Updates in reconstruction of skull base defects.

REVIEW URRENT C OPINION

Updates in reconstruction of skull base defects Devyani Lal and Rachel B. Cain

Purpose of review Skull base surgery has undergone a fundamental transformation with the development and rapid adoption of endoscopic endonasal expanded approaches. Defects created from these newer approaches have necessitated an evolution of novel reconstructive techniques, which are reviewed here. Recent findings New reconstructive techniques continue to be developed for repairing surgical defects from endoscopic endonasal skull base resections. Improvisations also allow well known flaps to be used in these approaches. Long term outcomes from repair using some of these techniques are now becoming available. Summary Endoscopic resection of previously unapproachable skull base lesions has become possible with advancements in technology, as well as reconstructive methods. These newer techniques may offer improved outcomes and lower morbidity over conventional surgery. Keywords cranial base reconstruction, endoscopic endonasal expanded approach, inferior turbinate flap, nasoseptal flap, pericranial flap, skull base reconstruction, temporoparietal fascial flap

INTRODUCTION The skull base (cranial base) is the region separating the brain from the cervicofacial structures. On the basis of its relationship with the corresponding cranial fossa, the skull base is divided into the anterior, middle and posterior cranial fossa [1]. The term ‘central’ skull base is often used to refer to the midline area at the junction of the anterior, middle and posterior cranial fossa and first two cervical vertebrae. The skull base harbors critical neurovascular structures, and surgery in this complex area is difficult.

EVOLUTION OF SKULL BASE SURGERY AND RECONSTRUCTION Although pituitary surgery was described by Cushing in 1914, [1] and Ketcham described the anterior craniofacial resection in 1963, [2] the modern era of skull base surgery did not begin until the 1980s [1,2,3 ]. The invention of high-definition endoscopes and monitors, computer-aided navigation, high-speed drills and instrumentation, as well as the experience gained from endoscopic sinonasal surgery have now led to the evolution of endoscopic expanded endonasal approaches (EEEA) to the cranial base. Novel vascularized reconstructive methods providing reliable airtight and watertight

seals have been critical to the development and adoption of these techniques [4,5]. This review will focus on recent advances in anterior and central skull base reconstructive techniques, as most novel advances pertain to the EEEA.

GOALS OF SKULL BASE RECONSTRUCTION Surgical resection of cranial base lesions, trauma and iatrogenic injury during sinonasal, otologic or orbital surgery are the most common causes of defects in the skull base. The excised tissue may include dura, cranial bone, scalp, facial skin and skeleton, orbit, temporal bone, ear, maxilla and mandible. The general goals of reconstructing any skull base defect are as follows: (1) dural defect repair to create a watertight and airtight seal,

&

Department of Otorhinolaryngology - Head and Neck Surgery, Mayo Clinic, Phoenix, Arizona, USA Correspondence to Devyani Lal, MD, Consultant in Otorhinolaryngology, Mayo Clinic, Assistant Professor, Mayo Clinic College of Medicine, 5777 E. Mayo Blvd, Phoenix, AZ 85054, USA. Tel: +1 480 342 2890; fax: +1 480 342 2626; e-mail: [email protected] Curr Opin Otolaryngol Head Neck Surg 2014, 22:419–428 DOI:10.1097/MOO.0000000000000082

1068-9508 ß 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

www.co-otolaryngology.com

Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

Head and neck reconstruction

KEY POINTS Development of novel endoscopic vascularized pedicled flaps has revolutionized skull base surgery, leading to the evolution of endoscopic expanded endonasal approaches. New ‘secondary’ flaps have been developed for situations in which the nasoseptal flap is not usable. Improvisations in some previously described pedicled and free flaps have made these suitable for endoscopic surgical defects. Multilayered repair using a combination of grafts and flaps, or a combination of endoscopic and external vascularized flaps, can be used for reconstruction of larger skull base defects.

