Figure 6.

Audiological assessment in adult with acquired auditory neuropathy spectrum disorder (ANSD) caused by bilateral cochlear nerve hypotrophia of unknown etiology. Unaided pure tone ((a), black line for right ear, gray line for left ear) and speech ((b), both ears in free field) thresholds are poor, with no improvement with hearing aids. Electrocochleography (ECochG) recorded after clicks at 90 dB and at a rate of 14.3 s ((c), grand average, above; superimposed, below) shows preserved summating potential (SP) and compound action potential (CAP). ECochG responses to tone-burst stimuli at different frequencies ((d), grand averages for 8, 4, 3, 2 and 1 kHz) show a large SP. Auditory brainstem responses (ABRs) are absent, except for the cochlear microphonic (CM) (e). The 3-Tesla magnetic resonance imaging of the right ear without contrast (f) shows the hypoplasia of the cochlear nerve.