Response Changes During Insertion of a Cochlear Implant Using Extracochlear Electrocochleography.
Christopher K Giardina, Tatyana E Khan, Stephen H Pulver and 5 others
PMID 29554036WHAT IT FOUND
Extracochlear monitoring during cochlear implantation is feasible but complex.
While most insertions showed stable responses, about 21% had temporary drops that recovered. Early response losses often resolve, so a single drop does not confirm permanent trauma.
Key findings
01Extracochlear recordings were successfully maintained in 85% of cases where initial signals were detected, with no significant difference in quality between stapes and promontory sites.
02During insertion, 60.1% of subjects showed no significant response change, while 20.6% experienced drops that recovered by the end of the procedure.
03Response drops occurring within the first 15 mm of insertion were always at least partially reversible, whereas drops at deeper insertion levels were more likely to be permanent.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study focused on the feasibility of the monitoring technique rather than long-term hearing outcomes. A single drop in response magnitude cannot definitively confirm trauma, as temporary mechanical interactions can also cause signal loss. The recording electrode sometimes lost contact during surgery, which prevented monitoring in 15% of cases where initial signals were present.
Declared interests
Some authors are consultants for implant manufacturers (Advanced Bionics, Cochlear Corporation, MED-EL) and hold equity in a diagnostics company (Advanced Cochlear Diagnostics). Others declared no conflicts.
The easy way to misread this
Do not assume that a drop in response magnitude during cochlear implantation indicates permanent trauma. Early drops often recover, and the technique is still being developed for clinical use.