Comparison of clinical phenotypic features across eight inner ear functional categories (excluding category 9: not determined). Cases with only one audiogram or a follow-up duration of less than 1 year were classified as “not available” (N/A) for hearing loss progression. Profound SNHL with thresholds ≥ 90 dB at 500 Hz on the initial audiogram was classified as “not determined” (N/D) for hearing loss progression. In cases with bilateral ear discrepancies in progressiveness, the overall category was defined as “substantial” if at least one ear showed substantial progression (e.g., substantial/mild, substantial/none, and substantial/N/D). If no ear was classified as substantial but at least one ear was classified as mild (e.g., mild/none and mild/N/D), the overall category was defined as “mild.” Furthermore, patients with mixed or asymmetric hearing loss were classified as N/D when analyzing severity and configuration of hearing loss.
