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