Auditory Neuropathy Spectrum Disorder/ANSD

  • Describes disorders that are operationally defined on a constellation (a group or cluster of related things) of clinical findings
  • Constellation of findings varies as a function of age
    • Environmental
      • hyperbilirubinemia
      • prematurity
      • hypoxia (deficiency in oxygen reaching the tissues)
    • Genetic basis
      • OTOF gene encoding otoferlin
      • DFNB59 gene encoding pejvakin
    • Older children
      • Absent auditory brainstem response (ABR)
      • Poor speech perception
      • Varying levels of hearing sensitivity loss
      • Absence of acoustic reflexes
      • Preservation of some cochlear function
        • evidence of otoacoustic emissions (OAE)
        • And/Or
        • evidence of cochlear microphonic
    • Infants
      • Absent ABR
      • Preserved OAEs
      • And/Or
      • Cochlear Microphonics
  • May Represent two fairly different disorders
    • Sensory
      • Sensory hearing disorder that represents a transduction problem
      • Failure of cochlea to transmit signals to the auditory nerve
      • Most likely the inner hair cells
      • Preservation of OAE and CM represents normal outer hair cell function without inner hair cells to sensitize
      • Absence of ABR is a reflection of the sensitivity loss of the system
      • accurately predicts substantial hearing loss
      • acts like any other sensitivity loss in terms of its influence on speech and language acquisition and its amenability to hearing aids and cochlear implants
    • Neural
      • loss of synchrony of neural firing
      • AKA auditory dys-synchrony
      • cause is typically unknown
      • may be observed in cases of syndromic peripheral pathologies
        • Friedreich Ataxia
        • Charcot-Marie Tooth syndrome
      • Age of onset is usually before 10 years
      • hearing sensitivity loss ranges from normal to profound
      • most often flat or reverse sloped in configuration
      • hearing loss often fluctuates and is progressive in some children
      • Speech perception is often substantially poorer than what would be expected from the audiogram
      • AN(N) may not be as amenable to conventional amplification and implant treatment as AN(S)

References

Pediatric audiology Madell, J. and Flexer, C. (2014). Pediatric Audiology; Diagnosis, Technology and Management. New York, NY : Thieme.