Continuing Education Activity
Tensor tympani syndrome, also known as the tensor tympani myoclonus, is a rare form of objective pulsatile tinnitus, which includes tensor tympani-associated tinnitus caused by the contraction of the tensor tympani (TT) muscle. The TT muscle is a striated muscle innervated by the mandibular branch of the trigeminal nerve and attaches from the greater wing of the sphenoid, forms connections with the bony and cartilaginous eustachian tube, passes through the cochleariform process, and inserts onto the head of the malleus in the middle ear. During contraction, the TT functions to open the eustachian tube and pull the malleus medially, which subsequently stiffens the tympanic membrane and decreases the propagation of sound throughout the ossicular chain. The TT muscle, tensor veli palatini, and muscles of mastication are all innervated by the trigeminal nerve. It is hypothesized that due to their analogous innervation, the TT muscle functions to decrease the intensity of sound during chewing and swallowing. TT syndrome is a type of middle ear myoclonus (MEM). Both TT and stapedius muscles are involved in the acoustic reflex, which is the involuntary contraction of these muscles following high-intensity sounds and is thought to protect the inner ear cells from damage. This activity reviews the evaluation and management of tensor tympani syndrome and highlights the role of interprofessional team members in collaborating to provide well-coordinated care and enhance outcomes for affected patients.
- Identify the risk factors for the development of tensor tympani syndrome.
- Explain how to rule out other differential diagnoses of tensor tympani syndrome.
- Summarize management considerations for tensor tympani syndrome.
- Outline how the facilitation of interprofessional team education and discussion can optimize the effective detection of tensor tympani syndrome and inform management.
Tinnitus is the perception of sound that does not originate from a source external to the individual's body. When discussing tinnitus, it is first crucial to categorize it between either subjective or objective, as well as between pulsatile and non-pulsatile tinnitus. In subjective tinnitus, which is more common, only the patient can perceive the sound. On the other hand, in objective tinnitus, both the individual and potentially the examiner can hear the sound. For example, subjective tinnitus is classically caused by a sensorineural hearing loss in patients experiencing presbycusis. The examiner is not able to perceive the tinnitus; however, the patient can.
Next, it is important to distinguish between pulsatile and non-pulsatile tinnitus. Pulsatile tinnitus is commonly caused by vascular-associated abnormalities such as a high-riding jugular bulb, jugular diverticula, atherosclerosis, hypertension, benign intracranial hypertension, or glomus tumors which may or may not coincide with the patient's heartbeat. Non-pulsatile tinnitus can be caused by sensorineural hearing loss, otosclerosis, or acoustic neuromas. Tensor tympani syndrome, also known as the tensor tympani myoclonus) is a rare form of pulsatile, objective tinnitus, which includes various types of tensor tympani-associated tinnitus caused by contraction of the tensor tympani (TT) muscle. The TT muscle is a striated muscle innervated by the mandibular branch of the trigeminal nerve (CN V). The TT attaches from parts of the greater wing of the sphenoid with connections to the bony and cartilaginous Eustachian tube and inserts onto the malleus head in the middle ear after passing through the cochleariform process. During contraction, it functions to open the Eustachian tube, as well as pull the malleus medially, which subsequently stiffens the tympanic membrane and decreases the propagation of sound throughout the ossicular chain. The TT muscle, tensor veli palatini, and muscles of mastication are all innervated by the CN V. It is hypothesized that due to their analogous innervation, the TT muscle functions to decrease the intensity of sound during chewing and swallowing. TT syndrome (or TT myoclonus) is a type of middle ear myoclonus (MEM). Myoclonus is the rhythmic contraction of the muscle. The contraction of the stapedius muscle causes another form of MEM. The stapedius muscle normally functions to contract the stapes of the oval window to decrease the propagation of high-intensity sound. Both TT and stapedius muscles are involved in the acoustic reflex, which is the involuntary contraction of these muscles following high-intensity sounds and is suspected of protecting the inner ear cells from damage.
There are various etiologies of TT syndrome and MEMs as a broader category, ranging from idiopathic, vascular, demyelinating disorders, traumatic, tumor, or infectious. There have been documented instances of bilateral TT syndrome due to multiple sclerosis. However, the process by which tinnitus is produced is not yet completely understood. Tonic tensor tympani syndrome (TTTS) has been described to cause TT spasms leading to tinnitus and hyperacusis. TTTS is believed to be an involuntary condition due to an overlying anxiety disorder, which causes a reduction in the threshold required to trigger the TT muscle reflex.
Although there is limited information regarding the epidemiology of TT syndrome specifically, there does not appear to be a predilection of gender for MEM. Additionally, early data regarding MEM indicates that it can more commonly occur in the third decade of life.
