Acta Neurochir (2015) 157:139–144 DOI 10.1007/s00701-014-2273-8

HOW I DO IT - NEUROSURGICAL TECHNIQUES

Reconstruction of the anterior skull base after major trauma or extensive tumour resection Stefan Alexander König & Sebastian Ranguis & Veronika Gramlich & Uwe Spetzger

Received: 22 July 2014 / Accepted: 31 October 2014 / Published online: 2 December 2014 # Springer-Verlag Wien 2014

Abstract Background The authors describe their experience with the reconstruction of complex anterior skull base defects after trauma or tumour resection using a “sandwich” technique with pericranial flap, titanium mesh and TachoSil. Methods Description of surgical anatomy, surgical technique, indications, limitations, complications, specific perioperative considerations and specific information to give to the patient about surgery and potential risks. A summary of ten key points is given. Conclusions After a bifrontal craniotomy and a subfrontal approach, it is possible to achieve a reliable reconstruction of the anterior skull base in a watertight manner by fixing a pericranial flap or a fascia lata graft to the orbital roofs and planum sphenoidale with an individually tailored titanium mesh and closing the frontobasal dura leasion with TachoSil. Keywords Anterior skull base . Reconstruction . Titanium mesh . Pericranial flap . Sandwich technique

Relevant surgical anatomy After performing a bifrontal craniotomy to achieve a subfrontal approach, the anterior skull base is exposed by retracting both frontal lobes. The anterior and posterior wall Electronic supplementary material The online version of this article (doi:10.1007/s00701-014-2273-8) contains supplementary material, which is available to authorised users. S. A. König (*) : V. Gramlich : U. Spetzger Neurochirurgische Klinik, Klinikum Karlsruhe, Moltkestr. 90, 76133 Karlsruhe, Germany e-mail: [email protected] S. Ranguis Department of Otolaryngology, Gosford Hospital, Gosford, Australia

of the frontal sinus is already exposed when completing the craniotomy because it usually leads to an opening of the frontal sinus. Releasing the dura around the crista galli exposes both orbital roofs and the cribriform plate, which is usually the area of injury to the anterior skull base (Figs. 1 and 2). If the patient suffers from a complete post-traumatic anosmia, it is possible to retract the frontal lobes back to the planum spheniodale during the skull base reconstruction (see below).

Description of the technique The head is fixed in a slightly extended position using the MAYFIELD Infinity skull clamp system (Integra, Ratingen, Germany). This position enables a self-retraction of the frontal lobes during surgery. The authors use a standard craniotomy setup for the described surgical procedure. After a bifrontal skin incision behind the hair line a soft tissue flap consisting of skin and galea is dissected by using the loose areolar tissue layer for dissection (Fig. 3a). Thus, the pericranial flap is left on the skull at this stage of the operation. The skin flap is fixed with hooks, and the pericranial flap is dissected from the outer layer of the skull (Fig. 3b). The average size of the soft tissue flap for duraplasty is a width of 10–12 cm and a length of 9–11 cm. After retracting the pericranial flap with hooks, a frontal burr hole is placed in the midline 3–4 cm anterior to the bregma (Fig. 3c). Since the burr hole is placed right above the superior sagittal sinus, the dura in and around the burr hole has to be dissected carefully before performing the craniotomy (Fig. 3d). During the bifrontal craniotomy the frontal sinuses are usually opened, taking into account that most severe lesions of the anterior skull base lead to fractures of the posterior wall of the frontal sinuses. Thus, they are often opened to the

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Fig. 1 A 54-year-old male patient with cerebrospinal fluid (CSF) rhinorrhea after multiple head injuries and previous anterior skull base reconstruction. Computed tomography (CT) scans (a, b) showed a skull base defect left of the crista galli and a significant deformity of the bony

forehead. The operative strategy for reconstruction of the skull base (c) included the placement of a pericranial flap (red layer) on the defect, and the attachment of titanium mesh (blue layer) to press the duraplasty on the skull base

