Chapter 11 - Combined Middle Fossa Craniotomy and Mastoidectomy for Cerebrospinal Fluid Leak Repair and Encephalocele Resection

Summary

Lateral skull base meningoencephalic herniations (MEH) are rare instances where dura mater (meningocele) or cerebral tissue (encephalocele) protrudes through skull base dehiscences, commonly in the tegmen tympani or mastoidium. Encephaloceles and cerebrospinal fluid (CSF) leaks carry great risk, as they provide a potential pathway from the middle ear to the subarachnoid space. Patients often present with non-specific clinical symptoms, so a high degree of clinical suspicion is needed, with a thorough radiologic assessment to confirm the diagnosis and location of bony defects. Early detection and surgical repair of encephaloceles or CSF leaks are imperative. Typical surgical approaches for lateral skull base encephaloceles are based on surgeon experience and include the transmastoid (TM), middle cranial fossa (MCF), and combined TM and MCF approach. In general, the TM approach is used for small defects, and for larger defects, the MCF or combined approach is typically the procedure of choice. When there is no possibility of hearing preservation or rehabilitation, a middle ear obliteration (MEO) can be considered as it has very low recurrence rates and provides definitive treatment. Our institution prefers the combined transmastoid and keyhole middle cranial fossa approach.