Semicircular canal fenestration – improvement of bone- but not air-conducted auditory thresholds

The effect of superior canal dehiscence on cochlear potential in response to air-conducted stimuli in chinchilla

“…We previously reported low-frequency increases in CP response to BC stimuli in chinchilla after the introduction of a SCD with a mean gain of 8.1 dB near 500 Hz . The increased sensitivity to BC in chinchilla is consistent with clinical observations of super-sensitive (<0 dB) BC thresholds in many patients with SCD syndrome (Minor et al, 2003;Mikulec et al, 2004) as well as those found in sandrat (Sohmer et al, 2004). At 500 Hz, the present study showed an 8.7 dB decrease in the chinchillas response to AC stimuli.…”

“…The decrease was largest (mean of 8.6 dB) at low frequencies (less than 500 Hz) and decreased in magnitude as frequency increased until the drop was no longer significant for frequencies above 4 kHz. A previous animal study of SCD in sandrat demonstrated no statistically significant changes in auditory sensitivity in response to air-conducted stimuli (Sohmer et al, 2004). Potential reasons for the differences in results between the two studies include:…”

“…Previous reports have investigated the role of SCDs on auditory sensitivity in response to boneconducted (BC) sound stimuli in an animal model Rosowski et al, 2004;Sohmer et al, 2004). These studies demonstrated that sensitivity to BC stimuli increases after the introduction of a dehiscence and that the increase is greatest at frequencies below 2 kHz .…”

Bilateral Dehiscence of the Bony Cochlear Basal Turn

“…Attempts to explain the possible functional implications of SCD itself have not reached an unequivocal statement. 5 It is even more difficult to explain the origin of auditory brainstem response anomalies, which might be associated with the carotid pulse, possibly leading to decreased detectability of the electrical activity of the cochlea. The strict contiguity between carotid artery and cochlea might also explain the onset or increased severity of tinnitus by some arterial wall alterations linked to age.…”

Bone conduction activation through soft tissues following complete immobilization of the ossicular chain, stapes footplate and round window

“…In addition, mechanical manipulations in experimental animals have also cast doubt on this classical mechanism of bone conduction activation of the cochlea, which requires two mobile windows with bulk fluid flow between them (Sohmer et al, 2004;Perez et al, 2011). These mechanical manipulations were extended in the present study by completely immobilizing the entire ossicular chain, stapes footplate and round window, and assessing bone conduction (and air conduction) thresholds by recording auditory nerve and brainstem evoked responses (ABR) before and after the manipulation of immobilization.…”