Making the diagnosis
Diagnosis & tests
No single test makes the diagnosis. It is made by concordance — symptoms, physiology and imaging agreeing — because a dehiscence on a scan is common and easily over-called.
The audiometric signature
A hearing test in SSCD can look like a middle-ear (conductive) problem — but the giveaway is that bone-conducted sound is heard better than normal, and the middle-ear reflexes still work. That combination points to the inner ear, not the middle ear.
The audiogram shows a low-frequency air–bone gap — but with supranormal bone conduction (thresholds better than 0 dB) and preserved acoustic reflexes, unlike true conductive loss.1
This is the crux that prevents a wrong operation: the same air–bone gap in otosclerosis comes with absent reflexes. Check reflexes before ever attributing a low-frequency gap to the stapes.1
Audiogram — affected ear
air (O) bone (<) gap shaded
Cervical-VEMP threshold
The affected ear responds at a lower threshold than the normal range (shaded) — the third window makes the saccule abnormally sound-sensitive. Ocular-VEMP amplitude is correspondingly raised.
VEMP — the physiologic test
VEMPs are the most useful physiologic test: the third window lowers the cervical-VEMP threshold and raises the ocular-VEMP amplitude on the affected side.2 See the VEMP chapter for technique and the full pattern library.
Imaging — confirm, don’t over-call
High-resolution temporal-bone CT confirms the defect, but axial slices over-call thin bone by partial-volume averaging. Reformat in the plane of the canal (Pöschl) and orthogonal to it (Stenvers):
For indications and protocols across vertigo, see Role of imaging.
Putting it together — the concordance check
Diagnosis requires the strands to agree. Note what happens with imaging alone: a dehiscence on CT without symptoms is an incidental finding, not the syndrome.3
Diagnostic-confidence checker
Switch on each strand that is present. Concordance of all three gives a confident diagnosis.
Key points
- Low-frequency air–bone gap with supranormal bone conduction and PRESERVED reflexes — not true conductive loss.
- VEMP: low cervical threshold, high ocular amplitude on the affected side — the key physiologic test.
- Confirm on CT reformatted in the Pöschl and Stenvers planes; axial slices over-call thin bone.
- Diagnose by concordance — imaging alone, without symptoms, is an incidental finding.