A 38-year-old woman presents with episodic vertigo lasting 20 minutes, triggered by loud sounds (Tullio phenomenon) and straining (Valsalva). She also reports autophony (hearing her own heartbeat). CT temporal bone shows thinning/absence of bone over the superior semicircular canal. The diagnosis is:
- A Benign paroxysmal positional vertigo (Bposterior canal)
- B Perilymphatic fistula
- C Superior semicircular canal dehiscence syndrome (SCDS) ✓
- D Meniere's disease
Explanation
Superior semicircular canal dehiscence syndrome (SCDS) results from absence of the bone overlying the superior (anterior) SCC at the arcuate eminence, creating a pathological 'third window'. This allows sound or pressure to create abnormal fluid movements in the membranous labyrinth. Characteristic features include Tullio phenomenon (sound-induced vertigo/oscillopsia), pressure-induced vertigo (Valsalva, nose blowing), pulsatile tinnitus, low-frequency conductive hyperacusis, and autophony. HR-CT temporal bone in coronal plane confirms the dehiscence. cVEMP shows abnormally low thresholds.
Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.