Vestibular Evoked Myogenic Potentials in Subject With Superior Canal Dehiscence Syndrome

Superior canal dehiscence syndrome (SCDS) is characterized by absence of the roof of the superior semicircular canal. Sound stimuli of higher decibels can cause vertigo and oscillopsia in these patients. A 38-year-old lady complaining about vertigo attacks associated with loud sounds as well as coughing and sneezing was evaluated. Her audiogram revealed a mild conductive type hearing loss on the left side. The caloric responses were normal. Vestibular evoked myogenic potential (VEMP) latencies recorded from the sternocleidomastoid muscles (SCM) were normal bilaterally (p13 and n 23 latencies were 13.0 ms, 20.7 ms on the left side and 12.7 ms, 22.6 ms on the right side). The amplitude of the n13-p23 potential was 204 mu V on the left and 78 mu V on the right side. Repeated recordings showed that the amplitude asymmetry was persisting. Dehiscence of the superior canal acts as a third window and causes pressure and sound sensitivity. VEMPs can be recorded easily in patients with the abovementioned complaints to support the diagnosis before a high resolution temporal bone CT is performed.