Learning Objectives:

Introduction: For a petrous apex lesion with serviceable hearing, the middle fossa (MF) craniotomy combined with transmastoid approach (TMA) is usually selected to preserve the labyrinth. However, this combination seems too invasive if the pathology is localized rather laterally. We have made a technical modification on TMA so that we can access a supralabyrinthine lesion more easily with an addition of partial MF craniectomy.

Case presentations: Case 1 was a 31-year-old female with right conductive hearing loss and no episodes of facial paralysis. CT/MRIs revealed a facial neuroma located in the genu through the tympanic segment. During the TMA the tumor was found to involve the labyrinthine segment, and thereby supralabyrinthine MF plate was drilled out to search the normal facial nerve proximally. This addition of partial craniectomy facilitated successful removal and cable graft.

Case 2 was a 42-year-old male with right conductive hearing loss. CT scans showed an epitympanic cholesteatoma extending to supralabyrinthine cells. Since the pathology was intraoperatively found to extend over the labyrinth and to invade the superior semicircular canal, tentative removal of the MF plate was decided during the TMA to achieve the complete removal without damaging the labyrinth.

Discussion: MF craniotomy usually needs an assistance of neurosurgeons, and therefore this approach seems difficult to add to TMA in a single operation depending on the intraoperative findings. Supralabyrinthine lesions still have a chance to be removed via TMA alone. If the pathology is found to extend more medially than expected during the TMA, an additional removal of the MF plate enables us to treat the lesions more easily under the more familiar surgical view.

Conclusion: Transmastoid MF craniectomy provides ear surgeons with better surgical access for laterally localized lesions in the petrous apex, and is indicated into supralabyrinthine cholesteatomas and facial neuromas.