Interest of Electro-physiological Findings in the Assessment of Symptoms Severity in Superior Semi-circular Canal Dehiscence Syndrome

Superior semi-circular canal dehiscence (SCD) syndrome can associate several cochlear and vestibular symptoms. Recent systematic reviews identified pulsatile tinnitus, autophony, sound-induced and pressure-induced vertigo as most specific signs of SCD. These signs are rarely all present and the symptomatology remains highly variable from a patient to another, with frequent though less evocative symptoms such as dizziness or ear pressure. A surgical treatment may be proposed when the symptoms become significantly incapacitating. Unfortunately to date, there is no objective marker of this severity and all surgical decisions rely on the importance of patients' complaints. High Resolution Computed Tomography (HRCT) of the temporal bone can confirm the diagnosis. Electro-physiological investigations such as Vestibular Evoked Myogenic potentials (VEMPs) have also been extensively described in the diagnosis of SCD but they have been reported as independent from the symptoms severity. Wideband tympanometry (WBT) and Electrocochleography (EcoG) have only been studied in few reports but the latter appears as a promising tool in the assessment of the symptoms because it explores inner ear biomechanics, directly involved in the pathophysiology of this condition.