FREE GRAFTS (TABLE 1; PART A) Autografts (such as fascia, mucosa, fat, bone and skin) can be obtained from nondiseased parts of the patient. These pieces of free, nonvascularized tissue can be used to repair small ASB defects. In larger defects, poor vascularization of free grafts can result in CSF leak, pneumocephalus, meningitis and even death. Fascial grafts (pericranium, temporal fascia and fascia lata) can be used for single or multilayered closure. Mucosa harvested from the nasal floor or contralateral septum can be used as an overlay graft. Free bone grafts can be harvested from septal bone or the middle turbinate in endoscopic techniques, and split thickness calvarial grafts can be obtained in external resections. Although some authors recommend osseous repair for skull base defects over 1 cm in size, Eloy et al. [9 ] have recently published that even larger ASB defects from tumor resection do not develop CSF leakage or brain sagging in the absence of osseous reconstruction. Allografts (lyophilized dura, acellular dermis, freeze-dried bone and fibrin glue) and xenografts (bovine collagen matrix and pig submucosa) from various sources are commercially available. These are usually used to supplement repair in multilayered closure. Artificial biomaterials, such as Gelfoam (Pharmacia, Kalamazoo, Michigan, USA), hydroxyapatite and bioabsorbable acrylic plates, have also been described. Internal carotid artery aneurysm attributed to a bioabsorbable plate used for sellar reconstruction has recently been published [10]. Allografts are conventionally thought to be inferior to autografts. However, Casiano et al. [11] have previously described their use of allografts without vascularized flaps in large endoscopic ASB defects. The same group also recently described the use of acellular dermis (Alloderm, LifeCell Corporation, Branchburg, New Jersey, USA) and fat grafts in sellar reconstruction. This retrospective study compared sellar repair with fat autograft versus inlay acellular dermis in 429 patients without intraoperative lumbar drainage. Intraoperative CSF leak occurred in 160 cases (35.5%). Of these, 95 underwent repair with acellular dermis and 46 with fat autograft, with postoperative CSF leak rates of 8.4 and 15.2%, respectively (P ¼ 0.34); 19 patients underwent repair with other techniques or no repair at all, with a postoperative leak rate of 0%. The total postoperative leak rate was 3.9% [12 ]. Porcine small intestinal submucosa (Biodesign, Cook Biomedical, West Lafayette, Indiana, USA) was reported for skull base reconstruction in 155 patients [13 ]. These patients underwent grafting by onlay, inlay or combined techniques in combination with nasoseptal flap (NSF), with or without bone grafts and lumbar drainage. The authors &

Osseous reconstruction may not always be necessary in large anterior skull base resections.

(2) separation of intracranial contents from the adjacent contaminated cavities of the nasopharynx, nose, paranasal sinuses and middle ear, (3) coverage of exposed major vascular structures [internal carotid artery (ICA), vertebral and basilar arteries], (4) vascularized soft tissue coverage in a previously irradiated field, (5) reconstruction of large osseous defects that cause functional or aesthetic deficits, (6) rehabilitation of cosmetically unacceptable defects (from maxillofacial or orbital exenteration).

RECONSTRUCTIVE MATERIAL FOR REPAIR OF SKULL BASE DEFECTS A wide variety of options, ranging from no repair to free grafts, alloplastic implants and vascularized local, regional or free flaps are available. The choice of the reconstructive technique depends on the site of the defect, presence and pressure of cerebrospinal fluid (CSF) leakage and amount and type of tissue needed, as well as availability of donor tissue [6,7,8 ]. The technical expertise of the surgical team, as well as the surgical approach (endoscopic, open or combined open-endoscopic) also affects these choices. Table 1 shows a comprehensive list of reconstructive materials used in repair of skull base defects, along with their salient applications, advantages and drawbacks. The remainder of this article will focus mainly on the reconstruction of anterior and central skull base (ASB) defects. &&

420


&

&

Volume 22 Number 5 October 2014



Overlay graft to cover

Mucosa

Small defects

Allografts and xenografts

Part of multilayered closure

Low-pressure CSF leak

Rarely used

Skin graft


Small defects

Exposed dura

Part of larger defect multilayered closure for defects over 1 cm (optional)


Packing in anterior and lateral skull base defects

Part of larger defect multilayered closure


Part of large defect multilayered closure Small defects


Small defects



Small defects

Indication

Bone

Fat

Pericranium

Fascia lata

Temporalis fascia

A. Free grafts

Technique

Anterior, middle central and posterior

May be grafted on a muscular flap as part of larger multilayered reconstruction

Small cutaneous defects

Anterior and central






Location in skull base most used for

No harvest site morbidity

Ease of harvest

Ease of harvest

Obliterates dead space, helps prevent CSF leakage

Ease of harvest, little donor morbidity

Ease of harvest


Advantages

(Continued )

Risk of infection or hypersensitivity (low)

Unsuitable for larger defects and for major vascular coverage

Unsuitable for large defects

Must be oriented to place submucosal side on the recipient bed

Unsuitable for larger defects and for major vascular coverage

Nonvascularized bone contraindicated if postoperative radiation required

Unsuitable for infected cavity

Loses up to 50% volume over time;

Requires incision in abdomen or thigh

Alopecia

Requires separate surgical site

Unsuitable for larger defects

Disadvantages

Table 1. Materials and techniques used in skull base reconstruction, along with associated indications, applicable locations, advantages and disadvantages

