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. 2013 Dec;74(6):369-85.
doi: 10.1055/s-0033-1347368. Epub 2013 Jun 17.

The extended nasoseptal flap for skull base reconstruction of the clival region: an anatomical and radiological study

Maria Peris-Celda  1 , Carlos Diogenes Pinheiro-Neto  2 , Takeshi Funaki  1 , Juan C Fernandez-Miranda  3 , Paul Gardner  3 , Carl Snyderman  2 , Albert L Rhoton  1
Affiliations

The extended nasoseptal flap for skull base reconstruction of the clival region: an anatomical and radiological study

Maria Peris-Celda et al. J Neurol Surg B Skull Base. 2013 Dec.

Abstract

Objective Reconstruction of large clival defects after an endoscopic endonasal procedure is challenging. The objective is to analyze the morphology, indications, and limitations of the extended nasoseptal flap, which adds the nasal floor and inferior meatus mucosa, compared with the standard nasoseptal flap, for clival reconstruction. Design Twenty-seven sides of formalin-fixed anatomical specimens and 13 computed tomography (CT) scans were used. Under 0-degree endoscopic visualization, a standard flap on one side and an extended flap on the other side were performed, as well as exposure of the sella, cavernous sinus, and clival dura mater. Coverage of both flaps was assessed, and they were incised and extracted for measurements. Results The extended flap has two parts: septal and inferior meatal. The extended flaps are 20 mm longer and add 774 mm(2) of mucosal area. They cover a clival defect from tuberculum to foramen magnum in 66.6% cases and from below the sella in 91.6%. They cover both parasellar and paraclival segments of the internal carotid arteries. The lateral inferior limits are the medial aspect of the hypoglossal canals and Eustachian tubes. CT scans can predict the need or limitation of an extended nasoseptal flap. Conclusions The nasal floor and inferior meatus mucosa adds a significant area for reconstruction of the clivus. A defect laterally beyond the hypoglossal canals is not likely covered with this variation of the flap. Preoperative CT scans are useful to guide the reconstruction techniques.

Keywords: cerebrospinal fluid leak; clival reconstruction; endoscopic endonasal; nasoseptal flap; skull base.

