Subtotal petrosectomy in cochlear implantation: Gruppo Otologico experience after 348 cases.

Objective: To discuss indications (unfavorable conditions), surgical steps, complications, and follow-up of subtotal petrosectomy (STP) in cochlear implantation based on our experience of 348 cases. Anatomical variations associated with or without cochlear malformations and differences between electrode insertions were included in our analysis.

Materials and methods: A retrospective case study was done in Gruppo Otologico (Piacenza, Italy), a quaternary referral center. Among 1002 cases that underwent subtotal petrosectomy, 348 were selected for cochlear implantation in the same setting. The study period was from 2004 to 2019. These patients' clinical and radiological follow-up ranged from 2 months to 180 months. Data were inspected, cleaned, and analyzed by SPSS software.

Results: The selected group's mean age was 57.236 years, including 178 male and 170 female patients. The follow-up period lasted up to 108.65 months. Out of 348 cases, 8 were children (under the age of 18 years old). Inclusion criteria to be eligible for cochlear implantation in the same setting of subtotal petrosectomy was a preoperative pure tone average (PTA) of more than 90 decibels associated with low speech discrimination ranging from 0% in most cases up to 50% in the minority. 329 patients had a complete electrode insertion intra-operatively. Minor complications were observed in 6 cases. These include one case of implant extrusion due to a middle ear infection leading to labyrinthitis, three cases of post-auricular fistula causing one device failure, one subcutaneous CSF collection, and one subcutaneous seroma collection.

Conclusion: Although in most cases, standardized trans mastoid facial recess technique for cochlear implantation is ideal as the surgical risks are minimal, in complicated cases such as concomitant chronic otitis media, prior canal wall-down cases, radical cavities, or inner ear abnormalities with high risk of cerebrospinal fluid leak subtotal petrosectomy should be the first choice of management with complete disease clearance. Close clinical and radiological follow-up is therefore mandatory. Single-stage implantation is preferred to staging the procedure unless one is unsure of disease clearance.