Updates in reconstruction of skull base defects Lal and Cain


421


422


Nasoseptal Flap

D. Endoscopic pedicled

Temporoparietal

Pericranial flap

Long-term risk of mucocele formation

Used as part of multilayered closure May be combined with pericranial flap

Pedicle may have been divided at previous surgery

Limited reach into the most anterior aspect of anterior skull base and lower clivus

Alopecia

Alopecia

Donor site morbidity

Needs repositioning to harvest

May be too bulk

Donor site morbidity

Needs repositioning to harvest

Too bulky

Limited reach to most skull base defects

Unreliable vascularity

Limited soft tissue bulk

Temporal wasting

Limited coverage and soft tissue bulk

Disadvantages

Prolonged crusting at donor site

Reliable vascularity

Ease of harvest

Ease of harvest

Very reliable vascularity

Thin and pliable caliber


Long arc of rotation

Long pedicle





Advantages

Bilateral flaps for larger defects

High-pressure CSF leaks

Anterior and central clival defects

Tunneled into endoscopic Anterior and central defects (nasopharyngectomy)

Large dural defects

Lateral and posterior

Soft tissue defects

Anterior

Lateral

Large dural defects


Can be tunneled through the nasion area into repair of endoscopic resection

Large defects from external approaches

Skin and soft tissue defects

Large skull base defects

Orbital reconstruction


Large soft tissue defect

Latissimus dorsi

Trapezius

Anterior, lateral and posterior


Anterior and lateral

Lateral

Lateral

Lateral


Pectoralis major

Small CSF leak

Small Soft tissue defect

C. Pedicled flaps

Cutaneous defects

Sternocleidomastoid

Small CSF leak

Soft tissue defect

Indication

Cervicofacial

Temporalis muscle

B. Local flaps

Technique

Table 1 (Continued)





Large defects from endoscopic resection by tunneling into defect

Small defects

Temporoparietal

Palatal

Anterolateral thigh

Defects from orbital, nasal or facial exenteration

Large soft tissue defects

Defects from orbital, nasal or facial exenteration


Large defects

Small defects

Middle turbinate

E. Free flaps

Small to moderate skull base defect


Large defects from external and endoscopic resection

Inferior turbinate

Endoscopic Pericranial

Anterior, lateral, posterior and orbital defects

Nasopharyngectomy

Sellar

Anterior

Anterior, lateral, central, nasopharyngectomy, infratemporal fossa

Anterior

Anterior, central and nasopharyngectomy

Anterior, central, posterior, clival and nasopharyngectomy defects

May be harvested with a single or double skin paddles

Can be used as a musculocutaneous or muscular flap

Adequate soft tissue to fill large defects

Ease of harvest

Limited donor site morbidity

Anteriorly based flaps also possible

May be bulky

Compromised by obesity

(Continued )

Difficult reach into most anterior skull base defects and clival defects

Alopecia

May result in vessel torsion

Flap is raised externally and then tunneled into endoscopic defect through the temporal fossa

Difficult to harvest as a mucosal flap

Separation from turbinate bone can lead to tears

Ease of harvest Usually raised as a posteriorly based flap

Limited reach anteriorly, superiorly and into lower clivus

Increased risk of tear with endoscopic technique, especially at the area in which the scalp meets the forehead

Endoscopic harvest is technically more challenging

Limited donor site harvest

Can be tunneled into endoscopic defect site through nasion area

Very reliable vascularity



423


424

Need for intraoperative patient repositioning; shorter pedicle length

Limited soft tissue bulk

Option of vascularized bone harvest with flap


LOCOREGIONAL FLAPS (TABLE 1; PART B AND C) Locoregional flaps have been well described for external approaches, and now modifications allow some of these vascularized locoregional flaps to be used in defects from EEEA [15,16 ,17,18]. However, these flaps provide limited external soft tissue reconstruction. The pericranial flap (PCF) is the workhorse flap for repair of ASB defects when external approaches are used. Modifications now describe endoscopic harvest of the PCF, as well as delivery to endoscopic ASB defects, by means of an opening drilled through the glabella [18]. The superficial temporal fascia, deep temporal fascia, temporalis muscle or parietal bone can also be used as a part of vascularized local flaps both in external and endoscopic approaches. The temporoparietal fascial flap (TPFF) is based on the superficial temporal artery. It can be rotated to seal dural defects in the infratemporal-middle fossa or posterior fossa. The TPFF can be tunneled transpterygoid to repair the nasopharynx and defects created by endoscopic transnasal approaches [16 ,17]. The modified facial artery musculomucosal flap was found to be useful for skull base reconstruction in a recent cadaver study [15]. Endoscopic vascularized techniques to repair skull base defects include the well known pedicled NSF, the inferior turbinate flap and the middle turbinate flap. These are vascularized flaps based on branches of the sphenopalatine artery [4,5,16 ]. The palatal flap based on the greater palatine artery is also described for skull base reconstruction [19]. The inferior turbinate flap can be harvested as either an anteriorly or posteriorly pedicled flap. Whereas Gil et al. [20] have recently published their experience with the anteriorly based flap, Yip et al. [21] have described their successful modification of the posteriorly based inferior turbinate flap in two patients undergoing revision sellar surgery when the pedicled septal flap was not available. The anterior pedicled lateral nasal wall flap was described in three patients with ASB defects by Hadad et al. [22] in 2011. In addition, the PCF and TPFF can also be utilized for endoscopic ASB defects, as described above. The use of ‘secondary’ flaps (situations in which the NSF was not available) was reported in a larger series of endoscopic endonasal skull base reconstructions, in which 34 of 330 flaps (10%) were secondary flaps [16 ]. These included 16 &&

