This bidirectional observational cohort study aims to establish a Hearing and Brain Development (HBD) cohort in children and adolescents with hearing loss across different hearing management pathways, including hearing aid fitting, cochlear implantation, auditory brainstem implantation, gene therapy, and follow-up without intervention, as well as in a normal-hearing control group. Participants will undergo longitudinal assessments of hearing, speech, language, neurodevelopment, and multimodal brain function.