Outcomes of Cochlear Implantation in Patients with Superficial Siderosis: A Systematic Review and Narrative Synthesis

This study aimed to establish outcomes following cochlear implantation (CI) in patients with superficial siderosis (SS). MEDLINE, Embase, Web of Science, Cochrane, and ClinicalTrials.gov databases were searched for this systematic review. No limits were placed on the language or the year of publication. The review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Of a total of 46 studies, 19 studies met the inclusion criteria reporting outcomes in 38 patients. Of the 44 implants, 23 implants (52.27%) had good hearing outcomes at the last follow-up, 9 (20.45%) were initially beneficial for the patient, but then the performance deteriorated (4 of which were re-implanted), and 12 (27.27%) were not beneficial for the patient. All studies were classified as grade 4 studies using the Oxford Centre for Evidence-Based Medicine (OCEBM) grading system, being retrospective in nature and consisting of case reports and noncontrolled case series with a small number of patients. Of the 44 implants, 32 (72.73%) showed improved hearing outcomes following CI for SS at some point in time, of which 23 (52.2%) implants showed sustained benefit at the last follow-up (average follow-up time was 21.97 months). It is difficult to predict the longevity of benefit owing to the progressive nature of the disease or the patients in whom it may be beneficial, as the preoperative investigations inadequately predict benefit. Preimplantation and postimplantation counseling with the patient and their family regarding the potential limited benefit and eventual parallel decline with the neurological disease are crucial, along with thorough clinical investigations.