Endoscopic Sellar Defect Reconstruction with Avascular Modified Gasket Seal Technique for Sellar Tumors

Abstract

Watertight repair of the skull base defect is necessary during endonasal skull base surgery to avoid postoperative CSF leak (poCSFl) and consequent intracranial complications. Various techniques have been described for reconstructing sphenoid-sellar defects with varying success rates. We have described the immediate and long-term outcomes following the reconstruction of sphenoid-sellar defects with our technique. A retrospective analysis of the patients following transsphenoidal sellar surgery underwent barrier restoring reconstruction by multi-layered (inlay-overlay) with autologous thigh fat, fascia lata, fibrin glue, knitted collagen, and absorbable gelatin sponge (modified gasket seal technique). A total of 44 patients were included in the study (n = 44). Reconstruction with modified gasket seal technique was done for all patients. 26 (59.1%) had intraoperative CSF leak (ioCSFl), and 9 (20.4%) patients had grade 3 Esposito-Kelly ioCSFl requiring adjunct short-term pressure reducing procedure (Lumbar drain) intraoperatively. 11/44 (25%) had poCSFl, 7/11 patients with poCSFl were managed conservatively, and 4/11 patients required rescue second surgery and ventriculoperitoneal shunting. 1 (2.3%) had severe meningitis and succumbed to it. Pneumocephalus was seen in 6 (13.6%). Multivariate analysis showed that revision surgery, GH-secreting tumors, and defects extending to the suprasellar region had higher chances of poCSFl (p < 0.001). All 43 alive patients had no CSF leak on long-term follow-up. The modified gasket seal technique is a viable technique for endoscopic sellar reconstruction for ioCSFl with an immediate success rate of 79.6% and 97.72% in the long term in preventing the postoperative CSF leak with a 13.6% rate of meningitis.

Introduction

The transsphenoidal method emerged through an evolutionary process as opposed to a revolutionary one. The development of transsphenoidal surgery is a complex story of revolutionary philosophical leaps intermingled with periods of intensive surgical experimentation and a time of outright rejection of the procedure. Endonasal techniques to the skull base have enabled minimally invasive and highly effective surgical removal of skull base tumors. These approaches are most frequently reported in the transsphenoidal approach to pituitary tumors [1]. Despite the purported advantages of endonasal methods, postoperative cerebrospinal fluid (CSF) rhinorrhoea is still a frequent issue that can lead to serious consequences such as meningitis, pneumocephalus, and the requirement for additional surgery [2]. Iatrogenic intraoperative rupture of the barrier separating the subarachnoid space from the sinonasal cavity causes CSF leak. In the majority of pituitary adenoma resections, this disruption may be unavoidable or unintentional [3]. A watertight repair of the skull base is essential for preventing postoperative CSF leaks (poCSFl), regardless of the reason. Over the years, many local vascularized pedicle and avascular grafts have been described for the reconstruction of the sellar defects [3–5]. Inlay and onlay graft techniques using autologous fascia lata, whose characteristics are similar to those of dura, have been performed, and the “gasket-seal” method using a rigid buttress with a fascial graft is also widely used for dura reconstruction [5–7]. Autologous fascia lata has been reported as the most used and effective graft material for multilayer reconstruction [8–10]. Surprisingly, poCSFl rates following endoscopic TSS operations range from 0.5 to 15% [11] despite contemporary reconstructive techniques. Reconstruction of the skull base is challenging—using long, rigid instruments in a restricted working space to place repair materials against the forces of gravity and overlying dependent intracranial structures [12]. In this study, we describe the efficacy of endoscopic sellar defect reconstruction with a multi-layered fascia lata-modified gasket seal technique for sellar tumors. We also explain the construct technique with thorough nomenclature that reinforces the principles of dural barrier restoration, CSF pressure relief, and the use of staged approaches to prevent poCSFl.

Subjects and Methods

This was a retrospective, single-center study conducted at the Department of Otorhinolaryngology and Head and Neck Surgery and the Department of Neurosurgery at All India Institute of Medical Sciences in Raipur. The study included patients with sellar tumors who had undergone transsphenoidal sellar surgery with barrier restoring reconstruction by multi-layered (inlay-overlay) using autologous thigh fat, fascia lata, fibrin glue, knitted collagen sheet, and absorbable gelatin sponge-modified gasket seal technique (described below) at our center from 1st Jan 2019 to 31st October 2022. Written and informed consent had been obtained from all participating patients. A detailed analysis of demographic data, investigations, intraoperative findings, postoperative care, and follow-up charts had been performed. The data analysis had been conducted using IBM SPSS Statistics for Windows, Version 25.0 (Armonk, NY: IBM Corp.). The primary objective had been to determine the efficacy of the modified gasket seal technique in preventing postoperative CSF leak, and the secondary objectives had been to determine the rates of postoperative complications. The institutional ethical clearance had been exempted for the study with deidentified patient data, as stated in letter no 2635/IEC-AlIMSRPR/2022 dated 2nd December 2022. All procedures performed in the study had been conducted in accordance with the ethical standards outlined in the 1964 Declaration of Helsinki, as revised in 2013. Data reporting had been carried out following the STROBE guidelines.

