Diagnostic criteria for superior semicircular canal dehiscence syndrome
Reviewed by Victor Osei-Lah

The latest Bárány Society’s consensus document on diagnostic criteria for vestibular disorders is one for superior semicircular canal dehiscence syndrome (SCDS). There are three major categories: (A) Symptoms consistent with a third mobile labyrinthine window; (B) Physiologic tests – clinical signs and/or diagnostic test; and (C) Imaging. To diagnose SCDS, the patient must meet at least one criterion under each of A, B and C. The symptoms under A are: 1. Bone conduction hyperacusis; 2. Sound-induced vertigo and/or oscillopsia time-locked to the stimulus (the Tullio phenomenon); 3. Pressure-induced vertigo and/or oscillopsia time-locked to the stimulus; and 4. Pulsatile tinnitus. Bone conduction hyperacusis stands for “hearing one’s voice loudly or distorted in the affected ear (autophony), abnormal perception of one’s own internal body sounds like hearing loudly one’s eye movements or blinking, borborygmi, crepitus from jaw or neck movements, and footfalls’’. Pressure-induced vertigo can be elicited by Valsalva, coughing, sneezing or application pressure on the external ear canal. The signs under B are: 1. Nystagmus characteristic of excitation or inhibition of the affected superior semicircular canal evoked by sound, or by changes in middle ear pressure or intracranial pressure; 2. Low-frequency negative bone conduction thresholds on pure tone audiometry; and 3. Enhanced VEMP responses (low cervical VEMP thresholds or high ocular VEMP amplitudes). Video Frenzel or video-oculography is recommended to observe nystagmus elicited by Valsalva, audiometry or pressure on the external ear canal. Category C is perhaps the most important: High resolution temporal bone CT imaging with multiplanar reconstruction (in the plane of the SCC and orthogonal). The authors argued against dividing the disorder into ‘probable’ and ‘definite’ to remove the need for surgery as the most definitive way of confirming the dehiscence. The document provides useful comments on several related issues such as near dehiscence, the prevalence of bilateral disorder, unreliability of ECochG, differential diagnoses of SCDS and preference of HRCT over MRI. It is worth a read.

Superior semicircular canal dehiscence syndrome: Diagnostic criteria consensus document of the committee for the classification of vestibular disorders of the Barany Society.
Ward BK, Van de Berg R, Van Rompaey V, et al.
J VESTIB RES
2021;31(3):131-41.