Thin and pliable caliber

Limited bulk Option of vascularized bone harvest with flap

Compromised by obesity; soft tissue contour compromised by atrophy

Donor site morbidity, especially with bone harvest Large, thin, pliable flap with long pedicle

Limited skin and soft tissue coverage

Disadvantages

reported a 94.7% success rate (no CSF leak) at 77 months mean follow-up. The same group also used porcine small intestinal submucosal grafts in orbital wall reconstruction, preventing enophthalmos in 16 of 17 patients [14].

CSF, cerebrospinal fluid.

Large skull base defects Submental


&&

Part of large defect multilayered closure

Lateral skull base defects


Subscapular and parascapular

Anterior

Anterior, lateral, posterior and orbital defects Large skull base defects Rectus abdominis

Large skull base defects Radial forearm


Indication

Anterior, lateral, posterior and orbital defects

&&

Technique

Table 1 (Continued)


Advantages


&&




endoscopic-assisted PCFs, seven tunneled TPFFs, three inferior turbinate flaps, two middle turbinate flaps, two anterior lateral nasal wall flaps, two palatal flaps, one occipital flap and one facial artery buccinator flap. There were 19 anterior cranial fossa defects, 10 clival defects, three sellar defects, one frontal and one lateral orbit/middle fossa defect. Twenty-five of the 34 cases (73.5%) had either prior or postoperative radiation therapy. The most common disease was sinonasal cancer, with 16 cases (47.1%). The postoperative CSF leak rate was 3.6% attributed to one middle turbinate flap necrosis. The authors concluded that ‘secondary flaps’ offer excellent success rates (97%) comparable with those of the NSF (>95%) and recommended that surgical expertise to repair complex skull base defects by multiple flaps must exist in comprehensive skull base surgery centers [16 ]. The use of dual flaps has also been recently reported for larger defects. These include the double pedicled NSF (‘Janus flap’) [23] and the pedicled NSF in combination with the PCF [24 ,25 ]. The use of the mucochondro-osteal flap utilizing a composite flap with septal cartilage and bone in addition to the traditional NSF was recently described for orbital floor reconstruction [26]. In addition, Eloy et al. [27 ] reported a three-layer technique to repair large defects of the ASB. They used an underlay dural reconstruction with fascia lata, followed by an overlay of acellular dermis, and then a final overlay layer of pedicled NSF. Using this technique in 10 patients who underwent endoscopic tumor resection of the ASB with large resultant defects (average cribriform defect size was 9.1; range, 5.0–13.8 cm2), the authors reported a 100% success rate with no CSF leak at 2-year follow-up [27 ]. Complications of the nasoseptal, inferior turbinate and middle turbinate flaps include prolonged crusting at the harvest site, nasal synechia and longterm risk of mucocele formation at the site of repair. Rawal et al. [28 ] have described the ‘nasoseptal rescue flap’ for decreasing postoperative crusting and donor site morbidity. Husain et al. [29] found that none of their 70 patients with repair of anterior cranial defects with the NSF developed mucoceles at mean follow-up of 11.7 months (range, 3–36.9 months). However, their method of ruling out mucocele formation was not described. They attributed their results to careful and wide removal of remnant sinonasal mucosa in the recipient field, as well as meticulous tissue handling in the sinonasal cavity [29]. Bleier et al. [30] found a 3.6% (one of 28 patients) rate of mucocele formation with the NSF. Vaezeafshar et al. [31] reported a case of sphenoid sinus mucocele under a vascularized NSF detected 4 months postoperatively. Nyquist et al. [23] &&

&

&

&

&

&

reported no mucocele formation in five patients who underwent skull base reconstruction using bilateral pedicled NSFs. In our opinion, longer term follow-up is needed to assess this complication.

