Hydrostatic fluid pressure in the vestibular organ of the guinea pig

Abstract

Since inner ear hair cells are mechano-electric transducers the control of hydrostatic pressure in the inner ear is crucial. Most studies analyzing dynamics and regulation of inner ear hydrostatic pressure performed pressure measurements in the cochlea. The present study is the first one reporting about absolute hydrostatic pressure values in the labyrinth. Hydrostatic pressure of the endolymphatic system was recorded in all three semicircular canals. Mean pressure values were 4.06 cmH(2)O ± 0.61 in the posterior, 3.36 cmH(2)O ± 0.94 in the anterior and 3.85 cmH(2)O ± 1.38 in the lateral semicircular canal. Overall hydrostatic pressure in the vestibular organ was 3.76 cmH(2)O ± 0.36. Endolymphatic hydrostatic pressure in all three semicircular canals is the same (p = 0.310). With regard to known endolymphatic pressure values in the cochlea from past studies vestibular pressure values are comparable to cochlear values. Until now it is not known whether the reuniens duct and the Bast's valve which are the narrowest passages in the endolymphatic system are open or closed. Present data show that most likely the endolymphatic system is a functionally open entity.

Intracochlear Pressure Changes due to Round Window Opening: A Model Experiment

“…The human cochlea and the vestibule are a functional unit. Fluid pressure transfer between the different labyrinthine compartments is widely described [21–23]. Therefore, a direct transfer to the saccus endolymphaticus as a pressure equalisation unit could be speculated.…”

Intracochlear Pressure Changes After Cochlea Implant Electrode Pullback—Reduction of Intracochlear Trauma

“…In contrast, the human cochlea and the vestibule are a functional unit. Fluid pressure transfer between the different labyrinthine compartments is widely described and should be considered when assessing these systems in vivo …”

“…Intracochlear pressure changes should be kept at a very low level before, during, and after the implantation . The cochlea has a dynamic fluid system, and as such, pressure applied to any part of the cochlea or to the electrode array itself is transferred through the cochlear partitions and can possibly interfere with the cellular structures. Pressure changes in the intracochlear fluid can be minimized by ensuring a large and/or laser supported opening of the round window membrane and a reduced insertion speed of the CI electrode array .…”

Lamellar projections in the endolymphatic sac act as a relief valve to regulate inner ear pressure

“…The force of this adhesion, in combination with the viscoelastic properties of the ES, likely determines the relief valve’s set point for volume and pressure homeostasis. For the inner ears of adult mammals, this set point is likely around 100–400 Pascals, although it is unknown how much the inner ear’s pressure and volume fluctuate ( Park et al, 2012 ). In our mutant over-inflation videos we observed an instance of an incomplete deflation ( Video 6 ) that contrasts with wild-type deflation cycles and mutant ES collapse after the otic vesicle was punctured ( Figure 6J ).…”