Auditory Neuropathy Spectrum Disorder (ANSD) Lecture Notes

Auditory Neuropathy Spectrum Disorder (ANSD)

A condition characterized by good cochlear function (OAEs or cochlear microphonic present) but a lack of brainstem response (no ABR), often resulting in poor speech audiometry and clarity that does not match pure tone thresholds.

Otoacoustic Emissions (OAEs)

Small responses from the outer hair cells (approximately $3\,dB$) that may be present at birth in ANSD patients but can dissipate over time because they are highly sensitive to any insult to the outer hair cells.

Cochlear Microphonic

A robust response from the outer hair cells occurring within the first $0$ to $1\,ms$ of an ABR test; it is confirmed by high intensity rarefaction and condensation clicks producing mirrored waveforms.

Auditory Dyssynchrony

A term for auditory neuropathy referring to the misfiring or lack of synchronous firing of signals from the hair cells to the afferent areas due to multiple affected regions.

Proximal Auditory Neuropathy (Type 1)

A lesion located closer to the brainstem involving the ganglion cells, axons, or proximal dendrites; typically results in harder to manage or more severe outcomes.

Distal Auditory Neuropathy (Type 2)

A lesion located further out toward the cochlea involving terminal dendrites, inner hair cells, or synapses; associated with a better prognosis.

Click Stimulus (Rarefaction vs. Condensation