REGIONAL FLAPS (TABLE 1, PART C) Regional flaps are used for external approaches. The reach of regional musculocutaneous flaps to the skull base is usually limited [3 ]. The inferiorly based trapezius island flap with blood supply from the dorsal scapular artery may be used for lateral skull base defects, both as a deepithelialized or musculocutaneous flap for dural and skin reconstruction, respectively. The latissimus dorsi flap based on the thoracodorsal artery has a very long arc of rotation across the axilla. It can reach most skull base defects, and is primarily used for repair of large soft tissue defects of the lateral cranial base. &

FREE FLAPS (TABLE 1, PART E) Free tissue reconstruction is usually employed for large skull base defects, as well as orbital and maxillofacial defects. Flaps used include the radial forearm flap, rectus abdominis flap, latissimus dorsi flap, anterolateral thigh flap and scapular/parascapular flaps. The indications, applications, advantages and drawbacks of these are well described [3 ] (Table 1, part E). The submental flap has been recently described by our group for repair of large ASB defects, with or without orbital reconstruction (presented at the North American Skull Base Society Meeting, in preparation). The flap is pedicled on the submental artery, a constant branch of the facial artery, with more variable venous drainage via the facial vein, internal jugular or external jugular system. The color match provided for facial defects is unrivaled. Flaps up to 150 cm2 can be harvested without causing significant donor site morbidity [3 ]. Two patients had ASB defects reconstructed using a musculocutaneous submental flap. Because of insufficient venous pedicle length and inadequate arterial vascular supply using a reverse-flow pattern, both flaps were transferred with free arterial and venous anastomoses. The largest flap was 10 cm 6 cm in size. There were no postoperative complications and 100% flap survival. Both patients are currently alive without evidence of disease recurrence. &

&

OUTCOMES FROM ENDOSCOPIC REPAIR OF SKULL BASE DEFECTS &&

Soudry et al. [8 ] performed a systematic review of the literature to assess repair methods of skull base defects from endoscopic skull base surgery. A total of 673 patients were extracted from the 22 case series



425



(level 4). Studies with fewer than five patients were excluded, and reports of successful reconstruction with inferior turbinate flaps, palatal flaps and temporoparietal fascia flaps were not analyzed. The overall postoperative CSF leak rate after intraoperative repair was 8.5%. In patients without evidence of intraoperative CSF leak, no postoperative leaks were reported regardless of the closure technique applied. Patients reconstructed with a vascularized pedicled flap with or without underlying free grafts achieved successful closure in 94%. Multilayered free grafts without a pedicled flap achieved a successful closure rate of only 82%. The lowest success rates occurred when reconstruction was performed with an inlay of fat and bovine collagen matrix material used as inlay and onlay grafts, with a success rate of only 55% (11/20). When the site of defect repair was studied, in the anterior cranial base (planum sphenoidale to posterior frontal sinus table), overall successful closure rate was 92%. Successful closures were described with both nonvascularized and vascularized techniques. In the series describing nonvascularized reconstruction, greater variance in success rates (67–93%) was observed. Free graft closure was less successful (67%) when a communication with the ventricle precluded the use of inlaid fat. Success was equivalent and high in small series using both pedicled vascularized nasoseptal and PCFs (96 and 100%) with underlay grafts. Sellar defects were closed successfully in 93%. Use of vascularized pedicled flaps resulted in excellent (94–100%) results in both high-flow and low-flow intraoperative sellar CSF leaks, whereas use of free graft/biomaterial reconstruction in the setting of a low-flow leak achieved 87–100% success in different series. No data regarding free graft reconstruction of sellar high-flow leaks were found. Clival reconstruction had an overall closure rate of 80%. In the only study presenting nonvascularized flap reconstruction, a 60% success rate was achieved with multilayer free grafts. This success rate improved to 100% when a pedicled septal flap was added as an onlay. Reconstruction of clival defects with free grafts only is likely insufficient [8 ]. The authors were unable to evaluate whether lumbar drain placement affected the outcome of skull base reconstruction. In 57 of 673 (8.5%) patients, primary skull base reconstruction resulted in a persistent postoperative CSF leak. Postoperative CSF leak was successfully managed by lumbar drainage alone in 38% and by revision of the skull base repair, with or without lumbar drain placement in 62%. This level 4 evidence suggests that placement of a lumbar drain may be indicated as a first-line &&

426


treatment for persistent postoperative CSF leak, whereas in cases in which a lumbar drain has already been placed, immediate revision of the reconstruction may be necessary [8 ]. &&

