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Pathophysiology of Subjective Tinnitus

One of the possible mechanisms relies in the otoacustic emissions. The inner ear contains thousands of minute hairs which vibrate in response to sound waves and cells which convert neural signals back into acoustical vibrations. The sensing cells are connected with the vibratory cells through a neural feedback loop, whose gain is regulated by the brain. This loop is normally adjusted just below onset of self-oscillation, which gains the ear spectacular sensitivity and selectivity. If something changes, it's easy for the delicate adjustment to cross the barrier of oscillation and tinnitus results. This can actually be measured by a very sensitive microphone outside the ear.

Other possible mechanisms of how things can change in the ear is damage to the receptor cells. Although receptor cells can be regenerated from the adjacent supporting Deiters cells after injury in birds, reptiles, and amphibians, in mammals it is believed that they can be produced only during embryogenesis. Although mammalian Deiters cells reproduce and position themselves appropriately for regeneration, they have not been observed to transdifferentiate into receptor cells except in tissue culture experiments.[1][2] Therefore, if these hairs become damaged, through prolonged exposure to excessive decibel levels, for instance, then deafness to certain frequencies occurs. In tinnitus, they may falsely relay information at a certain frequency that an externally audible sound is present, when it is not.

The mechanisms of subjective tinnitus are often obscure. While it is not surprising that direct trauma to the inner ear can cause tinnitus, other apparent causes (e.g., temporomandibular joint disorder (TMJ) and dental disorders) are difficult to explain. Recent research has proposed that there are two distinct categories of subjective tinnitus: Otic tinnitus, caused by disorders of the inner ear or the acoustic nerve, and somatic tinnitus, caused by disorders outside the ear and nerve but still within the head or neck. It is further hypothesized that somatic tinnitus may be due to "central crosstalk" within the brain, as certain head and neck nerves enter the brain near regions known to be involved in hearing.

While most discussions of tinnitus tend to stress physical mechanisms, there is strong evidence that the level of an individual's awareness of their tinnitus can be stress-related, and so should be addressed by improving the state of the nervous system generally, using gradual, unobtrusive, long-term treatments. [1]

Pathophysiology of Objective Tinnitus

In a minority of cases, a clinician can perceive an actual sound (e.g., a bruit) emanating from the patient's ears. This is called objective tinnitus. Objective tinnitus can arise from muscle spasms that cause clicks or crackling around the middle ear.[3] Some people experience a sound that beats in time with the pulse (pulsatile tinnitus[4]). Pulsatile tinnitus is usually objective in nature, resulting from altered blood flow or increased blood turbulence near the ear (such as from atherosclerosis or venous hum[5]), but it can also arise as a subjective phenomenon from an increased awareness of blood flow in the ear.[4] Rarely, pulsatile tinnitus may be a symptom of potentially life-threatening conditions such as carotid artery aneurysm[6] or carotid artery dissection.[7]


