Tinnitus and the Auditory System: Causes and Inner Ear Changes
Tinnitus is often associated with changes in the auditory system, including hearing loss or damage involving the inner ear. Changes in the cochlea or auditory nerve can alter the signals transmitted to the brain, where changes in neural activity and sound processing may contribute to the perception of tinnitus.¹˒² Here are some common mechanisms and conditions associated with tinnitus:
Hair Cell Damage in the Cochlea
Inside the cochlea, tiny sensory hair cells convert sound vibrations into electrical signals that travel through the auditory nerve to the brain. These cells can be damaged by:
- Loud noises (e.g., concerts, machinery).¹˒³
- Aging (presbycusis).¹˒³
- Ototoxic drugs (e.g., certain antibiotics, chemotherapy agents, or aspirin in high doses).¹
- Damage within the cochlea can alter normal auditory signaling, potentially contributing to changes in neural activity associated with tinnitus.²˒³
Loss of Auditory Input
When damage or hearing loss reduces the amount of auditory information reaching the brain, neural pathways involved in hearing may undergo compensatory changes. Research suggests that this reduced auditory input can contribute to increased neural gain, spontaneous activity, synchrony, and other forms of neuroplasticity within the central auditory system.²˒⁴˒⁶ These changes are among the leading mechanisms being studied to explain how tinnitus can develop or persist.
Changes in the Cochlear Nerve
The cochlear nerve carries sound signals from the cochlea to the brain. Changes or damage affecting the auditory nerve or surrounding auditory structures may be associated with tinnitus.¹ In some cases, unilateral tinnitus can occur in association with conditions affecting the vestibulocochlear nerve, such as vestibular schwannoma (acoustic neuroma).⁵
Inner Ear Disorders
Certain conditions affecting the ear or auditory system can be associated with tinnitus:¹
- Meniere’s Disease: A disorder of the inner ear that can involve tinnitus, hearing loss, dizziness, and a feeling of fullness in the ear.¹
- Labyrinthitis: Inflammation of the inner ear that can affect hearing and balance.
- Otosclerosis: Abnormal bone remodeling in the middle ear that can interfere with hearing and may be associated with tinnitus.
Blood Flow Abnormalities
Some forms of tinnitus are related to changes in blood flow. Pulsatile tinnitus, in particular, may sound rhythmic or pulse in time with the heartbeat and can sometimes be associated with vascular conditions.¹
Neuroplasticity in the Brain
The brain plays a significant role in tinnitus perception. When normal auditory input is reduced or altered, parts of the auditory system may adapt through neuroplastic changes. Research suggests these changes can include increased neural activity, altered neural synchrony, and changes in how auditory signals are processed.²˒⁴˒⁶
Key Takeaway:
Tinnitus is best understood as involving interactions between the ear and the brain rather than simply “starting” in the inner ear. In many cases, changes or damage within the peripheral auditory system, such as the cochlea, may alter the signals reaching the brain. The central auditory system may then undergo neuroplastic changes that contribute to the perception or persistence of tinnitus.¹˒²˒⁴
Because tinnitus can have many possible causes, identifying and appropriately evaluating an underlying condition can be an important part of tinnitus management.¹
References
1. National Institute on Deafness and Other Communication Disorders (NIDCD), National Institutes of Health. What Is Tinnitus? — Causes and Treatment.
NIH/NIDCD: What Is Tinnitus?
2. Henry JA, Roberts LE, Caspary DM, Theodoroff SM, Salvi RJ. Underlying mechanisms of tinnitus: review and clinical implications. Journal of the American Academy of Audiology. 2014;25(1):5–22. PMID: 24622858.
PubMed: Underlying Mechanisms of Tinnitus
3. Shore SE, Wu C. Mechanisms of Noise-Induced Tinnitus: Insights from Cellular Studies. Neuron. 2019;103(1):8–20. PMID: 31271756.
PubMed: Mechanisms of Noise-Induced Tinnitus
4. Noreña AJ. Neural plasticity and its initiating conditions in tinnitus. HNO. 2018;66(3):172–178. PMID: 29234817.
PubMed: Neural Plasticity and Its Initiating Conditions in Tinnitus
5. Javed A, Okoh M, Swords C, et al. Incidence of Vestibular Schwannoma in Patients with Unilateral Tinnitus: A Systematic Review and Meta-Analysis. Otology & Neurotology. 2023;44(9):894–897. PMID: 37621105.
PubMed: Vestibular Schwannoma and Unilateral Tinnitus
6. Noreña AJ. An integrative model of tinnitus based on a central gain controlling neural sensitivity. Neuroscience & Biobehavioral Reviews. 2011;35(5):1089–1109. PMID: 21094182.
PubMed: Central Gain Model of Tinnitus