Superior Semicircular Canal Dehiscence (SSCD)
The diagnosis is C. Superior semicircular canal dehiscence (SSCD), as this is the only condition among the options that characteristically presents with the complete triad of conductive hearing loss, autophony, tinnitus, AND a preserved stapedial reflex with a normal tympanic membrane. 1
Key Diagnostic Features That Point to SSCD
The clinical presentation contains several pathognomonic features:
- Autophony is a hallmark symptom of SSCD and is NOT typical of otosclerosis or patulous eustachian tube in this clinical context 1
- Preserved stapedial reflex is the critical distinguishing feature—this essentially rules out otosclerosis, which characteristically shows absent or abnormal stapedial reflexes even with minimal conductive hearing loss 2
- Normal tympanic membrane combined with conductive hearing loss indicates the pathology is beyond the tympanic membrane but affecting the ossicular chain or labyrinthine windows 1, 3
Why Not the Other Options
Otosclerosis (Option A) - Ruled Out
- Otosclerosis typically presents with absent or abnormal acoustic reflexes due to stapedial fixation, even when the conductive component is minimal (≤10 dB) 2
- The presence of a preserved stapedial reflex in this patient makes otosclerosis highly unlikely 2
- While otosclerosis can present with tinnitus and conductive hearing loss with normal tympanic membrane, the preserved reflex contradicts this diagnosis 4, 2
Patulous Eustachian Tube (Option B) - Less Likely
- Patulous eustachian tube can cause autophony, but it does NOT typically cause conductive hearing loss or tinnitus as primary features
- The combination of hearing loss with autophony points more specifically to a third window phenomenon like SSCD rather than eustachian tube dysfunction
Diagnostic Approach
The American Academy of Otolaryngology-Head and Neck Surgery recommends the following workup:
- Formal audiometry should be obtained to characterize the hearing loss pattern—SSCD typically shows low-frequency conductive hearing loss with supranormal bone conduction thresholds 1
- Tuning fork testing (Weber and Rinne) should be performed to confirm the conductive component 1, 5
- CT temporal bone without contrast is the definitive imaging modality to visualize superior semicircular canal dehiscence 4
Clinical Pitfall to Avoid
The preserved stapedial reflex is the key clinical finding that prevents misdiagnosis. Never assume otosclerosis based solely on conductive hearing loss with normal tympanic membrane—always check the stapedial reflex, as its presence effectively excludes otosclerosis 6, 2.