Usefulness of Genetic Testing in Deciding the Indication for Electric Acoustic Stimulation

Abstract

Electric-acoustic stimulation (EAS), which enables hearing of high-frequency sounds via electrical stimulation and of low-frequency sounds via acoustic stimulation, is useful for patients with steeply or gradually sloping high-frequency hearing loss. Herein, we report a case of a 32-year-old female with CDH23 mutation who was treated by EAS in the left ear and cochlear implantation (CI) in the right ear. The patient presented with a steeply sloping high-frequency hearing loss, which responded poorly to hearing aids. However, one year after EAS surgery on the left side, her hearing threshold improved to 20-30 dB. While the word and sentence recognition scores in the speech recognition test (CI2004) performed preoperatively were 20% and 63%, respectively, at one-year after the treatment, both the scores improved to 100%. After the initial surgery, genetic testing revealed a mutation in the CDH23 gene. Therefore, owing to the expected decrease in residual hearing on account of the gene mutation CI was performed on the right side to improve the hearing further. It is important to be aware that predicting the risk of residual hearing loss by methods such as genetic testing, before surgery is useful for artificial hearing device selection.