What is the role of lab studies in the diagnosis of tinnitus?

Updated: Feb 27, 2020
  • Author: Aaron G Benson, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Each patient with the symptom of tinnitus deserves complete audiologic testing with pure-tone air, bone, and speech discrimination scores. Order or perform these tests even if (as is common) the patient is unaware of hearing loss. During the audiometric evaluation, the audiologist can complete the subjective tinnitus matching evaluation to gain better understanding of the patient's symptom. Such thoroughness is often reassuring to the patient because the physician is taking the condition seriously.

Both pitch and loudness matching should be assessed. However, the examiner should remember that 90% of patients with tinnitus match their tinnitus at 20 dB or less and 84% match their tinnitus at 9 dB or less; thus, the reported severity of the condition may seem to be out of proportion to the measurement. Minimum masking levels should also be obtained if treatment with ear level devices is being considered.

Other examinations may also be necessary. Blood tests for syphilis (a fluorescent treponemal antibody-absorption [FTA-ABS]), a complete blood cell count, an autoimmune panel (ANA, sedimentation rate, rheumatoid factor), and thyroid function tests for hypermetabolism may be useful, but clinical signs may indicate this problem earlier. For pulsatile tinnitus, a magnetic resonance (MR) imaging with or without MR angiographic scanning may be needed to look for a glomus tumor, arteriovenous malformations, vascular anomalies, dural arteriovenous fistulas, and aneurysms of the carotid in the ear.

A computed tomography of the temporal bone will delineate a sigmoid sinus diverticulum or bony dehiscence over the jugular bulb. A hyperdynamic state, such as anemia, hyperthyroidism, or pregnancy, may cause a pulsatile tinnitus. For asymmetric hearing loss or unilateral tinnitus, MRI of the internal auditory canals is indicated to look for an acoustic tumor.

Positron emission tomography (PET) scanning is currently being studied as a diagnositic aid in tinnitus management. PET scanning helps identify areas of enhanced neural activity. Therefore, it has been suggested that this can be used pretreatment and posttreatment to identify changes in neural activity. [12]

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