Chronic tinnitus: a remarkable discovery in the neuroscientific field
Tinnitus is the sensation of hearing a ringing or buzzing sound in your ears or head. Tinnitus may be due to an underlying health condition or be a side effect of some medicines. It can also be caused by age-related hearing loss, acoustic trauma, circulatory problems, or a tumour affecting the auditory nerve. It is estimated that between 10 and 30% of the world's population suffers from this symptom. Even though tinnitus is not life threatening, it can be very impairing and result in depression.
While recent-onset tinnitus can be cured by medical treatment (which means making an appointment with an ENT specialist as soon as possible), chronic tinnitus is very difficult to treat.
However, a recent study carried out by neuroscientists based in Illinois (1) has found that chronic tinnitus is associated with changes in certain networks in the brain and gives new hope for future treatment options in this field.
Tinnitus is difficult to examine objectively. As a matter of fact, only people with tinnitus can perceive it. This condition cannot be measured by a device, as is the case with blood glucose or blood pressure. What is more, it can highly vary according to individuals, which makes studying this disorder very difficult.
By using functional MRI these researchers were able to objectify consistency in chronic tinnitus.
According to their study, published in "NeuroImage: Clinical" (1), chronic tinnitus occurs in a very specific region of the brain called precuneus.
The precuneus is connected to two inversely related networks in the brain; the "dorsal attention" network, which is active when something attracts our attention, and the "default mode" network, which is the background function of the brain, when the person is at rest and not thinking of anything in particular. When the default mode network is on, the dorsal attention network is off, and vice versa.
What emerges from the study is that in tinnitus patients the precuneus is more connected to the dorsal attention network and less to the default mode one. Basically, the brain is always on alert, a sort of "attention mode", and focused on perceiving tinnitus. Thus, chronic tinnitus causes the brain to stay permanently on alert and less at rest. This condition may accompany the patient throughout the day and also at night, "and this could explain why many report being tired more often," the experts explained.
In addition, as tinnitus increases in severity, the effects observed on neural networks increase accordingly. However, these symptoms have not been observed in patients with recent-onset tinnitus, and this is why a systematic medical treatment is recommended in such cases.
It is well known that a person suffering from chronic tinnitus does not feel truly at rest and this has a negative impact on their quality of life. The work of these researchers has made it possible to give objective evidence of tinnitus: this is crucial for recognising this disorder, which has been too often and wrongly labelled as "psychic". This study also presents new paths for seeking treatments.
Schmidt SA, carpenter-Thompson J, Husain FT. Connectivity of precuneus to the default mode and dorsal attention networks: a possible invariant marker of long-term tinnitus. Neuroimage: clinical 16 (2017);196-204