The pathophysiology of TT syndrome is not completely understood; however, it can be caused by various etiologies with different pathophysiological processes. For example, a case of bilateral TT-induced tinnitus in a patient with multiple sclerosis was suspected to be due to the demyelination of innervating nerves, leading to muscle spasms. Alternatively, the myoclonic activity may be due to medullary activity centers no longer receiving inhibitory signals by upper motor neurons. The tinnitus itself is caused by the contraction of the TT, which has been described as a clicking sound. It is possible that the muscle contraction itself, the vibration of the tympanic membrane, the opening and closing of the Eustachian tube, a combination of these mechanisms, or a different unknown mechanism is responsible for the perceived tinnitus.
History and Physical
It is crucial to keep a wide differential with any patient who presents with a complaint of tinnitus. While conducting a thorough history and physical, it is important to note the onset, laterality, duration, associated symptoms, and whether symptoms coincide with certain activities. CNV innervates the TT and tensor veli palatini (TVP) muscles. Due to the attachment of the TT muscle onto the malleus, during a spasm, the malleus is pulled anteromedially with inward movement of the tympanic membrane. This can be contrasted to otoscopic findings for stapedius myoclonus, in which movement of the posterior quadrant of the tympanic membrane has been reported. However, these otoscopic findings are subjective, not specific, and still not widely accepted. During swallowing, the TVP is activated to assist in elevating the palate. Due to this dual innervation by CNV, the TT muscle can be activated and possibly cause tinnitus in some patients. Additionally, CNV innervates the sensory component of the corneal reflex. As such, the corneal reflex can also activate the TT muscle, which can cause TT syndrome in some patients. Although the physical exam is largely unremarkable, some features can lead clinicians to suspect TT syndrome. For example, while conducting an otoscopic exam, rhythmic movements of the tympanic membrane have been described at rest and even during blinking. Additionally, while considering TT syndrome as a diagnosis, palatal myoclonus must be ruled out by direct visualization of the palate and whether it coincides with reported tinnitus symptoms. Patulous Eustachian tube with a common primary complaint of autophony must also be ruled out by tubo-tympano-aerodynamography. The more definitive way of diagnosing any MEM is by tympanotomy and direct visualization of the muscle spasm. MEM is characterized as objective tinnitus, so auscultation of the ear can be helpful during a physical exam.
After a thorough history and physical, additional testing is available to rule out other etiologies. As TT syndrome is a rare finding, there is no definitive guideline to assess for this disorder, although an algorithm for diagnosis has been proposed. Audiometry is not typically used for diagnostic purposes but can potentially aid in masking treatment. Tympanometry will assess the pressure of the middle ear at a given moment, but if the TT is not contracting, it may not be observed by tympanometry. For this reason, long-term tympanometry can be used. A saw-tooth-like pattern representing tympanic membrane movement can be seen, which supports the diagnosis of TT syndrome. An impedance audiogram is also helpful while diagnosing TT syndrome by assessing the status of the middle ear. Imaging such as CT and/or MRI can also be helpful to rule out other potential causes of tinnitus.
Treatment / Management
Management of patients with MEM, as well as specifically TT syndrome, varies depending on the patient’s severity of symptoms and expectations. If the patient is interested in treatment, there are various approaches to decreasing symptoms. Again, although there are no definitive guidelines as well as no definitive data regarding efficacy, there are medical and surgical approaches to decreasing symptoms. Several medications have been reportedly used for MEM with questionable efficacy, including benzodiazepines, carbamazepine, piracetam, botulinum toxin, as well as orphenadrine citrate with varying mechanisms of action. Benzodiazepines can be used to potentially decrease symptoms by targeting the anxiolytic component of the disorder as well as functioning as a muscle relaxant. Orphenadrine citrate also acts as a muscle relaxant due to its anticholinergic and antihistamine properties. Piracetam is a GABA derivative normally used to treat cortical myoclonus; however, there is extremely limited data on its use in MEM. Carbamazepine, a sodium-channel blocker, attenuates neuronal firing leading to decreased activity of their innervating muscles, which is why it is primarily used in epilepsy, primary hemifacial spasm, and trigeminal neuralgia. Another possible intervention that targets the contraction of the TT muscle is via botulinum toxin. Although the use of botulinum toxin is new to MEM, its use in non-cosmetic otolaryngology-associated disease processes like hemifacial spasm as well as laryngeal pathology such as spasmodic dysphonia is well documented. The mechanism of action of botulinum toxin is by preventing the release of acetylcholine from pre-synaptic neurons. The efficacy of botulinum toxin for MEM is still being examined due to its limited use. There has been a case report describing the use of botulinum soaked absorbable gelatin compressed sponge being applied intratympanically via a chronic tympanic membrane perforation. This particular patient was diagnosed with stapedius myoclonus by direct visualization of stapedius spasm. The patient experienced symptomatic relief for approximately 3 months, however similar to other disease processes treated with botulinum toxin, its effects were time-limited. The status of the TT was unknown, so if there was a component of TT myoclonus as well, it could not be determined if the botulinum toxin affected both middle ear muscles.
