- Clinical science
Hearing loss can be defined based on the location of dysfunction as either conductive or sensorineural hearing loss. Conductive hearing loss is due to dysfunction of the outer or middle ear, which prevents transmission of sound waves from reaching the inner ear. In comparison, sensorineural hearing loss is due to dysfunction of the inner ear or auditory nerve, which prevents neuronal transmission to the brain. Sometimes hearing loss can have both conductive and sensorineural components, which is referred to as mixed hearing loss. Patients who present with hearing loss should be screened with tests such as the whispered voice test. After confirming the diagnosis, Rinne and Weber testing should be performed to differentiate between conductive or sensorineural hearing loss. This may be followed by audiometry, pneumoscopy, laboratory tests, or imaging, depending on the underlying suspected cause. Treatment depends on the underlying etiology and can include hearing aids or cochlear implants for irreversible conductive or sensorineural hearing loss, respectively.
|Conductive hearing loss||Sensorineural hearing loss|
|Age of Onset|| || |
|Etiology|| || |
|Pathophysiology|| || |
|Clinical Features|| |
|(unilateral hearing loss)|| || |
|(unilateral hearing loss)|| |
Mixed hearing loss is a combination of conductive and sensorineural hearing loss!
Hearing loss in the first years of life can cause a delay in speech, language, and social development!
- : screening to determine extent of hearing loss
- : and to classify hearing loss as conductive or sensorineural
- Pneumoscopy: (evaluates the mobility of the tympanic membrane): for conductive hearing loss
- Audiometry: for all patients without any obvious cause to hearing loss
- Laboratory tests (e.g., blood glucose, CBC with differential, TSH, and/or syphilis testing depending on the suspected etiology): for patients with unexplained sensorineural hearing loss
- MRI or CT scan: (of the posterior fossa): indicated in patients with unilateral, gradual sensorineural hearing loss to exclude acoustic neuroma
- with or without serous effusion
Definition: congenitally absent or stenotic external auditory canal
- Clinical features
- Definition: buildup of tightly packed cerumen (earwax) in the outer ear .
- Risk factors
- Conductive hearing loss
- Ear discomfort
- Diagnostics: otoscopy
- Irrigation; (e.g., warm saline containing a bacteriostatic substance; cerumenolytics can be added as well)
- Cerumenolytics (e.g., docusate sodium)
- Mechanical removal (e.g., with a forceps, a curette, or with suction)
Always consider the possibility of cerumen impaction in patients presenting with hearing loss!
- Internal ear infections
- Definition: age-related, sensorineural hearing loss
- Pathophysiology: progressive damage of the organ of Corti, especially near the basal turn of the cochlea, which impairs high frequency hearing
- Most common cause of sensorineural hearing loss
Incidence increases with age:
- Age 50: 10-15%
- Age 75: > 50%
- Age 90: nearly 100%
- Progressive bilateral hearing loss, particularly of higher frequencies → Using a low-pitched and clear voice to speak with older patients can improve communication.
- Usually first noticed in the sixth decade of life
- Difficulty hearing in noisy, crowded environments.
- Can cause depression and/or isolation
- No definitive treatment is available.
Noise-induced hearing loss (NIHL)
- Definition: hearing loss that occurs due to exposure to loud sound
- Risk factors: repeated exposure to sounds louder than 85 dB or even a single exposure to sounds greater than 120–155 dB.
- Slowely progressive hearing loss with loss of high-frequency hearing first
- Difficulty hearing in noisy, crowded environments
- As it progresses, difficulty hearing high-pitched voices (eg, women's, children's) occurs
- No definitive treatment is available
- Prophylaxis is essential (hearing protection)
The differential diagnoses listed here are not exhaustive.
- Treatment depends on the underlying etiology of the hearing loss.
- For irreversible causes, hearing devices such as hearing aids (for conductive hearing loss) or cochlear implants (for cochlear dysfunction) can be considered.
- Definition: devices that amplify sound to assist individuals with impaired hearing
Prerequisite: All patients should undergo a thorough ENT-examination to rule out treatable causes and an audiological examination to determine the severity of hearing loss.
- Causes of hearing loss that can be treated surgically include tumors, cholesteatomas, and stenosis/atresia of the external auditory canal
- Pressure equalization tubes in the tympanic membrane can improve hearing in children with hearing loss from recurrent otitis media, middle ear effusions, or dysfunction or the eustachian tube.
- Adults: Most adults experience age-related hearing loss which is not treatable; other etiologies should nonetheless be investigated.
- Both conductive and sensorineural hearing loss (regardless of severity)
- Mild to severe hearing loss
- Children should be fitted with a hearing aid as soon as possible to avoid a developmental delay in speech.
Bilateral cochlear implants can improve speech discrimination in background noise.
- Definition: Prosthetic devices that are surgically implanted and function by electrical stimulation of the auditory nerve (CN VIII).
- Prerequisite: the auditory nerve and auditory system are intact.