Deafness: understanding hearing loss, causes…

A study published in the BMJ Global Health end of 2022 predicts that 670 million to 1.35 billion young people (12-34 years old) could be affected by hearing loss in the world, due to poor music listening practices (mp3 players, mobile phones, listening in bars, clubs, discotheques…). “Hearing loss is a public health issue that deserves global recognition and prioritization”, recalled the authors in the preamble to their publication. The Hearing loss affects a child’s academic performance. At the house of the adultit is associated with a impaired psychosocial well-being and to serious health problems like cognitive impairment. The tinnitus also have significant impacts on health and well-being individuals and is associated with a lower quality of life. What are the warning signs of hearing loss? What are the different types of deafness? The causes ? What to do before, after?

What is the definition of deafness?

Deafness or hypoacusis is a pathological condition characterized by the total or partial loss of hearing. There are several types of deafness: conductive hearing lossdue to a factor affecting the external ear or the middle ear, and the sensorineural hearing loss, the cause of which is located at the level of the inner ear or on the path of the nervous information brought to the brain. “Mixed” deafness results from joint impairment of the transmission apparatus and that of perception.

The level of hearing loss is classified in decibels of hearing loss by theHealth Insurance :

• the mild deafness : 20 to 39 decibels of hearing loss. The person makes his interlocutor repeat as soon as 30 decibels are lost, on high-pitched sounds;
• the moderate deafness : 40 to 69 decibels of hearing loss. The 40 decibel level is the first major level of handicap. Indeed, the person understands only if his interlocutor raises his voice. She is “hard of hearing”;
• the severe deafness: 70 to 89 decibels of hearing loss. The daily discomfort is major;
• the profound deafness : more than 90 decibels of hearing loss. The person no longer hears speech at all.

• The conductive hearing loss : Conductive hearing loss is due to damage to the structures of the outer ear and/or the middle ear responsible for “to transmit” the vibratory auditory message to the inner ear. “Any obstacle in the auditory canal, any lesion, interruption or even fixation of the chain of the ossicles, any lesion of the eardrum, any tumoral or inflammatory process occupying the middle ear leads to conductive hearing loss”explains Professor Vincent Darrouzet, ENT, head of the Center for Surgical Specialties and Dermatology at the Bordeaux University Hospital.
• The sensorineural hearing loss : Perceptual deafness results from damage to structures located downstream in the path of the sound message, i.e. the inner ear, the auditory nerve, the cerebral auditory pathways, or even more rarely the cerebral integrating centers . “Perceptual deafness is mainly linked to genetic or acquired diseases of the hair cells of the cochlea, responsible for transforming the vibrations of their eyelashes into nerve impulses. We have 16,000 in our ear, we are born with this capital and we die with what is left of it, they do not regenerate”adds the head of the ENT department of the Bordeaux University Hospital.
• The mixed deafness. Deafness is said to be mixed when it is both transmission and perception. For example, there may be lesions on the ossicles and also in the inner ear.

Sudden deafness is defined as sudden onset deafness most often unilateral and whose cause is not known (idiopathic). It may be associated with tinnitus and/or vertigo.

“Congenital deafness, most often genetic, concern 0.5 to 1.3 per thousand newborns. Their detection allows early rehabilitation care.notes the site Ameli.fr “Genetic deafness mainly affects the hair cells of the ear. It is then a question of structural anomalies of the hair cells or of their environment or of the connections which exist between them. When the genetic mutation is present, we observe a deafness of evolutionary perception with a very variable evolution between each individual. Deafness can occur from birth or in the extreme around the age of 40. And the parents are not necessarily affected since the mutations are often transmitted (such as that of Connexin 26) on a recessive mode, adds Vincent Darrouzet.

“The auditory organ begins at the level of the auricle, it continues through the auditory canal, to the eardrum, this vibrating membrane connected to the ossicles and more particularly to the malleus, to which the anvil is attached, itself attached to the stirrup. These parts make up the outer and middle ear. Thanks to the caliper and its piston movementthe fluid of the inner ear begins to vibrate, vibrations that stimulate the sensory cells of hearing. Thesei then transmit electrical information to the auditory nerve which in turn transmits information to the auditory cortex”, explains Prof. Vincent Darrouzet. That’s how we hear. The causes of deafness are extremely numerous.