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Figures

Fig. 1
Fig. 1
Technique of the extended nasoseptal flap performed with electrocautery (endoscopic tip) in an anatomical specimen, left side. (A) View of the inferior and middle turbinates. (B) Middle turbinate. (C) The middle turbinate is resected to increase the space to perform the flap. (D) The sphenoid ostium is found medial to the superior turbinate. (E) The incision begins below the ostium directed medially to the septum. (F) The incision runs parallel to the cribriform plate preserving the olfactory mucosa superiorly up to the attachment of the middle turbinate anteriorly. (G) At the level of the middle turbinate attachment, the incision is directed upwards to the dorsum. (H) The incision performed anteriorly in the dorsum. (I) Most anterior part of the incision in the septal cartilage (yellow arrows). (J) Gentle elevation of the inferior turbinate. (K) The anterior part of the inferior turbinate attachment is cut to allow more freedom for its superior dislocation. (L) Superior dislocation of the inferior turbinate. The septum acts as a buttress that holds the turbinate, facilitating the posterior and lateral flap incisions. (M) Inferior meatus and nasal floor after dislocation of the inferior turbinate. (N) Posterior incision in the septum (yellow arrows) and in the septal floor between the hard and the soft palate (arrowheads). (O) Lateral incision in the axilla of the inferior turbinate in the inferior meatus (green arrows). (P, Q) Dissecting the mucosa of the flap laterally. (R) Raising the flap medially and inferiorly. (S) Dissecting the flap from the septum. (T) Image of the nasal floor with the flap dissected superiorly. (U) The flap completely dissected laterally. The posterior septal arteries can be visualized in the mucosa of the septum. (V) The flap stored in the nasopharynx. Inf. Meatus, inferior meatus; Inf. Turb, inferior turbinate, Mid. Turb. Attach., middle turbinate attachment; Mid. Turb, middle turbinate; Post Sept. A, posterior septal artery; Septal Cart., septal cartilage; Sphen. Ostium, sphenoid ostium; Sup. Turb, superior turbinate.
Fig. 2
Fig. 2
The extended nasoseptal flap. (A, B) Steps of the septal incisions: (1) Incision parallel to the skull base below the sphenoid ostium to preserve the olfactory mucosa. (2) Anterior cut through the dorsum of the nose that extends laterally to the inferior meatus. (3) The anterior attachment of the inferior turbinate can be cut to elevate it easily. The turbinate is held by the septum after its elevation, creating a tunnel. (4) Posterior septal cut that extends across the junction between the hard and soft palate to the lateral nasal wall. (5) Lateral incision below the inferior turbinate attachment that extends significantly the surface of the nasoseptal flap. The blue line in A represents the inferior incision at the junction of the septum and the nasal floor in the standard nasoseptal flap. (C) Detail of the inferior turbinate elevation. The cut at the inferior turbinate axilla (step 3) is optional but facilitates the dissection.
Fig. 3
Fig. 3
Right extended nasoseptal flap and left standard nasoseptal flap of the same specimen. The nasal floor and inferior meatus add a significant surface for clival reconstruction although the width of the defect is more limited inferiorly. The measurements common to both flaps are D, distance from the superior to the inferior pedicular point (orange dots); I, distance in the vertical plane between both pedicular points; A, anteroposterior distance from the superior point of the pedicle to the anterior part of the flap; B, distance from the inferior point of the pedicle to the anterior part of the flap, parallel to A; C, anteroposterior distance in the floor of the standard flap and meatal part in the extended flap. The measurements that differ in the extended versus standard flap are G′ anteroposterior distance in the transition between the septal surface and the meatal surface of the extended flap. G′, anteroposterior distance in the inferior part of the extended flap that corresponds to the lateral incision; E, height of the flap in the pedicular part (up to the inferior incision in the standard flap and to the lateral incision in the extended flap); J, height of the extended flap in the pedicular part up to the nasal floor; F height of the flap in the anterior part at the level of the middle turbinate (up to the inferior incision in the standard flap and to the lateral incision in the extended flap), The green line with blue, red, yellow, and green dots represents the reference points for the radiological study (points 1 to 4).
Fig. 4
Fig. 4
Measurements in computed tomography (CT) scans. (A) Clival measurements in sagittal CT scans in anatomical specimens. K, measurement from tuberculum to foramen magnum adapted to the contour of the sella; L, distance from the inferior part of the sella to the foramen magnum. (B) Some measurements taken of the extended nasoseptal flap were translated to the CT scan of the same specimen. Point 1 represents a position immediately lateral and inferior to the sphenoid ostium, point 2 represents the inferior part of the pedicle, point 3 represents the junction of the septal and inferior meatal part of the flap, point 4 represents the inferior part of the flap. Point 2 is located at D distance from point 1, point 3 is located at distance J from point 1 and point 4 at distance E from point 1. (C and D) The measurements were taken considering two different positions of the flap to cover clival defects in reconstruction: tuberculum (C) and infrasellar (D). The blue line represents the oblique axial plane used for the measurements in the tuberculum and infrasellar position for point 1, and the parallel planes below this one for points 2 (red line), 3 (yellow line), and 4 (green line). The measurements in the CT in the axial plane are infraestimated for the infrasellar position, as the flap has more room to be tilted and adapted (orange arrow and blue dots). (E–H) Measurements in the tuberculum position; all of them have been repeated for the infrasellar position. (E), Measurement in point 1 (superior part of the flap), in the plane shown with the blue line in C up to the same level contralaterally. The flap would ideally need to cover at least both carotid arteries, cavernous sinus, and tuberculum. (F) Plane parallel to E (red dotted line in C), measurement from point 2 covering the same areas as in E. (G, H) These CT planes (yellow and green dotted lines) are parallel to previous ones. The flap in points 3 and 4 is free from the pedicle and only the osseous structure to cover has been considered in a curved and linear fashion, not the distance from the point to the target. The clival resection has been considered restricted laterally by the Eustachian tubes when visible (blue dashed lines in G) or medial hypoglossal canals in H (blue arrows). Sphen. Ostium, sphenoid ostium.
