Cochlear Dead Regions in Adults and Children: Diagnosis and Clinical Implications

The inner hair cells (IHCs) are the transducers of the cochlea; they convert mechanical vibrations to neural activity. When the IHCs and/or neurons are nonfunctioning over a certain region of the cochlea, this is referred to as a dead region. A dead region can be defined in terms of the characteristic frequencies of the IHCs and/or neurons immediately adjacent to the dead region. Dead regions can be detected, and their limits can be determined, using the threshold equalizing noise (TEN) test or by measurement of psychophysical tuning curves (PTCs). Both PTCs and the TEN test can be used to assess children as young as 7 years of age. The identification of dead regions can be helpful in determining the appropriate form of amplification. For both adults and children with restricted dead regions (“holes”), benefit is obtained from amplification of frequencies up to at least 4 kHz. For adults and children with extensive continuous dead regions starting at a relatively low frequency (≤ 1.5 kHz) there may be little or no benefit from amplification of high frequencies.