Chapter 34 The Pedicled Nasoseptal Flap
Until 2006, the only options for the endoscopic reconstruction of large skull base dural defects were the use of nonvascularized tissue grafts and of synthetic materials. The high postoperative cerebrospinal fluid (CSF) leak rate (12–20% for anterior skull base resection of sinonasal tumors, and even more unacceptable figures after the first endoscopic endonasal approaches [EEAs]) resulting from these reconstructive surgeries was the major obstacle to widespread acceptance of extended EEAs.1,2
To provide some history, the idea of developing the nasoseptal flap began in the early 1990s and came about due to a feeling of helplessness experienced by its authors when performing endoscopic surgery of the facial sinuses. During these procedures, an intraoperatory injury to the roof of the sinuses would sometimes occur with the consequent development of a CSF leak. At that time, nonvascularized free tissue grafts or synthetic materials were the only options available for closing the defect, both of which resulted in extremely low success rates. Faced with this problem, the authors hypothesized as to the possibility of imitating head and neck reconstructive surgery, which uses large vascular pedicles in trapezius, pectoralis, and temporal flaps. They then began their search for potential endonasal mucosal tissue donor sites that had their own vascular pedicle, encouraged by the words of Professor Mario Piazza, MD: “If it does have a pedicle, it will seal the defect.”
The pedicled nasoseptal flap (PNSF) was developed in the year 1996, at the Morphological Sciences Museum of the School of Medicine of the National University of Rosario, Argentina. Following this concept of obtaining a vascular pedicle, the authors further developed two additional flaps: the H-B 2 Flap (Anterior Pedicled Lateral Nasal Wall Flap) and the Carrau–Hadad flap (Posterior Pedicled Lateral Nasal Wall Flap).3
The PNSF became the method for the reconstruction of skull base defects, with a considerably high success rate and a marked decrease in both morbidity and mortality after the procedure. Counting on a defect closure resource that was both effective and safe, surgeons began to perform broader and more satisfactory resections. In time, the PNSF inspired other authors around the world to design other flap variants. Current skull base surgery demands that surgeons master each and every technique.2,4–13
The Hadad-Bassagaisteguy flap has become the workhorse for large skull base dural defects.
The HADAD flap consists of a vascularized pedicled flap harvested from the mucoperichondrial and mucoperiosteal coverage of the nasal septum. It is supplied by the nasoseptal artery, which stems from the sphenopalatine artery, terminal branch of the internal maxillary artery.7,13–18
The HADAD flap is considered the workhorse for the reconstruction of large (>2 cm) cranial base dural defects after EEAs. It is also indicated, independently of the size of the dural defect, for patients with high CSF leakage risk factors.1,2,8,13,17,19–24 These factors include the following:
Certain body habitus: a high body mass index is associated with high intracranial pressure.
Pathology to be treated: craniopharyngiomas and lesions involving the arachnoid cisterns.
Entry in arachnoid cisterns or ventricles.
Site and size of the defect.
Cushing′s disease with extrasellar adrenocorticotropic hormone–secreting tumors, because of the impaired wound healing response.
History of previous chemoradiation therapy.
34.3 Tips and Tricks
The PNSF design must be tailored to the anticipated size and location of the skull base defect resulting from the surgery. This is called “target-specific flap design.”21 If a large cribriform resection is necessary (transcribriform approaches in olfactory groove meningiomas or sinonasal tumors), it is convenient to harvest large flaps that extend as far anteriorly as the septocolumellar junction. These transcribriform defects are normally broader, stretching from one medial orbital wall to the other. As a consequence, an increase in the width of the flap is needed. This is achieved by expanding the incision further laterally along the mucoperiosteum of the nasal floor (hard palate). Adequate coverage of the skull base defect must be ensured. Never underestimate the size of a defect. Rather, harvest a larger flap.
The HADAD flap:
Has a wide rotation arc.
Renders a customizable surface area and target-specific flap design.
Can be stored in the maxillary sinus or nasopharynx during approach and resection phases.
Promotes quick healing.
Allows complete endonasal procedure.
Permits bilateral tailoring.
34.5 Surgical Steps
34.5.1 Posterior and Inferior Incision
Begin the posterior incision on the lateral nasal wall, right anteriorly to the anterior lip of the torus tubarius, and follow the line of the posterior choanal arch. In doing, so you will harvest a considerably long and mobile pedicle. Ensure that there is hard bone underlying your incision and cut to the bone ( Fig. 34.1 ). Once you have got to the free posterior edge of the septum, move slightly anteriorly (5–8 mm, so as to avoid injuring the soft palate vessels when coming to the floor of the nose; Fig. 34.2 ). Then reach the floor of the nose and start moving anteriorly while carrying out the inferior incision until you arrive at the transitional skin of the septocolumellar junction ( Fig. 34.3 ).
This incision can be extended laterally along the nasal floor, toward the inferior meatus, to harvest more tissue (floor component; Fig. 34.4 ).
34.5.2 Superior Incision
Commence the superior incision at the most inferior aspect of the sphenoid ostium ( Fig. 34.5 ); then advance anteriorly, cutting along the transected middle turbinate line at approximately 1.5 cm below the skull base. This will add to the preservation of the olfactory epithelium. A tendency exists to go downward as the incision is brought anteriorly, resulting in an inadequate flap. Using the transected middle turbinate line for guidance will help you fight this tendency. When the head of the middle turbinate has been reached, proceed upward until you get to the top of the nasal septum (there is no olfactory epithelium at that level) and once there, extend your cut to the septocolumellar junction ( Fig. 34.6 ).