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Hearing Loss in Childhood
Published in Raymond W Clarke, Diseases of the Ear, Nose & Throat in Children, 2023
Congenital (present at birth) hearing loss is traditionally divided into genetic (or inherited) causes – more often than not nowadays with a known chromosomal or gene abnormality – and environmental causes such as prenatal maternal infection or birth complications such as prolonged hypoxaemia (Figure 7.1). Overall, about 50% of cases of congenital deafness are genetically inherited. About another 25% are due to a non-genetic, environmental or acquired pathology.
Antimicrobials in Pregnant Women
Published in Firza Alexander Gronthoud, Practical Clinical Microbiology and Infectious Diseases, 2020
Streptomycin causes irreversible bilateral congenital deafness, especially during the first trimester of pregnancy, and is contraindicated. Other aminoglycosides have not been found to cause congenital deafness, and short courses may be used with caution.
Deafness
Published in Angus Clarke, Alex Murray, Julian Sampson, Harper's Practical Genetic Counselling, 2019
Even without access to specialised audiological testing, it is often possible to assess the genetic situation accurately if the following points are borne in mind: What does the pattern of inheritance in the particular family suggest?Is the hearing loss severe congenital deafness, or some milder form?If hearing loss is milder, is it static or progressive?Is there an identifiable syndrome involving other systems?
The applications of targeted delivery for gene therapies in hearing loss
Published in Journal of Drug Targeting, 2023
Melissa Jones, Bozica Kovacevic, Corina Mihaela Ionescu, Susbin Raj Wagle, Christina Quintas, Elaine Y. M. Wong, Momir Mikov, Armin Mooranian, Hani Al-Salami
It is also important to highlight the category of hereditary hearing loss, which may be one of the main benefactors in the development of an inner ear targeted gene therapy. Early onset forms of deafness, often presented as hereditary deafness, has been indicated to result from a wide array of genes, with an estimation that over 50% of congenital deafness presentations in newborns are hereditary in nature [33,34]. Classifications of genetic deafness are derived based upon the mutation inheritance mode, with ongoing novel discoveries of genes associated with hearing loss. Molecular genetic tests can be used to identify deafness, both syndromic and non-syndromic in nature. Genetic counselling is a key element in the diagnosis, with modes of inheritance listed as including autosomal recessive and dominant, in addition to X-linked Mendelian and mitochondrial inheritance from a maternal lineage. Syndromic hearing loss which is autosomal recessive in nature includes Usher syndrome and Pendred syndrome, whilst those which are autosomal dominant include Branchio-oto-renal syndrome and Waardenburg syndrome [35–37].
Effects of basilar-membrane lesions on dynamic responses of the middle ear
Published in Acta Oto-Laryngologica, 2023
Junyi Liang, Wen Xie, Wenjuan Yao, Maoli Duan
Some disorders of metabolism in the cochlear such as mucopolysaccharidosis can cause basilar membrane damage or an increase the sensory cell weight. In addition, the mass of the spiral limbus cells, spiral process, and the spiral ligament increases notably [16]. All these structures are within the organ of Corti, which attaches to the basilar membrane. As a result, added mass of the basilar membrane increases. In addition, some genetic defects can lead to congenital deafness. The main characteristics embody in the hypertrophy of Sertoli cells in cortis device, leads to the increase of the basilar membrane mass. Added mass in the basilar membrane was adopted as the following situation: average thickness increased 0.15 mm, while the added mass is 36 × 10−9 kg. Under 90 dB SPL, compared with the normal human ear, the frequency-response curve of displacement and velocity were respectively obtained, as shown in Figure 7.
Clinicians’ views of using cortical auditory evoked potentials (CAEP) in the permanent childhood hearing impairment patient pathway
Published in International Journal of Audiology, 2020
Kinjal Mehta, Merle Mahon, Bram Van Dun, Josephine Marriage, Deborah Vickers
CAEPs can be used to evaluate aided hearing by testing detection thresholds for speech sounds through hearing aids without requiring an active behavioural response. CAEP recording is conducted while the infant is awake, thus avoiding the need for sedation or natural sleep which is required for ABR and ASSR testing. Consequently, they can give supplementary information for evaluating the responses to speech at specific presentation levels in young infants or difficult-to-test children. Sharma and Dorman (2006) have shown that the latency of the P1 and morphology of the CAEP responses change with the development of the central auditory pathways and that there is a maximal period of cortical plasticity in the first 3.5 years. For children receiving cochlear implants, if they are implanted below this age they often achieve age-appropriate cortical responses within 3–6 months after stimulation. Cardon, Campbell, and Sharma (2012) have shown two major principles of neuroplasticity direct clinical outcomes: 1) adequate stimulation provided to the cortex and 2) appropriate timing of stimulation through hearing aids or cochlear implants. Early intervention with appropriate auditory input results in high likelihood of normal auditory cortical development in children with congenital deafness.