Background <p>Temporal bone osteomyelitis in necrotizing otitis externa is a threatening condition, especially in immune-deficient people, with a relatively high morbidity and mortality rate. The bone densitometry by computerized tomography scan is one of the best methods in the diagnosis of temporal bone osteomyelitis.</p> Methods <p>In this case–control study, 103 patients who suffered from unilateral temporal bone osteomyelitis were referred to two specialist referral hospitals in Tehran. The bone densities of different parts of the temporal bone and adjacent structures were compared with the contralateral healthy ear. The correlation between bone densitometry and the temporal osteomyelitis diagnosis was assessed.</p> Results <p>Seventy-five patients were male (72.8%), the mean age was 68 ± 10.2&#xa0;years, and the right ear was affected in 53 patients (51.5%). Twenty-seven patients (26.2%) had facial palsy. There was a significant difference in bone densities of four parts (mastoid cortex, external ear canal, mandibular condyle, and root of zygoma (paired <i>t</i>-test, <i>p</i>-value &lt; 0.05)) of eight regions in the temporal bone in the infected ear compared with the contralateral healthy ear. There was a significant correlation between mastoid cortex density decreasing and facial palsy. The linear regression test predicted a model for mastoid involvement based on the mastoid cortex density and facial palsy.</p> Conclusion <p>Bone density changes in temporal bone tomography can be an important predictive factor of disease and facial nerve involvement following temporal bone osteomyelitis.</p>