Tinnitus

Etiology

There are many causes of tinnitus:

• The most common cause of subjective tinnitus is noise trauma. For example, an employee who works in a noisy industry loses hearing at the 4000 Hz tone. Now the employee hears a sound that is similar to the 4000 tone.
• Metabolic diseases: Heart, hypertension, diabetes are associated with an onset of tinnitus. Various drugs are ototoxic to some individuals or at sufficient doses. For example, high doses of aspirin cause tinnitus, and the issue resolves when aspirin is stopped. 
• Ear diseases cause tinnitus including Meniere disease or lesions affecting the eighth cranial nerve.

Twenty percent of persons visiting tinnitus clinics have normal hearing. Some have somatosensory tinnitus. Here, stimulation from cervical or TMJD has activated the dorsal cochlear nucleus and sends impulses to the auditory center. Evidence for this is that stimulation similar to whiplash or TMJD has been shown to cause anatomical changes in the dorsal cochlear nucleus.[5][6][7]

A rare cause of tinnitus is the Chiari malformation. Tinnitus occurs when low-lying cerebellar tonsils cause auditory nerve tension and can be unilateral or bilateral.

Epidemiology

Almost everyone at one time experiences tinnitus. The American Tinnitus Association estimates that 10 million people suffer from tinnitus. It is also common in non-industrialized countries.

Military personnel has a high incidence of tinnitus due to loud explosions and gunfire. It is also seen in the movie and stage workers who prepare scenes with explosions and gunfire. Musicians who are exposed to loud noise get tinnitus, for example, drummers and those who perform in front of loudspeakers. Children may have tinnitus, but it is mostly unrecognized because they do not recognize the disorder. The usual history is a worker who was exposed to very loud factory noise where workers had to shout to be heard. Many workers develop high-tone hearing loss, but only a small percentage also have tinnitus. Hyperacusis also can accompany tinnitus. In these cases, certain ordinary sounds like closing doors, moving chairs, and books dropping so loud and strong that they are extremely uncomfortable or sometimes unbearable.

Pathophysiology

When there is a danger or threat, humans normally react with a typical fight or flight response. This is the reason why the onset of tinnitus can be so distressing. A broken finger does not necessarily trigger this response, but tinnitus does. Cognitive therapy is done to stop the unwanted reaction.

However, stress is not a cause of tinnitus. Because humans cannot objectify tinnitus, the pathophysiology is not understood. Lesions that put pressure on the eighth cranial nerve may cause tinnitus. An increase in fluid pressure in the inner ear causes tinnitus. Symptoms associated with increased inner ear pressure include hearing loss, vertigo, tinnitus, and feeling of pressure in the ear. MRI shows that many areas of the brain are involved in tinnitus including the cognitive and emotional areas, as well as the auditory. Sound first enters the brain via the amygdala center. Therefore, learning that tinnitus is not a danger is therapeutic.

Toxicokinetics

Many modern antineoplastic drugs are ototoxic including bleomycin, cis-platinum, methotrexate, and bumetanide. These cause hearing loss and tinnitus that may not be reversible.

• Ethacrynic acid, acetazolamide, are diuretics listed as ototoxic
• Aspirin in higher doses causes tinnitus. Fortunately, this is reversible. Tinnitus has been reported with other NSAID medications.

Caution must be exercised in evaluating tinnitus from a new drug because of the very high incidence of tinnitus in the population. In a double-blind study, tinnitus may be reported as occurring in the placebo group. When anti-neoplastic drugs are used, regular hearing tests are done to watch for the onset of hearing loss or tinnitus so that the drug can be stopped if possible.

History and Physical

The symptoms of tinnitus include ringing, buzzing, roaring, hissing, or whistling in the ears. The noise may be intermittent or continuous. Most of the time, only the person who has tinnitus can hear it.

A physical exam should focus on the ear and the nervous system. The ear canal should be inspected for discharge, foreign body, and cerumen. The tympanic membrane should be inspected for signs of infection and tumor (red or bluish mass). A bedside hearing test should be done. Cranial nerves, particularly vestibular function, are tested along with peripheral strength, sensation, and reflexes. A stethoscope should be used to listen for vascular noise over the course of the carotid arteries and jugular veins and over and adjacent to the ear.

Evaluation

X-rays and MRI are not usually done for tinnitus unless there is an unexplained difference in hearing and balance in the ears.

An audiogram is a hearing test measuring hearing levels to determine hearing loss. The patient is asked to match which of the tones matches their tinnitus. The audiologist introduces that sound as to volume, and the patient estimates how loud they hear their tinnitus. Hearing via the bone of the ear is tested and compared with the hearing via the earphone called an air-bone test. If the patient hears better with the bone test, this suggests a condition called otosclerosis which is treatable. Patients with otosclerosis, in whom the stapes fail to move well, can have surgery that corrects the otosclerosis and restores air conduction. In some patients, tinnitus is relieved. In others, tinnitus remains or becomes worse.

The audiologist measures how long tinnitus is relieved by masking tone. The longer the tinnitus is inhibited, the better the prognosis.[8][9][10]

Treatment / Management

The American Academy of Otolaryngology has issued clinical practice guidelines for tinnitus. These include:

• Stress Reduction: This includes using biofeedback, measured breathing, etc. Although stress itself is not a cause of tinnitus, as in any condition, stress and anxiety can make the condition worse.   
• Cognitive Therapy: The more the patient understands what tinnitus is and is not the less negative effect. Once the patient fully cognizes - understands that tinnitus is similar to itching, the symptoms are reduced. 
• Masking: When the body hears the same sound from the cell phone or sound device, this reduces the symptoms.  There are various forms of masking. Essentially these masking sounds take the attention away from the internal tinnitus sound and replace it with relaxing sounds.

1. Introduction of the same sound
2. Introduction of an altered sound
3. Music with the tinnitus sound removed
4. White noise or pleasant sounds

• Sleep improvement: Tinnitus can affect normal sleep and therapy should be directed to better sleep hygiene.

The official guidelines stress that no medication cures tinnitus. However various combinations of magnesium, alpha-lipoic acid, N-acetyl cysteine, and others have been tested for protection of hearing from noise. When these are effective, it is difficult to differentiate from the placebo effect or from the impact of having a program where the patient feels they are in charge of bringing the brain into the healing process.

Recently beneficial results have been reported using deep brain stimulation. In theory, this alters unwanted neural circuits.

Primary to management is that tinnitus patients must never be told to live with it. Emphasis should be on reducing stress and given a program to follow. Tinnitus Retraining Therapy and Neuronomics are common programs used in therapy by individuals trained in their application. In Tinnitus Retraining the patient adapts to hearing the tinnitus; in Neuronomics the patient learns to ignore the tinnitus. 

A hearing aid is always of benefit when tinnitus is associated with hearing loss. Some aids come with built-in soothing or masking sounds. Success is variable.

Medication such as alprazolam can reduce symptoms, but can have adverse effects including habituation.

Anti-depressants may be indicated for patients who do not respond to protocol therapy.[11][12]

Differential Diagnosis

• Cytomegalovirus

• Hypercholesterolemia

• Lyme disease

• Measles

• Meningitis

• Neoplasm

• Neurosyphilis

• Rubella

• Sickle cell anemia

• Small vessel disease

• Stroke

• Tumour