Karen Buch MD, Presenter: Nothing to Disclose

Alex Gutierrez, Abstract Co-Author: Nothing to Disclose

Akifumi Fujita MD, Abstract Co-Author: Nothing to Disclose

Anand Devaiah MD, Abstract Co-Author: Nothing to Disclose

Osamu Sakai MD, PhD, Abstract Co-Author: Royalties, The McGraw-Hill Companies

Labyrinthitis ossificans (LO) is a pathologic process involving ossification of the membranous labyrinth leading to hearing loss. Prior studies describe multiple causes of LO including infection, inflammation, trauma, surgery, and hematologic etiologies. However, no prior study describes the pattern of labyrinth involvement. The purpose of this study was to identify potential etiology-specific ossification patterns using CT scans of patients with LO.

Following IRB approval, temporal bone CT scans of 34 LO patients were identified from scans done between November 2005-January 2012. Membranous labyrinth structures were evaluated for the degree of ossification and were assigned a grading score from 0-4 based on degree of ossification (0: no ossification, 1: <25%, 2: 25-50%, 3: 50-75%, and 4: > 75%). Medical records were reviewed for etiology of LO.

Of the 34 patients with LO: 19 patients had local infection/inflammation or surgery, 6 had history of meningitis, 4 had sickle cell disease, and 5 had other etiologies. Overall, the lateral semicircular canal had the highest degree of ossification and the vestibule had the least. In cases of local infection/inflammation all of the semicircular canals were most severely affected followed by the basal cochlea, middle cochlea, apical cochlea, and lastly, the vestibule. In cases of meningitis, the posterior and superior semicircular canals were most affected followed by the middle cochlea, apical cochlea, basal cochlea, lateral semicircular canal, and lastly, the vestibule. In cases of SCD, the lateral semicircular canal was most severely affected, then followed by the other structures in the membranous labyrinth with an equal distribution.  

LO results in specific patterns of membranous labyrinth involvement. Overall, the lateral semicircular canals were most severely affected and the vestibules were the least affected. Different causes of LO may result in different ossification patterns.

Etiology specific patterns of ossification appear to occur in LO. These findings may identify an underlying cause or predict progression of ossification in patients with labyrinthitis ossificans.

Buch, K, Gutierrez, A, Fujita, A, Devaiah, A, Sakai, O, Patterns of Ossification in Patients with Labyrinthitis Ossificans.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13018613.html