Correlative studies of cochlear neuronal loss with speech discrimination and pure-tone thresholds.

Correlations were made between speech discrimination scores, pure-tone thresholds, and neuronal populations in 28 cochleae which were removed postmortem from elderly patients who had known premortem audiometric records. The predominant pathology present was loss of cochlear neurons. The capability for speech discrimination correlated directly with the innervation density of the 15- to 22-mm region (segment III) of the cochlea. Speech discrimination scores showed an inverse relationship to pure-tone thresholds in the middle frequency range of 1 kHz to 2 kHz.