Causes of Hearing Loss

There are two main types of hearing loss; acquired and congenital. As the names themselves suggest, acquired hearing loss is caused due to external factors that are acquired by an individual. For example, injury to the ear, fever, sudden exposure to very loud noise, unsuitable medication, and diets. Whereas, congenital hearing loss is hearing loss that occurs on its own due to family line or birth. 

Congenital Hearing Loss

Age

The term for age-related hearing loss is called presbycusis. Presbycusis comes gradually as an individual gets older. Age-related hearing loss usually affects both ears equally. Due to the progressive nature of the loss, a person with presbycusis may not be aware that they have partially lost their hearing. They may also experience symptoms of the diseases such as tinnitus, lack of coordination and lack of responsiveness. 

Heredity

More than half of hearing loss cases in children are caused due to genetics. There are situations when a gene does not develop as expected. This is referred to as a mutation. While certain mutations run in the families, others do not. When several members of the same family experience hearing loss, it is referred to as "familial" hearing loss. 

To put it in another way, it's a family affair. Connexin 26 is a protein that plays a critical part in the operation of the cochlea, and the GJB2 gene is the only gene that encodes for this protein. In some groups, the GJB2 gene has a mutation in roughly 40% of newborns hence causing hereditary damage to the cochlea. 

Birth conditions

Conditions like premature birth, low birth weight, ear deformities at birth, jaundice, and issues with the Rh factor, the infant's lack of oxygen, also known as anoxia, are all capable of causing hearing loss in new-borns. Even ear deformities such as internal tumors or underdeveloped parts of the middle or inner are a major cause of congenital hearing loss.

Congenital cytomegalovirus (CMV) infection

A prominent contributor to sensorineural hearing loss is CMV infection which accounts for 15% to 25% of all clinically significant hearing loss found in children. Even in infants without symptoms at birth, CMV is often shown to result in hearing loss. In fact, the most frequent infectious cause of birth abnormalities in India is cytomegalovirus, or CMV. CMV affects about 1 in 100 infants worldwide.

Acquired Hearing Loss 

Injury 

Results from physical damage such as perforated eardrum, traumatic brain injury (TBI), or skull fracture, among other illnesses. Sudden fluctuations in air pressure, such as those that happen when an aeroplane descends, can even cause sensorineural hearing loss. If you experience head trauma and notice a change in your hearing, make an appointment with your audiologist at the earliest.

Infection or Disease 

Diseases like measles, mumps, scarlet fever and meningitis are a well-known cause of hearing impairment. Typically, viruses cause sensorineural hearing loss, however, a virus like HIV can lead to conductive hearing loss through bacterial and fungal infections caused in your inner ear, which become more aggressive following the immunosuppression caused by that virus. 

Ear infection, abnormal bone growths and even tumors. In the outer or middle ear, any of these can cause hearing loss, ruptured eardrum (tympanic membrane perforation), loud blasts of noise, sudden changes in air pressure, poking your eardrum with an object, can affect your hearing. Coronary artery disease(heart disease) and strokes may also be considered as a  cause of deafness. 

Noise induced hearing loss 

Sudden exposure to a blast of loud noises are a common cause of hearing loss, especially to those who work in very loud environments like the aviation industry or factories, or at construction sites. The impact of a single loud noise on the inner ear(Cochlea) can be severe, and cause either temporary or permenant hearing loss. Even listening to loud music for prolonged durations of time can overwork and kill the hair cells in your Cochlea causing gradual loss of hearing. 

Side effects of medication 

The 5 most everyday medicines that are proven to cause some amount of hearing loss are; Aspirin, Nonsteroidal Anti-Inflammatory Drugs, Antibiotics and Chemotherapy Drugs.  Naturally, the risk of hearing loss and other side effects increases if a patient self-administers too much aspirin without a doctor's prescription.

Temporary hearing loss caused by aspirin is often only experienced at high doses, or 8 to 12 pills per day. Ibuprofen is an example of an NSAID pain reliever that might reduce blood flow to the cochlea, an organ in the inner ear that aids in hearing, which may affect how well it performs.

The most often prescribed class of antibiotics, aminoglycosides, exposes patients to a 20% to 60% likelihood of permanent hearing loss. Hearing loss has been linked to the chemotherapy(cancer) medicines cisplatin, carboplatin, and bleomycin. 

Conclusion

Drug and alcohol usage during pregnancy, maternal hyperglycemia, and high blood pressure during pregnancy are a cause of congenital hearing loss in infants. Expecting mothers are often advised to not drink alcohol or consume any amount of non-prescribed drugs. 

Sometimes during the delivery of infants, the doctors might accidentally use excessive force to pull out the infant, this can damage the fragile hearing organs and certain parts of the brain, thereby resulting in hearing impairment. 

As a precautionary measure to check congenital hearing loss, it is highly suggested to parents to get a BERA(Brainstem Evoked Response Audiometry) test done to their infants, as soon as they’re born, in order to help their children gets appropriate support for hearing in their early age of development.