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Gene Therapy Offers Hope for Patients with earing Loss
What is Hearing Loss?
- A person is said to have hearing loss if they are not able to hear as well as someone with normal hearing, meaning hearing thresholds of 20 dB or better in both ears.
- It often indicates defects in the ear’s process of converting sound into electrical signals sent to the brain.
- Hearing loss that comes on little by little as you age, also known as presbycusis, is common.
- Hearing loss is one of the most common disorders, affecting over one billion people worldwide.
- Approximately 1-2 out of every 1,000 newborns are born with congenital hearing loss.
- There are three types of hearing loss:
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- Conductive hearing loss: In this hearing loss, something keeps sound from passing through your outer ear (ear canal) or your middle ear.
- Sensorineural hearing loss: This hearing loss happens when something damages your inner ear over time.
- Rarely, sensorineural hearing loss happens very quickly.
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- Mixed: This happens when you have issues in your middle or outer ear (conductive hearing loss) and your inner ear (sensorineural hearing loss).
- Common hearing tests include:
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- Pure-tone testing.
- Otoacoustic emissions test.
- tympanometry.
Prevalence, Causes, and Genetic Factors:
- Causes: Genetic mutations, environmental factors such as maternal infections during pregnancy, and postnatal complications can cause hearing loss in infants.
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- Hearing loss is sporadic when it affects a single person in a family and familial when it runs in the family.
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- Genetic Factors: Approximately 50-60% of congenital hearing loss cases are due to genetic causes. Genetic variants play a significant role in different populations.
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- Caucasian, Asian, and Hispanic populations: Mutations in the GJB2 gene are the most common genetic cause.
- African populations: The MYO15A and ATP6V1B1 genes are more frequently implicated.
- Mitochondrial genetic defects can also lead to hearing impairment.
- Genetic variants can interact with other factors, such as medications.
- For example, a genetic defect in the mitochondrial MTRNR1 gene can predispose individuals to hearing loss when treated with aminoglycoside antibiotics, commonly used for TB treatment.
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About Mutation:
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Ear Overview:
- Ears are organs on either side of the head, over the temporal lobe (responsible for hearing, speech, memory, emotion).
Functions:
- Hearing:Sound waves enter ear canal → eardrum vibrates → ossicles in middle ear amplify/transmit sound → inner ear’s stereocilia convert vibrations to electrical signals sent to the brain.
- Balance: Head movement displaces fluid in semicircular canals → hairs send balance info to brain → brain signals muscles to maintain balance.
- Parts of the Ear:
- Outer Ear: Visible auricle made of cartilage and skin; secretes earwax; leads sound to eardrum.
- Middle Ear: Begins beyond eardrum; houses malleus, incus, stapes for sound transfer; includes eustachian tubes for pressure equalisation.
- Inner Ear: Contains cochlea for hearing; semicircular canals for balance; both transmit signals to the brain.
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Surprising Facts About Ears:
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