Abstract
Purpose
The vascularized pedicled nasoseptal flap (PNSF) represents a successful option for reconstruction of large skull base defects after expanded endoscopic endonasal approaches (EEA). This vascularized flap can be harvested early or late in the operation depending on the anticipation of high-flow CSF leaks. Each harvesting technique (early vs. late) is associated with different advantages and disadvantages. In this study, we evaluate our experience with early harvesting of the PNSF for repair of large skull base defects after EEA.
Methods
A retrospective review was performed at a tertiary care medical center on patients who underwent early PNSF harvesting during reconstruction of intraoperative high-flow CSF leaks after EEA between December 2008 and March 2012. Demographic data, repair materials, surgical approach, and incidence of PNSF usage were collected.
Results
Eighty-seven patients meeting the inclusion criteria were identified. In 86 procedures (98.9%), the PNSF harvested at the beginning of the operation was used. In 1 case (1.1%), the PNSF was not used because a high-flow intraoperative CSF leak was not encountered. This patient had recurrence of intradural disease 8 months later, and the previously elevated PNSF was subsequent used after tumor resection.
Conclusion
Based on our data, a high-flow CSF leak and need for a PNSF can be accurately anticipated in patients undergoing EEA for skull base lesions. Because of the advantages of early harvesting of the PNSF and the high preoperative predictive value of CSF leak anticipations, this technique represents a feasible harvesting practice for EEA surgeries.
1
Introduction
Transnasal endoscopic skull base surgery has revolutionized the treatment of skull base lesions. Previously morbid operations are now less invasive and have quicker recovery times with fewer complications . One key portion of skull base operations involves watertight repair of the skull base defect after excision of lesions to prevent postoperative cerebrospinal fluid (CSF) leaks. These defects may extend the entirety of the ventral skull base. Endoscopic repair of these large skull base defects can often be challenging.
Since its introduction in 2006 by Hadad et al, , the vascularized pedicled nasoseptal flap (PNSF) has become the “workhorse” of reconstructive techniques for large skull base defects with high-flow CSF leaks . The PNSF involves using a neurovascular pedicled flap harvested from the nasal septum mucoperiosteum and mucoperichondrium based on the nasoseptal artery, and rotating this flap to cover the skull base defect. The PNSF flap may be harvested at either the outset of the case, during the initial paranasal sinus exposure of the skull base (early harvest), and kept protected in the nasopharynx or maxillary sinus for later use, or it may be harvested at the end of the case after tumor resection (late harvest), when the full extent of the skull base defect can be appreciated. Potential advantages of the early harvest technique include allowing the maximum sized flap (when needed) to be harvested which may provide the most robust closure and prevention of PNSF and vascular pedicle avulsion and flap laceration during the initial exposure and tumor resection. This study offers a retrospective review of a single institution’s experience with early harvest of the PNSF, and discusses the advantages and disadvantages of this technique.
2
Materials and methods
2.1
Experimental design and study population
A retrospective analysis was performed between December 2008 and March 2012 to identify patients who underwent skull base surgery via an EEA approach where the PNSF was harvested early during the procedure (early harvest). We defined early harvest as intentional harvest of the PNSF during initial endonasal exposure of the skull base defect. Exclusion criteria included patients with small skull base defects (i.e. encephaloceles and spontaneous CSF leaks) since these small defects are typically treated without a PNSF in our institution. Patients with traumatic high-flow CSF leaks with large skull base defects that were repaired with a PNSF were included in this study. Patient age, sex, diagnosis, surgical procedure, repair technique, and use of PNSF were documented.
2.2
Data analysis
Data analyses were performed using Microsoft Office Excel 2007 (Microsoft Corp., Redmond, WA). The protocol for this study was reviewed and approved by the Institutional Review Board of the University of Medicine and Dentistry of New Jersey – New Jersey Medical School, Newark, New Jersey.
