![]() ![]() In general, most cochlear disorders such as otosclerosis are evaluated by high-resolution CT imaging. CT is sometimes diagnostic in lesions 1.5 cm or greater in diameter when dedicated techniques are used, but it does not readily detect small brainstem lesions such as infarctions or demyelination. 22, 23, 32 – 34 Gadolinium contrast enhancement may be used. 31 Following preliminary audiometric or auditory brain response testing, patients with retrocochlear localization should have a complete MR imaging study of the head to include the internal auditory canal, temporal bones, central nuclei in the brainstem, and the auditory pathways extending upward into the cerebral hemispheres. Initial evaluation of symmetric or unilateral SNHL requires determination of whether the site of the lesion is cochlear 30 or retrocochlear. The imaging findings must be correlated with audiometry. Patients with fluctuating SNHL may have congenitally enlarged vestibular aqueducts (apertures greater than 4 mm) detected by either CT or MR imaging. Sensorineural hearing loss (SNHL) results from the pathologic changes of inner ear structures such as the cochlea or the auditory nerve 1 and is best evaluated with gadolinium-enhanced MR imaging. 17 – 19 Diseases of the internal auditory canal and cerebellopontine angle, such as tumors, are readily evaluated with CT and MR imaging techniques. Superior semicircular canal dehiscence, another cause of vertigo, can be diagnosed by high-resolution coronal CT imaging of the temporal bones. 13 Gadolinium enhancement of the labyrinthine structures or vestibular nerves may also occur and should not be mistaken for hemorrhage. 3, 4 Progressive labyrinthitis obliterans may be diagnosed on high-resolution CT. Labyrinthitis is usually viral in origin with few sequelae however, bacterial labyrinthitis may progress to partial or complete occlusion of the lumen of the affected labyrinth, detectable on MR imaging as loss of the signal intensity of the fluid contents. Vestibular neuritis and labyrinthitis may also cause vertigo. CT or MR imaging, or both, may be used to evaluate the vestibular aqueduct, endolymphatic duct, and sac and to rule out associated infectious or neoplastic disease. 2, 4 Ménière disease manifests as paroxysmal attacks of whirling vertigo due to failure of regulation of endolymph. Patients with benign positional vertigo rarely demonstrate imaging findings. Benign Positional Vertigo, Ménière Disease, and Peripheral Vestibular Disorders ![]()
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