Neuroradiology of the Temporal Bone and Skull Base

Diagnostic imaging is indispensable in the evaluation of pathology of the temporal bone and lateral skull base. Magnetic resonance imaging (MRI), computed tomography (CT), angiography, and nuclear medicine studies aid otolaryngologists in the diagnosis of various conditions and are often crucial in surgical planning. High-resolution CT is the modality of choice for evaluation of bony anatomy. This imaging modality can be useful in the evaluation of pathologic conditions of the external auditory canal, mastoid, and petrous apex. High-resolution CT (HRCT) is also the best imaging modality to evaluate the bony labyrinth and key in the evaluation of superior semicircular canal dehiscence and for children with congenital sensorineural hearing loss. MRI is most helpful for visualizing the soft tissue structures and vasculature of the skull base using MR angiography and MR venography. Cholesteatoma and epidermoids have distinct imaging characteristics on MRI, with the most important being diffusion restriction (bright) on diffusion-weighted imaging (DWI), and MRI techniques for detection of residual cholesteatoma in lieu of a staged surgery are evolving. Other MRI sequences, including fast spin echo, fluid-attenuated inversion recovery (FLAIR), and fat-suppression, are helpful in distinguishing various pathologies of the temporal bone and lateral skull base. Often HRCT and MRI are used in tandem for diagnosis. Characteristic CT and MRI findings are critical to diagnose and define the extent of involvement of glomus tumors and in the identification of pathology of the cerebellopontine angle and petrous apex.