• Hearing loss can be caused by slow and gradual aging of hearing (presbycusis), exposure to noise, whether professional or recreational (amplified music), medication…
• Certain pathologies, such as Meniere’s disease (a dizzying illness), meningitis, ear infections, can cause deafness.
• As mentioned above, the deafness can be congenital. According to our expert, “these deafness are extremely frequent”.
• Sometimes the causes are trivial and simple to treat, such as presence of a foreign body located in the ear canalor a wax plug. “Earwax blockage is the most common cause of conductive hearing loss”specifies the ENT.
• “Cranial trauma (damage to the ossicles), perforated eardrum, auditory neuropathies (damage to the auditory nerves), ear infections – very common in children and very rare in adults – are all possible causes of deafness. “, lists Vincent Darrouzet.
• “Also be careful with unilateral sensorineural hearing loss – only one side is deaf during the audiogram -, this can hide a benign tumor, acoustic neuroma. Deafness can then appear gradually in one ear or acutely. It may be a therapeutic emergency.” insists the professional.

Symptoms suggestive of onset of deafness include difficulty perceiving surrounding soundsdifficulties in follow conversations, especially in noise. In case of sudden deafness, the patient notices a significant break with his previous hearing abilities. In children, signs to suspect congenital deafness arelack of reaction to noises, delay in learning to speak, behavioral problems and difficulties at school. “As part of a conductive deafness, we have the sensation of a blocked ear. The causes of this deafness are so vast that the symptoms are extremely numerous: pain, loss of hearing, balance disorders, dizziness, tinnitus…”, explains the ENT surgeon.

The diagnosis of deafness always requires a prior physical examination, carried out using a small instrument, the otoscope, provided with a light or at the ENT with a microscope. It allows you to examine the external auditory canal up to the eardrum, looking for an obstacle or an infection. A simple test using the vibration of a tuning fork makes it possible to distinguish conductive deafness from perceptual deafness. But in this context, theaudiogram is essential. This alone makes it possible to define the degree and nature of the hearing loss and to guide any additional examinations that may be necessary (scanner, MRI). “In newborns and infants, auditory evaluation is complex and requires very specialized audiometry techniques in these expert regional centers (behavioral audiometry, auditory evoked potentials, acoustic otoemissions) emphasizes Vincent Darrouzet. They are less precise but give a good indication.” In the context of a genetic disease, we can look for connexin 26 gene mutationsa protein whose deficiency is one of the most frequent causes of congenital deafness.

The treatments vary according to the type of deafness and especially the identified cause. Earwax plugs must be removed, infections treated… Certain anatomical problems are sometimes accessible to surgery. In case of persistence of disorders a hearing aid can sometimes be proposed. “In children, particularly affected by seromucous otitis and possible associated deafness, the treatments consist of paracentesis, a surgery which allows the aspiration of excess liquid, the installation of diabolo or yoyo often associated with the removal of vegetations” , adds Vincent Darrouzet. In the Bilateral congenital total sensorineural hearing loss that cannot be aided, a cochlear implant will be offered to families. Alternatively, in the event of refusal of the establishment, the learning of sign language, associated with an adapted schooling, can make it possible to limit the exclusion generated by this handicap.

He is possible to prevent deafness by reducing exposure to excessive sound, by the use of hearing protection, during concerts for example or during the use of certain very noisy machines. It is also recommended to avoid listening to music too loudly and for too long with headphones. Vaccination of children, especially against mumps, is recommended to avoid the risk of infectious diseases that can lead to deafness.

A person’s degree of disability is set by the Commission for the Rights and Autonomy of Persons with Disabilities (CDAPH). Rights can be opened from 50% disability. A tonal audiogram is performed, without equipment, to determine the loss, in decibels, of hearing. “For hearing loss beyond 80 decibels, a disability rate of 80% is determined”, notes the Surdi.info site.

Thanks to Professor Vincent Darrouzet, ENT, head of the Center for Surgical Specialties and Dermatology at the Bordeaux University Hospital.