Method for hearing preservation in cochlear implant surgery

Individuals with useful hearing in the lower frequencies (less than 1000 cycles per second) but with severe to profound losses in the higher frequencies often have poor speed discrimination scores, especially in noise. Conventional hearing aids only provide marginal increases in word discrimination for this class of individuals. Consequently, interest has developed in electrically stimulating those regions of the cochlear (apical) that subserve higher frequencies while permitting the individual to continue to hear (with or without a hearing aid) lower frequency sound acoustically. To successfully implement such a strategy, residual hearing must be maintained for lower frequency sounds. Technical alterations in the operative technique of cochlear implantation designed to preserve hearing include: (1) avoidance of acoustic trauma using low speed drills; (2) careful placement of the cochleostomy anterior and inferior to the round window membrane to avoid damage to the basilar membrane and ossea spiral lamina; (3) the use of steroids to protect against injury to the organ of Corti at the cellular level; (4) the use of shorter, thinner, atraumatic electrodes; and (5) a small cochleostomy to prevent buckling of the electrode and escape of perilymph.