AUTHORS’ APPROACH TO REPAIR OF ANTERIOR AND CENTRAL SKULL BASE DEFECTS Bony defects without CSF leak are either not repaired or repaired with free nasal mucosal grafts. For small (1cm) dural defects and defects with lowpressure CSF leaks, endoscopic repair with free mucosal graft, fascial lata graft or multilayered repair is conducted. Acellular dermis or porcine small intestine submucosal graft is used with autografts in such a multilayered closure. The recipient site is carefully denuded. An underlay technique is preferred, but this may be difficult without enlarging the bony defect in the cribriform area. In such situations, an overlay technique is used. The graft is positioned into place and sealed with fibrin glue. Next, a layer of Gelfoam is placed to prevent adhesion between the graft and any nasal packing. We use nonabsorbable sponge packs for larger defects or high-pressure CSF leak. These are removed after 2–5 days, depending on the size of the defect and the CSF pressure. For dural defects greater than 1 cm or for defects with high-pressure CSF leaks (intracranial hypertension, intraventricular or cisternal communication), we prefer vascularized local flaps. When possible and oncologically sound, the NSF is the vascularized flap of choice. The PCF is the next choice, followed by the TPFF. We use the externally harvested PCF or TPFF, which is then tunneled for endoscopic ASB defects. The inferior turbinate flap is usually used for vascularized coverage of an exposed ICA or for repair of nasopharyngectomy defects. When there is extensive loss of soft tissue, anterior frontal table, or the need for orbital reconstruction from a combined open-endoscopic resection, a locoregional flap or free flap is used. We have previously described the use of the submental flap, as well as the anterolateral thigh flap in situations in which a large component of soft tissue and skin is required, such as in orbital, maxillary or anterior frontal table defects. We have no personal experience outside of the cadaver lab with use of the middle turbinate flap, which we found difficult to reliably harvest and rotate into position without tears, particularly from small or atrophic middle turbinates. We do not use bone grafts or rigid plates routinely in endoscopic repairs. In selected cases, we may use these when high-pressure CSF leaks or very large defects make the primary repair prone to dislodging. Volume 22 Number 5 October 2014



When no loco-regional vascularized flap was available, we successfully used acellular dermis and porcine small intestinal submucosal graft for endoscopic repair of the anterior skull base and sella with a multilayered repair. An inlay–onlay technique with the NSF using fat, fascia lata, acellular dermis/porcine submucosa and fibrin sealant is used. Prior to dural resection, a roughly 1 cm circumferential elevation of dura is performed around the rim of the bony defect. Once the dura has been breached, this elevation is difficult. A piece of fat larger than the size of the bony defect is then positioned to obliterate the intracranial dead space. Next, a fascia lata graft about 50% larger than the defect is placed, such that it can be adequately and circumferentially tucked cranial to the bony ledge. The overlay layer of acellular dermis or porcine submucosa is then laid, and a thin layer of fibrin sealant is used to achieve adherence. This is again followed by placement of Gelfoam and the sponge pack. Nasal packing with nonabsorbable sponges for 3–5 days or longer is used. We consider routine placement of perioperative lumbar drains to be unnecessary for ASB or sellar defects, using them only in cases of persistent postoperative high-pressure CSF leaks.

CONCLUSIONS Development of novel endoscopic vascularized pedicled flaps has revolutionized skull base surgery, leading to the evolution and quick adoption of the EEEA to the skull base. A multilayered combination of grafts and flaps without osseous reconstruction can be used for large cranial base defects. Lumbar drainage is not routinely indicated in repairs, but may be used for drainage before undertaking revision surgery to address persistent CSF leak from failed primary repairs. Novel ‘secondary’ endoscopically harvested flaps and modifications to regional and free flaps have been developed for situations in which the nasoseptal flap is not available. These developments have improved outcomes and decreased complications from resection of even deep-seated skull base lesions. Studies of cranial base reconstruction should report results in a standardized fashion (size and location of defect, CSF pressure, use of lumbar drainage, reconstruction technique and outcome) so as to generate improved quality of evidence and stronger grade of recommendations. Acknowledgements None. Conflicts of interest The authors have no conflicts of interest to disclose.

