Simultaneous Intra- and Extracochlear Electrocochleography During Cochlear Implantation to Enhance Response Interpretation.
Leanne Sijgers, Flurin Pfiffner, Julian Grosse and 5 others
PMID 33710919WHAT IT FOUND
Early drops in intracochlear electrical signals during cochlear implant insertion often reflect electrode position changes rather than cochlear damage.
Simultaneous extracochlear recordings help distinguish these harmless shifts from true trauma, which typically appears as late signal decreases.
Key findings
01Early amplitude drops in intracochlear signals, when accompanied by phase shifts or distortion, were not matched by extracochlear drops and likely resulted from electrode movement rather than trauma.
02Late amplitude drops in intracochlear signals near full insertion were reflected in extracochlear recordings, suggesting they may correspond to cochlear trauma.
03No clear relationship was found between the observed intracochlear phase changes and pre- or postoperative hearing outcomes in this small cohort.
STILL TO COME
How it was doneWhat they found
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What it does not show
The study included only six subjects, making it impossible to draw general conclusions about efficacy or safety. The relationship between the observed signal patterns and actual hearing outcomes was inconsistent and not statistically established due to the small sample size. Intracochlear recordings were susceptible to noise, which affected the sum curves in several subjects. The study design was exploratory and did not test whether using this monitoring method improves patient outcomes.
Declared interests
The study was partially funded by Advanced Bionics, the manufacturer of the cochlear implant used, and by a Swiss innovation grant (Innosuisse). The authors declared no potential conflicts of interest.
The easy way to misread this
Do not interpret early drops in intracochlear ECochG signals as evidence of cochlear trauma. These changes often reflect the recording electrode moving past signal generators, a phenomenon distinguishable from true damage only by comparing against simultaneous extracochlear recordings.