Superior Semicircular Canal Dehiscence (SSCD)
The most likely diagnosis is superior semicircular canal dehiscence (SSCD), given the combination of unilateral hearing loss, tinnitus, autophony, and critically, a preserved stapedial reflex with a normal tympanic membrane.
Diagnostic Reasoning
The preserved stapedial reflex is the key distinguishing feature in this case:
- SSCD characteristically presents with autophony and hearing loss while maintaining a preserved stapedial reflex 1
- The stapedial reflex remains intact because SSCD creates a "third window" in the inner ear that does not affect middle ear mechanics or the stapedius muscle function
- Autophony of voice (but not necessarily breathing sounds) occurs in 94% of SSCD patients and can be easily mistaken for patulous eustachian tube 1
Why Not the Other Options
Otosclerosis (Option A) - Excluded
- Otosclerosis causes absent or diminished stapedial reflexes due to stapes fixation
- The preserved stapedial reflex in this patient rules out otosclerosis
- While otosclerosis can present with hearing loss and tinnitus, the combination with preserved reflexes is incompatible
Patulous Eustachian Tube (Option B) - Less Likely
- While patulous ET presents with autophony (voice and breath sounds in 92-93% of cases), it typically causes autophony of both voice AND breathing sounds 2
- The critical distinction is that SSCD autophony can be easily mistaken for patulous ET, but SSCD patients experience primarily voice autophony 1
- Patulous ET would show tympanic membrane movement with respiration on examination, which is not mentioned here 3, 4
- The normal tympanic membrane without respiratory movement makes patulous ET unlikely
Clinical Pearls and Pitfalls
Common diagnostic error: Confusing SSCD autophony with patulous eustachian tube 1. The key differentiator is:
- SSCD: Voice autophony predominates, preserved stapedial reflex, normal TM appearance
- Patulous ET: Both voice AND breath autophony, visible TM movement with respiration 3
Recommended Next Steps
- High-resolution CT temporal bone to visualize the superior semicircular canal dehiscence 5
- Comprehensive audiometry including bone conduction testing (SSCD typically shows supranormal bone conduction thresholds creating an apparent conductive hearing loss with normal middle ear function)
- Vestibular evoked myogenic potential (VEMP) testing would show reduced thresholds in SSCD
The combination of unilateral presentation, autophony, hearing loss, tinnitus, normal tympanic membrane, and preserved stapedial reflex creates a clinical picture most consistent with SSCD rather than the other options.