Tonic tensor tympani syndrome in tinnitus and hyperacusis patients: a multi-clinic prevalence study
Myriam Westcott et alter
Tonic tensor tympani syndrome (TTTS) is an involuntary, anxiety-based condition where the reflex threshold for tensor tympani muscle activity is reduced, causing a frequent spasm. This can trigger aural symptoms from tympanic membrane tension, middle ear ventilation alterations and trigeminal nerve irritability. TTTS is considered to cause the distinctive symptoms of acoustic shock (AS), which can develop after exposure to an unexpected loud sound perceived as highly threatening. Hyperacusis is a dominant AS symptom. Aural pain/blockage without underlying pathology has been noted in tinnitus and hyperacusis patients, without wide acknowledgment.
This multiclinic study investigated the prevalence of TTTS symptoms and AS in tinnitus and hyperacusis patients. This study included consecutive patients with tinnitus and/or hyperacusis seen in multiple clinics. Data collected: Symptoms consistent with TTTS (pain/numbness/burning in and around the ear; aural "blockage"; mild vertigo/nausea; "muffled" hearing; tympanic flutter; headache); onset or exacerbation from exposure to loud/intolerable sounds; tinnitus/hyperacusis severity. All patients were medically cleared of underlying pathology, which could cause these symptoms. 60.0% of the total sample (345 patients), 40.6% of tinnitus only patients, 81.1% of hyperacusis patients had ≥1 symptoms (P < 0.001). 68% of severe tinnitus patients, 91.3% of severe hyperacusis patients had ≥1 symptoms (P < 0.001). 19.7% (68/345) of patients in the total sample had AS. 83.8% of AS patients had hyperacusis, 41.2% of non-AS patients had hyperacusis (P < 0.001). The high prevalence of TTTS symptoms suggests they readily develop in tinnitus patients, more particularly with hyperacusis. Along with AS, they should be routinely investigated in history-taking.
The tensor tympani reflex is a startle reflex, which is exaggerated by high stress levels. The tensor tympani muscle contracts immediately preceding the sounds produced during self-vocalisation, suggesting it has an established protective function to loud sounds, assists in the discrimination of low frequency sounds, and is involved in velopharyngeal movements.
Tonic tensor tympani syndrome (TTTS) was originally described by Dr. I. Klockhoff. TTTS is an involuntary condition where the centrally mediated reflex threshold for tensor tympani muscle activity becomes reduced, so it is continually and rhythmically contracting and relaxing. This appears to initiate physiological reactions in and around the ear without objectively measurable dysfunction or pathology. Symptoms consistent with TTTS can include: tinnitus; rhythmic aural sensations such as clicks and tympanic membrane flutter; alterations in ventilation of the middle ear cavity leading to a sense of aural blockage or fullness, a frequent aural "popping" sensation and mild vertigo; minor alterations in middle ear impedance leading to fluctuating symptoms of "muffled" and/or "distorted" hearing; irritation of the trigeminal nerve innervating the tensor tympani muscle, leading to pain, numbness and burning sensations in and around the ear, along the cheek, neck and temporomandibular joint (TMJ) area.
The specific and consistent cluster of physiological symptoms of acoustic shock (AS) is consistent with TTTS, without underlying aural or TMJ pathology. AS can occur involuntarily after exposure to a sudden unexpected loud sound perceived as highly threatening (acoustic incident). AS becomes an acoustic shock disorder (ASD) if symptoms persist. AS was originally identified in call center staff, who are vulnerable to AS because of the increased likelihood of exposure near the ear(s) to an acoustic incident transmitted via a telephone headset. The research on AS has focused on this cohort, however acoustic incidents can occur anywhere.
Symptoms such as aural pain and a sensation of aural blockage/fullness, with no underlying aural or TMJ pathology, have been observed in tinnitus and hyperacusis patients. These symptoms have been linked to TTTS by Jastreboff and Hazell and Westcott. However, these symptoms have not been widely acknowledged or investigated in this patient population. TTTS has been more intensively investigated in temporomandibular disorder (TMD) research, with TTTS considered to be a secondary consequence of TMD and/or TMJ dysfunction, predominantly responsible for referred tinnitus, ear pain and other symptoms in and around the ear.
This multiclinic study aimed to investigate in a sample of tinnitus and hyperacusis patients the prevalence of:
- Symptoms consistent with TTTS
- Symptoms consistent with TTTS developing or being exacerbated by intolerable sound exposure
- AS aetiology triggering the onset of their tinnitus and/or hyperacusis.
The high prevalence of symptoms consistent with TTTS in this sample suggests they can readily develop as a primary phenomenon in patients with tinnitus, and more particularly in those with hyperacusis. These results support a central relationship between tinnitus, hyperacusis and TTTS, with further research indicated to explore this relationship and the efferent pathway triggering TTTS.
TTTS offers an explanation for the aural pain reported by many hyperacusis patients, often triggered or aggravated by intolerable sound exposure. Symptoms consistent with TTTS are subjective and can cause high levels of anxiety. This can lead to tinnitus escalation, the development and escalation of hyperacusis, and limit the efficacy of tinnitus/hyperacusis therapy. These symptoms should be routinely evaluated in history taking, de-mystified to patients to provide reassurance, and treated accordingly.
These results indicate that AS is a world-wide phenomenon, with significant clinical, medico-legal and military diagnostic/rehabilitation implications. It is recommended that evaluation of an acoustic incident at the time of tinnitus/hyperacusis onset is routinely carried out in history taking with tinnitus and hyperacusis patients.