intracranial space due to the trauma itself in most cases. The authors strip the mucosa from the frontal sinuses down to the nasofrontal duct and pack it down into the duct. Afterwards the bony wall of the sinuses is drilled with a diamond burr to remove remnants of mucosa that may form a mucocele. At the final stage of surgery, the frontal sinuses are covered with the pericranial flap (see below and accompanying video). After elevating the bone flap, the lesion of the anterior skull base can be identified by retracting the dura-covered frontal

lobes only as much as is necessary (Fig. 3e). At this stage of the operation it is sometimes necessary to refix fragments of the orbital roof (Fig. 3f, g) or the posterior wall of the frontal sinus. A major trauma of the anterior skull base usually leads to a lesion of the cribriform plate (Fig. 1). Therefore the defect is covered by the pericranial flap that is usually long enough to cover the orbital roofs, the cribriform plate and the planum speniodale. The pericranial flap is fixed by a tailored piece of titanium mesh (Figs. 1f and 3h), which provides maximum

Fig. 2 Postoperative result of the patient from Fig. 1. Coronal (a) and axial (b) CT scans show the fixation of the titanium mesh to the orbital roofs with self-drilling screws and an additional titanium mesh for the reconstruction of the forehead. Three-dimensional volume rendering images (c, d) showing the forehead and skull base reconstruction

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Fig. 3 Surgical technique of anterior skull base reconstruction after trauma with pericranial flap and titanium mesh. Dissection of the loose areolar tissue layer between galea and pericranium (a). Dissection of the pericranial flap that will be the soft tissue layer between the bony anterior skull base and the titanium mesh (b). Starting the craniotomy from a median burr hole with the craniotome after epidural dissection of the dura (c). Finishing the craniotomy by cutting the anterior wall of the frontal sinuses (d). Identification of the skull base defect (e). Refixation of the left orbital roof: medial side (f) and lateral side (g). After the pericranial flap is put on the opened frontal sinuses and the anterior skull base, it is pressed against the bony structures with an individually tailored piece of titanium mesh (h)

pressure on the duraplasty. This ensures a watertight closure of the skull base defect. The titanium mesh is fixed by small selfdrilling screws. Finally, the dura lesion on the basal side of the frontal lobes is covered with TachoSil (Nycomed, Konstanz, Germany) to protect the brain and to increase the chance of a watertight closure. TachoSil is a collagen sponge coated with fibrinogen and thrombin that adheres to the surrounding dura after it is irrigated with Ringer’s solution. Thus, the described technique leads to a “sandwich“ construct with a reliable reconstruction of the anterior skull base. The whole surgical procedure is shown in the accompanying video.

Indications Since the described technique is of a very invasive nature, it should only be used for extensive and complex post-traumatic

lesions of the anterior skull base. Smaller lesions can be elegantly treated by an endoscopic transnasal procedure [1, 3, 5]. Especially in cases of preserved olfaction after trauma, the endoscopic technique should be preferred to avoid a lesion of the olfactory nerve. Another indication for the described technique is an extensive anterior skull base defect after tumour resection (Figs. 4, 5 and 6) [4].

Limitations Anterior skull base fractures including the spenoid sinus should be treated by using the endoscopic technique, because the fixation of the pericranial flap and/or the titanium mesh cannot be done in a reliable way in this anatomical region. In cases of recurrent infections, multiple surgeries or previous radiation, the anterior skull base reconstruction can be

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Fig. 4 A 58-year-old male patient with an extensive anterior skull base meningioma. Removal of the tumour in the nasal cavity after finishing tumour resection in the anterior fossa, microscopic view (a). Navigation screen with MRI in three different planes (bd)

very challenging [2]. It might be impossible to harvest an adequate pericranial flap. Thus, reconstruction requires a fascia lata graft or even a radial forearm free flap [2].

How to avoid complications When fixing the titanium mesh to the posterior aspect of the anterior skull base, it should be estimated where the optic canals are located because the self-drilling screws might perforate the bony roof of the optic canals. When dissecting the pericranial flap it is mandatory to avoid any hole in that tissue layer to ensure a watertight reconstruction of the anterior skull base. Retraction of the frontal lobes should be applied very carefully to avoid secondary trauma to the brain.

