From the Guidelines
Otosclerosis is a significant condition that can cause conductive hearing loss and is characterized by abnormal bone growth in the middle ear.
Key Points
- Otosclerosis can appear as a pinkish retrotympanic lesion (Schwartz sign) on otoscopy 1
- High-resolution thin-section temporal bone CT (HRCT) without IV contrast is the imaging modality of choice for diagnosing otosclerosis and other conditions that cause pulsatile tinnitus or conductive hearing loss 1
- Otosclerosis can be identified on CT by changes of otospongiosis, which can lead to ossicular erosion or fusion and round window occlusion 1
- The use of bone windows is essential for evaluating the temporal bone and identifying details of temporal bone morphology, such as ossicles 1
- Otosclerosis is one of the possible causes of tinnitus in the setting of asymmetric hearing loss or vertigo, and imaging should be guided by the ACR Appropriateness Criteria “Hearing Loss and/or Vertigo” 1
From the Research
Significance of Otosclerosis
The significance of otosclerosis, a bone condition affecting the stapes bone within the otic capsule, lies in its impact on hearing loss, particularly conductive hearing loss, and its potential to cause secondary symptoms such as sensorineural hearing loss and mixed hearing loss 2, 3.
Causes and Risk Factors
- The exact cause of otosclerosis is still unknown, but it is characterized by a lack of proper remodeling of newly formed vascular and woven bone, leading to the development of abnormal osteons and the formation of sclerotic bone 2.
- Genetic factors play a significant role in the manifestation of otosclerosis, with rare autosomal dominant forms caused by a single gene, and complex forms caused by an interaction between genetic and environmental factors 4.
- Environmental factors such as estrogens, fluoride, and viral infection have also been implicated in the etiopathogenesis of otosclerosis 4, 5.
Clinical Symptoms
- The primary clinical symptom of otosclerosis is conductive hearing loss, but sensorineural hearing loss and mixed hearing loss can also occur as secondary symptoms of the condition 2, 3.
- Tinnitus is another symptom present in patients with otosclerosis 2.
- The onset of symptoms typically occurs by the early third decade of life, and bilateral otosclerosis is seen in 80% of patients, with 60% having a family history of the condition 2.
Histopathological Features
- Histopathological studies of otosclerosis have shown that osteoblasts, osteoclasts, vascular proliferation, fibroblasts, and histiocytes are observed in the stapes footplate 2.
- The stapes specimen may exhibit osteoarthritis, with features such as surface fissuring, cartilaginous erosion, and irregularity of the osteochondral interface 6.