Tinnitus refers to a sensation of sound in one or both ears and is usually experienced as a high-pitched ringing, buzzing or whistling noise. This sound occurs without an external stimulus. Broadly tinnitus is divided into pulsatile and non-pulsatile forms which have distinct aetiologies and imaging strategies.
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Epidemiology
It is thought that as many as 40 million people in the United States may have tinnitus. The reported prevalence range is around 7-32%.
Clinical presentation
Individuals who experience tinnitus will hear sounds, typically high pitched buzzing or ringing or whistling that do not result from external sound sources. Tinnitus is broadly divided into:
- pulsatile tinnitus: coincides with the patient's heartbeat and usually arises from vascular lesions or structures
- non-pulsatile tinnitus
Additionally, tinnitus is described as being "subjective", meaning only the patient can hear it, or "objective" meaning that a clinician with a stethoscope can also hear an abnormal noise, and clearly implies a greater likelihood of discovering a structural (usually vascular) abnormality.
The remainder of this article focuses on non-pulsatile tinnitus. Pulsatile tinnitus is discussed separately.
Radiographic features
In the setting of non-pulsatile tinnitus with a normal tympanic membrane, magnetic resonance imaging is preferred if a retrocochlear lesion is suspected, while high-resolution CT of the temporal bones is recommended if a cochlear abnormality is thought likely.
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