9.3  Principles of Skull Base Reconstruction

The collagen fiber network functions as a matrix, which the connective tissue cells invade and ultimately transform to a neo-dura (Chaplin et al. 1999; Christmann 2003).

a transcranial, extradural approach (Draf and Samii 1983; Probst 1986; Probst and Tomaschett 1990).

9.2.3  Alloplastic Synthetic Dural

Substitutes

Dural substitutes comprise a diversity of synthetic materials, among them polytetrafluoroethylene (ePTFEGORETEX), biosynthetic cellulose and polyesterurethane (NEUROPATCH).

Neuropatch

Neuropatch is a fine fibrillate microporous fleece manufactured from ultrapure aliphatic polyurethane. Its structure is characterized by open micropores on the surface of the fleece, which significantly facilitate an efficient immigration of cells. It is also characterized by exceptional tissue compatibility and biostability.

Fibroblasts migrate into the microporous structure and deposit collagen, so anchoring the fleece to the tissues. There is an absence of giant cell foreign body infiltration. There is no aggregation of lymphocytes, eosinophils, and neutrophil granulocytes or mononuclear macrophages within the implant, which could suggest a chronic inflammatory or hyperallergic reaction. Neomembranes are formed, which encase the dural substitute-fleece. These neomembranes remain very thin and do not form material-induced adhesions with the brain.

The appropriately trimmed fleece should be fixed with nonabsorbable sutures (polyester, polypropylene). Atraumatic sutures enable fixation without damaging the fleece; additionally it is sealed with fibrin glue.

9.3  Principles of Skull Base

Reconstruction

Before the skull base is reconstructed, a debridement of the traumatized paranasal sinuses (ethmoid cells, frontal sinus) has to be done in order to prevent ascending intracranial infections. Recommendations range from radical transethmoidal or subcranial-transethmoi- dal debridement to conservative ethmoidectomy from

9.3.1  Debridement of the Ethmoid Cells

According to neurosurgical experience, removal of debris in the region of the paranasal sinuses can be reliably achieved from the cranial aspect using the surgical technique from Unterberger (1959) (Probst and Tomaschett 1990).

In particular, debridement of the frontal sinus, anterior, and middle ethmoid can be carried out efficiently starting in the extradural space.

Debridement of the anterior and middle ethmoid from the cranial aspect provides sufficient communication to the nose to ensure secretion drainage from the posterior ethmoid and the sphenoid sinus into the nasopharynx (Probst and Tomaschett 1990).

If fractures without significant comminution exist, the treatment may be alternatively carried out from a frontoorbital or endonasal approach without ethmoidectomy through the cranial approach. A similar treatment can be used, if the posterior ethmoid and the sphenoid sinus are involved (Imhof 2000; Ernst et al. 2004).

The extradural restoration of the posterior ethmoid cells and the sphenoid sinus, however, is problematic. Following severe injury, the subarachnoidal space often cannot be identified and the comminuted paranasal sinuses are communicating with the subarachnoidal space (Probst and Tomaschett 1990).

If the basal dura over the posterior ethmoid cells (arachnoidal and dural tears) and over the sphenoid sinus is severely injured, it has to be repaired by a combined endonasal (ENT) and intradural approach (NC) (Ernst et al. 2004).

9.3.2  Debridement (Cranialization)

of the Frontal Sinus

Whenever possible, the anterior sinus wall is preserved or reconstructed when performing an osseous debridement in the region of the frontal sinus (Ewers et al. 1995).