Penetrating skull base injury is not the same as a skull base injury associated with closed head injury. Accepted management of cerebrospinal fluid leakage in the setting of skull base injury or disruption associated with closed head injury may include a period of observation to determine if the leak will seal without intervention104,105. This will likely not occur in penetrating skull base injury, especially with penetration through air sinuses. It is the opinion and experience of the current authors that significant delay in repair will simply guarantee infection and not resolution. With this in mind, penetrating skull base injury repair should occur as soon as safe and feasible (i.e., assembly of appropriate operative resources including multi-disciplinary expertise (plastic surgery, ENT/OMFS, ophthalmology)106,107 as appropriate; associated cerebrovascular injury diagnosed and potentially addressed). In the authors' experience, it is the anterior fossa that is most often injured, followed by middle fossa injury through the lateral wall of the sphenoid sinus.

It is beyond the scope of this algorithm to address the specific technical nuances of individual skull base approaches and repair techniques. The following will address the main areas that should be considered during penetrating injury repair. The goals of surgery remain first and foremost cranial decompression and control of hemorrhage, followed by skull base repair and prevention of cerebrospinal fluid leak. Patient positioning and operative exposure should therefore account for the location of the skull base injury, and the possible need for cerebral decompression. Harvest of a large vascularized pericranial flap during exposure adds little time to the procedure and can facilitate adequate repair. Assuming adequate cranial decompression without rapid and malignant swelling, it is then necessary to approach the area of skull base disruption. Exenteration and cranialization of the frontal sinuses may be necessary if the anterior fossa is disrupted. Approach to orbital or ethmoidal penetrating injury may include an intra- and extra-dural exposure, and may also require endoscopic augmentation with naso-septal flap or other techniques107-111. If significant bone disruption is present, repair with autologous (split thickness) cranial bone is preferable over synthetic materials (i.e. timesh). Most importantly, every effort should be made to avoid CSF leak, including the use of dural sealants, primary dural closure where possible, and cerebrospinal fluid diversion. The importance of achieving a water tight dural closure takes precedence over the desire to avoid the use of synthetic materials or devascularized tissues within a contaminated wound in this context. Broad spectrum antibiotic coverage, depending on the wounding mechanism and degree of contamination, will likely be necessary for a period of time.