Patterns of Long-term Hearing Loss in Hearing Preservation Cochlear Implant Surgery.

Objective: To describe patterns of hearing loss in patients with low-frequency residual hearing after cochlear implantation. Study Design: Retrospective chart review. Setting: Tertiary referral center. Patients: Cochlear implant candidates with immediate postoperative residual low-frequency hearing. Interventions: Hybrid or traditional cochlear implant. Main Outcome Measure: Audiograms to measure postoperative hearing. Results: Of the 166 patients reviewed, 17 ears met the inclusion criteria. The age ranged from 3 years 2 months to 86 years. Etiology was unknown (n = 6), presbycusis (n = 5), genetic (n = 4), acoustic trauma (n = 1), and measles virus (n = 1). The Nucleus Hybrid S8 and S12 (n = 7) was the most common electrode array, and then Nucleus 422 (n = 6), Nucleus Contour Advance (n = 2), Med-El Flex 28 (n = 2), and Advanced Bionics Mid Scala (n = 1). Cochleostomy was performed in nine, and round window approach in nine patients. Average follow-up was 28 months (2-68 mo). Postoperative loss was mixed in eight and purely sensorineural in eight. The most common patterns of hearing loss were gradual decline (n = 7), and then fluctuating hearing (n = 6), stable (n = 3), and sudden loss (n = 1). One patient only had one postoperative audiogram. Conclusion: Some long-term hearing preservation was achieved in 94% of patients with immediate postoperative hearing preservation. Patients developed both mixed and sensorineural loss postoperatively. A majority of patients with mixed hearing loss had a supra-preoperative bone curve. Gradual decline and fluctuating hearing loss were the most common patterns of hearing loss; few patients had stable hearing and one had a sudden loss.