The Sensorineural hearing loss (HNS) is the decrease or loss of hearing as a result of damage to the cochlea or auditory nerve. Both the cochlear organ and the vestibule-cochlear nerve (VIII pair) are responsible for the reception and transmission of sound..
Currently, hearing loss from different causes -including sensorineural origin- is a form of significant disability. Hearing is one of the components of human communication and its partial or total loss is a limitation for both social relationships and work activity.
Various structures are involved in the hearing process. This sense consists of a system of reception, conduction and transformation of sounds into nerve impulses..
Sounds arrive by air to the pinna, travel through the external auditory canal (outer ear) to the eardrum, which vibrates when receiving sound waves. Tympanic vibration goes through the ossicles (middle ear) to the cochlea (inner ear) which converts the vibration into electrical impulses.
So, the sensory deficit can be conductive or sensitive. In the first, it affects structures of the outer and middle ear, while the second involves damage to the cochlear organ or the auditory nerve.
The symptoms of hearing loss do not only include partial or total loss of hearing. Other symptoms such as vertigo, headache, earache can accompany this condition.
In general, the prevalence of hearing loss is even higher than that of diabetes. Currently, the estimate of sensorineural hearing loss - of variable degree - is around 30% of the world population.
The goal of treating hearing loss is to compensate for the hearing loss. The use of electronic devices or surgery are some of the indicated treatments, according to the severity of the condition..
Article index
The decrease in hearing capacity is the main symptom of this disorder. Depending on the cause of the neurosensory deficit, other related symptoms may be found, such as vertigo and tinnitus..
This symptom can present in an acute form, but in general it is installed progressively. Congenital hearing loss is already present at birth, but it often takes time to diagnose. It consists of the decrease to perceive or discern sounds.
The normal human auditory frequency range is from 20 Hz to 20 KHz. The intensity of sounds is expressed in decibels (dB) whose lowest value is 0 dB and the maximum value tolerated by a person is 130 dB. The classification of hearing loss is based on the intensity of sound that can be perceived.
- Incipient, when it goes from 15 to 25 dB.
- Mild, 26 to 40 dB.
- Moderate, from 41 to 60 dB.
- Severe, 61 to 90 dB.
- Deep, when it is greater than 90 dB.
When the hearing loss is progressive, it goes unnoticed and the person adapts without noticing the deficit. Audiometry, a study of hearing ability, is a useful tool to establish the level of hearing loss.
They consist of sounds perceived by an individual in the absence of sound stimuli. These are usually sounds such as a whisper, buzz, tinkle, hiss, blow through a tube, or screech.
Tinnitus often accompanies hearing loss and is quite annoying. It may be transitory, but it represents an alarm symptom that warns of potential hearing damage.
Vertigo translates into the impossibility of staying stable when perceiving the movement of fixed objects in the environment. The cause of vertigo is an alteration in the labyrinth or the portion of the auditory nerve that is responsible for balance. As both nerves -buccal and cochlear- are related, the symptoms are usually associated.
Ménière's disease, a degenerative disorder of unknown cause, is associated with vertigo, tinnitus, and progressive hearing loss.
It is a nonspecific symptom that appears as a feeling of fullness inside the ear. Individuals who manifest this symptom report having something inside their ear that prevents them from hearing..
Headache, earache, otorrhea or even motor disorders represent symptoms associated with the triggering cause. In infants, there may be signs of deficits in psychomotor development, language, or deformities that indicate the congenital nature of the condition..
The alteration or damage of the auditory nerve has multiple causes, from genetic problems to trauma or age-related deficits. A simple way to classify the causes of sensorineural hearing loss is to divide it into genetic and acquired.
Genetic diseases refer to all those disorders of a hereditary nature, transmitted by parents to their offspring. The terms genetic and congenital are often confused. Genetic causes are congenital, but not all congenital causes are genetic in origin.
Congenital hearing loss refers to all those disorders that occur during the prenatal period, whether genetic or acquired.