Specific perioperative considerations Fig. 5 Surgical strategy for anterior skull base reconstruction after meningioma resection (patient from Fig. 4). A fascia lata graft (red layer) is fixed to the skull base with a titanium mesh (blue layer)

The preoperative diagnosis of an extensive anterior skull base defect can be made up with a CT scan in most cases. In some

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Fig. 6 Postoperative result of the patient from Figs. 4 and 5. Axial (a-c) and coronal (d-g) CT scans showing the fixation of the titanium mesh to the orbital roofs with self-drilling screws and an additional titanium mesh for the reconstruction of the forehead. Furthermore, the medial wall of the

right orbit was also reconstructed with titanium mesh (f, g). Threedimensional volume rendering images (h, i) showing the forehead and skull base reconstruction (the defect in the frontal bone resulted from the meningioma)

cases of secondary CSF rhinorrhea, it is necessary to add a magnetic resonance imaging (MRI) scan to visualise the lesion. On the other hand, those lesions are usually small and will be treated endoscopically. In the authors’ institution, the placement of a lumbar CSF drainage for 7 days is a standard procedure in cases of complex anterior skull base reconstruction to avoid revision surgery. Postoperatively every patient receives a CT scan to document the position of the titanium implant(s). A perioperative antibiotic i.v. prophylaxis with 960 mg cotrimoxazole twice daily is given for 7 days in each case. Since most cases require a postoperative lumbar drainage for 5–

7 days, those patients have to be kept on bed rest during that time.

Specific information to give to the patient about surgery and potential risks The preoperative prevalence of anosmia after extensive anterior skull base lesions is close to 100 %, but nevertheless the patient should be informed that a complex reconstruction of the anterior skull base usually leads to a loss of the sense of smell . Every extensive skull base procedure bears the risk of

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persistent CSF rhinorrhea and subsequent meningitis. Fixation of the titanium mesh with self-drilling screws close to the optical canal bears the risk of optic nerve injury.

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9. Check that adequate coverage of the frontal sinuses by the pericranial flap is confirmed before replanting the bone flap to avoid a secondary CSF leak. 10. Use a lumbar drainage for 7 days after complex reconstructions of the anterior skull base.

Summary 1. One burr hole in the midline is usually enough to perform a bifrontal craniotomy and a subfrontal approach respectively. 2. Any lesion of the pericranial flap should be avoided during dissection. 3. If it is impossible to harvest an adequate pericranial flap the use of a fascia lata graft or even a radial forearm free flap should be considered. 4. Always retract the frontal lobes just as much as necessary to avoid secondary complications. 5. The pericranial flap should cover the anterior skull base as much as possible. 6. The titanium mesh must be cut and bent to adapt it to individual anatomy and to avoid brain injury, especially near the lesser sphenoid wing. 7. Use as many screws as possible to fix the titanium mesh to the anterior skull base to push the pericranial flap against the skull base. 8. Cover the dura lesion of the frontobasal brain with TachoSil or a similar material.

Conflicts of interest None.

References 1. Bernal-Sprekelsen M, Rioja E, Enseñat J, Enriquez K, Viscovich L, Agredo-Lemos FE, Alobid I (2014) Management of anterior skull base defect depending on its size and location. Biomed Res Int. doi:10. 1155/2014/346873 2. Biron VL, Gross M, Broad R, Seikaly H, Wright ED (2012) Radial forearm free flap with titanium mesh sandwich reconstruction in complex anterior skull base defects. J Craniofac Surg 23(6):1763– 1765 3. Chin D, Harvey RJ (2012) Endoscopic reconstruction of frontal, cribiform and ethmoid skull base defects. Adv Otorhinolaryngol 74: 104–118 4. Eloy JA, Patel SK, Shukla PA, Smith ML, Choudhry OJ, Liu JK (2013) Triple-layer reconstruction technique for large cribriform defects after endoscopic endonasal resection of anterior skull base tumors. Int Forum Allergy Rhinol 3(3):204–211 5. Giovannetti F, Ruggeri A, Buonaccorsi S, Pichierri A, Valentini V (2013) Endoscopic endonasal approaches for cerebrospinal fluid leaks repair. J Craniofac Surg 24(2):548–553

Reconstruction of the anterior skull base after major trauma or extensive tumour resection.

The authors describe their experience with the reconstruction of complex anterior skull base defects after trauma or tumour resection using a "sandwic...
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