Clinical meaning
Tinnitus is the perception of sound in one or both ears or in the head when no external sound source is present. It is often described as ringing, buzzing, hissing, whistling, clicking, roaring, or humming. Tinnitus is classified as either subjective (heard only by the patient, accounting for more than 95% of cases) or objective (heard by both the patient and the examiner, typically caused by vascular abnormalities, muscular contractions, or patulous Eustachian tube). Subjective tinnitus results from abnormal neural activity in the auditory pathway that the brain interprets as sound. The most common underlying mechanism involves damage to the outer hair cells of the cochlea, which are highly specialized sensory cells in the organ of Corti that amplify and fine-tune sound vibrations. When outer hair cells are damaged (most commonly by noise exposure, aging, or ototoxic medications), they can no longer properly modulate auditory nerve signals. The auditory cortex, deprived of normal input from the damaged frequency range, undergoes neuroplastic changes and begins generating spontaneous neural activity that is perceived as phantom sound. This is analogous to phantom limb...