Computed tomography and otosclerosis: a practical method to correlate the sites affected to hearing loss

We present a practical method for correlating computed tomography (CT) scans with hearing loss in otosclerosis.

We reviewed the CT scans of 18 patients (34 ears) with clinical otosclerosis who were seen between 2007 and 2008. The scans were reviewed by an otologist in a clinical office setting, followed by a blinded radiologist working at an imaging workstation. The 5 most commonly affected sites in otosclerosis were evaluated for evidence of otospongiosis and then correlated with the degree of air-bone gap and sensorineural hearing loss.

Positive CT findings were noted in 70.5% of ears, with a 94% concordance between readings. The sites affected included the ante fenestram (21 ears), round window niche (12), cochlear promontory (4), cochlear apex (3), and posterior fenestram (2). The average air-bone gap increased with each additional site of involvement within an otic capsule (p = 0.004). The bone conduction threshold also increased, on average, with each additional affected site (p = 0.047).

Most patients with clinical evidence of otosclerosis have evidence of otosclerosis on CT that is readily detected in the office setting. Ears with more affected sites have a significantly greater degree of air-bone gap and sensorineural hearing loss.