Sensorineural hearing loss

Sensorineural hearing loss (SNHL) occurs when there is damage or malfunction of the inner ear (cochlea), or  the nerve pathways from the inner ear to the brain. It is typically described as irreversible condition. SNHL result in a loss of loudness. Even when speech is loud enough to hear, it may still be unclear.

One way to describe hearing loss is as “congenital” or “acquired”. Acquired hearing loss is a hearing loss that present after birth. The hearing problem can occur at any time in one’s life, as a result of an illness or injury. It can be due to many factors include presbycusis which is age- related hearing loss. Mostly it occurs bilaterally and occurs gradually over time, thus it is sometime difficult to notice. Besides, noise could also cause sensorineural hearing loss. It is due to over exposure to loud noise for a period of time. In most cases, those who work in machine factory or high intense noise environment are more susceptible to get noise induce hearing loss. Diseases and infections such as measles, meningitis and mumps can also cause sensorineural hearing loss.

Congenital hearing loss means the babies was born with hearing loss. They are identified through newborn hearing screening test. For many cases the cause of hearing loss among baby is unknown. It is estimated 1 in 500 newborn baby develops hearing loss during early childhood. There are many causes of hearing problem among children; some are genetic which is caused by a baby’s genes or non-genetic such as certain infections the mother has during pregnancy, or infections the newborn baby has. The genetic forms of hearing loss are diagnosed by a team that includes an Ear Nose and Throat (ENT) doctors, an audiologist through physical examination, family history, ancillary testing (e.g., CT examination of the temporal bone), and molecular genetic testing.

It is estimated that 70% of genetic hearing loss are due to recessive causes while 15% have a dominant cause; and the remaining 15% include all the other forms of inheritance. Connexin 26 (abbreviated CX26) gene is the most common cause of congenital sensorineural hearing loss and responsible for half of all the recessive cases of hearing loss. It is genetically transmitted from parent to child in a recessive manner, which means that an affected individual must inherit one copy of the non-functioning gene from each parent. Carriers who only have one copy of the gene (i.e. one normal gene and one mutated gene) do not manifest any of the signs of the condition, but have a 1 in 2 chance of passing on the defective gene to their children (who would then also be carriers only), and a 1 in 4 chance of having an affected child if the other parent is also a carrier.

Unlike conductive hearing loss, sensorineural hearing loss cannot be corrected by medical or surgical. It is irreversible, therefore permanent.  Sensorineural hearing loss generally managed through aural rehabilitation, which may include amplification with hearing aids, cochlear implants, or an assistive listening device. In some instances, medical treatment may be required – for example, surgical removal of acoustic neuroma – but these cases are less common.