Type I includes tumors mainly confined to Meckel’s cave (MC).
Type II includes MC meningiomas with major extension into the middle fossa with or without extension to the cavernous sinus (CS)
Type III includes MC meningiomas with major extension into the cerebellopontine angle (CPA)
Type IV includes MC meningiomas with extension both into the middle fossa and into the CP angle with or without infiltration of the CS.
Meningiomas affecting MC may extend in different directions and may therefore show distinct surgical problems. In the surgical decision-making process, the following factors must be considered:
(1) tumor mass extension into the neighboring structures, principally into the CPA and middle fossa
(2) the presence of CS infiltration and carotid artery encasement
(3) typical images of en plaque tumor growing
(4) petrous apex erosion and involvement of the petrous bone. Cranial nerve (CN) impairment, especially of III, IV and VI CNs, can provide additional information about tumor invasion of the CS 1).