2.3
Surgical procedure
The PNSF is harvested at the beginning of the operation for cases in which the senior authors (JAE and JKL) anticipate a high-flow CSF leak. These included all cases with intradural pathology, extradural pathology with dural and intradural involvement, and pituitary adenoma with anticipated large skull base and dural defects. The PNSF is placed in the nasopharynx or maxillary sinus during tumor resection or leak site preparation. Our PNSF design is typically tailored to the expected type of defects which we term “target-specific- flap design.” Consequently, not all PNSF are designs identically. We have previously described our technique and nuances for harvesting the flap for transcribriform , transplanum , and transclival defects . While harvesting the flap, the first incision is made at the junction between the floor of the nose and the nasal septum starting from a posterior to anterior course. In cases in which the maximum PNSF size is desired, this incision can be taken more laterally along the floor of the nose or under the inferior turbinate in order to include the soft tissue covering of the nasal floor as part of the flap. When this variation is performed, care should be taken not to injure the nasolacrimal duct opening (Hasner’s valve) in order to prevent postoperative epiphora. The next incision is made from the most inferior aspect of the sphenoid opening and is advanced anterosuperiorly until the preferred length is attained. This incision can be made as far anterior as the septocolumellar junction if a longer PNSF is necessary (typically for cribriform defects extending to the frontal sinus posterior table). If possible, we attempt to preserve the olfactory mucosa located posterosuperiorly to prevent postoperative anosmia. Our third incision involves a vertical cut that connects the most anterior aspects of the first two incisions. The PNSF is then elevated anteroposteriorly using a Cottle elevator in a submucoperichodrial and submucoperiosteal plane until the choana is reached. We then perform a relaxing incision along the arc of the choana for flap mobilization and to increase surgical freedom. Typically, a flap extending to the nasal floor laterally, the collumella anteriorly, the choana posteriorly, just under the nasal bone anterosuperiorly, and just beneath the cribriform posterosuperiorly is adequate for coverage of the entire anterior skull base in our experience.
After EEA and resection of the tumor, approximately 1 cm of mucosa circumferentially surrounding the skull base defect is denuded to prevent trapping of the sinus mucosa and subsequent mucocele formation . The sphenoid sinuses (including lateral recesses) are denuded of mucosa in the transsellar and transplanum transtuberculum EEAs to prevent sphenoid sinus mucocele formation . This is also performed in cases of large lateral sphenoid defects with high-flow intraoperative CSF leaks. Denuding of the circumferential mucosa also has additional benefits including greater PNSF adherence to the bone, and prevents residual intervening mucosa from causing delayed flap dehiscence. A multilayer closure is subsequently performed. Our technique for multilayer closure of high-flow CSF leaks and our postoperative management after PNSF repair of large skull base defects have previously been described .
2
Materials and methods
2.1
Experimental design and study population
A retrospective analysis was performed between December 2008 and March 2012 to identify patients who underwent skull base surgery via an EEA approach where the PNSF was harvested early during the procedure (early harvest). We defined early harvest as intentional harvest of the PNSF during initial endonasal exposure of the skull base defect. Exclusion criteria included patients with small skull base defects (i.e. encephaloceles and spontaneous CSF leaks) since these small defects are typically treated without a PNSF in our institution. Patients with traumatic high-flow CSF leaks with large skull base defects that were repaired with a PNSF were included in this study. Patient age, sex, diagnosis, surgical procedure, repair technique, and use of PNSF were documented.
2.2
Data analysis
Data analyses were performed using Microsoft Office Excel 2007 (Microsoft Corp., Redmond, WA). The protocol for this study was reviewed and approved by the Institutional Review Board of the University of Medicine and Dentistry of New Jersey – New Jersey Medical School, Newark, New Jersey.
