Imaging Technique Detects Location of Tinnitus Foci in the Brain

Researchers at Henry Ford Hospital (Detroit, MI, USA) developed the new technique, called magnetoencephalography (MEG) to determine the site of perception of tinnitus in the brain, which could in turn allow physicians to target the area with electrical or chemical therapies to lessen symptoms. To test the new technique, the researchers collected MEG results from 17 patients with tinnitus, and from 10 control patients without tinnitus. The MEG data were collected for 10 minutes, and then digitally filtered. Study participants wore earplugs to eliminate outside sounds, and kept their eyes open and fixated on one point on the ceiling in the room during testing.

The results showed that with tinnitus patients who had ringing in one ear (unilateral tinnitus) MEG detected the greatest amount of activity in the auditory cortex on the opposite site of the brain from their perceived tinnitus. For patients with ringing in the head or both ears (bilateral tinnitus), MEG revealed activity in both hemispheres of the brain, with greater activity appearing in the opposite side of the brain of the strongest perception of tinnitus. Patients without tinnitus had multiple small active areas in the brain, but no particular areas were found to be highly coherent during the 10-minute MEG scan. The results of the study were presented at the 2009 American Academy of Otolaryngology – Head and Neck Surgery Foundation (AAO-HNSF) annual meeting, held during October 2009 in San Diego (CA, USA).

"Since MEG can detect brain activity occurring at each instant in time, we are able to detect brain activity involved in the network or flow of information across the brain over a 10-minute time interval,” said coauthor Susan Bowyer, Ph.D., a senior researcher in the department of neurology. "Using MEG, we can actually see the areas in the brain that are generating the patient's tinnitus, which allows us to target it and treat it.”

Tinnitus, meaning, "ringing" in Latin, is the perception of sound within the human ear in the absence of corresponding external sound. Tinnitus is not a disease but a symptom resulting from a range of underlying causes that can include ear infections, foreign objects or wax in the ear, nose allergies that prevent (or induce) fluid drain and cause wax build-up, and injury from loud noises. Tinnitus can also be caused by hearing impairment and as a side effect of some medications. Imaging techniques currently used to study tinnitus in the brain, such as positron emission tomography (PET) and functional Magnetic Resonance Imaging (fMRI), provide a general location but are not successful at determining the specific site in the brain that is generating tinnitus symptoms.

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