Intracochlear position and cochlear implant outcomes using the Nucleus Slim Modiolar Electrode and the (extended) round window approach: a follow up study

Rationale:
Due to the continuingly expanding indications for cochlear implantation, preservation of residual hearing has become an important objective. Evidence suggests that overall outcome and hearing preservation are influenced directly by occurrence of insertional trauma (i.e. lateral wall/modiolar trauma, translocation from scala tympani to scala vestibuli, tip fold-over) during surgery. Therefore there is an increasing interest in hypotraumatic insertion techniques as well as hypotraumatic electrode arrays. The Slim Modiolar Electrode (SME) was developed in 2016 to be atraumatic, more flexible and thinner than previous generations of precurved electrode arrays by the manufacturer. Heutink et al. confirmed the potential for the SME to preserve residual hearing once the electrode was positioned entirely in the scala tympani (ST). However, they observed cochleostomy associated translocation to the scala vestibuli (SV) in more than one third of the participants, resulting in significant hearing loss. They therefore advise to use the round window (RW) or extended round window ((e)RW) approach when using the SME.

Objective:
To evaluate the intracochlear position of the Slim Modiolar Electrode array when inserting using the (e)RW approach.

Study design:
Prospective observational study

Study population:
The first 23 patients selected for implantation with the Slim Modiolar Electrode (CI532/CI632) using the (extended) round window approach at our center willing to participate.

Follow-up:
1 year.

Primary outcome measure:
Occurrence of intraoperative tip fold-over and evaluation of the intracochlear position of electrode contacts (ST or SV) per participant.

Secondary outcome measures:
Residual hearing thresholds and speech perception in relation to intracochlear location of electrode contacts per participant.

Previously published research by Heutink et al. performed in our center found cochleostomy associated translocations in over a third of the patients implanted with the Slim Modiolar Electrode. Therefore, we would like to evaluate the translocation rate in a similar group of patients implanted with the SME using the (extended) round window approach. We expect to find a lower rate of electrode translocation in patients using this surgical technique.

1. <6 months prior to surgery
2. 2 months
3. 1 year

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