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 etiologies and imaging strategies.
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%.
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.
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.