Imaging evalutation in otosclerosis: Single Photon Emission Computer Tomograhy versus Computed Tomograhy

OBJECTIVES: The aim of our study was to demonstrate the utility of diphosphonate bone single photon emission computed tomography (SPECT) in diagnosing otosclerosis and to correlate the findings from SPECT with age, gender, and sensorineural hearing loss. We also evaluated the ability of high-resolution computed tomography (HR-CT) in detecting otospongiotic and otosclerotic foci and correlated the HR-CT findings with the SPECT results. METHODS: Seventy-three subjects with surgically confirmed otosclerosis underwent SPECT, and 45 of the 73 patients also underwent HR-CT of the petrous bones. RESULTS: In the patient sample examined in this study, SPECT demonstrated a sensitivity of 95.2% and a specificity of about 96.7%. By correlating the SPECT findings, we found an inverse relationship between bone radioactivity and age (i.e., greater disease activity in younger patients) and a direct relationship between bone radioactivity and the severity of sensorineural impairment in younger patients. In the 45 patients who also underwent HR-CT, the sensitivity of HR-CT (58%) was lower than that of SPECT, and the comparison between SPECT activity and the HR-CT findings (fenestral or retrofenestral type) demonstrated a statistically significant correlation between the morphological finding of bone demineralization (pericochlear foci) and a high uptake index. CONCLUSIONS: The use of SPECT seems to be highly effective in differentiating normal from pathological petrous bone. It also provides a quantitative evaluation of disease activity and shows a significant correlation with bone demineralization revealed by HR-CT.