REFERENCES AND RECOMMENDED READING Papers of particular interest, published within the annual period of review, have been highlighted as: & of special interest && of outstanding interest 1. Cappabianca P, Califano L, Iaconetta G. Cranial, craniofacial and skull base surgery. Milan: Springer; 2010. 2. Ketcham AS, Wilkins RH, VanBuren JM, Smith RR. A combined intracranial facial approach to the paranasal sinuses. Am J Surg 1963; 106:698– 703. 3. Hayden RE, Nagel TH. The evolving role of free flaps and pedicled flaps in & head and neck reconstruction. Curr Opin Otolaryngol Head Neck Surg 2013; 21:305–310. This is a great review on the evolution of flaps used for head and neck reconstruction. 4. Hadad G, Bassagasteguy L, Carrau RL, et al. A novel reconstructive technique after endoscopic expanded endonasal approaches: vascular pedicle nasoseptal flap. Laryngoscope 2006; 116:1882–1886. 5. Snyderman CH, Kassam AB, Carrau R, Mintz A. Endoscopic reconstruction of cranial base defects following endonasal skull base surgery. Skull Base 2007; 17:73–78. 6. Patel MR, Stadler ME, Snyderman CH, et al. How to choose? Endoscopic skull base reconstructive options and limitations. Skull Base 2010; 20:397– 404. 7. Harvey RJ, Parmar P, Sacks R, Zanation AM. Endoscopic skull base reconstruction of large dural defects: a systematic review of published evidence. Laryngoscope 2012; 122:452–459. 8. Soudry E, Turner JH, Nayak JV, Hwang PH. Endoscopic reconstruction of && surgically created skull base defects: a systematic review. Otolaryngol Head Neck Surg 2014; 150:730–738. [Epub ahead of print] This is an excellent systematic review of outcomes from endoscopic skull base defect repair. The methodology is very well described. The authors discuss the outcomes in terms of site, CSF pressure, as well as the use of free grafts and vascularized pedicled flaps. The use of lumbar drainage is also discussed. It provides a comprehensive review of different techniques and clinical scenarios. 9. Eloy JA, Shukla PA, Choudhry OJ, et al. Assessment of frontal lobe sagging & after endoscopic endonasal transcribriform resection of anterior skull base tumors: is rigid structural reconstruction of the cranial base defect necessary? Laryngoscope 2012; 122:2652–2657. The question of whether bony reconstruction is necessary for large anterior skull base defects is addressed very nicely in this limited series of patients. Results indicate that in the absence of osseous reconstruction, brain sagging did not occur at 3-month follow-up period. No CSF leak was noted. 10. Tuchman A, Khalessi AA, Attenello FJ, et al. Delayed cavernous carotid artery pseudoaneurysm caused by absorbable plate following transsphenoidal surgery: case report and review of the literature. J Neurol Surg Rep 2013; 74:10–16. 11. Germani RM, Vivero R, Herzallah IR, Casiano RR. Endoscopic reconstruction of large anterior skull base defects using acellular dermal allograft. Am J Rhinol 2007; 21:615–618. 12. Gaynor BG, Benveniste RJ, Lieberman S, et al. Acellular dermal allograft for & sellar repair after transsphenoidal approach to pituitary adenomas. J Neurol Surg B Skull Base 2013; 74:155–159. This is a large series describing acellular dermal graft in sellar reconstruction. 13. Illing E, Chaaban MR, Riley KO, Woodworth BA. Porcine small intestine & submucosal graft for endoscopic skull base reconstruction. Int Forum Allergy Rhinol 2013; 3:928–932. This study describes the authors’ experience with porcine small intestine submucosal graft as a part of multilayered closure with pedicled flaps. 14. Phillips J, Riley KO, Woodworth BA. Porcine small intestine submucosal grafts for post-tumor resection orbital reconstruction. Laryngoscope 2014; 124:E219–E223. [Epub ahead of print] 15. Xie L, Lavigne F, Rahal A, et al. Facial artery musculomucosal flap for reconstruction of skull base defects: a cadaveric study. Laryngoscope 2013; 123:1854–1861. 16. Patel MR, Taylor RJ, Hackman TG, et al. Beyond the nasoseptal flap: out&& comes and pearls with secondary flaps in endoscopic endonasal skull base reconstruction. Laryngoscope 2014; 124:846–852. This is an excellent study that describes the use of ‘secondary flaps’ for reconstructing skull base defects when the pedicled nasoseptal flap is not available. 17. Fortes FS, Carrau RL, Snyderman CH, et al. Transpterygoid transposition of a temporoparietal fascia flap: a new method for skull base reconstruction after endoscopic expanded endonasal approaches. Laryngoscope 2007; 117:970–976. 18. Patel MR, Shah RN, Snyderman CH, et al. Pericranial flap for endoscopic anterior skull-base reconstruction: clinical outcomes and radioanatomic analysis of preoperative planning. Neurosurgery 2010; 66:506–512. 19. Oliver CL, Hackman TG, Carrau RL, et al. Palatal flap modifications allow pedicled reconstruction of the skull base. Laryngoscope 2008; 118:2102– 2106.



