What causes chronic tinnitus?

Causes of Chronic Tinnitus

Tinnitus is not a disease itself but a symptom associated with multiple underlying causes, with hearing loss being the most common etiology, particularly sensorineural hearing loss from noise exposure, aging (presbycusis), and ototoxic medications. 1, 2

Primary Causes of Chronic Tinnitus

Otologic Causes

• Hearing loss: Most common cause 1, 3
  • Noise-induced hearing loss
  • Age-related hearing loss (presbycusis)
  • Sudden sensorineural hearing loss
• Middle ear disorders:
  • Otosclerosis
  • Chronic otitis media
  • Tympanic membrane perforation
  • Cerumen impaction 4
• Inner ear disorders:
  • Menière's disease
  • Labyrinthitis

Neurologic Causes

• Vestibular schwannoma (acoustic neuroma) - especially with unilateral tinnitus 1, 4
• Head or neck injury 5
• Multiple sclerosis
• Cerebellopontine angle tumors

Vascular Causes (often presenting as pulsatile tinnitus)

• Arteriovenous malformations (AVMs)
• Arteriovenous fistulae (AVFs)
• Carotid artery stenosis/atherosclerosis
• High-riding jugular bulb
• Glomus tumors 6, 1

Medication-Related Causes

• Ototoxic medications 5, 7:
  • Certain antibiotics (aminoglycosides)
  • Salicylates (aspirin)
  • NSAIDs
  • Loop diuretics
  • Some chemotherapeutic agents

Systemic Disorders

• Hypertension
• Diabetes
• Thyroid disorders
• Anemia
• Intracranial hypertension 6

Psychological Factors

• Depression and anxiety (both as cause and effect) 5, 3
• Stress
• Sleep disorders

Classification of Tinnitus Types

Based on Perception

1. Subjective tinnitus: Heard only by the patient (most common) 2, 4
2. Objective tinnitus: Can be heard by an examiner (rare) 4

Based on Sound Characteristics

1. Pulsatile tinnitus: Synchronous with heartbeat, often vascular in origin 1
2. Non-pulsatile tinnitus: Constant sound, typically associated with auditory pathway disorders 1

Based on Laterality

1. Unilateral tinnitus: Often requires more urgent evaluation, especially with asymmetric hearing loss 1
2. Bilateral tinnitus: More commonly associated with systemic causes or bilateral hearing loss 1, 7

Red Flags Requiring Urgent Evaluation

• Pulsatile tinnitus
• Unilateral tinnitus
• Tinnitus with sudden hearing loss
• Tinnitus with focal neurological symptoms
• Visible abnormality on otoscopic examination 1

Common Pitfalls in Diagnosis

1. Failing to remove cerumen before assessment
2. Overlooking non-otologic causes
3. Not performing comprehensive audiologic evaluation
4. Delayed referral for unilateral tinnitus
5. Missing red flags that warrant urgent evaluation 1

Pathophysiological Mechanisms

The anatomical location of chronic subjective tinnitus is rarely in the ear but more often in the auditory nervous system. Neural plasticity plays a central role in many forms of chronic subjective tinnitus, potentially causing:

• Changes in the balance between excitation and inhibition
• Hyperactivity in the auditory system
• Reorganization of specific parts of the nervous system
• Redirection of information to non-classical auditory pathways 7

Since tinnitus has many different forms and causes, there is no single cure that works for all cases. The heterogeneity of tinnitus patients also makes clinical trials challenging 5, 7.