SSCD occurs when there is a thinning or loss of bone in the superior semicircular canal, a portion of the vestibular system located in the inner ear. This loss or thinning of bone can results in a multitude of systems for patients. Most commonly, patients will report vertigo and/or disequilibrium and hearing loss.

Patients also often report an increase of their own internal bodily sounds, such as their heartbeat, digestive sounds, or even eye movements. Additional symptoms such as tinnitus, sound sensitivity (hyperacusis), pressure sensitivity, aural fullness, and even headaches may occur.

For some patients, dizziness symptoms can even be brought on by a change in pressure. When symptoms are noticeable or severe, SSCD may be referred to as SCDS or superior canal dehiscence syndrome.

While we don't know the exact cause of this bone loss or thinning, SSCD is most commonly diagnosed in middle age. Diagnosis includes audiologic testing, vestibular testing, and electrophysiologic testing such as ECochG or VEMP. Radiographic imaging studies, such as a high-resolution CT (HRCT) are also used in the diagnosis of SSCD.

For some individuals with SCD, symptoms are very mild and may not require any intervention. For others, simply avoiding provoking behaviors, such as pressure changes, strenuous activities, or straining and heavy lifting, may be sufficient. If symptoms are severe, surgical intervention to plug the dehiscence may be required.

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A review of confirmed cases of SSCD was performed to assess the validity of using Electrocochleography as a diagnostic tool when looking for SSCD. After review of 20 confirmed cases, including 29 affected ears, it was shown that all affected ears presented with an abnormal ECochG.

For those with unilateral SSCD, a statistically significant difference was reported in the SP/AP value between the normal and affected ears. There was no significant relationship noted between abnormal SP/AP ratios and the degree of air-bone gap noted on the audiogram.

This study confirmed that ECochG is an effective diagnostic tool when assessing an individual for SSCD.

Source: Kileny PR, Cherry MM, McCaslin DL. Electrocochleography in the diagnosis of third window conditions. Front Neurol. 2024 Jan 4;14:1263513. doi: 10.3389/fneur.2023.1263513. PMID: 38239317; PMCID: PMC10795530.

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