2.3
Surgical procedure
The PNSF is harvested at the beginning of the operation for cases in which the senior authors (JAE and JKL) anticipate a high-flow CSF leak. These included all cases with intradural pathology, extradural pathology with dural and intradural involvement, and pituitary adenoma with anticipated large skull base and dural defects. The PNSF is placed in the nasopharynx or maxillary sinus during tumor resection or leak site preparation. Our PNSF design is typically tailored to the expected type of defects which we term “target-specific- flap design.” Consequently, not all PNSF are designs identically. We have previously described our technique and nuances for harvesting the flap for transcribriform , transplanum , and transclival defects . While harvesting the flap, the first incision is made at the junction between the floor of the nose and the nasal septum starting from a posterior to anterior course. In cases in which the maximum PNSF size is desired, this incision can be taken more laterally along the floor of the nose or under the inferior turbinate in order to include the soft tissue covering of the nasal floor as part of the flap. When this variation is performed, care should be taken not to injure the nasolacrimal duct opening (Hasner’s valve) in order to prevent postoperative epiphora. The next incision is made from the most inferior aspect of the sphenoid opening and is advanced anterosuperiorly until the preferred length is attained. This incision can be made as far anterior as the septocolumellar junction if a longer PNSF is necessary (typically for cribriform defects extending to the frontal sinus posterior table). If possible, we attempt to preserve the olfactory mucosa located posterosuperiorly to prevent postoperative anosmia. Our third incision involves a vertical cut that connects the most anterior aspects of the first two incisions. The PNSF is then elevated anteroposteriorly using a Cottle elevator in a submucoperichodrial and submucoperiosteal plane until the choana is reached. We then perform a relaxing incision along the arc of the choana for flap mobilization and to increase surgical freedom. Typically, a flap extending to the nasal floor laterally, the collumella anteriorly, the choana posteriorly, just under the nasal bone anterosuperiorly, and just beneath the cribriform posterosuperiorly is adequate for coverage of the entire anterior skull base in our experience.
After EEA and resection of the tumor, approximately 1 cm of mucosa circumferentially surrounding the skull base defect is denuded to prevent trapping of the sinus mucosa and subsequent mucocele formation . The sphenoid sinuses (including lateral recesses) are denuded of mucosa in the transsellar and transplanum transtuberculum EEAs to prevent sphenoid sinus mucocele formation . This is also performed in cases of large lateral sphenoid defects with high-flow intraoperative CSF leaks. Denuding of the circumferential mucosa also has additional benefits including greater PNSF adherence to the bone, and prevents residual intervening mucosa from causing delayed flap dehiscence. A multilayer closure is subsequently performed. Our technique for multilayer closure of high-flow CSF leaks and our postoperative management after PNSF repair of large skull base defects have previously been described .
3
Results
A total of 87 patients with a PNSF harvested early in the case (because of anticipated large defects with high-flow CSF leaks) who met the inclusion criteria were identified and are included in this analysis. The overall mean age was 47.1 years (range, 12–81 years). There were 51 females (59%) and 36 (41%) males. Of these 87 patients, 86 PSNF (98.9%) were utilized to repair the skull base defect due to the presence of high-flow intraoperative CSF leaks. One (1.1%) skull base defect was not repaired with the harvested PNSF because a high-flow intraoperative CSF leak was not encountered. The PNSF was replaced in its anatomic position to redrape the nasal septum. This patient was a 15 year-old female with a massive right anterior skull base osteoblastoma removed endoscopically. She developed intradural recurrence of her disease 8 months later, and underwent endoscopic re-resection of the cribriform osteoblastoma. The created 5.0 cm 2 skull base defect was subsequently repaired using the previously harvested PNSF ( Figs. 1–3 ). In 9 other patients out of the 87 cases (10.3%), the PSNF was successfully taken down and reused for revision surgery. In total, 96 skull base defects with high-flow CSF leaks were repaired using the PNSF. Repair sites included 47 sellar (including 2 revision cases: 1 recurrence and 1 residual tumor), 24 planum/tuberculum (6 revision cases: 3 CSF leaks and 3 residual tumors), 19 cribriform (1 revision for a hematoma), 4 clival, and 2 lateral sphenoid recess defects. The postoperative CSF leak rate in these cases was 3.1%. In all cases of early harvest, the PNSF was adequate to cover the skull base defect.
