A case–control study in Japan examined seven polymorphisms in genes implicated in free-radical/redox pathways—methionine synthase (MTR; rs1805087), methionine synthase reductase (MTRR; rs1801394), nitric oxide synthase 3 (NOS3; rs1799983), caveolin-1 (CAV1; rs3840634), melatonin receptor 1B (MTNR1B; rs1387153), the NADPH oxidase p22phox subunit (CYBA; rs4673), and mitochondrial 5178 (MT5178; rs28357984)—in 83 patients with SSNHL and 83 with MD. This evidence concerns the gene MTRR and Menkes disease.