In superior semicircular canal dehiscence (SSCD) syndrome, which combination of findings is PATHOGNOMONIC?
- A Horizontal nystagmus on Dix-Hallpike, relieved by Epley manoeuvre
- B Fluctuating sensorineural hearing loss with tinnitus and aural fullness
- C Vertical-torsional nystagmus induced by Valsalva and loud sounds (Tullio phenomenon), with low-threshold air-bone gap and enhanced VEMPs ✓
- D Progressive unilateral SNHL with absent ipsilateral acoustic reflex
Correct answer: C. Vertical-torsional nystagmus induced by Valsalva and loud sounds (Tullio phenomenon), with low-threshold air-bone gap and enhanced VEMPs
Explanation
SSCD creates a third mobile window in the inner ear. The clinical hallmark is pressure- or sound-evoked vertigo/nystagmus (Valsalva and Tullio phenomenon), with a low-frequency conductive hearing loss without ossicular pathology (apparent air-bone gap on audiometry), absent stapedial reflexes on the affected side, and abnormally low-threshold cVEMPs. CT temporal bone (Pöschl plane) confirms dehiscence. This combination distinguishes SSCD from Meniere's disease, BPPV, and otosclerosis.
Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.
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