29 Closure Techniques for the Pediatric Skull Base: Gasket Seal

10.1055/b-0040-177085

29 Closure Techniques for the Pediatric Skull Base: Gasket Seal

Harminder Singh, Vijay K. Anand, and Theodore H. Schwartz

Abstract

The gasket seal is based on the concept of creating a “gasket” that forms a watertight seal, isolating the intracranial contents from the sinonasal space. The indications, technique, and limitations of this closure will be discussed in this chapter.

29.1 Introduction to Gasket Seal

As endoscopic endonasal surgery extended across the skull base, the difficulty of achieving a watertight closure through the endoscope became a central preoccupation for skull base surgeons. Most effective closure techniques are based on a few simple principals. These include (1) multilayer closure (redundancy is effective in case any one layer by itself is inadequate); (2) buttressing (fluctuations in intracranial pressure during the early postoperative period can dislodge closure material); and (3) vascularized tissue (allows for long-term security in closure).

The first principle was initially addressed with inlay and only graft materials such as fat, fascia lata, alloderm. and matrix materials. Although fat has historically been the mainstay in transsphenoidal closures, it has been used mostly for adenomas, where the sella holds the fat and the opening requiring closure is a small arachnoidal opening. For extended transsphenoidal approaches, placement of intracranial fat can have certain drawbacks. First, intradural fat can impair the interpretation of postoperative imaging and the ability to discern residual or recurrent tumors. Second, fat grafts are not initially vascularized and can become infected, particularly when dragged through the nostrils. Fat grafts in the sphenoid can also have drawbacks, as they are bulky and can impair mucous drainage and necrose, creating a foul smell.

Fascia lata is an attractive material, since it is an autograft and has the appropriate thickness and malleability for skull base repair. Buttressing is also important to prevent graft dislodgement and can be addressed in several ways. Initial use of a foley balloon was effective, but it was difficult to know exactly how much to inflate the balloon, and the round contour never perfectly fitted the sphenoid sinus, so it was difficult to control the amount of pressure exerted in each region. Moreover, the patient had a catheter emerging from their nostril that may need to be left in place for several days, which is uncomfortable and can impair nasal drainage and slow down patient discharge.

Grafts that wedge into the bone around the opening can be useful to reconstruct the defect and hold softer grafts in place, as is done when reconstructing the floor of the sella after pituitary surgery. Autologous vomer is often used for this purpose, but with extended skull base approaches, the defects are often large and irregularly shaped, and one cannot rely on having the perfect vomer graft in every case. MEDPORE (Porex) provides a nice alternative that can be cut to custom sizes based on need and has some flexibility to wedge into exiting bone defects more easily. Bone cement is also an option, but the initial soft consistency makes it difficult to control and the speed of hardening is also difficult to manage.

The advent of the pedicled nasoseptal flap (NSF) was a giant step forward in managing high-flow cerebrospinal fluid (CSF) leaks. To address several of the issues and limitations described, the “gasket seal” was developed at Cornell as a workhorse closure for extended skull base approaches. ¹ ^, ² The combination of the NSF with the gasket seal produces the lowest rate of CSF leak of any closure technique published to date. ³ ^, ⁴ ^, ⁵ ^, ⁶ The indications, technique, and limitations of this closure will be discussed in this chapter.

29.2 Procedure

The gasket seal technique is based on the concept of creating a “gasket” that forms a watertight seal, isolating the intracranial contents from the sinonasal space. For conceptual understanding, this technique can be broken down into four steps.

29.2.1 Step 1: Harvesting of Fascia Lata

A piece of autologous fascia lata is harvested from the contralateral thigh from which the primary surgeon is standing, so as to not disrupt the endonasal procedure while the harvest is being performed. The fascia lata graft is fashioned such that it circumferentially extends 1 cm beyond the margins of the bony defect. The vertical and horizontal diameters of this defect are measured either with a ruler or with a cottonoid. If fascia lata is unavailable for any reason, bovine pericardium or alloderm may be used as a substitute. The harvested graft is placed over the bony opening (▶ Fig. 29.1a, b).