Cardiovascular Aortic regurgitation , arteriosclerosis, atherosclerosis of the carotid artery,carotid artery dissection, heart murmur , hypercholesterolemia, hyperlipidemia, hypertension, venous hum
Chemical/Poisoning Lead poisoning, mercury poisoning
Dental No underlying causes
Dermatologic Allergies, arterial angioma, glomus tumor, lyme disease, measles, rubella, systemic lupus erythematosus
Drug Side Effect Amikacin, aminoglycoside , aminophylline, amphotericin B, angiotensin converting enzyme inhibitors, antimalarial drugs, aspirin, benzodiazepines, bismuth, bleomycin, bumetanide, Calcium channel blockers, carbamazepine, chloramphenicol, chlordiazepoxide, chloroquine, cisplatin, clarithromycin, clomifene, Cox-2 inhibitors, cyclobenzaprine, dapsone, diflunisal, doxazosin, doxepin, erythromycin, febuxostat, fluoroquinolone, fosaprepitant, furosemide, gallium nitrate, gentamicin, ]hydroxychloroquine, indomethacin, interferon, isotretinoin, kanamycin, L-dopa, lidocaine, lincomycin hydrochloride, loop diuretics, mechlorethamine, mefloquine, methotrexate, nabilone, naltrexone, netilmicin, nitroprusside, nonsteroidal anti-inflammatory drugs, olsalazine, ototoxic medications, oxcarbazepine, pegylated interferon-alpha-2b, platinum-based chemotherapy, prazosin, propranolol, proton pump inhibitors, quinidine, rifaximin, rizatriptan, salicylates, sertraline, sibutramine, sulfasalazine, sulindac, temozolomide, tetracycline, thalidomide, tolbutamide, tolmetin, toluene, tricyclic antidepressants, valproic acid, vancomycin, vincristine
Ear Nose Throat Acoustic neuroma, acoustic shock, acute otitis externa, acute otitis media, allergies, auditory tube dysfunction, aural polyps, autoimmune inner ear disease , blocked eustachian tube, cerumen impaction, cholesteatoma, chronic otitis media, chronic sinusitis, cogan syndrome, ear infection, earache, ethacrynic acid, eustachian tube patency, foreign body in ear, glomus tumor, hearing loss, late-onset congenital hearing loss, meniere's disease, middle ear effusion, otosclerosis, ototoxicity, presbyacusis, suppurative labyrinthitis, tympanic membrane perforation, Vogt-Koyanagi-Harada syndrome
Endocrine Diabetes mellitus, diabetic vasculopathy, hyperparathyroidism, thyroid disease
Environmental Chronic exposure to noise
Gastroenterologic No underlying causes
Genetic Episodic ataxia type 2, fibrous dysplasia, osteogenesis imperfecta, sickle cell anemia
Hematologic Anemia , hypercoagulable states, leukemia, sickle cell anemia
Iatrogenic No underlying causes
Infectious Disease Chronic sinusitis, cytomegalovirus, Lyme disease, measles, meningitis, neurosyphilis, rubella, syphilitic disease,typhoid
Musculoskeletal/Orthopedic Cervical spondylosis, Costen syndrome, fibrous dysplasia, hypertonia , ossicle dislocation, osteogenesis imperfecta, Paget's disease of bone, temporomandibular joint disorder
Neurologic Altitude sickness, basilar artery migraine, carotico-cavernous fistula, carotid artery dissection, cerebral aneurysmcongenital intracranial aneurysm , dural arteriovenous fistula, episodic ataxiatype2, hypnagogia, internal carotid thrombosis, Meniere's disease, meningitis, migraine, posterior cervical sympathetic syndrome, pseudotumor cerebri
Nutritional/Metabolic Hypercholesterolemia, hyperlipidemia, vitamin B12 deficiency
Obstetric/Gynecologic No underlying causes
Oncologic Acoustic neuroma, arterial angioma, glomus tumor, leukemia, vascular tumors
Ophthalmologic Measles, Vogt-Koyanagi-Harada syndrome
Overdose/Toxicity Caffeine, excess coffee, marijuana
Psychiatric Anxiety, depression, hypnagogia, psychological disorders, Sleep paralysis
Pulmonary Altitude sickness, chronic sinusitis, sarcoid
Renal/Electrolyte Chronic nephritis, chronic renal failure, uremia
Rheumatology/Immunology/Allergy Allergies, autoimmune inner ear disease , cervical spondylosis, cogan syndrome, fibromyalgia, rheumatoid arthritis, sarcoid, susac syndrome, systemic lupus erythematosus, Vogt-Koyanagi-Harada syndrome
Sexual No underlying causes
Trauma Closed head injury, cochlear trauma, head injury, skull fracture, whiplash injury
Urologic No underlying causes
Miscellaneous Idiopathic, small vessel disease

Causes in Alphabetical Order

Common Causes of Tinnitus[8]

Tinnitus can be perceived in one or both ears or in the head. It is usually described as a ringing noise, but in some patients it takes the form of a high pitched whining, buzzing, hissing, humming, or whistling sound, or as ticking, clicking, roaring, "crickets" or "locusts", tunes, songs, or beeping.[9] It has also been described as a "whooshing" sound, as of wind or waves.[10] Tinnitus is not itself a disease but a symptom resulting from a range of underlying causes, including ear infections, foreign objects or wax in the ear, and injury from loud noises. Tinnitus is also a side-effect of some oral medications, such as aspirin, and may also result from an abnormally low level of serotonin activity.

The sound perceived may range from a quiet background noise to one that can be heard even over loud external sounds. The term "tinnitus" usually refers to more severe cases. Heller and Bergman (1953) conducted a study of 80 tinnitus-free university students placed in a soundproofed room found that 93% reported hearing a buzzing, pulsing or whistling sound. Cohort studies have demonstrated that damage to hearing (among other health effects) from unnatural levels of noise exposure is very widespread in industrialized countries.[11]

Because tinnitus is often defined as a subjective phenomenon, it is difficult to measure using objective tests, such as by comparison to noise of known frequency and intensity, as in an audiometric test. The condition is often rated clinically on a simple scale from "slight" to "catastrophic" according to the practical difficulties it imposes, such as interference with sleep, quiet activities, or normal daily activities.[12] For research purposes, the more elaborate Tinnitus Handicap Inventory is often used.[13]

Physical examination

The ears should be examined for wax and a foreign body.

