Tinnitus does not represent a disease itself, but instead is a symptom of a variety of underlying diseases. Otologic causes include noise-induced hearing loss, presbycusis, otosclerosis, otitis, impacted cerumen, sudden deafness, Meniere’s disease, and other causes of hearing loss. Neurologic causes include head injury, whiplash, multiple sclerosis, vestibular schwannoma (commonly called an acoustic neuroma), and other cerebellopontine-angle tumors. Infectious causes include otitis media and sequelae of Lyme disease, meningitis, syphilis, and other infectious or inflammatory processes that affect hearing. Tinnitus is also a side effect of some oral medications, such as salicylates, nonsteroidal anti-inflammatory drugs, aminoglycoside antibiotics, loop diuretics, and chemotherapy agents (e.g., platins and vincristine). Temporomandibular-joint dysfunction and other dental disorders can also cause tinnitus. However, in many cases no underlying physical cause is identifiable. For many years, hearing loss has been understood to be the most common cause of tinnitus,29 and population-based data indicate that excessive noise exposure represents the second most common cause of tinnitus. However, about 40% of patients cannot identify any cause associated with tinnitus onset.
Any pathologic lesion in the auditory pathway or any reduction in auditory nerve function has the potential to produce tinnitus. The location of the hearing problem (i.e., in the middle ear or in the inner ear) and the otologic disorder causing the hearing loss do not appear to influence the etiologic potential. Interestingly, most patients with tinnitus complain about a sensation of fullness or blockage in the middle ear, suggesting a problem with middle ear pressure or increased impedance of the ossicular chain.
Unilateral high-frequency hearing loss combined with poor speech discrimination suggests the presence of a tumor, usually a vestibular schwannoma/acoustic neuroma or a meningioma. Bilateral subjective tinnitus requires assessment of hearing and can be associated with presbycusis, noise-induced hearing loss, endolymphatic hydrops, and a vascular labyrinthine lesion. However, most cases of unilateral tinnitus are not associated with life-threatening otologic disease.
References: Han BI, Lee HW, Kim TY, Lim JS, Shin KS. Tinnitus: characteristics, causes, mechanisms, and treatments. J Clin Neurol. 2009 Mar;5(1):11-9. doi: 10.3988/jcn.2009.5.1.11. Epub 2009 Mar 31. PMID: 19513328; PMCID: PMC2686891.