This defect of the anterior skull base typically involves the area between the orbits, and include the cribriform plate and ethmoid sinus. The defect can extend anteriorly to the anterior table of the frontal sinus and posteriorly to the sphenoid sinus.
This typically results from the resection of an ethmoid or maxillary sinus tumor invading the skull base. It can also be created by the resection of a primary olfactory tumor. This defect can also result from severe frontal sinus and skull base trauma.