Objectives: To investigate the prevalence and risks factors associated with electrode migration in cochlear implant (CI) recipients. Design: Retrospective cohort study of all CIs performed between 1 January 2018-1 August 2021 in a single tertiary adult and paediatric cochlear implant centre in the UK. Main outcome measures: The primary aim is to determine the prevalence of electrode migration, based on comparing intraoperative surgeon report and results of a routine plain X-ray performed 2 weeks after surgery. Electrode migration is defined as the detection of movement of 2 or more electrodes out of the cochlea from time of surgery. Multivariate analysis was performed to investigate risk factors including preoperative factors and intraoperative factors that might predispose to migration. Results: 465 patients, having 516 distinct surgery sessions, with 628 implants were analyzed. Electrode migration occurred in 11.5% of all implants. Pre-existing cochlear abnormality was an independent associated risk factor for electrode migration (OR:3.40<1.20-9.62> p=0.021). Demographics, surgical technique, usage of a precurved electrode, CSF leak, surgeon seniority and intraoperative telemetry did not influence risk of migration. There were 5 implants which migrated later than 2 weeks, median: 263days, for which head injury was a common precipitating factor. There was some difference between different lateral wall electrodes Conclusion: Electrode migration in the early postoperative period is a common occurrence and is more likely in implant recipients with obstructed or malformed cochleae. Keywords : Cochlear implants, Electrode migration, Risk factors, Cochlear abnormalities, Postoperative X-ray

Objectives : Primary : To determine the rate of occult cervical metastasis in primary temporal bone squamous cell carcinomas (TBSSC). Secondary : to perform a subgroup meta-analysis of the risk of occult metastasis based on the clinical stage of the tumour and its risk based on corresponding levels of the neck Design : A systematic review and meta-analysis of papers searched through Medline, Cochrane, Embase, Scopus and Web of Science up to January 2021 to determine the pooled rate of occult lymph node/parotid metastases. Quality assessment of the included studies was assessed through the Newcastle-Ottawa scale. Setting : Centres around the world that perform surgery for TBSCC Participants : Patients with TBSCC Results : Overall, 9 out of 1034 screened studies met the inclusion criteria, for a total of 907 patients of which 388 had TBSCC. Out of the 191 patients who underwent a neck dissection, 21 had positive lymph nodes giving a pooled rate of occult metastases of 11% (95% CI: 7%-17%). When analysed using the Modified Pittsburg staging system, 21 pT2 cases had a pooled occult metastases rate of 3% (95% CI: 0%-21%), 27 pT3 cases had a pooled occult metastases rate of 12% (95% CI: 1%-60%), and 65 pT4 cases had a pooled occult metastases rate of 14% (95% CI: 7%-25%). Data available showed that most of the positive nodes were in Level II. Conclusion: The rate of occult cervical metastases in TBSCC increases based on the tumour (T) staging of the disease with majority of nodal disease found in level 2 of the neck.