Whenever I tell someone I am conducting research on tinnitus, or ringing in the ears, the usual surprisingly enthusiastic response I get is: “Oh, interesting, my mom/dad/friend/… suffers from tinnitus!” Tinnitus, indeed, is a very common symptom, with a prevalence of 10 to 15% in the adult population. It is defined as the perception of a sound in the absence of a corresponding external sound (1).
However, what most people don’t know is that about two-third of tinnitus patients can modulate the loudness or pitch of their tinnitus by moving their jaw or neck, or by applying pressure to their jaw joint (temporomandibular joint) or masticatory muscles (2-5). This is one of the possible characteristics of somatic, or somatosensory, tinnitus (6).
Typically, tinnitus is related to hearing loss or a noise trauma (1). In most patients, however, tinnitus is triggered by several causes with many potential influencing factors (7), one of them being the somatosensory system (6). The somatosensory system is a component of the nervous system that detects and allows for perception of pain, temperature, head and body position and movement, and touch (8). When tinnitus is influenced by the cervical or temporomandibular somatosensory system, we refer to it as somatic or somatosensory tinnitus (9).
Diagnosis of somatic tinnitus
Patients with somatic tinnitus can present with a large set of different symptoms. There used to be no agreed standards for clinical assessment, which made it unclear how to diagnose somatic tinnitus. To resolve this, a group of somatic tinnitus experts created diagnostic criteria in 2018. This is a list of items that, if present, strongly suggests an influence of the somatosensory system on the patient’s tinnitus. Three sets of items were included in this list. The first one being the ability to modulate his or her tinnitus by voluntary movements, somatic manoeuvres, or pressure on myofascial trigger points. The ability to modulate their tinnitus strongly suggests somatic tinnitus, but is no absolute requirement. The second set of items includes characteristics that often exist in patients with somatic tinnitus, for instance: the simultaneous onset and aggravation of tinnitus and pain symptoms in the neck or jaw area, possibly preceded by a head or neck trauma. In addition, the increase in tinnitus during certain postures and the presence of variations in pitch, loudness, and location of tinnitus are also included in this set. The third and final set of items includes symptoms that accompany the patient’s tinnitus, including: frequent pain in the head, neck or shoulder girdle, temporomandibular disorders, pressure-tender myofascial trigger points in the head-neck region, increase in muscle tension in the neck extensor muscles, bruxism or teeth clenching, and dental diseases. It is generally accepted that the more criteria present, the stronger the somatic influence on tinnitus (6).
Treating tinnitus by treating the jaw
Our research group recently investigated whether we can treat somatic tinnitus by physical treatment of temporomandibular disorders or the neck. After nine weeks of treatment of temporomandibular disorders followed by a follow-up period of nine weeks, tinnitus decreased clinically significant in 61% of the patients (10). Michiels et al. (11) concluded that 53% of patients experienced a substantial improvement of tinnitus after six weeks of cervical physical treatment. This effect was maintained in 24% of patients after follow-up at six weeks. Moreover, research showed that patients who have a higher score on the somatic subscale in a tinnitus questionnaire (TQ) have a higher chance for better outcome with orofacial treatment. A greater somatic component in tinnitus might thus be a predictive factor for better treatment outcome (12).
Tinnitus and the neck, more closely related than you might think
How is it possible that some people are able to alter their tinnitus loudness or pitch by moving their neck? And how can we explain tinnitus improvement following physical therapy? Up to today, the mechanisms behind (somatic) tinnitus are not fully discovered yet. Several animal studies have found connections between the somatosensory system of the cervical or temporomandibular area and the auditory system, more specifically at the dorsal cochlear nucleus situated in our brainstem (13-15). Scientists believe these connections are also present in humans, but direct evidence for this is still very limited, being demonstrated by one study only (16). Therefore, the door is still open to further study these connections in order to fully understand somatic tinnitus.
Written by Laura Jacxsens
MD and PhD student at the University of Antwerp.
For more information about this research project, feel free to contact me at firstname.lastname@example.org
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