The role of surgical intervention is also more clearly defined. The most common procedure for TT syndrome as well as stapedius myoclonus is tympanotomy with TT or stapedius tenotomy. It is believed that by releasing the muscle's attachment site, it can reduce or eliminate tinnitus. A limited number of case series evaluating the role of tenotomy in MEM has been described. Bhimrao et al. reference 13 patients who underwent stapedius tenotomy, nine patients who underwent both stapedius and TT tenotomy, and one patient who underwent TT tendon sectioning. The decision to undergo single TT tenotomy was due to direct visualization of isolated TT spasms. All the patients in this series reported resolution except for one who had associated palatal myoclonus. Additionally, Park et al. reported a case series of 44 patients who were initially treated with medical therapy. Seventy-five percent of patients reported a decrease in symptoms based on visual analog scales and tinnitus handicap index scores. Of the eleven patients who did not improve from medical therapy, nine of them elected for surgical intervention. Two patients in this group underwent bilateral tenotomy, and seven patients underwent unilateral tenotomy. However, the distribution of the middle ear muscles sectioned is not specified. Surgical intervention does show promise to treat MEM. However, more studies should be conducted to more clearly define its role. Bhimrao et al. advocate a 3-month trial of medical and/or supportive therapy before discussing tenotomy with possible TT or stapedius muscle sectioning.
When evaluating a patient with a complaint of tinnitus, the history and physical will help refine the differential diagnosis. All causes of objective tinnitus should be considered when developing a differential diagnosis. Stapedius myoclonus and palatal myoclonus are very high on the differential in a patient with TT syndrome as all three can present similarly. History, physical, as well as tympanometry can direct a clinician to one or more potential diagnoses, but the most definitive diagnosis is by direct visualization of TT spasm. Other conditions to be considered are a patulous Eustachian tube, arteriovenous fistula or malformations, glomus tumors, carotid artery stenosis, and other atherosclerotic diseases. However, these other disorders will most likely present with different history and physical exams as well as more definitively distinguished by audiometry and imaging.
Tinnitus is not harmful; however, depending on the etiology, the underlying process can be life-threatening, such as multiple sclerosis. Other than the underlying disease process, tinnitus can cause a range of emotional distress to patients, from severely debilitating to causing little to no distress to the patient. Additionally, there is not enough data at this time to predict whether symptoms will discontinue or reduce, regardless of whether there is an identifiable cause for the tinnitus or idiopathic in origin.
When an otolaryngologist is unsure about a diagnosis or is not comfortable with diagnostic workup or treatment, consultation with a neuro otolaryngologist is an option.
Pearls and Other Issues
- Tensor tympani syndrome (tensor tympani myoclonus) is a type of middle ear myoclonus such as stapedius myoclonus.
- Tensor tympani syndrome is categorized as objective pulsatile tinnitus like stapedius myoclonus.
- Tensor tympani and stapedius myoclonus are most definitively diagnosed with direct visualization of muscle spasms.
- Sawtooth patterns on long-term tympanometry can indicate tensor tympani myoclonus.
- Medical therapy mostly involves inhibiting spasms of muscle, and tenotomy can be used after medical failure with current data indicating some promise.
Enhancing Healthcare Team Outcomes
When patients complain of a ringing sensation in the ear, the differential diagnosis is extensive. Thus healthcare workers, including the nurse practitioners, should refer these patients to an ENT surgeon for further workup. Management of patients with MEM, as well as specifically TT syndrome, varies depending on the patient’s severity of symptoms and expectations. Several medications have been reportedly used for MEM with questionable efficacy, including benzodiazepines, carbamazepine, piracetam, botulinum toxin, as well as orphenadrine citrate with varying mechanisms of action. Benzodiazepines can be used to potentially decrease symptoms by targeting the anxiolytic component of the disorder as well as functioning as a muscle relaxant.
Another possible intervention that targets the contraction of the TT muscle is via botulinum toxin. Although the use of botulinum toxin is new to MEM, its use in non-cosmetic otolaryngology-associated disease processes like hemifacial spasm as well as laryngeal pathology such as spasmodic dysphonia is well documented.
The role of surgical intervention is also more clearly defined. The most common procedure for TT syndrome as well as stapedius myoclonus is tympanotomy with TT or stapedius tenotomy.
Tinnitus itself is not harmful; however, depending on the etiology, the underlying process can be life-threatening, such as multiple sclerosis. Other than the underlying disease process, tinnitus itself can cause a range of emotional distress to patients, from severely debilitating to causing little to no distress to the patient. Additionally, there is not enough data at this time to predict whether symptoms will discontinue or reduce, regardless of whether there is an identifiable cause for the tinnitus or idiopathic in origin.