Causes and Types of Hearing Loss
Congenital Hearing Loss
Acquired Hearing Loss
Sensorineural Hearing Loss ( Cannot be corrected)
Conductive Hearing Loss ( Can be corrected)
The ear and the hearing mechanism in the human being are made up of a number of tiny, specialised parts and millions of nerve cells. Malformation, damage or reduction of any of these, owing to various factors, causes hearing impairment.
Some types of hearing loss are present from birth. Several factors may be responsible for this.
Genetic: The most common congenital factor is genetic. A child with one or both parents with hearing impairment can inherit the dominant gene for hearing loss. It is possible to inherit hearing loss even if a grandparent is deaf.
Infections: Diseases like jaundice, rubella, pox in the prenatal, peri natal and post natal periods can affect hearing.
Problems relating to birth: Prematurity or anoxia ( “blue babies”/lack of oxygen at the time of birth).
Malformation: A part of the hearing mechanism may be malformed.
Mother’s condition during pregnancy: Some conditions affecting the mother, such as toxemia, syphilis, Rh incompatibility, or diabetes can affect hearing of the foetus.
Acquired Hearing Loss
Hearing loss may be acquired after birth, at any age. These may be reversible or permanent. Some factors that produce hearing loss are:
Infections: Infections in the ear can cause hearing loss.
Viral or bacterial infections like Encephalitis, Chicken pox, Measles, Mumps, Meningitis, Syphilis etc may also cause hearing loss in some people.
Trauma: Head injury, concussion or trauma that affects the hearing mechanism. Some times water sports can, due to pressure differences, rupture parts in the ear, leading to hearing loss.
Medication: Medicines called “ Ototoxic” drugs are capable of causing reversible or permanent hearing loss in some people. Salicylates ( Aspirin containing medicines), Non steroid anti inflammatory drugs, some Antibiotics ( Aminoglycosides, Erythromycin, Vancomycin), Diuretics, Chemotherapy agents, Quinine are some Ototoxic drugs.
Noise: Continued exposure to noisy environments like factories or blast sites can affect hearing. At first the high frequency hearing is affected. If exposure continues, hearing loss is progressive.
Age: Some people experience hearing loss as they age. This condition is called Presbycusis.
Others: There are some rare conditions like tumour in the Acoustic nerve or Otosclerosis ( hardening of bones/or parts of the hearing mechanism). Hearing impairment can also occur abruptly, without any apparent cause!
Conductive Hearing Loss ( Can Be Reversed)
External or middle ear problems, which are often mechanical in nature cause hearing loss. This can usually be corrected by medication or surgery. Middle Ear Infections (Otitis Medea) are a common cause.
Ear discharge or accumulation of ear wax can also cause hearing loss.
Absence or malformation of parts of the external or middle ear can cause conductive hearing loss.
Sensorineural Hearing Loss (Cannot Be Reversed)
Problems in the inner ear involving the cochlea, the hair cells or nerve cells cause sensorineural hearing loss. This type of hearing loss is irreversible. This can be congenital or acquired.
Neither medication nor surgery can make the patient regain the ability to hear. However, hearing devices and implants are used, along with auditory training, to help these patients hear.