Armstrong, Michael F

Objective: Recent research demonstrates a potential association between metformin use and reduced sporadic vestibular schwannoma (VS) growth in patients undergoing conservative observation. The current study was designed to elucidate the effect of metformin on tumor growth in sporadic VS using volumetric analyses. Study Design: Retrospective cohort. Setting: Tertiary referral center. Patients: Patients with sporadic VS who elected initial conservative treatment with at least two serial magnetic resonance imaging (MRI) scans were included. Interventions: Metformin use among patients with observed sporadic VS. Main Outcome Measures: Tumor growth, defined as an increase in volume of at least 20% from the initial MRI. Results: A total of 361 patients were evaluated. Thirty-four patients (9%) had a diagnosis of diabetes at baseline. Nineteen patients (5%) were taking metformin at the time of the initial MRI. Metformin use was not significantly associated with a reduced risk of volumetric tumor growth in a univariable analysis in all patients undergoing observation for VS (hazard ratio [HR] 0.75; 95% confidence intervals [CI] 0.40–1.42; p = 0.38) or within the diabetic subset (HR 0.79; 95% CI 0.34–1.83; p = 0.58). Additionally, diabetes status, insulin dependence, hemoglobin A1c value, and metformin dose were not significantly associated with volumetric tumor growth. Conclusion: Despite promising initial results in several previous studies, our data suggest that metformin use does not significantly reduce the risk of volumetric tumor growth in sporadic VS.

Objective: Recurrent laryngeal nerve injury is a potential complication of cardiothoracic surgery and cause of unilateral vocal fold paralysis (UVFP). Injection laryngoplasty (IL) is an intervention offered to patients with UVFP to alleviate symptoms including dysphagia, dysphonia and weak cough. There is no definitive evidence that IL prevents pneumonia. In this study, we compare rates of pneumonia in patients with UVFP secondary to cardiothoracic surgery who did or did not undergo IL. Methods: A retrospective chart review identified patients diagnosed with UVFP by an otolaryngologist using flexible laryngoscopy following cardiothoracic surgery from January 1, 2008 to December 31, 2017. Each subject was grouped by IL status and assessed for subsequent pneumonia within 6 months of their diagnosis of UVFP. The association of IL with pneumonia was evaluated using Cox proportional hazards regression. Results: Of 92 patients who met inclusion criteria, 35 (38%) underwent IL and 57 (62%) did not. Twenty patients developed pneumonia, four who had undergone IL and 16 who had not; 12 patients developed aspiration pneumonia including two having undergone IL and 10 who had not. Those who had IL were less likely to develop total pneumonia compared to those who had not (HR = 0.33, P = .045). The protective effect of IL was not as clearly sustained when measuring for aspiration pneumonia, specifically (HR = 0.34; P = .10). Discussion: Injection laryngoplasty may reduce the risk of pneumonia in patients with UVFP secondary to cardiothoracic surgery; however, further research is needed to quantify the potential protective nature of IL in this patient population. Level of evidence: 3 (A retrospective cohort study).