Hearing loss or deafness is a decrease in sensitivity or hearing that affects the ears. The complexity of this disorder is that it is relatively common, may occur for different reasons, present in different degrees, and can start at any stage of life.
To understand how it can be diagnosed and what the appropriate treatment is, it is necessary to know how hearing works.
How does hearing work?
The first thing to consider in understanding how hearing works, and ultimately how we hear, is to understand the role of sounds, which are invisible vibrations that travel through the air.
There are different sources or emitters of sound such as speech, the rustling of leaves, the ringing of the telephone, or in general when a sound is emitted. The air is responsible for carrying these vibrations, known as sound waves, in different directions.
The sound waves, which are picked up by the ears, are mostly unique and have different characteristics: according to their frequency they can be high (high) or low (low).
Our brain is in charge of interpreting the messages previously picked up by the ears as sound waves. If our ears work well, the information that is brought to the brain will be clearer, allowing the person to hear and develop their language skills normally.
How is the ear composed?
There are three main parts to the ear:
The outer ear: It captures sound waves through the auricle, concentrating them and driving them through the ear canal until they hit the eardrum. It is made up of:
- The auricle or pinna, which is the external part of the ear.
- The external ear canal, which is the one that connects the external ear to the middle ear.
- The eardrum or tympanic membrane, precisely the membrane that separates the outer ear from the middle ear.
The middle ear: this part, which is between the eardrum and the oval window, is key as it is responsible for transmitting the vibrations from the outer ear to the inner ear. The middle ear or “tympanic cavity” is made up of
- The three small bones: the hammer, anvil and stirrup.
- The Eustachian tube, which basically prevents the accumulation of both air and fluid pressure inside the ear, a key process since a balanced pressure is necessary for the correct transfer of sound waves.
The inner ear: as its name indicates, this kind of “labyrinth” is located in the inner region of the ear, and that is where they are:
The vestibule, or “the organ of balance”.
The cochlea, which looks like a snail shell, is where sound waves are converted into electrical impulses that, after being sent to the brain, the latter can recognize as sounds.
That’s how it works:
In the first phase, a sound enters the ear canal.
When a sound is produced, vibrations or sound waves enter and travel through the ear canal until they hit the eardrum.
The tympanic membrane or eardrum vibrates.
This causes the three ossicles to vibrate in turn, transmitting the sound to the inner ear.
The vibrations travel through the “labyrinth”.
The vibrations travel through the fluid in the inner ear, this spiral-shaped labyrinth, and activate the cochlea, which is in charge of the process of converting them into electrical impulses or chemical signals so that they are recognized by the auditory nerve.
The brain interprets the sound.
After the auditory nerve sends the information to the brain by means of electrical impulses or signals, the brain has the task of interpreting them, finally recognizing a certain sound.
Causes of hearing loss
Just as there are different types of hearing loss, the causes are also many and varied. Hearing involves a complex and delicate transmission of sound through the outer, middle and inner ear, so damage to any of these parts can affect hearing
Also, hearing loss can appear from birth or be caused by
- An injury.
- Infection, from treatments with ototoxic drugs (certain aminoglycoside antibiotics, in particular gentamicin, streptomycin and neomycin, and drugs used in chemotherapy for the treatment of cancer such as cyclophosphamide, cisplatin, bleomycin and carboplatin).
- Prolonged exposure to very loud and constant noise.
As part of the aging process, progressive hearing loss often occurs. When this loss is more severe it can affect language comprehension.
Types of hearing loss
There are different types of hearing loss or deafness that, according to the location of the lesion, can be differentiated from the following:
This type of deafness, whether partial or total, is the one that occurs from birth, with the aggravating factor that, in some cases, is detected late and rarely before the first six months of life.
And what are the causes of congenital deafness?
It can be presented by two variables: either by changes or mutations in the genes, or by agents known as teratogens that, during the baby’s development in the uterus, damaged the ear.
The complexity of congenital deafness lies in the fact that there are more than 80 known genes whose mutation can generate non-syndromic congenital deafness, that is, without associated defects.
But what about children who hear well in their early years, learn to speak, but then progressively lose their hearing?
What happens in these cases is that deafness is not always congenital. Genetic factors, both in childhood and adolescence, as well as in adulthood, play a key role.
In non-syndromic cases, approximately  75% to 85% are autosomal recessive; 15% to 24% are autosomal dominant; and 1% to 2% are chromosomally related.