Tinnitus, temporomandibular dysfunction and the conundrum of the loops

The concept of tinnitus, from a generic point of view, with its multiple causes, is not the subject of this article. Those cases that have already gone to the otorhinolaryngologist or neurologist and whose conclusion was that the triggering factors did not originate in their areas of competence probably come to our consultation. “Go to your dentist, this could be a temporomandibular joint (TMJ) problem.” And this is where we have to participate, in what some authors call a somatosensory subtype of tinnitus, normally without hearing loss but associated with temporomandibular joint dysfunction (TMD).

It is important that this exclusion criterion that we take for granted (non-neurological or otorhinolaryngological origin) is truly true since, on occasion, an accumulation of circumstances can make us fall into this trap. The title of the article published by McFerran DJ et al. in 2019 “Why is there no cure for tinnitus?” [5] already puts us on notice; Having medical reports that prove these exclusion diagnoses is the best way to get to work.

Tinnitus is the perception of a sound in the absence of an external sound source. It is therefore a symptom, not a disease. At the phenotypic level, it can be perceived unilaterally, bilaterally or centrally in the head, as a tone or a noise and may be accompanied by insomnia, anxiety or depression [2].

The association between tinnitus and TMD has been confirmed in two recent reviews by Bousema et al. [9] and Mottaghi et al. [10]. Some authors, such as Veronika Vielmeier, propose TMD as a criterion to classify a subtype of tinnitus that is regulated by somatic or auditory stimuli [2].

To understand a little the etiological factors and the pathogenesis, here are some relevant data:

1. Around 40% of patients do not know how to identify a cause that triggers tinnitus and around 75% are related to emotional stress, rather than cochlear injuries [6].
2. Tension and contraction of the masticatory muscles can trigger a reflex contraction in the tensor veli palatini and tensor tympani muscles due to common motor innervation of the trigeminal mandibular branch. Dysfunction of the tensor veli palatini muscle can modify the medial position of the malleus and tympanic membrane [7].
3. The development of a series of movements implies a joint participation of intra and extra tympanic muscles. Talk, swallow, chew, yawn, laugh, sneeze, breathe in. These muscles share trigeminal motor innervation [7].
4. There is a sensory trigeminal and auditory confluence in the dorsal cochlear nucleus. Alterations in the processing of the stimuli received in this nucleus by both TMJ and auditory sensory sources can modulate the levels of tinnitus perception in this subgroup of patients, leading to feedback [2].

The myofascial pain approach described by Travell and Simons [8] is an essential guide to understanding tinnitus associated with TMD. Let’s review the basics:

1. Unilateral tinnitus may be related to the presence of primary trigger points in the deep masseter, lateral pterygoid, and medial pterygoid or to satellite trigger points in these primary trigger point muscles in the sternocleidomastoid, upper trapezius, and scalenus.
2. In his opinion, it may be a referred sensory symptom or a motor alteration of the tensor tympani and/or stapedius of the middle ear.
3. Bilateral tinnitus is usually due to a systemic cause, although sometimes the masseter can be bilaterally affected, fluctuating between both sides and without hearing impairment.
4. The masseter is one of the first muscles to be affected by stress, remaining in contraction for very long periods. All those factors that activate trigger points on the masseters must be taken into account:
   • Repeated and sustained abusive oral habits: nail or gum biting, pen biting, thumb sucking in late childhood.
   • Tooth clenching or grinding.
   • Occlusal imbalance in the bite due to: loss of vertical dimension due to occlusal wear or loss of posterior teeth.
   • Natural forward head position, tongue swallowing and oral breathing due to nasal obstruction or surgical mask.
   • TMJ overload.
   • Cervical whiplash with suprahyoid and infrahyoid involvement.

I want to highlight two studies that reflect the influence of gastroesophageal reflux on tinnitus and TMD. On the one hand, in 2018 Ban MJ and her collaborators [4] published a paper that relates chronic laryngitis (mainly due to reflux) and tinnitus. And on the other, as I mentioned in a previous article, the conclusions of Li Yuanyuan and his research team [1]:

1. The presence of acid in the esophagus produces an increase in nocturnal rhythmic masticatory muscle activity or diurnal masseter activity.
2. Reflux is related to chronic TMJ pain, somatization, anxiety and sleep disturbances moderately influence this association.
3. Professionals and patients may overlook the association between chronic musculoskeletal pathologies and digestive pathology, especially Irritable Bowel Syndrome with high comorbidity with reflux, thus prolonging its chronification.

But back to the clinic, where to start?

There is no exact pattern that defines the patients with tinnitus who come to my clinic but, in general, it coincides with the existing literature: association of tinnitus with TMJ dysfunction and, depending on the time of evolution, they manifest their degree of desperation and/or adaptation to the lack of previous effective solutions that leads to pessimism and skepticism that will clearly mark how we approach this relationship.

Thus, the answer cannot be unique since, as we can see, there are multiple approaches, we must take into account individualizing the treatment options, sometimes in well-differentiated stages that allow us to identify, among the multiple biases, the causal relationships sustained over time. The reciprocity in the development of these pathologies and their comorbidity is frequently stated by the cited authors.

Successfully addressing the treatment of tinnitus associated with TMD will therefore depend on teamwork between different medical specialties. I like to deal with it from an approach that, graphically, I would represent through loops of causality that interrelate and feed each other: stress, depression, anxiety, TMJ dysfunction, bruxism, trigger points, occlusal instability, oral and parafunctional habits. , metabolic, digestive factors, sleep disorder… . The resolution will be achieved by applying therapies that allow progressively reducing the participation of each of these loops in their reciprocity, canceling one is never easy or enough; this will motivate the patient’s confidence and reduce her stress load, which in turn feeds back into the resolution of the problem as a whole.