Surgical Technique

A standard endoscopic transsphenoid approach was utilized for tumor excision. Initial soft tissue dissection, nasal septectomy, sphenoid entry, and sellar entry were done. Following surgical extirpation of the sellar tumor, the presence of intraoperative CSF leak (ioCSFl) based on the grading system was provided by Kelly and colleagues [13]. Intraoperative CSF leaks were classified as grade 0, no leak noticed; grade 1, a small leak without a clear diaphragmatic defect; grade 2, a moderate leak; or grade 3, a substantial diaphragmatic/dural defect. The reconstruction of the defect was broadly divided into barrier restoring and pressure diversion procedures (Table 1). The dural barrier restoration is as follows (Fig. 1).

1. Intradural (inlay) repair – This was performed by filling the sellar cavity with the autologous fat, which was harvested along with the fascia lata. The fat was packed in such a way as to ensure there is no back pressure or compression over the neurovascular structure.

2. Dural (overlay) repair – The facia lata was draped over the fat tissue, and the fascia is tucked under the bony sellae and the dura beyond its margins.

3. To ensure a watertight closure, the fascia lata layer was reinforced with knitted collagen and fibrin glue; this formed a thick barrier that acted as a gasket which sealed the dural defect. The original gasket seal technique was described by colleagues from Weill Cornell university [6]; they used a bony fragment with a vascular pedicled flap overlay. Our modification included the use of avascular tissue and collagen matrix reinforced with tissue glue (modified gasket seal).

4. The bony skull base layer was reconstructed with further layering of fascia lata and fibrin glue, which formed a dense structure to hold the previous construct in place.

5. A final barrier was placed with the fragments of absorbable gelatin and knitted collagen.

6. A temporary nasal construct stabilization was provided by a nasal sponge.

Table 1.

Synopsis of the repair technique as per the anatomical layer

Reconstruction	Defect	Technique	Material
Barrier restoring	Intradural (inlay)	Layering	Autologous fat
		Buttoning	Fascia lata
	Dural(overlay)	Layering
		Modified gasket seal	Knitted collagen + fibrin glue
	Bony (skull base)	Layering	Fascia lata + tissue glue
	Barrier		Knitted collagen + absorbable gelatin
	Nasal construct stabilization	Temporary	Sterile nasal sponge (Merocel)
Pressure diversion	Long term	Shunting procedure
	Short term	Lumbar drain

Fig. 1.

Sagittal illustration and coronal endoscopic image of the skull base highlighting various levels of repair and repair techniques used per level

The pressure diversion procedures viz, shunting or lumbar drain placement were performed in grade 2 and 3 ioCSFl. The nasal sponge was removed on postoperative day 3 under aseptic precautions. Any CSF leaks following the nasal pack removal were noted. Postoperatively, patients were observed in the neurosurgical intensive care unit (NICU) and are placed on intravenous antibiotics for surgical infection prophylaxis. Antibiotics are continued if a lumbar drain has been inserted. Patients may be required to spend two to three days in bed rest with the head of the bed elevated by 30 to 45 degrees in cases of CSF leak including lumbar drainage. Every patient was evaluated for symptoms of meningeal irritation, improvement in eyesight, vital signs, and sodium and cortisol levels immediately following surgery and each morning throughout their hospital stay. The patient’s sodium and fluid status were monitored carefully to look for diabetes insipidus. A postoperative computerized tomography was done within 24 h of surgery to look at the pneumocephalus, completeness of resection, and hematoma.

Results

We had 44 patients with sellar tumors, 30 patients had pituitary macroadenoma (15 GH secreting, 7 ACTH secreting, 4 Prolactin secreting, and 4 non-secreting) and 14 craniopharyngiomas. The ages of the patients ranged from 4 to 52 years; 11 patients were <18 years old. Males constituted 28 patients, and 16 were females. A total of 44 patients were included in the study (n = 44); the transsphenoid endoscopic approach was employed in all the patients for tumor excision. Reconstruction with the modified gasket seal technique was done. In 26 (59.1%) patients, intraoperative CSF leak (ioCSFl) was noticed, and 9/26 patients had grade 3 Esposito-Kelly ioCSFl. In patients with grade 3 ioCSFl, an adjunct short-term pressure-reducing procedure, Lumbar drain, was performed intraoperatively to reduce the CSF pressure.

