Tinnitus has long been an issue for many individuals. In the US and around the world audiologists are treating tinnitus with a myriad of techniques and with variable successes and failures. In the past, tinnitus was thought 
to be primarily involved in the cochlea and/or the auditory regions of the brain prompting otolaryngologists (ENT Physicians) to tell their tinnitus suffers to “just live with it” or “get used to it”. Recent success in treatment of this malady indicates that there are new discoveries about the origins of tinnitus. These days, new research suggests that tinnitus has its origins in the brain and that the cochlea and that the auditory areas of the brain are probably only secondarily responsible for these symptoms. As new discoveries are made, we’re gaining a better understanding of tinnitus and its brain origins. Since it is a brain function, could it be that tinnitus and epilepsy related? This is the topic of this week’s Hearing International.
Tinnitus is the perception of sound when no actual external noise is present. According 
to ATA (2016), it is commonly referred to as “ringing in the ears” and can present with many different perceptions of sound, including buzzing, hissing, whistling, swooshing, and clicking. In some rare cases, tinnitus patients even report hearing music. Tinnitus, which may be pronounced as either tinnitus or Tin-NI-Tis, can be both an acute (temporary) condition or a chronic (ongoing) health malady. Tinnitus, a noise in the head or in the ear is now thought to affect an extensive network of the brain and not just the auditory region of the brain. Millions of Americans experience tinnitus, often to a debilitating degree, making it one of the most common health conditions worldwide. The Hearing Health Foundation estimates that 48 million people in the US and ~360 million worldwide suffer from tinnitus. They further estimate that the disorder affects:
- 1 in 5 teens
- 1 in 5 adults
- 3 in 5 US veterans returning from war
- Hearing loss and tinnitus are the top two reported health concerns among service members both active duty and veterans.
These numbers concur with the U.S. Centers for Disease Control that estimates nearly 15% of the general public, over 50 million Americans,
experience some form of tinnitus. In the past 15 years or so the number of individuals with tinnitus in the US has doubled. Of the number with tinnitus in the US, about 20 million people struggle with burdensome chronic tinnitus and 2 million have extreme and debilitating cases. On the world stage the number of tinnitus cases has increased by 44% across the globe as well.
The Relationship
Researchers have determined that epilepsy and tinnitus are both caused by overly excitable nerve cells. They indicate that healthy nerves have a built-in system that sort of “slams on the brakes” when they get too excited. In their opinion, this braking system does not work in some individuals causing the nerves to malfunction by signaling so much that the brain gets overloaded, causing an epileptic seizure or the hearing of 
phantom noises (tinnitus).
Researchers Phillip Gander of the University of Iowa (USA) and William Sedley of the University of Newcastle (UK) had the rare opportunity to record activity directly from the brain of a person with tinnitus to find the brain networks responsible for the condition where there is sound perception when there is no external source. Dr. Sedley felt that this was a big step forward in the understanding of tinnitus as it was the first time that clear association of a subjective tinnitus experience was demonstrated with direct and precise measurements of brain activity. Gander and Sedley felt that, “perhaps the most remarkable finding of their study was that the brain activity was directly linked to tinnitus was found to be very extensive spanning a large portion of the part of the brain measured while the brain responses to a sound played mimicking the tinnitus were localized to a tiny area.”
An image from their study shows a 3D presentation of the left hemisphere of a patient with tinnitus and part of that hemisphere containing primary 
auditory cortex. The black dots indicate the sites from which recording were taken and the colored circles indicate electrodes at which the strength of ongoing brain activity correlated with t he current strength of the perceived by the patient. The different colored areas indicate the various frequencies of brain activity (blue was low, magenta, middle, and orange was high) whose strength changed with the subjective perception of the tinnitus. The green areas indicated 
sites that changed along with the perception of the tinnitus.
Dr. Anastasios Tzingounis, an epliepsy researcher at the University of Connecticut and Dr. Thanos Tzounopoulos, a tinnitus researcher from the University of Pittsburgh have also taken advantage of the opportunity to record directly from the brain of a person with tinnitus to find the brain networks responsible for these “phantom noises”. Their research is more in the area of drugs that could be beneficial for both epilepsy and tinnitus.
Current drugs used to treat epilepsy don’t always work and can have serious side effects. One of the more effective, called retigabine, helps open KCNQ potassium channels, which shut down the signaling of overly excited nerves. Unfortunately, retigabine has significant adverse side effects, including sleepiness, dizziness, problems with urination and hearing, and an unnerving tendency to turn people’s skin and eyes blue. Because of this, it’s usually only given to adults who don’t get relief from other epilepsy drugs. There are five different kinds of KCNQ potassium channels in the body, but only two are important in epilepsy and tinnitus: KCNQ2 and KCNQ3. The problem with retigabine is that it acts on other KCNQ potassium channels as well, and that’s why it has so many unwanted side effects. Tzingounis’ research has found that a new drug – SF0034, which is chemically identical to retigabine, except with an extra fluorine atom – seems to open only KCNQ2 and KCNQ3 potassium channels, not affecting KCNQ4 or 5. It was more effective than retigabine at preventing seizures in animals, and it was also less toxic. The drug company now plans to start FDA trials to see whether the drug is safe and effective in people. Treating epilepsy is the primary goal, but tinnitus can be similarly debilitating, and sufferers would welcome a decent treatment.
Other studies are on going in the relationship of disorders that may have possible treatment for tinnitus but receive much less publicity than typical treatments for tinnitus, such a masking or hearing devices. As we learn more about tinnitus and its origins as well as its association to other disorders, there may be a future treatments, even drugs that really work for this debilitating disorder.
References:
American Tinnitus Association (2016). Understanding the facts. www.ata.org. retrieved October 25, 2016.
Hearing Health Foundation (2016). Hearing loss and tinnitus statistics. Retrieved October 25, 2016.
Kwan, N., (2015). Researchers identify brain network responsible for tinnitus. Foxnews.com. Retrieved October 26, 2016.
Sedley, W., Gander, P., Kumar, S., Oya, H.,Kovac, C., Nourski, K., Kawasaki, H., Howard, M., & Griffiths, T., (2015). Intercranial mapping of a cortical tinnitus system using residual inhibition. Current Biology, Vol 25., pp 1208-1214. Retrieved October 26, 2016.
Images:
Pacific eye and ear specialists (2016). Web site: Physician discussing issues with patient. Retrieved October 26, 2016.
Tinnitusandme.com (2012). Statistics on Tinnitus worldwide. Retrieved October 25, 2016.