Measuring tinnitus

The basis of quantitative measurement of tinnitus relies on the brain’s tendency to select out only the loudest sounds heard. Based on this tendency, the amplitude of a patient's tinnitus can be measured by playing sample sounds of known amplitude and asking the patient which he or she hears. The tinnitus will always be equal to- or less than sample noises heard by the patient. This method works very well to gauge objective tinnitus (see above.) For example: if a patient has a pulsatile paraganglioma in his ear, he will not be able to hear the blood flow through the tumor when the sample noise is 5 decibels louder than the noise produced by the blood. As sound amplitude is gradually decreased, the tinnitus will become audible, and the level at which it does so provides an estimate of the amplitude of the objective tinnitus.

Objective tinnitus, however, is quite uncommon. Often patients with pulsatile tumors will report other coexistent sounds, distinct from the pulsatile noise, that will persist even after their tumor has been removed. This is generally subjective tinnitus, which, unlike the objective form, cannot be tested by comparative methods.

If a subject is focused on a sample noise, they can often detect it to levels below 5 decibels, which would indicate that their tinnitus would be almost impossible to hear. Conversely, if the same test subject is told to focus only on their tinnitus, they will report hearing the sound even when test noises exceed 70 decibels, making the tinnitus louder than a ringing phone. This quantification method suggests that subjective tinnitus relates only to what the patient is attempting to hear. Patients actively complaining about tinnitus could thus be assumed to be people who have become obsessed with the noise. This is only partially true. The problem is involuntary; generally complaining patients simply cannot override or ignore their tinnitus. The noise is often present in both quiet and noisy environments, and can become quite intrusive to their daily lives.

Subjective tinnitus may not always be correlated with ear malfunction or hearing loss. Even people with near-perfect hearing may still complain of it. Tinnitus may also have a connection to memory problems, anxiety, fatigue or a general state of poor health. There are many treatments that are effective for objective tinnitus. But there are no clear effective treatments for subjective tinnitus. Conversely, tinnitus may resolve without any treatment. In the subjective tinnitus the treatment of the associated problems like fatigue, anxiety and a bad healthy status is essential to achieve success. Effective treatments include:

Objective tinnitus:

  • Gamma knife radiosurgery (glomus jugulare)[14]
  • Shielding of cochlea by teflon implant[15]
  • Botulinum toxin (palatal tremor)[16]
  • Propranolol and clonazepam (arterial anatomic variation)[17]

Subjective tinnitus:

  • Drugs and nutrients
    • Lidocaine, injection into the inner ear found to surpress the tinnitus for 20 minutes, according to a Swedish study. [18]
    • Benzodiazepines (xanax, ativan, klonopin)
    • Avoidance of caffeine, nicotine, salt[19][20][21]
    • Avoidance of or consumption of alcohol[22][21]
    • Zinc supplementation (where serum zinc deficiency is present)[23][24][25]
    • Acamprosate[26]
    • Etidronate or sodium fluoride (otosclerosis)[27]
    • Lignocaine or anticonvulsants (usually in patients responsive to white noise masking)[28]
    • Carbemazepine[29]
    • Melatonin (especially for those with sleep disturbance)[30]
    • Sertraline[31]
    • Vitamin combinations (lipo-flavonoid)[32]
  • Electrical stimulation
    • Transcranial magnetic stimulation or transcranial direct current stimulation[33][34]
    • Transcutaneous electrical nerve stimulation[35]
    • Direct stimulation of auditory cortex by implanted electrodes[36]
  • Surgery
    • Repair of perilymph fistula[37]
  • External sound
  • Psychological
    • Cognitive behavior therapy[46]
  • Light-based

Although there are no specific cures for tinnitus, anything that brings the person out of the "fight or flight" stress response helps symptoms recede over a period of time. Calming body-based therapies, counseling and psychotherapy help restore well-being, which in turn allows tinnitus to settle. Chronic tinnitus can be quite stressful psychologically, as it distracts the affected individual from mental tasks and interferes with sleep, particularly when there is no external sound. Additional steps in reducing the impact of tinnitus on adverse health consequences include: a review of medications that may have tinnitus as a side effect; a physical exam to reveal possible underlying health conditions that may aggravate tinnitus; receiving adequate rest each day; and seeking a physician's advice concerning a sleep aid to allow for a better sleep pattern.

