Inner Ear Pathologies

due to disorders of
1. cochlea
2. cranial nerve VIII
3. cochlear nuclei
Classification
1. Degree & type
  1. i.e. profound sensory, mild conductive
2. Origin
  1. Hereditary / acquired
3. Onset
  1. congenital / delayed
4. Structural pathology
Characteristics
1. irreversible
2. except for
  1. some Meniere's
  2. HL due to perilymphatic fistula
  3. obstruction of blood flow to the cochlea
Acquired SNHL
1. Meniere's
  1. watery swelling of the inner ear
  2. episodic; gradually gets worse
  3. Symptoms
    1. Vertigo
    2. Tinnitus
    3. Hearing loss
  4. Usually occurs between 40-60y
  5. Usually unilateral
  6. Clinical cause:
    1. 1. Sudden vertigo & nausea
      1. 2. Pressure & ear fullness
        3. Roaring tinnitus
        4. Hearing sensitivity decreases (usually undetected)
        5. Vertigo reduces to unsteadiness that may last a couple of weeks
        6. Hearing may improve, and extent of tinnitus decreases
        7. Remission period is followed by subsequent attacks that have a reduce in vertigo but increased hearing loss and tinnitus
  7. Aetiology
    1. Allergies, diseases, vascular problems, head trauma, infections etc.
      1. Increases endolymphatic pressure hence membrane breaks and endolymph enters the vestibular system, depolarising it
  8. Management
    1. Adopting a hypoallergenic diet
    2. Drugs for vertigo and sedatives
    3. Bed rest
  9. Hearing results
    1. sensorineural HL with rising audiometric configuration
    2. As Meniere's progresses, the degree of HL increases over time
2. Sudden Ideopathic SNHL
  1. > 30db hearing loss in less than 3 days
  2. Recovery patterns
    1. Initial rapid recovery but quickly reaches a plateau
    2. Very gradual and slow recovery and poorer plateau level
      1. Remaining noticeable balance dysfunction, tinnitus, some hearing loss, fatigue and diminished ability to concentrate
      2. Difficulty walking around in crowds, when surrounded by movement, in moderate wind
      3. Cannot distinguish direction of sounds, difficulty listening to conversation in a crowded room/ when there is background noise
    3. delayed recovery
  3. Causes
    1. VIral infection
    2. Interruption to blood supply
3. NOise Injury
  1. Hearing loss due to long term repeated exposure to noise levels over 85dB for 8h/day
  2. NOise is hazardous if:
    1. it is difficult to communicate in the noise
    2. TInnitus occurs after exposure to the noise
    3. Sounds seem muffled after being in the noise
  3. How does noise injury come about?
    1. NOise causes metabolic and mechanical exhaustion in the cochlea; decrease in O2 and blood supply to the cochlea & hair cells swell
      1. Initially reversible due to the Temporary Threshold Shift (TTS)
      2. COntinuous exposure results in irreversible and progressive damage to the cochlea, resulting in a Permanent Threshold Shift (PTS)
      3. Accompanied by tinnitus and the feeling of fullness in the ear, as well as sensation of muffled speech
  4. Hearing results
    1. Characteristic noise notch between 3-6kHz
    2. Sensorineural and typically bilateral
    3. Magnitude of loss dependent on:
      1. Intensity
      2. Duration
      3. Spectrum of noise
      4. Pattern of noise
      5. Individual differences
      6. Work place
4. Acoustic Trauma
  1. Hearing loss due to the impact of sound, often accompanied by severe tinnitus
  2. Recovery may take months
  3. Temporary or permanent
Genetic

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Inner Ear Pathologies

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	Created by Cheryl Lew about 8 years ago