Neuromonitoring of cochlea and auditory nerve with multiple extracted parameters during induced hypoxia and nerve manipulation.
A system capable of comprehensive and detailed monitoring of the cochlea and the auditory nerve during intraoperative surgery was developed. The cochlear blood flow (CBF) and the electrocochleogram (ECochGm) were recorded at the round window (RW) niche using a specially designed otic probe. The ECochGm was further processed to obtain cochlear microphonics (CM) and compound action potentials (CAP). The amplitude and phase of the CM were used to quantify the activity of outer hair cells (OHC); CAP amplitude and latency were used to describe the auditory nerve and the synaptic activity of the inner hair cells (IHC). In addition, concurrent monitoring with a second electrophysiological channel was achieved by recording compound nerve action potential (CNAP) obtained directly from the auditory nerve. Stimulation paradigms, instrumentation and signal processing methods were developed to extract and differentiate the activity of the OHC and the IHC in response to three different frequencies. Narrow band acoustical stimuli elicited CM signals indicating mainly nonlinear operation of the mechano-electrical transduction of the OHCs. Special envelope detectors were developed and applied to the ECochGm to extract the CM fundamental component and its harmonics in real time. The system was extensively validated in experimental animal surgeries by performing nerve compressions and manipulations.
Bohórquez
Jorge
J
Department of Biomedical Engineering, University of Miami, 219A Mc.Arthur Annex, PO Box 248294, Coral Gables, FL 33124-0621, USA. jbohorquez@miami.edu
Ozdamar
Ozcan
O
Morawski
Krzysztof
K
Telischi
Fred F
FF
Delgado
Rafael E
RE
Yavuz
Erdem
E
D000200:Action Potentials; D000465:Algorithms; D000818:Animals; D001783:Blood Flow Velocity; D003055:Cochlear Microphonic Potentials; D003056:Cochlear Nerve / Q000503:physiopathology*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D006198:Hair Cells, Auditory / Q000503:physiopathology; D000860:Hypoxia / Q000175:diagnosis* / Q000503:physiopathology; D007430:Intraoperative Care / Q000379:methods; D007511:Ischemia / Q000175:diagnosis / Q000503:physiopathology; D017078:Laser-Doppler Flowmetry / Q000379:methods; D008991:Monitoring, Physiologic / Q000379:methods; D009408:Nerve Compression Syndromes / Q000175:diagnosis* / Q000503:physiopathology; D011817:Rabbits; D000160:Vestibulocochlear Nerve Diseases / Q000175:diagnosis* / Q000503:physiopathology