Tinnitus

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List of terms related to Tinnitus

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Kiran Singh, M.D. [2] Sabeeh Islam, MBBS[3]

Historical Perspective

• In the early 19th century, Frenchman and Jean Marie Gaspard Itard introduced the concept of masking.  They were the first ones to differentiate between subjective and objective tinnitus.
• Later in the 19th Century, with the introduction of germ theory and anesthesia, surgical therapy such as incudectomy was established.
• Tinnitus is derived from the Latin word tinnire, meaning to ring.

Classification

Tinnitus can be classified as subjective and objective.  This classification not only explains the underlying etiology but also directs the management of tinnitus.

Subjective tinnitus:

• It is only experienced by the affected individual in the absence of any auditory stimulation
• More common, usually described as continuous ringing, high pitch sound

Objective tinnitus:

• It is experienced not only by the affected individual but also by anyone else
• Relative rare, usually described as intermittent venous hum, low pitch sound
• It has an underlying vascular (abnormality of the carotid artery, jugular bulb or jugular vein) or muscular etiology (degenerative conditions such as amyotrophic lateral sclerosis) and usually caused by sound produced in ear, head or neck.
  

Pathophysiology

In the normal functioning auditory pathway, there is ordered tonotopic frequency mapping from the cochlea to the auditory cortex via midbrain.  Conditions associated with cochlear damage result in altered tonotopic organization and ultimately tinnitus. The pathophysiology of tinnitus can be explained by the tinnitus model.

Lesion projection zone (LPZ):

This zone is defined as the area in the auditory cortex that represents the damaged cochlear input.  The neurons in the LPZ zone show 2 main changes:

• Accelerated spontaneous firing rate
• Increased representation of neurons that represent the damaged cochlear region also known as lesion edge frequencies in the LPZ

Tinnitus model:

This model explains 2 major phenomena in the auditory cortex caused by lack of sensory peripheral auditory input (cochlea)

• Hyperactivity in the lesion projections zone (LPZ)
• Increased cortical representation of the lesion-edge frequencies in the LPZ

Causes of subjective tinnitus

Common Causes

Sensorineural hearing loss:

• Ototoxicity
• Presbycusis
• Noise induced hearing loss
• Late onset congenital hearing loss
• Idiopathic

Cochlear injury:

• Ménière disease
• Loop diuretics
• Platinum based chemotherapy
• Antibiotics
• Salicylate
• Trauma

Vascular causes:

• Systemic hypertension
• Sickle cell anemia
• Small vessel disease
• Hypercholesterolemia
• Hypercoagulable state
• Diabetic vasculopathy

CNS causes:

• Pseudotumor cerebri
• Stroke
• Vascular malformations
• Tumor
• Sarcoid
• Multiple sclerosis

Infections:

• Rubella
• Cytomegalovirus
• Chronic otitis media
• Neurosyphilis
• Measles
• Lyme disease
• Meningitis

Bone disease:

• Otosclerosis
• Fibrous dysplasia
• Osteogenesis imperfecta
• Paget disease

Metabolic disorders:

• Hyperparathyroidism
• Chronic renal failure
• Diabetes mellitus
• Thyroid disease

Autoimmune diseases:

• Autoimmune inner ear disease
• SLE
• Rheumatoid arthritis

Medications:

• ACE inhibitors
• Antimalarial medications
• Aminoglycosides
• Dapsone
• Doxazosin
• Calcium channel blockers
• Benzodiazepines
• Cisplatin
• Clarithromycin
• COX-2 inhibitors
• Loop diuretics
• Tricyclic antidepressant
  

Epidemiology and Demographics

• Tinnitus affects 10 to 15% of the population.
• 85% of the population presenting with ear symptoms/disorders report tinnitus as an associated symptom.
• The incidence rate of tinnitus increases with age and is more prevalent in older people.

Risk Factors

• Age
• Sensorineural hearing loss

Natural History, Complications and Prognosis

• Early clinical features may include ear fullness, huming or ringing sensations in the ear
• If left untreated, patients may progress to functional impairment, insomnia and depression.

Diagnosis

History and Symptoms:

• Sounds such as ringing, buzzing, pulsatile, roaring and humming
• Progressive hearing loss
• Recent exposure to excessive or loud noise or head trauma
• Poor hygiene leading to cerumen impaction
• Ear pain
• History of certain medication exposure

Physical Examination:

• The ear examination may show signs of cerumen impaction, underlying infection or tympanic membrane perforation.
• Auscultation of neck, orbits and periauricular areas as helpful in establishing the diagnosis of vascular causes
• An extensive neurological examination may rule out underlying brainstem damage or hearing loss
• The Weber and Rinne test are done to establish sensorineural or conductive hearing loss

Laboratory Findings:

• There are no specific lab findings associated with tinnitis.

Imaging:

• MRA and CTA are the gold standard diagnostic tests for arteriovenous fistula related tinnitus.
• MRI with contrast is the initial preferred diagnostic test of choice for suspected vascular tinnitus.
• MRI with contrast is followed by CT/CTA and ultimately interventional angiography, if needed.

Other Diagnostic Testing:

• Initial audiometric tests are done to identify asymmetries between the ears and to locate the site of abnormality such as middle ear, cochlea, and brainstem.  These tests include:
  • Pure-tone audiogram
  • Tympanometry
  • Auditory reflex testing
  • Determination of speech discrimination abilities
  • Otoacoustic emissions testing
  • Auditory brainstem response testing (ABR)

Treatment

Tinnitus is a symptom and not a disease itself.  It is a chronic condition that can be managed by treating the underlying etiology.