Change in endocochlear potential during experimental insertion of a simulated cochlear implant electrode in the guinea pig. 2014

Hidetoshi Oshima, and Ryoukichi Ikeda, and Kazuhiro Nomura, and Muneharu Yamazaki, and Hiroshi Hidaka, and Yukio Katori, and Takeshi Oshima, and Tetsuaki Kawase, and Toshimitsu Kobayashi
*Department of Otolaryngology-Head and Neck Surgery, Tohoku University School of Medicine; and †Division of Otorhinolaryngology, Sendai Municipal Hospital, Sendai, Japan.

OBJECTIVE Preservation of residual hearing during cochlear implantation is important. This study investigated changes in endocochlear potential (EP) during simulated cochlear implant (CI) electrode insertion. METHODS Laboratory animal study. METHODS Academic hospital laboratory. METHODS Guinea pigs were divided into 4 groups: cochleostomy only (4 animals), suction after cochleostomy (5 animals), simulated CI electrode insertion parallel to the longitudinal axis of the scala tympani without suctioning (7 animals), and simulated CI electrode insertion toward the modiolus without suctioning (7 animals). The EP was measured from the second turn of the cochlea, and the values after 20 minutes were compared. RESULTS The EP showed little change at 20 minutes after cochleostomy with a nearly normal value of 84.83 ± 2.12 mV. Suctioning of the perilymph from the cochleostomy site caused a slight acute reduction in EP by about 6 mV, and the value at 20 minutes after cochleostomy was 78.64 ± 4.42 mV. Insertion of the simulated CI electrode parallel to the longitudinal axis of the scala tympani caused a slight decrease in EP to 78.91 ± 5.06 mV. Insertion toward the modiolus caused a marked decrease in EP to 54.13 ± 4.42 mV at 20 minutes after the treatment, significantly lower compared with the other 3 groups. CONCLUSIONS EP was well preserved during carefully performed surgical procedures of simulated CI electrode insertion, but it decreased significantly if the simulated CI electrode was inserted toward the modiolus. Careful attention is necessary to ensure the correct direction of CI electrode insertion to preserve residual hearing. Use of suction should be minimized if possible.

UI MeSH Term Description Entries
D008297 Male Males
D008564 Membrane Potentials The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization). Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D010498 Perilymph The fluid separating the membranous labyrinth from the osseous labyrinth of the ear. It is entirely separate from the ENDOLYMPH which is contained in the membranous labyrinth. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1396, 642) Perilymphs
D003051 Cochlea The part of the inner ear (LABYRINTH) that is concerned with hearing. It forms the anterior part of the labyrinth, as a snail-like structure that is situated almost horizontally anterior to the VESTIBULAR LABYRINTH. Cochleas
D003054 Cochlear Implants Electronic hearing devices typically used for patients with normal outer and middle ear function, but defective inner ear function. In the COCHLEA, the hair cells (HAIR CELLS, VESTIBULAR) may be absent or damaged but there are residual nerve fibers. The device electrically stimulates the COCHLEAR NERVE to create sound sensation. Auditory Prosthesis,Cochlear Prosthesis,Implants, Cochlear,Auditory Prostheses,Cochlear Implant,Cochlear Prostheses,Implant, Cochlear,Prostheses, Auditory,Prostheses, Cochlear,Prosthesis, Auditory,Prosthesis, Cochlear
D006168 Guinea Pigs A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research. Cavia,Cavia porcellus,Guinea Pig,Pig, Guinea,Pigs, Guinea
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012533 Scala Tympani The lower chamber of the COCHLEA, extending from the round window to the helicotrema (the opening at the apex that connects the PERILYMPH-filled spaces of scala tympani and SCALA VESTIBULI). Scala Tympanus,Tympani, Scala,Tympanus, Scala
D019929 Cochlear Implantation Surgical insertion of an electronic hearing device (COCHLEAR IMPLANTS) with electrodes to the COCHLEAR NERVE in the inner ear to create sound sensation in patients with residual nerve fibers. Cochlear Prosthesis Implantation,Cochlear Implantations,Cochlear Prosthesis Implantations,Implantation, Cochlear,Implantation, Cochlear Prosthesis,Implantations, Cochlear,Implantations, Cochlear Prosthesis,Prosthesis Implantation, Cochlear,Prosthesis Implantations, Cochlear

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