In 11/44 (25%) patients, poCSFl was noticed (7 patients had pituitary macroadenoma; GH secreting = 4, ACTH secreting = 2, prolactin secreting = 1; 4 patients had craniopharyngioma; 3 patients with craniopharyngioma were <18 years). Among the 11 poCSFl patients, 9 patients had grade 3 Esposito-Kelly ioCSFl and 2 patients had grade 2 ioCSFl; an intraoperative lumbar drain was inserted in 9 patients with grade 3 leaks. The postoperative CSF leak was seen from the 2nd to the 4th postoperative day. The CSF leak was confirmed by beta trace protein levels in the clear fluid from the nasal cavity. In 7/11 patients with poCSFl, conservative management leads to complete resolution. In 4/11 patients required rescue second surgery and ventriculoperitoneal shunting. The vascular flap reconstruction was done in the rescue 2nd surgery. Fortunately, none of the patients required open craniotomy for the CSF leak repair.

Meningitis was evident in 6/44 (13.6%) cases, and 5/6 cases of meningitis resolved with antibiotic upgradation and conservative measures. Only one patient (2.3%) had severe meningitis and died due to it. The patient who succumbed to meningitis had grade 3 ioCSFl; an adjunct lumbar drain was placed for CSF pressure reduction; the postoperative HPR suggested GH-secreting pituitary macroadenoma. Overall, 6/44 (13.6%) patients had pneumocephalus, identified on the postoperative screening CT scan. All six patients with pneumocephalus were managed conservatively with high flow nasal oxygenation. Multivariate analysis showed that revision surgery, GH-secreting tumors, and defects extending to the suprasellar region had higher chances of poCSFl (p < 0.001). All 43 alive patients had no CSF leak on long-term follow-up.

Discussion

Reconstruction of the skull base is often challenging, i.e., using a long rigid endoscope and instruments through a narrow and restricted nasal cavity to reconstruct the region of the middle cranial fossa. This must be done through antigravity and opposing the dependent intracranial neurovascular structures. Various methods are employed in the reconstruction of the sellar defect, ranging from simple fat plugging to complex multi-layered vascular flap reconstruction [12]. Unfortunately, there is no consensus on the type of reconstruction for the sellar defects. The reconstruction can be divided into multiple layers based on the anatomy of the defect. We must always try to match the reconstruction tissue characteristics with the various anatomical layers.

Intradural Layer

It is mainly to obliterate dead space following the tumor resection. It can be achieved with autologous fat grafts or synthetic grafts such as collagen sponge or absorbable gelatine sponge. Rebuilding this layer aids in absorbing CSF pulsations and provides enough support to nearby neurovascular structures. By anchoring the graft with a buttress to the dura using the “bath-plug approach,” dislodgment can be avoided [14]. We must be cautious to avoid over-packing which may lead to compression of optic apparatus. If the fat is pushed further inwards into the ventricular system, then there is a risk of obstructive hydrocephalus. In order to prevent the disintegration of the fat lobules, the fat graft can be wrapped in oxidized cellulose.

Barrier Restoring: Dural (Dural Onlay and Overlay)

The main aim of this is to repair the dural defect with dural sutures, fascia lata, allografts like cadaveric fascia, and synthetic grafts such as artificial dura. One must ensure a watertight seal to prevent poCSFl. Utilizing sutures or clips can be technically difficult, time-consuming, have high learning curves, and can only be used for minor defects unless grafts are used in a patchwork manner [15]. The use of autologous grafts leads to donor-site morbidity. In allografts and xenografts, there is a risk of donor infection transmission [16]. Almost all phases of repair include descriptions of tissue glues and hemostatic agents that can be used to strengthen the dural step.

Bony Layer

To repair the bony skull base – sellar floor – using rigid or semi-rigid grafts. Autologous grafts such as septal cartilage or bone have been used. Septal cartilage or bone has been used as autologous transplants. With varied degrees of success, allografts, xenografts, and synthetic grafts have been employed. This rebuilding layer shields the underlying components and must be able to tolerate greater stresses across the repair site [17].

Nasal Construct Stabilization

This mainly helps in support of underlying repair (buttresses and nasal packing). This can be achieved with a local pedicled flap [18], autologous buttress, or nasal packing. It is hypothesized that vascularized repairs have the potential to adhere firmly to the skull base and maintain supporting strength for a very long time. Sinonasal morbidity, including crusting, loss of smell, sinusitis, nasal perforations, adhesions, synechiae, and potential iatrogenic injury to the elevated flap or pedicle intraoperatively, are the primary drawbacks of vascularized pedicled flaps [19]. Nasal packing and buttressing may protect the underlying repair from forces across the repair site. The use of synthetic buttress may lead to decreased biocompatibility, infection, extrusion, chronic sphenoid sinusitis, and radiological artifacts [20]. The nasal packing may lead to discomfort, risk of dislodgement, and risk of adhesion to underlying repair [21].