427


Head and neck reconstruction 20. Gil Z, Margalit N. Anteriorly based inferior turbinate flap for endoscopic skull base reconstruction. Otolaryngol Head Neck Surg 2012; 146:842– 847. 21. Yip J, Macdonald KI, Lee J, et al. The inferior turbinate flap in skull base reconstruction. J Otolaryngol Head Neck Surg 2013; 42:6. 22. Hadad G, Rivera-Serrano CM, Bassagaisteguy LH, et al. Anterior pedicle lateral nasal wall flap: a novel technique for the reconstruction of anterior skull base defects. Laryngoscope 2011; 121:1606–1610. 23. Nyquist GG, Anand VK, Singh A, Schwartz TH. Janus flap: bilateral nasoseptal flaps for anterior skull base reconstruction. Otolaryngol Head Neck Surg 2010; 142:327–331. 24. Eloy JA, Choudhry OJ, Christiano LD, et al. Double flap technique for & reconstruction of anterior skull base defects after craniofacial tumor resection: technical note. Int Forum Allergy Rhinol 2013; 3:425–430. This study describes the use of multiple pedicled vascularized flaps (the nasoseptal and pericranial flap) in reconstruction of large anterior skull base defects. 25. Chaaban MR, Chaudhry A, Riley KO, Woodworth BA. Simultaneous pericranial & and nasoseptal flap reconstruction of anterior skull base defects following endoscopic-assisted craniofacial resection. Laryngoscope 2013; 123:2383– 2386. This study also describes the use of multiple pedicled vascularized flaps (the nasoseptal and pericranial flap) in reconstruction of large anterior skull base defects.

428


26. Kalyoussef E, Schmidt RF, Liu JK, Eloy JA. Structural pedicled mucochondralosteal nasoseptal flap: a novel method for orbital floor reconstruction after sinonasal and skull base tumor resection. Int Forum Allergy Rhinol 2014; 4:577–582. 27. Eloy JA, Patel SK, Shukla PA, et al. Triple-layer reconstruction technique for & large cribriform defects after endoscopic endonasal resection of anterior skull base tumors. Int Forum Allergy Rhinol 2013; 3:204–211. This study very nicely describes the authors’ experience in performing multilayered repair of skull base defects. They describe the technique of underlay using fascia lata with overlay acellular dermis and pedicled vascularized flap. 28. Rawal RB, Kimple AJ, Dugar DR, Zanation AM. Minimizing morbidity in & endoscopic pituitary surgery: outcomes of the novel nasoseptal rescue flap technique. Otolaryngol Head Neck Surg 2012; 147:434–437. The authors describe the use of a modified technique for the nasoseptal flap to minimize morbidity at the harvest site. 29. Husain Q, Sanghvi S, Kovalerchik O, et al. Assessment of mucocele formation after endoscopic nasoseptal flap reconstruction of skull base defects. Allergy Rhinol 2013; 4:e27–e31. 30. Bleier BS, Wang EW, Vandergrift WA 3rd, Schlosser RJ. Mucocele rate after endoscopic skull base reconstruction using vascularized pedicled flaps. Am J Rhinol Allergy 2011; 25:186–187. 31. Vaezeafshar R, Hwang PH, Harsh G, Turner JH. Mucocele formation under pedicled nasoseptal flap. Am J Otolaryngol 2012; 33:634–636.



Rhinology and skull base surgery: key updates in our field.

In reference to "extended inferior turbinate flap for endoscopic reconstruction of skull base defects".

Histopathology of idiopathic lateral skull base defects.

Extended inferior turbinate flap for endoscopic reconstruction of skull base defects.

Endoscopic reconstruction of surgically created skull base defects: a systematic review.

Modified Facial Artery Musculomucosal Flap for Reconstruction of Posterior Skull Base Defects.

Endoscopic skull base reconstruction: a review and clinical case series of 152 vascularized flaps used for surgical skull base defects in the setting of intraoperative cerebrospinal fluid leak.

Surgical technique for repair of complex anterior skull base defects.

Spontaneous CSF rhinorrhea: prevalence of multiple simultaneous skull base defects.

Principles in Skull Base Reconstruction following Expanded Endoscopic Approaches.

Endoscopic Endonasal Reconstruction of Skull Base: Repair Protocol.

Free rectus abdominis muscle reconstruction of the anterior skull base.

In response to simultaneous pericranial and nasoseptal flap reconstruction of anterior skull base defects following endoscopic-assisted craniofacial resection.

In reference to simultaneous pericranial and nasoseptal flap reconstruction of anterior skull base defects following endoscopic-assisted craniofacial resection.

Skull base in trigonocephaly.

Ganglioneuroblastoma of Skull Base.

Management of large dural defects in skull base surgery: an update.

Skull base surgery.

[The predictive value of so-called secondary reconstruction in fractures of the frontal skull base].

Skull Base Trauma: Commentary.

Analysis of morbidity and mortality in patients undergoing skull base reconstruction.

Outcomes following Microvascular Free Tissue Transfer in Reconstructing Skull Base Defects.

[Endonasal, endoscopically controlled repair of dura defects of the anterior skull base].

Skull base reconstruction in cases of intracranial teratoma extending into the extracranial structures.