Subjective and Objective Findings in Patients With True Dehiscence Versus Thin Bone Over the Superior Semicircular Canal

Abstract

Among the objective tests, cervical VEMP and pure-tone audiometry are the only tools to distinguish between true dehiscence and thin bone over the SSC. DHI does not differentiate between these two groups. Furthermore, no correlation exists between DHI and any objective finding. Further investigation is necessary to develop a validated subjective symptom index of patients with SSC syndrome.

Superior semicircular canal dehiscence syndrome

“…92,94 The VEMP can also distinguish between patients with near dehiscence, or thin bone, versus those with true dehiscence over the SSC, both of whom can present with similar symptoms. 53 Following successful repair of the dehiscence, the VEMP normalizes. 13,88…”

“…11 Some prefer the transmastoid approach for repair of medially located SSCD adjacent to the superior petrosal sinus. 53,80 This surgical approach, however, offers more limited visualization of the dehiscence and may be less favorable in the setting of a poorly pneumatized temporal bone, low-lying temporal fossa, or extensive concurrent tegmen defects. Concurrent plugging of the defect, along with reconstruction or resurfacing of the floor, is achievable through either a middle fossa or a transmastoid approach.…”

Is MRI Equal to CT in the Evaluation of Thin and Dehiscent Superior Semicircular Canals?

“…Dehiscence of the posterior semicircular canal has also been described 3,4 as well as thin or near-dehiscence of the semicircular canals. 5,6 Workup includes audiogram with tympanometry and acoustic reflexes as well as vestibular evoked myogenic potential (VEMP) thresholds, which are usually abnormally low in SSCD, 7 but generally relies on imaging for confirmation.…”

Neuro-otology- some recent clinical advances

“…Similarly, if the patient has only an impaired posterior canal vHIT, then an absent ipsilateral cervical VEMP supports the diagnosis of inferior vestibular neuritis [101, 106]. VEMPs can also help decide if a radiologically suspected superior canal dehiscence is likely to be symptomatic [155]: if the air-conducted oVEMP from that side has a low threshold and a large amplitude, then it probably is [156–158]. …”