CSF Diversion

Lowering of CSF pressure and pulsations to facilitate repair; this can be done long term with ventriculoperitoneal shunting or short term with a lumbar drain. There is level 1 evidence in favor of this (perioperative lumbar drainage) [22]. The main disadvantages of this include low-pressure headaches, infection, pneumocephalus, bleeding, neural injury, catheter dislodgment, increased length of stay, retained catheter, decreased mobility, anesthetic complications, and venous thromboembolism [23, 24].

In our study, the poCSFl was seen in 20.4% of cases following the reconstruction with the modified gasket seal technique. The incidence of CSF leak during transsphenoidal surgery ranges from 2 to 16% [25] and is mostly brought on by injury to the diaphragma sellae, on which sellar tumors are usually adherent [26]. We must take care to limit harm to the diaphragma sellae by carefully dissecting the tumor and avoiding straining at it. The diaphragma may infiltrate and become disrupted in rare cases, which invariably causes an intraoperative CSF leak [27]. The integrity of the sellar reconstruction is crucial for preventing postoperative CSF leaks in all situations when CSF is seen intraoperatively.

We had slightly higher rates of meningitis compared to the overall incidence in the literature, 0.4 to 9% [28, 29]. It is significant to highlight that the most frequent complication in more recent series, spanning the past 15 years, is still infectious in character but now occurs extracranially or at least extradurally [28–30]. Table 2 shows the summary of complications following the sellar reconstruction. Reliable surgical methods have reduced postoperative infection in addition to the conventional perioperative antibiotic regimen. Meningitis risk is significantly increased by prolonged usage of lumbar drainage with persistent leakage and recurrent operations to address CSF leaks [51]. We must acknowledge that a pedicled nasoseptal flap has demonstrated the potential to either improve or augment the outcomes of the layered application of gasket and bath-plug techniques. This has been particularly effective in preventing significant occurrences such as persistent CSF leaks and meningitis, especially in the context of salvage cases.

Table 2.

The summary of the literature review of complications following the skull base reconstruction

Author	Year	poCSFl (%)	Meningitis (%)	Other complications (%)
Luk et al. [31]	2019	0/16 (0)	0/16 (0)	0/16 (0)
Roca et al. [32]	2019	14/380 (4)	4/380 (1)	4/380 (1)
Lam et al. [33]	2018	1/16 (6)	0/16 (0)	1/16 (6)
Mattavelli et al. [34]	2018	11/186 (6)	0/186 (0)	6/186 (3)
Kuan et al. [35]	2018	3/205 (1)
Fishpool et al. [36]	2017	0/32 (0)	0/32 (0)	0/32 (0)
Borsetto et al. [37]	2017	4/108 (4)	0/108 (0)
Fonmarty et al. [38]	2016	1/29 (3)	2/29 (7)	2/29 (7)
Emanuelli et al. [39]	2015	0/17 (0)	0/17 (0)	0/17 (0)
Sanders-Taylor et al. [40]	2015	4/235 (2)	2/235 (1)	3/235 (1)
Kong et al. [41]	2013	0/22 (0)	0/22 (0)	2/22 (9)
Gaynor et al. [42]	2013	8/87 (9)		0/87 (0)
Kong et al. [43]	2011	3/58 (5)	4/58 (7)
Prickett et al. [44]	2011	0/17 (0)	0/17 (0)	1/17 (6)
Cassano et al. [45]	2009	7/125 (6)
El-Banhawy et al. [46]	2008	3/55 (5)	1/55 (2)	0/55 (0)
Germani et al. [47]	2007	2/25 (8)	0/25 (0)	0/25 (0)
Leong et al. [48]	2006	0/6 (0)	2/6 (33)	0/6 (0)
Locatelli et al. [49]	2006	0/5 (0)	0/5 (0)	0/5 (0)
Marton et al. [50]	2005	1/20 (5)	1/20 (5)	2/20 (10)

A well-controlled randomized study is required to precisely compare the multilayer avascular reconstruction with the pedicled vascular reconstruction.

Conclusion

The modified gasket seal technique is a viable technique for endoscopic sellar reconstruction for ioCSFl with an immediate success rate of 79.6% and 97.72% in the long term in preventing the postoperative CSF leak. This technique is on par with the vascularized tissue transfer techniques in preventing the poCSFl, and the rate of meningitis is 13.6%. On multivariate analysis, revision surgery, GH-secreting tumors, and defects extending to the suprasellar region had higher chances of postoperative CSF leak.

Author Contribution

All authors have contributed equally toward this manuscript.

Declarations

Ethics Approval and Informed Consent

Exempted for study vide letter no 2635/IEC-AlIMSRPR/2022 dated 2^nd December 2022. The article was presented at the Annual Conference of Indian Association of Surgical Oncologists in 2021 by the corresponding author.

Conflict of Interest

The authors declare no competing interests.