Lesions of the eighth cranial nerve and central audiovestibular pathways produce neural hearing loss and vertigo (Table 8–3) One characteristic of neural hearing loss is deterioration of speech discrimination out of proportion to the decrease in pure tone thresholds Another is auditory adaptation, wherein a steady tone appears to the listener to decay and eventually disappear Auditory evoked responses are useful in distinguishing cochlear from neural losses and may give insight into the site of lesion within the central pathways The evaluation of central audiovestibular disorders usually requires imaging of the internal auditory canal, cerebellopontine angle, and brain with enhanced MRI