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AJNR - American Journal of Neuroradiology

Published ahead of print on March 25, 2009
doi: 10.3174/ajnr.A1558

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American Journal of Neuroradiology 30:1435-1439, August 2009
© 2009 American Society of Neuroradiology

HEAD & NECK

CT Grading of Otosclerosis

T.C. Lee^a, R.I. Aviv^a, J.M. Chen^b, J.M. Nedzelski^b, A.J. Fox^a and S.P. Symons^a

^a Division of Neuroradiology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
^b Department of Medical Imaging, and Department of Otolaryngology–Head and Neck Surgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada

Please address correspondence to Sean Symons, BASc, MPH, MD, FRCPC, DABR, Sunnybrook Research Institute, 2075 Bayview Ave, AG31, Toronto, Ontario, Canada M4N 3M5; e-mail: sean.symons{at}sunnybrook.ca

BACKGROUND AND PURPOSE: The CT grading system for otosclerosis was proposed by Symons and Fanning in 2005. The purpose of this study was to determine if this CT grading system has high interobserver and intraobserver agreement.

MATERIALS AND METHODS: All 997 petrous bone CTs performed between December 2000 and September 2007 were reviewed. A total of 81 subjects had CT evidence of otosclerosis on at least 1 side; 68 (84%) had bilateral disease. Because otosclerosis was clinically suspected in both ears of all 81 subjects even if CT evidence was only unilateral, both petrous bones (162 in total) were included. Two blinded neuroradiologists independently graded disease severity using the Symons/Fanning grading system: grade 1, solely fenestral; grade 2, patchy localized cochlear disease (with or without fenestral involvement) to either the basal cochlear turn (grade 2A), or the middle/apical turns (grade 2B), or both the basal turn and the middle/apical turns (grade 2C); and grade 3, diffuse confluent cochlear involvement (with or without fenestral involvement). One reviewer repeat-graded the petrous bone CTs to determine intraobserver agreement with a 7-month intervening delay to mitigate recall bias.

RESULTS: There were 154 agreements (95%) comparing the first grading of reviewer 1 with that of reviewer 2 ( = 0.93). When the repeat 7-month delayed grading of reviewer 1 was compared with that of reviewer 2, there were 151 (93%) agreements ( = 0.90). Therefore, mean interobserver agreement was excellent (mean = 0.92). There were 155 agreements (96%) comparing the original grading of reviewer 1 with the delayed grading ( = 0.94), demonstrating excellent intraobserver agreement.

CONCLUSIONS: A recently published CT grading for otosclerosis on the basis of location of involvement yielded excellent interobserver and intraobserver agreement.