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Mitochondrial Dysfunction and Hearing Loss
Published in Shamim I. Ahmad, Handbook of Mitochondrial Dysfunction, 2019
The MT-TS1 gene, which causes some syndromic HL, has several allelic variants that also give rise only HL: Heteroplasmic T-to-C transition at nucleotide 7510, homoplasmic 7511T-C transition, 7445A-C transversion, homoplasmic 7505T-C transition.2 Other involved genes are: MT-RNR1, MT-CO1, MT-TH, MT-ND1 and MT-T1.
Current status on researches of Meniere’s disease: a review
Published in Acta Oto-Laryngologica, 2020
Yupeng Liu, Jun Yang, Maoli Duan
Intratympanic gentamicin (ITG), a chemical labyrinthine resection treatment, is recommended as a fourth line treatment in refractory MD [11]. The risk of hearing loss should not be ignored for its otoxic effects. Mitochondrial mutation of the gene MTRNR1 is not screened in most of the countries. This mutation exposes to a complete and definitive deafness after a single injection of gentamicin. Patients receiving ITG should be well informed before treatment. A double-blinded, randomized, placebo-controlled trial revealed that ITG can be an effective treatment for vertigo in MD. The potential risk of hearing loss exists, but the trials showed no difference in hearing level between pre-treatment and post-treatment [16]. Patel et al. [17] compared the effectiveness between ITG and intratympanic methylprednisolone in a randomized, double-blind trail. The result showed an 87% reduction in vertigo frequency in ITG group and 90% reduction in vertigo frequency in intratympanic methylprednisolone group. There is no significant statistical difference in vertigo control and hearing levels. Both intratympanic methylprednisolone and gentamicin are safe and effective therapeutic options for refractory MD.
Monitoring neonates for ototoxicity
Published in International Journal of Audiology, 2018
Angela C. Garinis, Alison Kemph, Anne Marie Tharpe, Joern-Hendrik Weitkamp, Cynthia McEvoy, Peter S. Steyger
In addition to prematurity and ototoxic medications, genetic factors as well as common clinical conditions, such as hyperbilirubinemia or hypoglycaemia, can also increase the risk of hearing loss in NICU admissions (ACMG, 2002; Declau et al, 2008; Smit et al, 2013; Zimmerman & Lahav, 2013; Vedovato et al, 2015; Olds & Oghalai, 2016). Crucially, polymorphisms in the mitochondrial gene MTRNR1 lead to an “idiosyncratic” adverse event of hearing loss with aminoglycoside dosing that is distinct from the ototoxicity associated with supra-therapeutic levels of these drugs. Aminoglycosides bind more avidly to MTRNR1 polymorphism in the ribosomal subunit, impairing mitochondrial protein synthesis, leading to reduced mitochondrial activity that is insufficient for optimal hair cell function (Guan, 2011; Gopel et al, 2014). The American College of Medical Genetics (ACMG) recommends testing for MTRNR1 mutations in patients exposed to aminoglycosides who already have hearing loss (ACMG, 2002). Although this panel notes that avoiding aminoglycosides in polymorphism-positive individuals reduces the risk of developing hearing loss, clinical testing for this maternally-inherited trait in pregnant women is not yet performed in an anticipatory manner (Linden Phillips et al, 2013).
Identification of causative variants in patients with non-syndromic hearing loss in the Minnan region, China by targeted next-generation sequencing
Published in Acta Oto-Laryngologica, 2019
Xiaohui Wu, Xingqiang Gao, Peng Han, Yulin Zhou
After checking the subject’s inheritance pattern and phenotype, we were able to make a molecular genetic diagnosis from 20 (22.2%) of 90 subjects on two genes GJB2 and SLC26A4 (Table 2). Among 20 diagnosed individuals, 12 patients suffered from AR NSHL (DFNB1A) due to six mutations in GJB2, and seven suffered from AR NSHL (DFNB4) due to five mutations in SLC26A4, only one patients were associated with AD NSHL (DFNA3A) due to one variant in GJB2. Missense, deletion, splice, and duplication variants made up 43.8, 31.3, 21.9, and 3.1% of recessive and 100, 0, 0, and 0% of dominant diagnoses. In addition, we found two NSHL cases with MT-RNR1 mutations.