What are the diagnostic procedures and treatment options for otosclerosis (abnormal bone growth in the middle ear)?

Diagnosis of Otosclerosis

Otosclerosis is primarily a clinical diagnosis based on history, pneumatic otoscopy, pure-tone audiometry, and tympanometry, with high-resolution CT of the temporal bone (HRCT) reserved for cases requiring definitive confirmation. 1

Clinical Diagnostic Approach

The diagnosis follows a structured algorithm prioritizing clinical findings before imaging:

History and Physical Examination

• Pneumatic otoscopy is the primary examination method, typically revealing a normal-appearing tympanic membrane with normal mobility 1
• Look specifically for Schwartz sign (pinkish retrotympanic lesion visible on otoscopy), which represents increased vascularity over the promontory in active otosclerosis 1
• Patients commonly present with progressive conductive hearing loss, tinnitus (present in 73% of cases), and occasionally ear fullness (4% of cases) 2

Audiometric Testing

• Pure-tone audiometry is essential and typically demonstrates conductive hearing loss with characteristic patterns 1, 2
• Tympanometry should be performed, with most patients (68%) showing a type A tympanogram and 22% showing type As 2
• The Carhart notch (bone conduction dip at 2 kHz) is present in approximately 80.79% of cases, though its absence does not exclude otosclerosis 2, 3
• The Gelle test shows negative results in 92.09% of otosclerosis cases 2

Key Audiological Differential Diagnostic Features

• The difference between air-bone gap at 0.25 kHz and 4 kHz (0.25-4 kHzABG) is particularly useful for distinguishing otosclerosis from other conditions like incudostapedial disconnection 3
• If the 0.25-4 kHzABG is greater than 10 dB, otosclerosis is more likely; if less than 10 dB, consider alternative diagnoses like ossicular discontinuity (sensitivity 81.1%, specificity 55.0%) 3
• Reversed ipsilateral acoustic reflex at 0.5 kHz and negative contralateral acoustic reflex are statistically significant indicators favoring otosclerosis over ossicular chain disruption 3

Imaging Studies

When to Order HRCT

• HRCT without IV contrast is the definitive imaging modality when clinical diagnosis is uncertain or surgical planning requires anatomical confirmation 1, 4
• HRCT demonstrates positive findings in approximately 45.66% of otosclerosis cases 2

Technical Specifications

• Bone algorithm reconstructions are essential to visualize the subtle bony changes characteristic of otosclerosis 1
• IV contrast is not beneficial because diagnosis relies on evaluating bone contour and density changes 1
• Reconstructions should include axial, coronal, and sometimes oblique planes for complete assessment 5

Critical Imaging Pitfall

• Standard head CT is inadequate and should not be used, as it lacks the resolution to detect otosclerotic foci 1, 5

Differential Diagnosis Considerations

When evaluating for alternative diagnoses, HRCT can distinguish:

• Ossicular chain abnormalities: HRCT demonstrates ossicular erosion, fusion, or displacement 1
• Superior semicircular canal dehiscence: HRCT with Pöschl plane reconstructions shows bony dehiscence 1
• Congenital middle ear anomalies: HRCT reveals structural abnormalities 1

Diagnostic Algorithm Summary

1. Obtain detailed history focusing on progressive conductive hearing loss and tinnitus
2. Perform pneumatic otoscopy looking for normal tympanic membrane mobility and Schwartz sign
3. Complete pure-tone audiometry and tympanometry (type A or As pattern expected)
4. Calculate 0.25-4 kHzABG and assess for Carhart notch
5. Perform acoustic reflex testing (reversed ipsilateral and negative contralateral reflexes support diagnosis)
6. If clinical findings are diagnostic (normal otoscopy, conductive hearing loss, characteristic audiometric pattern), proceed with treatment planning without imaging 1
7. Order HRCT without contrast only when diagnosis is uncertain or surgical planning requires anatomical confirmation 1, 4