The skull base includes the frontal bone, the sphenoid bone, the temporal bone, and the occipital bone. Tumors of the temporal bone and skull base tend to arise in one of three locations: (1) the mastoid or middle ear, (2) the jugular foramen, or (3) the petroclival junction or petrous apex. Tumors of the cerebellopontine angle and Meckel cave are not considered in this chapter (see Chapter 61, Nonacoustic Lesions of the Cerebellopontine Angle). Tumors arising within the skull base are rare and usually cause few symptoms until they grow to a size in which they begin to affect cranial nerves. Table 65–1 lists the various skull base neoplasms and their imaging characteristics.
Table 65–1. Radiographic Appearance of Skull Base Neoplasms. ||Download (.pdf)
Table 65–1. Radiographic Appearance of Skull Base Neoplasms.
|Neoplasm||Most Common Site of Origin in Skull Base||CT||T1-Weighted MRI||T2-Weighted MRI||Contrast Enhancement|
|Paraganglioma||Jugular foramen and middle ear||Bone destruction||Intermediate, with flow voids||High, with flow voids||Strong|
|Facial nerve schwannoma||Geniculate ganglion||Smooth remodeling and dilation of the surrounding bone of the facial canal||Intermediate||Intermediate||Strong; follows the course of the facial nerve|
|Geniculate hemangioma||Geniculate ganglion||Erosion of surrounding bone with bony spicules within tumor||Intermediate||High||Strong|
|Leukemia, lymphoma, and plasmacytoma||Petrous apex||Lytic lesion||Low||Intermediate||Moderate|
|Langerhans cell histiocytosis||Mastoid||Irregular bone destruction; may have other skull lesions as well||Intermediate||High||Moderate|
|Chondrosarcoma||Petroclival junction||Bone destruction, but can produce calcium matrix in 50% of tumors||Intermediate||High||Moderate or mixed|
|Chordoma||Clivus||Bone destruction, but can have bone remnants within it||Intermediate, with some areas of low signal representing mucus||High||Moderate or mixed|
|Meningioma||Posterior face of temporal bone||Surrounding hyperostosis and intratumoral calcification||Intermediate||Intermediate||Strong; characteristic dural tail|
|Intralabyrinthine schwannoma||Within the inner ear||Mass within labyrinth; no bone erosion||Low||Intermediate||Strong|
|Schwannoma of jugular foramen||Jugular foramen and middle ear||Soft tissue mass posterior to jugular bulb; mild, smooth bone erosion||Low||Intermediate||Strong|
|Rhabdomyosarcoma||Anywhere, predominant tumor of children||Bone destruction||Intermediate||High||Strong|
|Osteosarcoma||Anywhere||Either lytic osteoblastic or osteolytic; may have concentric rings of calcium||Intermediate||High||Strong|
|Adenoma||Middle ear||Middle ear soft tissue mass; no bone erosion||Low||Intermediate||Strong|
|Endolymphatic sac tumor||Posterior face of temporal bone||Bone destruction and erosion of otic capsule||Mixed, due to localized areas of mucus||Mixed||Strong|
|Carcinoma||Middle ear||Bone destruction||Intermediate||Intermediate||Strong|
|Metastatic disease||Petrous apex and internal auditory canal (IAC)||Lytic lesion||Intermediate||High||Strong|
The majority of skull base tumors are benign and can typically be successfully managed by an otolaryngologist specialized in neurotology and skull base surgery. Surgical approaches to these three areas are numerous, and the nomenclature is confusing. To remove a lesion of the middle ear or mastoid, a mastoidectomy through a postauricular incision or a middle ...