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Hearing loss

Hearing loss: Description

Hearing loss refers to an impairment of a person's hearing ability. It ranges from slight impairment to a complete loss of hearing ability, and can be temporary or permanent. Previously one spoke of deafness for people who hear only individual sounds or none at all, but today this is more usually termed hearing loss or impairment. A distinction is made between conductive hearing loss, sensorineural hearing loss, sound perception hearing loss and combined hearing loss.

Hearing loss is divided into five stages: normal hearing, mild hearing loss, moderate hearing loss, severe hearing loss, and hearing loss verging on complete inability to hear (deafness).

Hearing loss: Symptoms

Hearing loss is characterized by diminished ability, or even the complete inability, to hear certain frequencies and sound volumes. The accompanying symptoms are highly dependent on the underlying cause and extent of the disease. For example, pathological changes in the inner ear often lead to simultaneous tinnitus, dizzy spells and vertigo, because the organ of equilibrium (balance) is located in the inner ear.

People who are hard of hearing become exhausted faster because of the increased effort and concentration associated with the hearing process.

Hearing loss: Causes and Risks

Hearing loss arises when there is a disorder or disease on the path between the auditory (ear) canal and the brain. The causes are divided into different categories, although in each case both acute and chronic forms can occur:

Conductive hearing loss can be caused by a foreign body or water in the outer auditory canal, acute auditory tube disorder (closed eustachian tube), infectious middle ear disease, eardrum perforation, inflammation-induced skin swelling in the auditory canal, middle ear injury or a skull fracture with disrupted ossicular chain.

Causes of chronic conductive hearing loss are: chronic otitis media (inflamed middle ear), chronic auditory tube disorder (closed eustachian tube), ossification of the junction between the third ossicle and stapedial bones and the inner ear (otosclerosis), constrictions in the auditory canal by scarring or inflammation (stenosis), excessive bone growth in the auditory canal (exostoses), malignant or benign tumors in the ear canal or middle ear, or congenital malformations and disorders of the outer or middle ear.

Sensorineural hearing loss can be caused by inner ear disorders, infectious diseases that may affect the inner ear (mumps, measles, scarlet fever, typhoid, syphilis, herpes zoster oticus, meningitis, AIDS, toxoplasmosis, borreliosis), noise over the 120 dB pain threshold, skull fracture through the inner ear (transverse fracture of temporal bone), torn membrane between the middle and inner ear with formation of a perilymphatic fistula, Meniere's disease, multiple sclerosis, side effects of certain medications (quinine and antimalarials, aspirin, diuretics, cytostatics, aminoglycoside antibiotics), poisoning by carbon monoxide, aniline, nitrobenzene, mercury, lead, etc.

Causes of chronic sensorineural hearing loss are: presbycusis (age-associated hearing loss), several hours of noise over 80 dB daily without ear protection, acoustic neuroma, diseases of the auditory nerve, metabolic disorders, arteriosclerosis or disturbance in the auditory cortex, usually accompanied by other neurological changes as for example after a stroke or brain tumor, cervical syndrome, congenital malformations or disorders of the inner ear.

The term sensorineural hearing loss indicates that both the sensory cells and nerve portions of the hearing organ have limited function. Damage to the auditory nerve causes a neural hearing loss. Disorders in the brain may be responsible for a "central" hearing loss due to impaired auditory processing. These individual forms cannot always be clearly distinguished: often several auditory centers are affected.

Combined (conductive and sensorineural) hearing loss occurs when there is simultaneous disease of the middle and inner ear, as is the case with ear infections involving the inner ear (e.g. labyrinthitis).

Hearing loss: Examination and Diagnosis

At the start of the examination the ear, nose and throat specialist (otorhinolaryngologist) records the patient's medical history. Here, the doctor asks about the onset and progress of the hearing loss as well as any situations that are particularly problematic for hearing. Afterward he makes a detailed ear, nose and throat examination, including testing the sense of balance. An otoscopy is used to check the eardrum for changes and defects. Various hearing tests are used to check the ability to hear different volumes, frequencies and speech. Impedance measurements give information about the pressure within the eustachian tube and the functioning of the auditory ossicles.