Fig. 5
Fig. 5
The standard and extended nasoseptal flap dissected in an anatomical specimen cut in the sagittal plane. (A) Standard nasoseptal flap on the left side, the superior incision is performed below the sphenoid ostium, preserving the olfactory mucosa superiorly, the inferior incision is placed in the junction between the floor and the septum. (B) Extended nasoseptal flap on the right side, showing the septal part (perichondrial-periosteal surface). (C) Standard nasoseptal flap reflected laterally. In the reconstruction, the flap will be placed in the opposite direction with the perichondrial-periosteal surface facing the defect. (D) The extended nasoseptal flap completely dissected. This flap has two parts: the septal part, which is superior and common to the standard flap, and an inferior portion; the inferior meatal part includes the mucosa over the nasal floor and inferior meatus. (E) The standard flap can be placed over the clivus in an oblique inferior fashion. The pedicle has to be folded downward, which reduces the effective surface for reconstruction. This flap limits both the width of the clival defect and the craniocaudal extension that can be covered. (F) Extended flap dissection that shows both parts of the flap. (G) The standard flap has been placed in a horizontal fashion. Although it does not cover in the studied cases a panclival approach defect, it would be suitable for smaller defects craniocaudally but would cover wider defects in the axial plane, such as contralateral cavernous sinus or even middle fossa in certain cases. (H) Placement of the extended nasoseptal flap toward the clivus. In this specimen it would cover the defect down to the foramen magnum. This flap gives valuable additional surface for reconstruction inferiorly. Ext. Nasoseptal Flap, extended nasoseptal flap; Front. A., frontopolar artery; Inf. Meatal Part, inferior meatal part; Inf. Turb., inferior turbinate; Mid. Turb, middle turbinate; Nasoseptal Flap Perichon.-Periost., nasoseptal flap perichondrial. periosteal. surface; Orb. A., orbitofrontal artery; Olf. Mucosa, olfactory mucosa; Sphen. Ostium, sphenoid ostium.
Fig. 6
Fig. 6
Pictures showing the coverage area of the extended nasoseptal flap. (A-D). View with the 0-degree endoscope. (A) The clivus has been drilled and the clival dura mater exposed below the sella with the anterior arch of C1 partially exposed as a reference. The inferior limit of the foramen magnum and medial limit of the hypoglossal canals are represented with the green dashed lines. The extended flap on the left side is folded superiorly, showing its perichondrial surface. (B) The extended flap is being positioned over the clivus. (C) Extended flap placed over the clivus below the sella. Both parts of the flap, septal and meatal, can be recognized with orange and green dashed lines. (D) In this specimen the flap covers the surface from the tuberculum to the foramen magnum and its septal part laterally covers completely both parasellar carotid segments and cavernous sinus. When placed over the tuberculum recess, the weakest coverage point is the superior aspect of the ipsilateral carotid artery that requires more attention when placing the flap. (E) Anatomical specimen cut in the coronal plane. The clivus has been drilled and the dura mater resected. The border of the foramen magnum and anterior arch of C1 have been kept intact, as have the hypoglossal canals. The Eustachian tubes are displaced to the side. (F) The extended nasoseptal flap covers the sellar region and clivus up to the foramen magnum in 66% of cases. It covers the hypoglossal canals but does not reach the jugular foramina laterally. Car. A., carotid artery; Cerv. Seg., cervical segment of the internal carotid artery; CN, cranial nerves; ET, Eustachian tube; Ext. nasoseptal flap, extended nasoseptal flap; Hypogl., hypoglossal; For. Mag., foramen magnum; Inf. Meatal Part, inferior meatal part; Med. Hypogl. Canal, medial hypoglossal canal; Pit. Gland, pituitary gland; Seg., segment; Tuberc. Recess, tuberculum recess; Vidian N., vidian nerve.
Fig. 7
Fig. 7
Nose dissection. (A) Sagittal nasal dissection on the left side at the level of the middle turbinate. (B) View of the nasal septum. (C) Nasal septum after mucosal resection that shows its structure: the perpendicular plate of the ethmoid superiorly, vomer inferiorly, and quadrangular cartilage anteriorly. (D) Septal mucosa of the right-side periosteal-perichondrial surface. The posterior septal arteries—branches of the sphenopalatine artery—provide vascularization to the extended and standard nasoseptal flap. Ethmoid Perp. Plate, perpendicular plate of the ethmoid bone; Mid. Turb., middle turbinate; Odont., odontoid; Post. Septal Aa., posterior septal arteries; Quad. Cart., quadrangular cartilage; Sphen. Sinus, sphenoid sinus.
Fig. 8
Fig. 8
Predictive model to estimate the flap coverage with a preoperative computed tomography (CT) scan. After the measurements explained in these pictures are estimated, the process is the same as described in Figure 4. (A) Predictive A is calculated in the septum from a point inferior to the sphenoid ostium (seen in a more lateral CT plane) to the dorsum of the nose. (B) Predictive G′ is obtained lateral to the septum measuring the hard palate. (C) Predictive G is measured as an anteroposterior distance below the inferior turbinate attachment (orange dashed line). (D) Predictive J is taken in the coronal plane, inferior to the sphenoid ostium (seen in a more posterior coronal plane) to the septum-floor junction and extended to the posterosuperior aspect of the inferior meatus to obtain E. These two measurements are taken in a coronal plane located at the level of the junction between the soft and hard palate.
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