Etiology of Tinnitus
Tinnitus is not a disease but a symptom that can result from numerous underlying causes, ranging from cerumen impaction to vascular abnormalities, with primary tinnitus being idiopathic and secondary tinnitus associated with an identifiable underlying source. 1
Classification of Tinnitus
By Perception
- Subjective tinnitus: Perceived only by the patient, most common type, often associated with sensorineural hearing loss 1
- Objective tinnitus: Audible to the examining healthcare provider, should prompt evaluation for underlying vascular abnormality 1
By Pattern
- Pulsatile tinnitus: Repetitive sound coinciding with heartbeat, often vascular in origin 1, 2
- Non-pulsatile tinnitus: Continuous or constant non-synchronous sound 1
By Cause
- Primary tinnitus: Idiopathic, may have concomitant sensorineural hearing loss, typically no cure 1, 3
- Secondary tinnitus: Associated with an identifiable underlying cause 1, 4
Common Etiologies
Otologic Causes
- Cerumen impaction 1, 4
- Middle ear effusion or infection 4
- Otosclerosis 5
- Presbycusis (age-related hearing loss) 1, 3
- Noise-induced hearing loss 5, 3
- Menière's disease 4, 3
- Vestibular schwannoma (acoustic neuroma) 1, 4
Vascular Causes (Often Resulting in Pulsatile Tinnitus)
- Arterial dissection 2
- Fibromuscular dysplasia of carotids 2
- Dural arteriovenous fistulas 2
- Arteriovenous malformations 2
- Carotid cavernous sinus fistulas 2
- Transverse sinus stenosis 2
- Sigmoid sinus diverticulum 2
- Persistent petrosquamosal sinus 2
- Prominent mastoid or condylar emissary veins 2
- Paragangliomas (glomus tumors) 2
- Vascular middle ear tumors 2
Bony Abnormalities
- Superior semicircular canal dehiscence 2
- Sigmoid sinus wall dehiscence 2
- High jugular bulb 2
- Paget disease affecting temporal bone 2
Neurologic Causes
Other Causes
- Ototoxic medications (certain antibiotics, etc.) 1, 3
- Metabolic disorders 4
- Psychogenic factors (anxiety, depression) 1, 5
- Myoclonus (palatal myoclonus) 6
- Patulous eustachian tube 6
- Stapedial/tensor tympani muscle spasm 6
- Head trauma 5
Pathophysiological Mechanisms
- Neural plasticity plays a central role in many forms of chronic subjective tinnitus 3
- Changes in the balance between excitation and inhibition in the nervous system 3
- Hyperactivity in the auditory pathway 3
- Reorganization of specific parts of the nervous system 3
- Redirection of information to parts of the nervous system not normally involved in sound processing 3
Important Clinical Considerations
- Unilateral tinnitus plus hearing loss should increase suspicion for acoustic neuroma 4
- Pulsatile tinnitus requires thorough evaluation for vascular abnormalities 1, 2
- Tinnitus with severe anxiety or depression requires prompt identification and intervention due to increased suicide risk 1
- Different pathophysiology may underlie unilateral versus bilateral tinnitus 3
- No single cure exists due to the heterogeneity of tinnitus types 3, 7
- No proven effective pharmacological treatments specifically for chronic tinnitus 7
Understanding the specific etiology of tinnitus is crucial for appropriate management, as treatment approaches vary significantly based on the underlying cause.