Head and Neck ImagingLabyrinthitis
inflammation of the inner ear. Common symptoms are
sensorineural hearing loss and
vertigo. Labyrinthitis can be classified according to the mode of entry to the inner ear of the offending mechanism (tympanogenic, haematogenic, meningogenic, post-traumatic), or according to the aetiological agent (bacterial, viral, autoimmune, toxic).
Enhancement of the inner ear on gadolinium-enhanced T1-weighted MR images may be seen in labyrinthitis; this enhancement is usually not very pronounced and unsharply defined (Fig.1); see stapedectomy (VI:2), Fig. 2. In more chronic stages, fibrous obliteration of the fluid-filled labyrinth may occur; the normal high signal intensity of the fluid-filled labyrinth on thin-section T2-weighted images is then lost and a slightly elevated signal intensity on nonenhanced T1-weighted images may be seen. In a final stage, intralabyrinthine calcification occurs, visible on thin-section CT-images as calcification of the normally very hypodense inner ear structures; this last condition is known as labyrinthitis ossificans (Fig.2); see mastoidectomy (VI:2), Fig. 2)), and is most commonly seen as an end-stage of bacterial labyrinthitis.
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Axial T1-weighted spin-echo images of the temporal bones. The left posterior labyrinth (arrow) shows slightly increased signal intensity compared to the cochlea (arrowhead) on the plain image (a). After injection of gadolinium, moderate enhancement is seen in both labyrinths (b). Autoimmune labyrinthitis causing bilateral sensorineural deafness.
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Labyrinthitis, Fig.1 (a) | | Labyrinthitis, Fig.1 (b) | | Labyrinthitis, Fig.2 |