Special computer-aided examination techniques that do not require patient cooperation are particularly suitable for babies and small children. For example, if a recorded sound is played for a healthy ear, the cochlea returns the sound waves (otoacoustic emissions). In brainstem audiometry, electrical brain waves are measured in response to auditory stimuli.

Clinical laboratory tests are performed, particularly of the blood, to detect any metabolic diseases. With the help of magnetic resonance imaging a possible tumor on the auditory nerve can be evaluated.

Hearing loss: Treatment

The treatment of hearing loss depends on its cause and extent. Underlying diseases must be treated and simple measures such as the removal of foreign bodies or earwax plugs must be carried out.

With certain disorders, the surgical use of tympanoplasty can improve sound conduction dysfunction, in which the chain of sound transmission in the middle-ear is restored or the eardrum is sealed.

In sensorineural disorders the inner ear is often damaged beyond repair, so that neither medicines nor surgery can restore hearing again. However, using a number of tools, hearing and speech comprehension can be improved or else replaced by acoustic signals:

As soon as possible the affected person should be provided with a hearing aid. Nowadays there are high-quality models in many different versions, adapted to individual needs. When there is an intact auditory nerve but no inner ear function, an auditory prosthesis called a cochlear implant can be used. Aside from this, one can learn lip-reading or sign language, have auditory training or speech support, and there is also early intervention with hearing and speech education for hard of hearing or deaf children, and psychotherapeutic measures for depression, anxiety or extreme emotional situations.

Hearing loss: Course and Prognosis

The course of hearing loss can vary widely and depends on the underlying cause. With children it is especially important to determine as early as possible whether a hearing impairment is congenital or acquired, since language difficulties can also develop during the course of the disease.

Hearing loss: Miscellaneous/Other Comments

The cochlear implant is a groundbreaking technological achievement. It is the only medical technology that can replace a human sense organ. For people with hearing loss that is severe or bordering deafness, who still have functioning auditory nerves but for whom hearing aids do not allow sufficient understanding, the cochlear implant provides the opportunity to participate in acoustic life.

Functionality: sound signals are picked up by the microphone of the speech processor and converted into electrical impulses. These pulses are forwarded to the transmitter coil. Through this coil, the electrically encoded sound signals are transmitted to the implant beneath the skin. The implant conducts the electrical pulses to the electrode array in the cochlea. The auditory nerve receives the electrical pulses that are emitted from the electrode carrier and sends them to the auditory center in the brain. Here these stimuli are perceived as sound.

Deaf or severely hard of hearing children, as well as adults who after language acquisition are deaf and despite optimal hearing aids do not have sufficient understanding of speech, can be supplied with a cochlear implant. Children should be implanted as soon as possible, as the maturing of the auditory system occurs in the first three years of life, and this as well as language acquisition are dependent on acoustic impressions. Early implantation also applies to people who are made deaf by meningitis, because the cochlea can quickly ossify from the disease and then implantation is no longer possible.

Good prospects of success are dependent on various factors such as the functioning of the auditory nerve, the duration of the deafness and the patient's motivation.

The indication for implantation will be developed in the Department of Oto-Rhino-Laryngology by experienced clinicians using a complex diagnostic program.

The Auditory Brainstem Implant (ABI), like the cochlear implant a technical hearing prosthesis, is used when the hearing nerve is disrupted or absent.

EAS/Hybrid (electric-acoustic stimulation) and BAHA (bone anchored hearing aid) are other implantable systems. The EAS/Hybrid system is a combination of a hearing aid and cochlear implant. BAHA is a bone-anchored hearing system. Here the sound is transmitted via the skull to the inner ear.

Medical Center - University of Freiburg

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