Tensor Tympani Syndrome

Middle ear myoclonus is an uncommon condition characterized by abrupt, involuntary contractions of the stapedius or tensor tympani muscles. First identified in the 19th century, it remains a puzzling clinical phenomenon. Some individuals also experience psychological symptoms, drawing parallels to facial tics. Most patients report tensor tympani myoclonus or tensor tympani syndrome (TTS), which encompasses a range of aural and vestibular issues, eg, feelings of fullness in the ear, muffled or distorted hearing, tinnitus, hearing impairment, dysacusis, tension headaches, and vertigo similar to Meniere's disease. TTS can also cause a clicking noise, whereas stapedius myoclonus typically produces a buzzing sound.  The tensor tympani muscle arises from the greater wing of the sphenoid bone and connects to the bony and cartilaginous portions of the eustachian tube. It attaches to the head of the malleus in the middle ear after traversing the cochleariform process. When the tensor tympani contracts, it opens the eustachian tube and influences the malleus, stiffening the tympanic membrane and diminishing sound transmission through the ossicular chain. The specific role of the tensor tympani remains obscure. This muscle, along with the tensor veli palatini and the muscles used for chewing, is innervated by the trigeminal nerve (CN V). Some researchers propose that the tensor tympani may help lower sound intensity while speaking, chewing, or swallowing due to their shared innervation. However, the tensor tympani also contracts in response to nonauditory stimuli such as a puff of air onto the orbit, in anticipation of sounds, or as a result of a strong, threatening sound. The audiometric findings with voluntary tensor tympani contraction suggest a resultant low-frequency mixed hearing loss, specifically at 250 Hz, where air and bone conduction thresholds increase.  When the tensor tympani muscle contracts, it medializes the tympanic membrane by pulling the malleus anteriorly and medially. This movement is opposite to the stapedius muscle contraction, which displaces the tympanic membrane laterally by moving the stapes posteriorly. The stapedius and tensor tympani contractions generate low-frequency attenuation; however, this attenuation is more pronounced for the stapedius. The tensor tympani undergoes phasic or tonic contraction lasting less than 1 second, is highly fatigable, and has a long latency of 100 to 200 milliseconds. The phenomenon of TTS has an unknown etiology and is primarily reported in case studies within the field of otolaryngology literature. The tinnitus may be subjective or objective, indicating whether the sound is perceivable by an external listener.  The diagnosis of middle ear myoclonus relies on the following criteria:  : Pulsatile tinnitus : Subjective tinnitus, which is more common, is heard only by the patient and is often linked to sensorineural hearing loss. It results in a ringing or buzzing sound. In contrast, objective tinnitus can be heard by both the patient and the examiner. In theory, a perceptive examiner might detect tinnitus or muscle contractions during the evaluation of objective tinnitus related to TTS. Tensor tympani myoclonus has been reported in a case involving objective pulsatile tinnitus and observable tympanic membrane movement. . Descriptions of stapedial myoclonus may not be accurate because tympanic membrane movement may not be visible because of how the incudostapedial joint articulates. Observation of rhythmic movements of the tympanic membrane synchronous with the tinnitus. Associated demonstration of the impedance changes on tympanometry  : Tensor tympani myoclonus has been described as exhibiting a saw-toothed pattern on tympanometry, similar to stapedius myoclonus, which makes the distinction unreliable. . The acoustic reflex, suspected to protect inner ear cells from damage, involves the involuntary contraction of the tensor tympani and stapedius muscles in response to high-intensity sounds. Some have speculated that the function of the tensor tympani contraction during vocalization and chewing may help attenuate low-frequency noise, thereby preserving sensitivity to high-frequency sounds; however, this role remains unconfirmed. Tonic contractions of the tensor tympani may be triggered by sound stimulation when a startle reflex occurs. The involuntary contraction of the tensor tympani muscle, a unique striated muscle in the middle ear innervated by the mandibular branch of the trigeminal nerve, the fifth cranial nerve (CN V), causes a type of middle ear myoclonus that is known as TTS.  TTS is not well-defined or widely recognized among otolaryngologists, and some speculate that overuse, overload, and potential injury to the tensor tympani may contribute to the symptoms of TTS. TTS is thought to be a rare, involuntary condition linked to anxiety , and several theories have been proposed regarding its etiology: Abnormal stimulation of the trigeminal nerve results in chronic irritation. Reduced activity of the tensor tympani muscle may lead to frequent spasms. This causes symptoms related to increased tension in the tympanic membrane and changes in middle ear ventilation. TTS may lead to symptoms of acoustic shock after exposure to loud noise, even in the absence of any underlying ear issues or temporomandibular joint (TMJ) disorders, as TTS has also been linked to TMJ dysfunction. Treatment of TTS includes pharmacological treatment, surgical tenotomy, and other supportive measures, including relaxation therapy, psychotherapy, tinnitus masking, and biofeedback. Management remains a controversial and individualized approach, mostly centered on tinnitus and hyperacusis.