Tinnitus: imaging algorithms.

The causes of tinnitus can be grouped according to whether the noise is continuous or pulsatile, whether it is subjective or objective and whether there is a retrotympanic mass. Imaging algorithms can be based on these symptoms and signs. For patients with nonpulsatile tinnitus and a normal drum, magnetic resonance imaging is preferred if a retrocochlear lesion is suspected, whereas high-resolution computed tomography (HRCT) is recommended if a cochlear abnormality is likely. If a chronic inflammation in the middle ear is suspected, HRCT is the study of choice to differentiate cholesteatoma from chronic otitis media. If the bruit is objective and the tympanic membrane normal, selective cerebral angiography should be the initial investigation, because most such patients have an acquired vascular abnormality, usually a dural arteriovenous fistula. If there is pulsatile tinnitus and a retrotympanic mass, HRCT should be the first examination because this technique allows differentiation of a vascular variation, such as an aberrant carotid artery or jugular dehiscence, from a paraganglioma.