*3.3. Indication of the IES CMD*

The IES CMD was used in our clinic for different indications. The possible applications included the penetration into a cochlea obstructed with fibrotic or ossified tissue, which could not be achieved by common electrodes due to their lack of stiffness and their inability to dilate the lumen. It was also used as an aid in re-implantations. Furthermore, the IES CMD was utilised as an instrument to estimate the depth of possible electrode insertion in the malformed cochleae.

Thus, the IES was deployed in the evaluated IES group to measure the depth of the cochlea prior to implantation (*n* = 7; 21.2%), due to intracochlear tissue which hampered the insertion of the electrode array (*n* = 10; 30.3%), as well as to ossify the basal turn or the round window region (*n* = 9; 27.3%). The IES was also used four times (12.1%) as a tool during device re-implantation to clear out fibrotic tissue. In three cases (9.1%), the reason for using the IES was to eliminate any resistance that occurred when trying to insert the stimulation electrode.

In the evaluation above, a variable was disregarded, depending on whether the surgical intervention was a first implantation or a re-implantation of a CI. In the IES group, 22 subjects (66.7%) underwent first implantation with an average duration of hearing loss of 8.57 years (range: 1 month–31 years). Eleven cases (33.3%) underwent re-implantation surgery due to soft failure or malfunction of the implant. The previous implant was in situ for a mean of 9.82 years (range: 6 month–31 years).

In the REGULAR group, patients were matched to the IES group (*n* = 22 first implantations and *n* = 11 re-implantations). An exact adjustment to the duration of hearing loss or the duration of the previous implant in situ was not possible due to the limited number of patients available.

In the SPLIT group, six cases (75%) were provided with a Split-Array CMD during the initial implantation procedure and showed an average duration of deafness of 5.04 years (range: 6 month–24 years). Two cases (25%) received a Split-Array CMD during a reimplantation procedure after 25 years in the first case and after 1 year in the second case.
