The effect of superior canal dehiscence on cochlear potential in response to air-conducted stimuli in chinchilla.
A superior semicircular canal dehiscence (SCD) is a break or hole in the bony wall of the superior semicircular canal. Patients with SCD syndrome present with a variety of symptoms: some with vestibular symptoms, others with auditory symptoms (including low-frequency conductive hearing loss) and yet others with both. We are interested in whether or not mechanically altering the superior canal by introducing a dehiscence is sufficient to cause the low-frequency conductive hearing loss associated with SCD syndrome. We evaluated the effect of a surgically introduced dehiscence on auditory responses to air-conducted (AC) stimuli in 11 chinchilla ears. Cochlear potential (CP) was recorded at the round-window before and after a dehiscence was introduced. In each ear, a decrease in CP in response to low frequency (<2 kHz) sound stimuli was observed after the introduction of the dehiscence. The dehiscence was then patched with cyanoacrylate glue leading to a reversal of the dehiscence-induced changes in CP. The reversible decrease in auditory sensitivity observed in chinchilla is consistent with the elevated AC thresholds observed in patients with SCD. According to the 'third-window' hypothesis the SCD shunts sound-induced stapes velocity away from the cochlea, resulting in decreased auditory sensitivity to AC sounds. The data collected in this study are consistent with predictions of this hypothesis.
Songer
Jocelyn E
JE
Eaton-Peabody Laboratory of Auditory Physiology, Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114, USA. jocelyns@mit.edu
Rosowski
John J
JJ
D000161:Acoustic Stimulation; D000388:Air; D000818:Animals; D002682:Chinchilla / Q000033:anatomy & histology / Q000502:physiology*; D003055:Cochlear Microphonic Potentials / Q000502:physiology*; D004195:Disease Models, Animal; D006801:Humans; D007759:Labyrinth Diseases / Q000473:pathology* / Q000503:physiopathology*; D008954:Models, Biological; D012665:Semicircular Canals / Q000473:pathology* / Q000503:physiopathology*; D013045:Species Specificity; D013577:Syndrome