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Communication Disorders
Communication Disorders

Auditory Neuropathy Spectrum Disorder (ANSD)

Auditory Neuropathy Spectrum Disorder (ANSD) is a hearing disorder in which the hearing organ located in the inner ear (cochlea) seems to receive sounds normally, however, signals leaving the cochlea may be disorganized or the hearing nerve itself may not process sound normally.

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The exact incidence of ANSD has varied among different publications.  Overall, ANSD is rare and can be found in estimated 1-3 children per 10,000 births.  Most patients with ANSD have other significant perinatal risk factors, however one third of the patients have no definable etiologic cause.  ANSD occurs with near equal frequency in males (55%) and females (45%).

Risk factors associated with ANSD include

  • Neonatal history of anoxia (not enough oxygen to the brain)
  • Neonatal history of hyperbilirubinemia (high levels of bilirubin in the blood)
  • Neonatal history of mechanical ventilation, hypoxia or both
  • Congenital brain abnormalities
  • Low birth weight
  • Extremely premature birth (<28 weeks)
  • Genetics or family history of ANSD
  • ANSD has been reported in association with viral diseases, seizure disorders and high fever and with or without accompanying neurological disorders

ANSD was first identified in the late 1980s when advanced testing procedures became available to measure the action within the cochlea.  The diagnosis of ANSD is based on a certain pattern of results from a number of different hearing tests.  Auditory Brainstem Response (ABR) and Otoacoustic Emissions (OAEs) are primarily the tests used to identify this condition. The most striking finding with ANSD is that OAEs are normal and ABR is abnormal.  This means that most or part of the cochlea is working normally but there are poor responses leading up to or from other parts of the cochlea and/or the hearing nerve. 

Common features that are seen with ANSD include:

  • Hearing loss of some degree, which can vary from mild to profound.  The degree of hearing loss is NOT predictable
  • Difficulty understanding speech, especially in noise
  • Hearing can appear to fluctuate

The location of the problem that causes ANSD cannot usually be detected.  It also may be different from person to person.  This may explain why outcomes with ANSD can be so different.

The goal in managing ANSD is for the child to be able to communicate - this may take on many different forms and is child specific.  Management of ANSD may involve the use of assistive therapy to promote understanding of sounds and development of speech (such as audio-verbal therapy), hearing aid(s) or cochlear implant(s).  No medications are available to treat ANSD.  It is difficult to predict how well any one child will be able to hear and which of these treatments they might benefit from.  It is important to note that ANSD outcome is not predictable ABR and OAE results alone.  Behavioural hearing tests and information regarding development of communication provide the key to measuring a child’s progress with ANSD.