Advances in transnasal endoscopic approaches and the development of instrumentation and imaging technology have turned endoscopic endonasal surgery into the mainstay for treating inflammatory diseases and neoplasms involving the paranasal sinuses and skull base.1 The expanded endonasal approach (EEA) and its modifications provide access to the anterior skull base, planum, sphenoid, sella, clivus, cervical spine, and infratemporal fossa via the two nostrils.2–9 This approach enables endoscopic extradural and intradural tumor resection and skull base reconstruction in a single procedure.
Technical advances in reconstruction methods and the development of vascularized locoregional flaps have improved our ability to seal the cranio-basal diaphragm after tumor extirpation.10–14 Use of a nasal septal flap (NSF) has reduced the rate of complications and allowed increasing numbers of patients with skull base neoplasms to undergo curative surgical resections by means of minimally invasive techniques.15 One drawback of this technique is the difficulty of stabilizing the multilayered reconstruction in place after its application. Currently, a 12-French Foley catheter latex balloon is used to support the multilayered reconstruction during the 1st week after surgery.12 The main disadvantages of this method are: 1) the balloon surface is spherical, thus providing inadequate support to the flat surfaces of the skull base; 2) decrease in the balloon's volume due to frequent leaks may impair the support of the flap; 3) the latex balloon is weak and frequently bursts due to exposed bone chips; 4) inability to use this balloon in patients who are allergic to latex; and 5) it is inconvenient for patients because it interferes with their nasal breathing. An alternative support for skull base reconstruction that is free of these limitations is needed. In this report we describe a novel anatomically shaped graft stabilizer for endonasal skull base reconstruction.
TECHNICAL SPECIFICATIONS OF THE TETRAHEDRAL SILICON BALLOON
The tetrahedral silicon balloon (TSB) is a silicon pyramid-shaped hypoallergenic radio-opaque balloon (Fig. 1). The shape of its base is that of an isosceles triangle, and it is reinforced by Dacron. Its peripheral length is 3.5 cm and it covers an area of 5.75 cm2. The pyramid's volume is 14 cm3, and it is filled with 12 to 20 mL of saline to reach a pressure of 20 to 30 cm H2O (14–21 mm Hg). Its inflation catheter is a 20-cm flexible silicon tube. The TSB (Antra, Spiggle & Theis, Overath, Germany, http://www. spiggle-theis.com/en/products/rhinology/epistaxis-catheter) was initially designed for maxillary sinus surgery. We hypothesized that its three-dimensional shape, molding features, and safety make it applicable for skull base reconstruction. We prospectively reviewed the clinical, surgical, and outcome data of five patients who underwent reconstruction of skull defects with the TSB after having undergone endoscopic tumor resection with dural resection.
Surgery was performed via the expanded endoscopic approach as described earlier.8 We routinely use an inlay fascia lata graft as the first layer of the dural reconstruction. The NSF is then rotated toward the defect where it is meticulously placed over the bare edges of the bony and the fascia lata. The mucoperiosteum surface of the flap should overly the dural defect. After placing the flap, the reconstruction is covered with strips of Surgicel (Ethicon Inc., Johnson and Johnson, Somerville, NJ) and fibrin glue, followed by strips of Gelfoam sponge (Pfizer Inc., New York, NY).
At this stage, we insert the TSB through the nasal cavity, and position its base to cover the graft over the defect under endoscopic guidance. The pyramid is placed in an upright or inverted position according to the area that needs to be covered. Specifically, it is placed in an inverted position with its Dacron-reinforced base facing upward against the defect in cases of anterior skull base defects (e.g., cribriform plate and planum) or sellar defects (Fig. 2A). In posteriorly based defects (e.g., clivus or cervical spine), it is placed in an upright position, with its base positioned against the clivus (Fig. 2B). Next, 10 to 15 mL of saline are injected to inflate the balloon to support the flap against the defect. Inflation of the TSB is monitored by direct endoscopic inspection for correct positioning and adequate inflation of the balloon (Fig. 3).
The TSB is removed on the 5th to 7th postoperative day. The patient can be discharged with the inflated balloon in place.
We assessed the flap survival, graft coverage, adequacy of the seal, and incidence of complications (pneumocephalus, meningitis, and bleeding) in five patients who underwent anterior skull base reconstruction with TSB support of the reconstruction. The patients' demographic and clinical data are summarized in Table I. All five patients had a high-flow intraoperative cerebrospinal fluid (CSF) leak (dural defect >5 mm, opening to ventricle or cistern, or violation of the arachnoid space).16 Reconstruction with the TSB achieved complete covering of the entire skull base defect in all patients. They all reported adequate nasal breathing and no inconvenience related to the TSB. There were no events of balloon failure or saline leak from the TBS. There were no postoperative CSF leaks or other complications. Nasal crusting was reported up to 8 weeks following surgery, as is expected after EEA.
Table I. Clinical and Demographic Characteristics of the Patients
Site of Reconstruction
Type of Leak
Type of Reconstruction
F = female; CSF = cerebrospinal fluid; AITF = anteriorly based inferior turbinate flap; NSF = nasal septal flap; M = male.
Postcraniotomy CSF leak
Frontal sinus and cribriform plate
AITF and NSF
Planum, cribriform plate, frontal sinus
AITF and NSF
Recurrent nasopharyngeal carcinoma
Postcraniotomy CSF leak
Fascia lata and AITF
Middle turbinate flap
Vascularized flaps harvested from the nasal cavity were first described in 1952 and are commonly used for reconstruction to this day.17 The selection of reconstruction method is usually made according to the anatomical position and size of the skull base defect, as well as on the available grafts. Proper positioning of the flap is crucial for the prevention of a CSF leak. It is critical that the graft be kept in place from the first postoperative days until it has become permanently adhered to the underlying tissue. Several fixation techniques have been proposed, the most common among them being nasal packing by means of tampons or a 12- to 14-French Foley catheter. Displacement of the flap may lead to severe complications, such as CSF leak, pneumocephalus, and meningitis, which may require a second operation.18
Flap migration and reconstruction breakdown may occur for several reasons: 1) the support is not anatomically shaped as in the case of a balloon catheter, leading to unequal pressure vectors over the flap and to its traction; 2) malpositioning of the support that is placed blindly and not under endoscopic guidance; and 3) migration or change in the shape of the support during the early postoperative period, such as in the case of leaking Foley catheters. The TSB precisely addresses these drawbacks of conventional supporting methods. First, it has a flat base, allowing equal distribution of the pressure over the flap no matter how it is placed (upward or posteriorly). Second, the inflatable pyramidal shape allows the surgeon to monitor its positioning during inflation. Third, it is associated with minimal leakage of saline. Fourth, its Dacron reinforcement can withstand damage from bone chips left in the sinuses, further minimizing the risk of the balloon bursting and failure. Finally, it can be used in patients who are allergic to latex.
Neurovascular compromise is a well-documented pitfall of nasal packing.12, 19 The pressure within the TSB is significantly lower than the systolic blood pressure, thereby obviating the likelihood of graft ischemia. The TBS's pressure is also equally distributed on a pyramid base (area = 5.85 cm2) and does not reach the level of venous pressure, unlike the case of a spherical catheter in which the pressure is applied on a single tangential point.
Patient discomfort due to the nasal packing is well documented after endoscopic surgery.20 One of the important advantages of the TBS over nasal tampons is that it does not interfere with nasal breathing.
We describe the use of a novel anatomically shaped tetrahedral silicon balloon for stabilizing grafts during endoscopic skull base reconstruction. The technique for using this device is safe, simple, and quick, and it is better tolerated by patients than conventional nasal packing.