Physiology of the semicircular canals after surgical plugging

Inactivation of individual semicircular canals by surgical occlusion (plugging) of the slender duct has been used in basic studies to elucidate the role of individual canal inputs to vestibular-mediated control systems and in clinical applications to treat certain vestibular disorders. The procedure has been shown to be highly effective in blocking sensitivity of individual canals, at least for moderate angular motion stimuli. Effectiveness does not extend to stimuli involving high accelerations where a residual response persists even after complete occlusion of the duct. The residual can be quite large at high-stimulus frequencies where sensitivity to angular motion approaches that of patent canals. The overall physiological effect of canal plugging is reported here in terms of the frequency-dependent attenuation in gain and phase shift of primary afferents. Plug-canal responses are quantitatively described in terms of biomechanics of the deformable labyrinth.