Tinnitus and Hyperacusis

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What is tinnitus?

Tinnitus is an involuntary perception of sound that originates in the head and is not attributable to a perceivable external source. The word tinnitus is derived from the Latin tinnire , which means “to ring”. Tinnitus is often described as a “ringing” sound in the ear but also includes descriptions such as buzzing, humming, roaring, hissing, and chirping. Tinnitus is a symptom and not a disease in itself.

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What is the prevalence of tinnitus?

It is generally accepted that approximately 10% to 15% of the population suffers from some degree of tinnitus, and 1% to 2% report that tinnitus has a severely negative impact on quality of life.

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How can tinnitus be classified?

Tinnitus has historically been classified as either objective (audible to an observer other than the patient) or subjective (perceptible by the patient alone). More useful classification includes description of tinnitus as either pulsatile or nonpulsatile, or categorization by location of injury or generation (external ear, middle ear, sensorineural, or central).

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What are somatosounds?

A more specific term for many forms of objective tinnitus, somatosounds are objective sounds that are created by the body and potentially audible to the examiner. Examples of somatosounds include perception of myoclonic contractions of the tensor tympani or pulsatile variations in blood flow in vessels near the ear.

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What are the proposed mechanisms to explain subjective tinnitus?

Both central and peripheral mechanisms have been proposed to explain the origin of tinnitus, but the exact cause remains unclear. Most tinnitus is associated with a cochlear abnormality, although not all patients with tinnitus have associated measurable changes in hearing. It has been proposed that sensory deprivation at the periphery leads to alterations in neural function at higher levels and persistence of these neural changes may contribute to the subjective perceptions of tinnitus. Tonotopic maps in the auditory cortex have been shown to reorganize in animal studies after sensory deprivation in a manner similar to somatosensory cortical organization changes after amputation, leading to the description of tinnitus as a “phantom limb” perception of the auditory cortex.

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How is tinnitus evaluated?

No objective test is available to definitively verify tinnitus or identify its cause in most cases. An evaluation of tinnitus consists of a thorough case history, complete otologic exam, and an audiometric evaluation. Evaluation may also consist of administration of one of several validated questionnaires, such as the Tinnitus Handicap Inventory, the Tinnitus Handicap Questionnaire, or the Tinnitus Severity Index. Though these surveys provide little objective data, they can help to quantify the severity of impact on quality of life and may be used to track changes in tinnitus perception across various therapy modalities. Additional studies, such as imaging or vestibular evaluation, may be indicated depending on the initial presentation and differential diagnosis.

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What is tinnitus matching and what is its value in the assessment and treatment of subjective tinnitus?

Tinnitus matching is an audiometric evaluation that generally consists of pitch matching, loudness matching, and minimal suppression level (the amount of masking required to subjectively mask an individual’s tinnitus). These objective measures of tinnitus have little validity or clinical application, as tinnitus loudness, pitch, and maskability typically bear no relationship to the severity of the patient’s experience or ability to benefit from treatment. Some treatment modalities, including individualized sound stimulation devices, may rely on pitch matching or minimum suppression levels to create customized listening programs targeted at masking an individual’s tinnitus.

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What signs or symptoms are suggestive of a vascular cause of tinnitus?

A pulsatile or throbbing quality that parallels the heartbeat should raise the index of suspicion. A reddish or blue mass behind the tympanic membrane may indicate a glomus tumor arising within the middle ear or a dehiscence of the jugular bulb or carotid artery. Arteriovenous malformations are uncommon but may occur between the occipital artery (passing medial to the mastoid process) and the transverse sinus. A venous hum may represent one of the more common causes of vascular tinnitus. It may signify impingement of the jugular vein by the second cervical vertebrae or suggest an underlying high-output cardiac condition, such as anemia, exercise, pregnancy, or thyrotoxicosis.

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What is the imaging study of choice for nonpulsatile tinnitus?

MRI with gadolinium is the study of choice to exclude a vestibular schwannoma or other neoplasm of the cerebellopontine angle. Steady-state gradient echo sequences (such as CISS or FIESTA) are also helpful in the workup for vestibular schwannoma. This type of sequence emphasizes T2 signals, making it useful for the evaluation of small structures that are surrounded by cerebrospinal fluid such as cranial nerves.

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