Superior Semicircular Canal Dehiscence (SSCD)
The most likely diagnosis is C. Superior semicircular canal dehiscence (SSCD), based on the combination of hearing loss, tinnitus, autophony, and critically, a preserved stapedial reflex with a normal tympanic membrane. 1, 2
Key Diagnostic Features That Point to SSCD
The preserved (intact) stapedial reflex is the critical distinguishing feature in this case. In SSCD, the acoustic reflex remains present in 89% of cases despite conductive hearing loss, which differentiates it from otosclerosis where reflexes are typically absent. 2
Why Each Option Fits or Doesn't:
Otosclerosis (Option A) - EXCLUDED:
- Otosclerosis characteristically presents with absent acoustic reflexes due to stapes fixation 3
- The preserved stapedial reflex in this patient essentially rules out otosclerosis
- While otosclerosis can present with hearing loss and tinnitus, the intact reflex is incompatible with this diagnosis 3
Patulous Eustachian Tube (Option B) - EXCLUDED:
- While patulous eustachian tube does present with autophony, patients typically report autophony of nasal breathing as the predominant symptom 2
- SSCD mimics patulous eustachian tube with autophony of voice and blocked ear sensation (94% of cases), but without autophony of nasal breathing 2
- Patients with patulous tube typically get relief with Valsalva or supine position (50% in SSCD also report this, creating diagnostic confusion) 2
Superior Semicircular Canal Dehiscence (Option C) - CORRECT:
- The hallmark audiologic triad is: pseudoconductive hearing loss (86% of cases) + intact stapedial reflex (89%) + normal tympanic membrane 2
- Autophony of voice and "blocked ear" sensation occur in 94% of SSCD patients 2
- Tinnitus is present in approximately 27% of SSCD cases 4
Diagnostic Confirmation Required
High-resolution CT scan of the temporal bone with superior semicircular canal reformations (Pöschl and Stenvers views) is the definitive imaging test. 2, 5
Formal audiometry should be obtained immediately, looking specifically for: 1
- Low-frequency conductive hearing loss pattern
- Supranormal bone conduction thresholds (better than 0 dB HL at 250 and/or 500 Hz) - present in 60% of SSCD ears 2
- This "better than normal" bone conduction is pathognomonic for SSCD 2
Tuning fork testing (Weber and Rinne) should be performed to confirm the conductive component. 1
Common Diagnostic Pitfall
SSCD is a "great otologic mimicker" that frequently masquerades as otosclerosis or patulous eustachian tube. 2, 5 The key is recognizing that conductive hearing loss with a normal tympanic membrane and preserved acoustic reflexes cannot be otosclerosis. This combination should immediately trigger consideration of SSCD and prompt CT imaging. 5
Vestibular evoked myogenic potential (VEMP) testing has 91.4% sensitivity and 95.8% specificity for SSCD, potentially superior to CT alone. 2 Abnormally low VEMP thresholds support the diagnosis. 2