Conductive hearing loss - what is it and what can help?
Conductive hearing loss prevents sound waves from reaching sensory cells in the inner ear. Both obstructions and malformations of the ear canal can cause a blockage, as can interfering factors in the middle ear. These include infections, a tympanic effusion and malformations. In order to make an appropriate diagnosis, various examinations are performed, which in turn provide indications for appropriate treatment methods.
Causes of conductive hearing loss
To describe the causes, a distinction must be made between acute and chronic conductive hearing loss
Possible causes of acute conductive hearing loss:
- Congestion of the ear canal (e.g., due to earwax or foreign bodies)
- Water in the external ear canal (often occurs in swimmers)
- Acute middle ear infection
- Other inflammation of the ear
- Injuries to the eardrum
- Infections leading to swelling of the ear canal
Possible causes of chronic conductive hearing loss:
- Consequence of chronic middle-ear infection.
- Scarring/inflammation leading to narrowing of the ear canal (stenosis)
- Excessive bone growth in the ear canal (exostosis)
- Misformation of the external or middle ear
Diagnosis: How is a conductive hearing loss detected?
There are several measures to detect a conductive hearing loss:
- Otoscopy: The external auditory canal and eardrum are examined for foreign bodies or obstructions, or with regard to injuries or pathological changes.
- Sound threshold audiogram: Sounds are played to the patient through headphones to create a sound threshold audiogram. The patient indicates at what point the tones are audible to him. Then, a repeat of the test takes place with a bone-conduction earphone behind the ear. In this way, bone conduction and air conduction are recorded separately, and it is possible to differentiate between conductive and acoustic hearing loss. In addition, assumptions about the causes of hearing loss can be made based on the audiogram.
- Speech audiogram: A speech audiogram is generated on the basis of the patient's repeated utterance of monosyllabic and polysyllabic words. The result allows conclusions to be drawn about performance in speech comprehension.
Further tests help to specify the causes of hearing loss:
- Weber test: For the Weber test, a tuning fork is placed on the mastoid (the bone behind the ear) and checked to see how long the patient hears the resulting sound. Repeating the test on the other ear will tell if there is equal hearing on both sides. If the hearing loss is unilateral, i.e., pronounced in only one ear, the Weber test will show this.
- Rinne test: The tuning fork is also placed on the mastoid for the Rinne test until no sound is heard. The fork is then held next to the ear - the sound should be audible again. If no sound is audible when held next to the ear, the test is considered negative. This can be used to infer conductive damage.
- Tympanogram: By means of a tympanogram, the ability of the eardrum to vibrate can be recorded. Provided that there is the same pressure in the middle and outer ear, the eardrum vibrates normally. An altered vibration behavior consequently results from a pressure difference and influences the sound conduction in the ear. Increased pressure (e.g., in a tympanic effusion) or decreased pressure (e.g., in a ventilation disorder) accordingly provide clues to the cause of conductive hearing loss.
Conductive hearing loss audiogram
In the audiogram, conductive hearing loss shows a drop in the air conduction hearing threshold curve (see audiogram below: line with circles). Thus, the air conduction hearing threshold is lower than the bone conduction hearing threshold (see audiogram below: line with arrows). That is, the bone conduction values are largely standard, while those for air conduction are striking.
Symptoms: recognizing conductive hearing loss
The particular symptom of conductive hearing loss is hearing quieter but maintaining intelligibility. Affected people describe the hearing condition as "like having absorbent cotton in the ears." A muffled perception of sounds thus indicates this form of hearing loss. In this case, all pitches are equally affected by the restriction.
Treatment: treat conductive hearing loss
The appropriate intervention for a conductive hearing loss depends largely on the cause of the hearing impairment. If the cause is inflammation, congestion or a cold, hearing is usually only temporarily impaired. Antibiotics or minor surgery help to relieve the symptoms or dissolve the blockage.
Treating conductive hearing loss with surgery
If chronic or particularly severe conductive hearing loss is present, surgery may be necessary. For example, this treatment method is often used for conductive hearing loss caused by otosclerosis.
Treating conductive hearing loss with a hearing aid or hearing aid implant
To support hearing, hearing aids are conventionally used for conductive hearing loss. These amplify sound, contributing to appropriate hearing levels. If the provision of hearing aids is not sufficient, implantation of a cochlear implant is also a possible solution. Also, bone-conduction-hearing-aids find an area of use in the treatment of conductive hearing loss when the outer ear, middle ear, or ear canal are damaged or absent. Both bone conduction hearing aids and middle ear implantsare considered in cases of atresia, which is the closure of a body opening - in this case, the ear.
Conductive hearing loss vs. sensorineural hearing loss: differences at a glance
Sound conduction hearing loss