MT-TL1 and External ophthalmoplegia: The m.1555A > G mutation in MTRNR1 is associated with aminoglycoside ototoxicity and nonsyndromic SNHL, while MTTL1 m.3243A > G is associated with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS); maternally inherited diabetes and deafness syndrome (MIDD); and chronic progressive external ophthalmoplegia (CPEO).