Introduction:
With regard to intraoperative quality assurance during cochlear implantation, recording
telemetrically evoked compound action potentials (TECAPs) alongside impedance recordings
have been the diagnostic mainstay for many years. In addition, the recently developed
spread of excitation (SOE) measurements are expected to reflect the position of the
cochlear implant electrode carrier inside the cochlea. We examined intraoperative
SOE recordings in terms of practicability and meaningfulness.
Methods:
Between 20th December 2016 until 2nd November 2017, 14 patients (8 female, 6 male),
aged between 6 and 71 years, received a cochlear implant type CI 532 (Cochlear Ltd.,
Melbourne, Australia). Implantation was performed in 6 left and 8 right ears. After
establishing SOE measurements starting from June 2017, we performed intraoperative
measurements in 12 patients.
Results:
SOE responses could be recorded in 10 patients. In five cases SOE results suggested
a tip fold over although the manufacturer's recommendations for electrode insertion
were adhered to. Tip fold over occurred in various positions between electrode 11
and 19, as confirmed by intraoperative x-ray. In all cases, impedance values and TECAPs
were normal. After reinserting the electrode carrier, SOE measurements were only partially
recordable, while intraoperative x-ray confirmed the carrier's correct position.
Conclusions:
SOE recordings indicated abnormalities of the electrode carrier's position after its
primary insertion with high reliability. A prerequisite is the measurability of TECAPs,
which can be absent in cases of long-standing deafness. Furthermore, SOE responses
are only partially recordable after reinsertion, thus intraoperative x-ray is mandatory
to confirm the electrode carrier's correct position.