Related Chapters

External Links

  1. ↑ Supporting cell proliferation after hair cell injury in mature guinea pig cochlea in vivo
  2. ↑ Mammalian cochlear supporting cells can divide and trans-differentiate into hair cells
  3. ↑ ENT Health Information > Hearing > Tinnitus
  4. ↑ 4.0 4.1 RNID.org.uk: Information and resources: Our factsheets and leaflets: Tinnitus: Factsheets and leaflets
  5. ↑ Diagnosis and cure of venous hum tinnitus
  6. ↑ Otologic manifestations of petrous carotid aneurysms
  7. ↑ Carotid Artery Dissection
  8. ↑ Diagnostic approach to tinnitus
  9. ↑ RNID.org.uk: Information and resources: Tinnitus: About tinnitus: What is tinnitus
  10. ↑ Medline Plus Medical Encyclopedia: Ear noises or buzzing
  11. ↑ Noise exposure and subjective hearing symptoms among school children in Sweden
  12. ↑ Guidelines for the Grading of Tinnitus Severity
  13. ↑ Development of the Tinnitus Handicap Inventory
  14. ↑ Treatment of glomus jugulare tumors in patients with advanced age: planned limited surgical resection followed by staged gamma knife radiosurgery: a preliminary report
  15. ↑ Pulsatile tinnitus and the intrameatal vascular loop: why do we not hear our carotids?
  16. ↑ Botulinum toxin is effective and safe for palatal tremor: a report of five cases and a review of the literature
  17. ↑ Pulsatile tinnitus: treatment with clonazepam and propranolol
  18. ↑ Swedish website about tinnitus
  19. ↑ Rogers, June: "Only When I Eat: Hope at Last". Ki Publishing Co-operative. UK ISBN 0951 0769 06
  20. ↑ Vascular decompression of the cochlear nerve in tinnitus sufferers
  21. ↑ 21.0 21.1 Meniere's disease: differential diagnosis and treatment
  22. ↑ Patients' reports of the effect of alcohol on tinnitus
  23. ↑ The role of zinc in the treatment of tinnitus
  24. ↑ The role of zinc in management of tinnitus
  25. ↑ Zinc in the management of tinnitus. Placebo-controlled trial
  26. ↑ Tinnitus treatment with acamprosate: double-blind study
  27. ↑ Etidronate for the the neurotologic symptoms of otosclerosis: preliminary study [sic]
  28. ↑ Drugs in the treatment of tinnitus
  29. ↑ Typewriter tinnitus: a carbamazepine-responsive syndrome related to auditory nerve vascular compression
  30. ↑ The effects of melatonin on tinnitus and sleep
  31. ↑ The effects of sertraline on severe tinnitus suffering--a randomized, double-blind, placebo-controlled study
  32. ↑ Williams HL, Maher FT, Corbin KB, et al: Eriodictyol glycoside in the treatment of Meniere’s disease. Ann Otol Rhinol Laryngol 72:1082, 1963.
  33. ↑ Transcranial magnetic stimulation for the treatment of tinnitus: a new coil positioning method and first results
  34. ↑ Transient tinnitus suppression induced by repetitive transcranial magnetic stimulation and transcranial direct current stimulation
  35. ↑ Treatment of tinnitus with transcutaneous electrical nerve stimulation improves patients' quality of life
  36. ↑ Primary and secondary auditory cortex stimulation for intractable tinnitus
  37. ↑ Perilymph fistula--45 case analysis
  38. ↑ Tinnitus masker - sonic designs by Jon Dattorro...
  39. ↑ Long-term clinical trial of tinnitus retraining therapy
  40. ↑ Outcomes of clinical trial: tinnitus masking versus tinnitus retraining therapy
  41. ↑ Auditive stimulation therapy as an intervention in subacute and chronic tinnitus: a prospective observational study
  42. ↑ OHSU Tinnitus Clinic: Comprehensive Treatment Programs including Tinnitus Retraining Therapy (TRT)
  43. ↑ Ultra-high-frequency ultrasonic external acoustic stimulation for tinnitus relief: a method for patient selection
  44. ↑ Tinnitus improvement with ultra-high-frequency vibration therapy
  45. ↑ Subdividing tinnitus into bruits and endogenous, exogenous, and other forms
  46. ↑ Treatment of tinnitus in the elderly: a controlled trial of cognitive behavior therapy
  47. ↑ http://www.tinnitusformula.com/infocenter/articles/treatments/LLLT.aspx
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