Hemorrhagic labyrinthitis.

Acute labyrinthitis can be caused by a variety of factors, such as toxicity, suppurative and viral infections, and autoimmune disorders. Symptoms can also be produced by neoplastic processes. The hallmark of all types of labyrinthitis on magnetic resonance imaging (MRJ) is enhancement of the membranous labyrinth on T1-weighted images following the administration of intravenous contrast medium (gadolinium). [1]

In the case presented here, a 25-year-old woman complained of symptoms of acute labyrinthitis, which manifested as a sudden and acute hearing loss accompanied by vertigo. Her case is unusual in that the T1-weighted MRI without contrast revealed diffuse, increased signal intensity throughout the membranous labyrinth, which extended into the endolymphatic sac (figure). Such a finding is consistent with a hemorrhagic process. Methemoglobin, with its shortT1 relaxation time on T1-weighted imaging, is easily identified in the membranous labyrinth because of the distinct contrast between it and the surrounding bony signal void of the otic capsule. [2] However, the high intensity of the hemorrhage in the labyrinth should be differentiated from lipomatous and proteinaceous material.

Labyrinthine hemorrhage occurs most often in trauma. However, in some cases, labyrinthitis in the acute stage may be hemorrhagic as well. Coagulopathies and neo-plastic processes are also unusual causes of labyrinthine hemorrhage.

From the Department of Radiology, MacNeal Hospital, Berwyn, Ill.

References

(1.) Valvassori GE, Buckingham RA. Acute otitis media, mastoiditis and malignant necrotizing external otitis. In: Valvassori GE, Mafee MF, Carter BL, eds, Imaging of the Head and Neck. New York: Thieme Medical Publishers, 1995:67-74.

(2.) Weissman JL, Curtin HD, Hirsch BE, Hirsch WL Jr. High signal from the otic labyrinth on unenhanced magnetic resonance imaging. AJNR Am J Neuroradiol 1992;13:1183-7.