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Reconstruction after transtuberculum and transplanum approaches to suprasellar pathology
Introduction
Endoscopic reconstruction following transtuberculum and transplanum approaches to suprasellar pathology is an area of ongoing evolution. The cornerstones of endoscopic repair remain similar to open surgical approaches with the aims of reestablishing separation of the cranial vault and sinonasal cavity and preventing postoperative cerebrospinal fluid (CSF) leak.
Since the inception of endoscopic endonasal approaches (EEAs) to intracranial pathology, anterior skull base reconstruction has continued to evolve, including vascularized and nonvascularized techniques. In original descriptions of these techniques, CSF leak rates were in excess of 30% from early reconstructive efforts. The introduction of vascularized flaps vastly improved postoperative CSF leak rates to 3.1% to 8.3%. Advancements in endoscopic instrumentation, neuronavigation systems, and improved understanding of surgical corridors have allowed endoscopic skull base surgery to push the limits in minimally invasive surgical resection and reconstruction including trans-planar and trans-tubercular approaches. , , With increased complexity of intradural and extradural expanded approaches, the need for robust, reliable reconstructive options has similarly increased. ,
Reconstruction following transtubercular and transplanum approaches for suprasellar pathology brings unique challenges because of larger dural defects, high-flow CSF leaks, and more extensive intracranial dissection. With these challenges, techniques used to repair small, transsellar defects do not demonstrate the same efficacy following transtubercular and transplanum approaches. , , To address suprasellar pathology, a thorough understanding of the reconstructive ladder and surgical techniques for both nonvascularized and vascularized skull base repair is paramount. ,
Historical perspective on reconstructive approaches
Nonvascularized reconstructive options: Autografts
An autograft is harvested from native donor patient tissue and transplanted to the recipient site without vascular supply. , Fat, muscle, fascia, bone, cartilage, pericranium, perichondrium, and mucosa have all been described for use of anterior skull base repair. The first report of endoscopic endonasal application of a free tissue onlay graft for the treatment of CSF rhinorrhea was made by Wigand in 1981. Following this pioneering work, endoscopic free mucosal graft harvests were described from the septum by Mattox and Kennedy in 1990, turbinates by Lee et al. in 2004, and the nasal floor by Suh et al. in 2012. In 1989, Papay et al. described a case series of four patients in which transsphenoidal endoscopic repair of CSF leaks was addressed using a fascia lata free graft augmented with quadricep muscle and fat. Subsequently, the bilayered fascia lata button graft was originally described in 2010 by Luginbuhl et al. for reconstruction of high-flow, open-cistern defects commonly seen in suprasellar pathology. This technique allowed the authors to decrease postoperative CSF leak rates in high-flow, open-cisternal cases from 45% to 10%.
Other methods of nonvascularized reconstruction of tuberculum defects were described by Ceylan et al. in 2010 using a multilayer closure. The reconstruction demonstrated in this case-series used autogenic fat inserted into the defect cavity, subdural inlay placement of DuraGen, epidural inlay placement of autogenic fascia lata, and methyl methacrylate fixed onto the defect. Mucoperichondrium from the middle turbinate was then placed as an onlay graft followed by fibrin glue and inflated 12-Fr balloon. Notably, this technique did not rely on a vascularized nasoseptal flap (NSF). Modern use of adjunctive autografts, such as fat or fascia lata, are commonly used alongside pedicled flaps.
Nonvascularized reconstructive options: Allografts
Early description of the use of acellular human cadaveric dermis, such as AlloDerm (LifeCell Corp.) in skull base surgery was made by Citardi et al. in 2000. From 1997 to 1999, the authors describe sellar reconstruction with AlloDerm, including patients with suprasellar pathology without postoperative CSF leak.
Similarly, the use of collagen matrix allografts emerged in the late 1990s with applications in spinal dural repair. Narotam et al. performed a retrospective review from 1995 to 2003 for patients who underwent repair and regeneration using the collagen matrix graft DuraGen (Integra Lifescience Corp.) with successful results. DuraGen was later described by Harvey et al. for successful close of large skull base defects. In 2011, Zanation et al. described use of DuraGen to obliterate intradural dead space followed by an epidural inlay graft of acellular dermis such as AlloDerm. The authors suggest the pliability, texture, ease of sizing, and handling characteristics of these grafts allow the endoscopic skull base to tackle the challenges of transtubercular and transplanum reconstruction.
Vascularized reconstructive options: The nasoseptal flap
Because the NSF has an ideal central location, robust vascular supply, and limited donor site morbidity and affords wide coverage area, it is considered the modern workhorse of endoscopic skull base reconstruction. Anatomic and radiographic studies suggest the NSF provides adequate coverage of an average reconstructive area of 17.12 cm. , Hadad et al. are credited for the modernization and expansion of utility of the NSF from 2006 with their description of large dural reconstruction following endoscopic skull base surgery.
Modern use of the NSF in transsphenoidal, transplanum, and transtuberculum approaches has been described by Liu et al in which an autologous fascia lata graft is placed as a subdural inlay graft, stamp-sized pieces of Surgicel (Ethicon) are placed over the bony defect and a vascularized NSF is rotated superiorly to cover the dural and bony skull base defects. This is followed by placement of a thin layer of tissue sealant such as DuraSeal (Covidien) or Tisseel (Baxter) fibrin glue, Gelfoam pledgets, and nasal packing.
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