On the cutting edge: anterior transpetrosal approach – the middle fossa approach. Clinical application, surgical anatomy, and results

Nowadays, the middle cranial fossa approach (MFA) is one of the most useful operative procedures in skull base surgery. When performed properly, it provides a relevant adjunct to treating complex skull base lesions. MFA allows one to resect the anterior petrous bone (anterior petrosectomy), open the internal auditory canal (IAC), and access the lateral wall of the cavernous sinus and the infratemporal fossa. Knowledge of the anatomical structures of the middle cranial fossa and cavernous sinus is mandatory to perform this approach. We report in detail the standard extradural subtemporal route for the anterior petrosectomy and MFA. The main indications for this approach are intradural lesions localized medially to the trigeminal nerve, subtemporal interdural and extradural tumours and neoplasms involving the IAC (including IAC pathology). Moreover, we describe the extended middle fossa approach, consisting in the anterior extension of MFA, indicated for intradural tumours of the superior cerebello-pontine angle and of prepontine clivus (retroclival lesions, ventral brainstem tumours, and cavernomas), for infratemporal fossa lesions, and cavernous sinus pathologies. Even if the anatomical landmarks of the middle cranial fossa and lateral skull base are well known, training with cadaver dissection is necessary for any skull-base surgeon to perform an optimum MFA. The cadaver-lab dissections simplify the learning of anatomical structures, and prepare the surgeon properly for this technically challenging approach.