Inner Ear Pathologies

Inner Ear Pathologies

1. due to disorders of

   • cochlea
   • cranial nerve VIII
   • cochlear nuclei

2. Classification

   • Degree & type
     • i.e. profound sensory, mild conductive
   • Origin
     • Hereditary / acquired
   • Onset
     • congenital / delayed
   • Structural pathology

3. Characteristics

   • irreversible
   • except for
     • some Meniere's
     • HL due to perilymphatic fistula
     • obstruction of blood flow to the cochlea

4. Acquired SNHL

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

5. Genetic

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