HIGH-RESOLUTION COMPUTED TOMOGRAPHIC EVALUATION OF THE COCHLEAR CAPSULE IN OTOSCLEROSIS - RELATIONSHIP BETWEEN DENSITOMETRY AND SENSORINEURAL HEARING-LOSS

Otosclerotic cochlear involvement is a rather frequent disease that ha s not been clearly understood in terms of diagnosis and management. Ob jective evaluation methods are needed to confirm the clinical diagnosi s, investigate the relationship with hearing impairment, and validate the results of treatment. In this study two ear groups with bone condu ction hearing loss (BCHL) were investigated with audiometry and high-r esolution computed tomography (HRCT). In the first group (n = 22) the diagnosis of fenestral otosclerosis was confirmed at operation; the se cond group (n = 9) was composed of ears clinically suspicious for pure ly cochlear involvement. Additionally, a control group (n = 14) of oto logically normal ears was also studied. Foci of demineralization were demonstrated in 58% of the ears in the two groups; the sensorineural h earing loss (SNHL) in those ears was significantly worse than in those with normal radiologic findings. Three methods of MCT densitometry we re used to determine the abnormal regions in the cochlear capsule; the results suggested that hypodense regions were consistent with a great er degree of SNHL, in contrast to the hyperdense ones in ears with bet ter cochlear reserves. Agreement was found between the location of the density change and the frequency topography of the SNHL; densitometri c values were correlated with the bone conduction thresholds for certa in frequencies. It is concluded that the spongiotic foci are responsib le for the SNHL, since there was a correlation between their location and the SNHL frequency. The determination of better hearing in those e ars with sclerotic foci supports the hypothesis that the sclerotic pha se may not be a healing process following the spongiotic phase, and th at it can be the first stage of the disease.