Hearing loss

Last updated: May 19, 2022

Summarytoggle arrow icon

Hearing loss can be defined based on the general type of hearing loss (conductive or sensorineural) and the location of the dysfunction. Conductive hearing loss typically occurs due to dysfunction of the outer or middle ear, which prevents transmission of sound waves from reaching the inner ear. Sensorineural hearing loss, on the other hand, occurs 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 with a complaint of hearing loss should be screened with techniques such as the whispered voice or finger rub tests. Subsequently, tuning fork tests should be performed to differentiate between conductive and sensorineural hearing loss. This may be followed by otoscopy, audiometry, 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.

Overview of hearing loss types [1]
Types Conductive hearing loss Sensorineural hearing loss
Etiology
Pathophysiology
  • External or middle ear pathology that disrupts conduction of sound into the inner ear
  • Inner ear, cochlear, or auditory nerve pathology that impairs neuronal transmission to the brain
Clinical features
  • Hearing worsens in noisy environments
  • Volume of voice may be loud because nerve transmissions are impaired
  • Tend to lose higher frequencies preferentially, such that sounds may be distorted
  • Often associated with tinnitus
  • Features of external auditory canal pathology are absent.
Weber test (unilateral hearing loss)
  • Lateralization to impaired ear (cannot hear ambient room noise well, so detection of vibration is greater)
  • Lateralization to unimpaired ear (sound is not transmitted by damaged inner ear or auditory nerve)
Rinne test (unilateral hearing loss)
  • Bone conduction > air conduction (vibrations bypass blockage to reach the cochlea)
  • Air conduction > bone conduction (the inner ear or auditory nerve cannot transmit sound information well regardless of how vibrations reach the cochlea)
Speech audiometry
  • No discrimination loss.
  • Discrimination loss is common.
Audiogram
  • Difference between air and bone conduction
  • Hearing loss for higher frequency sounds.

Impedance audiometry

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!

Presbycusis

  • Definition: : age-related, sensorineural hearing loss
  • Pathophysiology: progressive and irreversible damage of the hair cells of the organ of Corti (especially near the basal turn of the cochlea) that impairs high-frequency hearing
  • Epidemiology
    • Most common cause of sensorineural hearing loss
    • Usually first noticed in the sixth decade of life
    • Incidence increases with age:
      • Age 50: 10-15%
      • Age 75: > 50%
      • Age 90: nearly 100%
  • Clinical features
    • Progressive bilateral hearing loss, particularly of higher frequencies (using a low-pitched and clear voice to speak with older patients can improve communication)
    • Difficulty hearing in noisy, crowded environments.
    • Can cause depression and/or isolation
  • Treatment

Sudden sensorineural hearing loss (SSNHL)

Assess response to initial treatment with follow-up audiometry, 2 weeks and 6 months post-treatment. [4]

Initial diagnostic tests [1]

Further diagnostic tests [1]

Audiogram (Pure Tone Testing)

  • Procedure: The patient is played various frequencies through a headphone (air conduction) and a bone oscillator (bone conduction) placed on the mastoid bones. Various frequencies are played and the patient gives a signal (e.g., raising a finger or pressing a button) as soon as a sound is heard. The auditory threshold is determined using the decibel level at which the patient's signals are 50% correct.
  • Interpretation: The connection of the individual auditory threshold points results in the generation of an auditory threshold curve for air and bone conduction, which allows the degree of hearing loss for individual frequencies to be determined.
    • In conductive hearing loss (damage to the middle or external ear), the auditory threshold is increased in air conduction; however, the auditory threshold is normal in bone conduction
    • In sensorineural hearing loss (cochlear or retrocochlear damage), the auditory threshold for air and bone conduction are proportionally increased.

Speech audiometry

  • Procedure: The patient is played increasingly loud words, which should be repeated by the patient. The speech reception threshold is calculated from the level at which a patient can correctly repeat 50% of words.
  • Interpretation: Increasing loudness eventually leads to a speech comprehension of 100% in patients with conductive hearing loss, but not in patients with sensorineural hearing loss. Loss of word comprehension is referred to as discrimination loss.

Impedance audiometry

Tympanometry

Otoacoustic emissions (OAE)

  • Description: sound emissions originating from the cochlea that arise spontaneously or in response to acoustic stimulation and can be measured in the auditory canal to assess cochlear function
  • Types of OAE
    • Spontaneous OAE (SOAE): physiological, acoustic emissions that originate from the outer hair cells of the ear and reach the auditory canal via the auditory ossicles and tympanic membrane
    • Evoked OAE (EOAE): acoustic emissions that arise in response to acoustic stimuli
  • Measurement of OAE
    • Indication: newborn hearing screening (EOAE)
    • Procedure: noninvasive OAE measurement using a microphone within the external auditory canal
    • Interpretation
      • Detectable OAE: normal outer hair cell function (cochlear function intact)
      • Absent OAE: cochlear hearing loss > 30 dB

Conductive hearing loss

Sensorineural hearing loss

Other

The differential diagnoses listed here are not exhaustive.

Hearing aids [1]

  • 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.
  • Indications
    • 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.

Cochlear implants [1]

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.
  • Indications
  1. Bickley L. Bates' Guide to Physical Examination and History-Taking. Lippincott Williams & Wilkins ; 2012
  2. Singh A, Kumar Irugu DV. Sudden sensorineural hearing loss – A contemporary review of management issues. Journal of Otology. 2019; 15 (2): p.67-73. doi: 10.1016/j.joto.2019.07.001 . | Open in Read by QxMD
  3. Alexander TH, Harris JP. Incidence of Sudden Sensorineural Hearing Loss. Otology & Neurotology. 2013; 34 (9): p.1586-1589. doi: 10.1097/mao.0000000000000222 . | Open in Read by QxMD
  4. Chandrasekhar SS, Tsai Do BS, Schwartz SR, et al. Clinical Practice Guideline: Sudden Hearing Loss (Update) Executive Summary. Otolaryngology–Head and Neck Surgery. 2019; 161 (2): p.195-210. doi: 10.1177/0194599819859883 . | Open in Read by QxMD
  5. Bayoumy AB, van der Veen EL, Alexander de Ru J. Assessment of Spontaneous Recovery Rates in Patients With Idiopathic Sudden Sensorineural Hearing Loss. JAMA Otolaryngology–Head & Neck Surgery. 2018; 144 (8): p.655. doi: 10.1001/jamaoto.2018.1072 . | Open in Read by QxMD

3 free articles remaining

You have 3 free member-only articles left this month. Sign up and get unlimited access.
 Evidence-based content, created and peer-reviewed by physicians. Read the disclaimer