- Cochlear or retrocochlear anomaly/pathology that interferes with transmission of auditory information from the cochleae to the brainstem, resulting in severe to profound bilateral deafness (thresholds of 90 dB or worse in both ears on pure tone audiometry ranging from 250 to 2,000 Hz and speech recognition scores ≤ 30% in both ears). All subjects will undergo bone conduction audiometry and tympanometry to confirm sensorineural hearing loss and rule out potential middle ear disorders.