10.1016/j.wneu.2018.06.219. [DOI] [PubMed] [Google Scholar]
- 11.Babu A R, Prakash B G, Kadlimatti V I, Sandhya D, Kamath S. Contrasting surgical management of CSF leak from lateral recess of sphenoid sinus and its surgical outcomes: our experience. Indian J Otolaryngol Head Neck Surg. 2019;71(04):531–536. doi: 10.1007/s12070-019-01715-w. [DOI] [PMC free article] [PubMed] [Google Scholar]