Performance Phenotypes and Early Prognostic Benchmarking After Adult Cochlear Implantation.

OBJECTIVES

To characterize the temporal dynamics of post-activation improvement, identify cochlear implant (CI) performance phenotypes, and establish an early prognostic benchmark following CI activation in adults.

METHODS

Retrospective longitudinal cohort at a tertiary academic medical center. Adult CI recipients (N = 530 patient-ears) were analyzed across a within-subjects improvement cohort (n = 125, complete consonant-nucleus-consonant [CNC] data at 1, 3, 6, and 12 months) and a prognostic validation cohort (n = 205, paired 1- and 12-month CNC). Outcomes included CNC word recognition, improvement rates, device datalogging, and 1-month prognostic validity.

RESULTS

CNC improvement was front-loaded. Early-period (1 → 3 month) rates of 4.44 ± 6.95 points/month were approximately 35-fold faster than late-period (6 → 12 month) rates of 0.13 ± 1.84 points/month (Friedman χ2 = 26.97, p < 0.001). k-means clustering identified three performance phenotypes distinguishable at 1 month (p < 0.001). Preoperative CNC did not differ across clusters (p = 0.25). Device usage was a stable patient-level trait. It differed between clusters (p < 0.001) but did not predict CNC improvement (ρ = 0.02, p = 0.82). However, sustained or increasing engagement through 6 months was associated with higher 12-month CNC than declining engagement (p = 0.004). The 1-month CNC score strongly predicted 12-month outcomes (ρ = 0.68, p < 0.001; R2 = 0.45), a 15-fold gain over preoperative CNC. A 1-month CNC ≥ 44% predicted functional success (12-month CNC ≥ 50%) with AUC 0.82 (95% CI: 0.76-0.88; sensitivity: 0.66, specificity: 0.89).

CONCLUSIONS

Adult CI recipients undergo accelerated auditory adaptation concentrated in the first 3 months post-activation, with performance trajectories largely established by 1 month. A 1-month CNC threshold of ≥ 44% represents a clinically actionable prognostic checkpoint, and sustained device engagement through 6 months is associated with optimal long-term outcomes.