Of the total of congenital causes, between 70 and 80% correspond to simple genetic alterations, which include malformations or dysfunctions of the auditory apparatus. The remaining 20 to 30% involve the presence of SNH accompanying clinical syndromes.
Both syndromic and non-syndromic hearing loss have several inherited patterns. They can be present as autosomal dominant, autosomal recessive, or X-linked defects.
Acquired is the adjective that indicates any process that develops in a structurally and functionally normal organism. An example of acquired hearing loss is SNH related to infections during pregnancy or toxicity from some drugs. Acoustic trauma and barotrauma are also examples of acquired causes of hearing loss..
Presbycusis, age-related hearing loss, may have a genetic predisposition but develops from exposure to noise.
The most common and treated causes of HNS are:
- Congenital, such as idiopathic malformations, infections during pregnancy, Rh incompatibility, and use of teratogenic or ototoxic drugs by the mother.
- Genetic predisposition.
- Presbycusis.
- Infections, such as meningitis, mastoiditis, or suppurative labyrinthitis.
- Head injury including skull fracture.
- Ménieré disease.
- Autoimmune diseases, such as lupus erythematosus or other collagen diseases.
- Complications of rheumatoid arthritis.
- Ototoxic drugs, such as aminoglycosides, vancomycin, quinine, furosemide, among others.
- Long-term exposure to loud noises.
- Barotrauma. Pressure accidents during diving can cause SNH, especially if they are related to fistulas..
- Auditory neuropathy and acoustic neuroma.
- Multiple sclerosis and other demyelinating diseases.
- Meningeal tumors.
Hearing is one of the five senses and allows the individual's relationship with others and with their environment. It is one of the elements of human communication, essential for interpersonal relationships.
The partial or total loss of hearing is, then, an important limitation for human and occupational activity. The objective of treatment, when it is an alternative, is to provide the necessary means to restore or compensate for the loss of this sense..
Currently there is no pharmacological treatment for the treatment of SNH. Although there are preventive measures, the only possible interventions are the use of amplifying hearing aids and surgery..
When medical treatment and instrumental help is not possible, patient education represents an alternative.
Its use is intended for those with a mild to moderate hearing deficit (between 26 and 60 dB). They consist of reception and amplification systems that are placed in the external auditory canal. Its use requires the integrity of the peripheral and central nervous system.
One of the drawbacks for the use of hearing aids is the adaptation to them. In some cases, its use must be discontinued due to the progression of hearing loss. For some people the cost is a limitation at the time of purchase.
The goal of surgery is to repair any defect that prevents hearing function or the placement of a cochlear implant..
The cochlear organ is responsible for converting sound vibrations into nerve impulses that travel via the auditory nerve to the brain. This organ has cilia that allow it to fulfill its function. In some cases, the hair cells of the cochlea are lost or damaged, causing loss of function.
The cochlear implant is an implantable electronic device that replaces the cochlear organ, converting sound waves into electrical impulses. These impulses are sent to the nerve ganglia, where the device has been connected.
It consists of an external receiver system -by means of a microphone- a microprocessor and a coil connected to two electrodes as part of the internal or implantable device. The surgery is relatively safe and with few complications.
The inclusion criteria for surgery are the diagnosis of cochlear damage, children who retain neural plasticity (less than 5 years) and adults with learned language. After surgery, language rehabilitation is necessary.
In the last decade, other therapeutic alternatives for HNS have been proposed. One of them consists of the introduction of stem cells and cell regeneration in the inner ear. The purpose is to repair damaged tissues in the cochlea and even the auditory nerve.
Although it is still under study, its success would be a breakthrough for medical science and hope for the hearing impaired..
In cases where there are no therapeutic alternatives for HNS, education becomes a valuable tool. The objective is to provide the necessary tools for adaptation to the social environment, including language. Lip reading and sign language are useful forms of communication that can be learned..
Yet No Comments