Tensor Tympani and Stapedial Tendon Reconstruction for Postoperative Hyperacusis after Tendon Lysis for Middle Ear Myoclonus.

OBJECTIVE: To present a method for repair of the stapedial and tensor tympani tendons in a patient with hyperacusis after a tendon lysis procedure. PATIENTS: A 71-year-old professional musician who presented to clinic with debilitating hyperacusis following a tensor tympani and stapedial tendon lysis procedure to treat middle ear myoclonus. INTERVENTIONS: A novel procedure for reapproximation of the tensor tympani and stapedial tendons into their native insertion points using periosteal grafts and nitinol wire. MAIN OUTCOMES MEASURES: Stapedial reflex measurements, uncomfortable loudness level, and subjective patient experience. RESULTS: Postoperatively, the patient had objective improvement in hyperacusis with return of acoustic reflexes in the affected ear and durable improvements in their frequency-specific uncomfortable loudness levels. CONCLUSIONS: This case describes the debilitating complication of hyperacusis following tendon lysis and highlights the importance of maximizing behavioral and medical measures prior to undergoing surgical intervention for middle ear myoclonus.

Transcanal Endoscopic Stapedial and Tensor Tympani Tenotomy for Middle Ear Myoclonus: A Retrospective Case Series of Surgical Outcomes.

OBJECTIVE: To describe and analyze the surgical outcomes of transcanal endoscopic resection of the stapedial tendon (ST) and tensor tympani tendon (TT) in the management of middle ear myoclonus (MEM). STUDY DESIGN: A retrospective case series. SETTING: Tertiary academic center. PATIENTS: Seven consecutive patients (seven ears) with tinnitus were diagnosed with MEM. INTERVENTION: Transcanal endoscopic resection of both the ST and TT using either microinstruments or a laser. MAIN OUTCOME MEASURES: The symptom of tinnitus, based on visual analog scale and Tinnitus Handicap Inventory scores, was analyzed preoperatively and postoperatively for each patient. The intraoperative findings and postoperative complications were also evaluated. RESULTS: Amelioration of objective tinnitus with significant improvement in visual analog scale and Tinnitus Handicap Inventory scores was noted in all seven patients. The ST and TT were easily identified in the same endoscopic field, with minimal or no removal of the scutum. There was no need to perform an anterior tympanotomy to expose the TT. Resection of both the ST and TT and creating a gap between the cut edges were achieved by using either microinstruments or a laser under an endoscopic field. Conversion to or conjunction with the microscopic approach was unnecessary for any of the seven patients. No hearing loss or hyperacusis occurred postoperatively. CONCLUSIONS: Transcanal endoscopic resection of the ST and TT successfully ameliorated the symptom of tinnitus in patients with MEM. A transcanal endoscopic approach provides an alternative method to manage MEM, providing excellent visualization and minimal invasiveness.

Unique fiber phenotype composition and metabolic properties of the stapedius and tensor tympani muscles in the human middle ear.

The middle ear muscles have vital roles, yet their precise function in hearing and protection remains unclear. To better understand the function of these muscles in humans, the morphology, fiber composition, and metabolic properties of nine tensor tympani and eight stapedius muscles were analyzed with immunohistochemical, enzyme-histochemical, biochemical, and morphometric techniques. Human orofacial, jaw, extraocular, and limb muscles were used as references. The immunohistochemical analysis showed that the stapedius and tensor tympani muscles were markedly dominated by fibers expressing fast contracting myosin heavy chain MyHC-2A and MyHC-2X (79 ± 6% vs. 86 ± 9%, respectively, p = 0.04). In fact, the middle ear muscles had one of the highest proportions of MyHC-2 fibers ever reported for human muscles. Interestingly, the biochemical analysis revealed a MyHC isoform of unknown identity in both the stapedius and tensor tympani muscles. Muscle fibers containing two or more MyHC isoforms were relatively frequently observed in both muscles. A proportion of these hybrid fibers expressed a developmental MyHC isoform that is normally absent in adult human limb muscles. The middle ear muscles differed from orofacial, jaw, and limb muscles by having significantly smaller fibers (220 vs. 360 µm2 , respectively) and significantly higher variability in fiber size, capillarization per fiber area, mitochondrial oxidative activity, and density of nerve fascicles. Muscle spindles were observed in the tensor tympani muscle but not in the stapedius muscle. We conclude that the middle ear muscles have a highly specialized muscle morphology, fiber composition, and metabolic properties that generally showed more similarities to orofacial than jaw and limb muscles. Although the muscle fiber characteristics in the tensor tympani and stapedius muscles suggest a capacity for fast, fine-tuned, and sustainable contractions, their difference in proprioceptive control reflects different functions in hearing and protection of the inner ear.

Human middle-ear muscle pulls change tympanic-membrane shape and low-frequency middle-ear transmission magnitudes and delays.

The three-bone flexible ossicular chain in mammals may allow independent alterations of middle-ear (ME) sound transmission via its two attached muscles, for both acoustic and non-acoustic stimuli. The tensor tympani (TT) muscle, which has its insertion on the malleus neck, is thought to increase tension of the tympanic membrane (TM). The stapedius (St) muscle, which has its insertion on the stapes posterior crus, is known to stiffen the stapes annular ligament. We produced ME changes in human cadaveric temporal bones by statically pulling on the TT and St muscles. The 3D static TM shape and sound-induced umbo motions from 20 Hz to 10 kHz were measured with optical coherence tomography (OCT); stapes motion was measured using laser-Doppler vibrometry (LDV). TT pulls made the TM shape more conical and moved the umbo medially, while St pulls moved the umbo laterally. In response to sound below about 1 kHz, stapes-velocity magnitudes generally decreased by about 10 dB due to TT pulls and 5 dB due to St pulls. In the 250 to 500 Hz region, the group delay calculated from stapes-velocity phase showed a decrease in transmission delay of about 150 µs by TT pulls and 60 µs by St pulls. Our interpretation of these results is that ME-muscle activity may provide a way of mechanically changing interaural time- and level-difference cues. These effects could help the brain align head-centered auditory and ocular-centered visual representations of the environment.

Exploring the middle ear function in patients with a cluster of symptoms including tinnitus, hyperacusis, ear fullness and/or pain.

Middle ear muscle (MEM) abnormalities have been proposed to be involved in the development of ear-related symptoms such as tinnitus, hyperacusis, ear fullness, dizziness and/or otalgia. This cluster of symptoms have been called the Tonic Tensor Tympani Syndrome (TTTS) because of the supposed involvement of the tensor tympani muscle (TTM). However, the putative link between MEM dysfunction and the symptoms has not been proven yet and the detailed mechanisms (the causal chain) of TTTS are still elusive. It has been speculated that sudden loud sound (acoustic shock) may impair the functioning of the MEM, specifically the TTM, after an excessive contraction. This would result in inflammatory processes, activation of the trigeminal nerve and a change of the MEMs state into a hypersensitive one, that may be associated to the cluster of symptoms listed above. The goal of this study is to provide further insights into the mechanisms of TTTS. The middle ear function of 11 patients who reported TTTS symptoms has been investigated using either admittancemetry and/or measurement of air pressure in the sealed external auditory canal. While the former method measured the middle ear stiffness the latter provides an estimate of the tympanic membrane displacement. Most patients displayed results consistent with phasic contractions of the TTM (n = 9) and/or Eustachian Tube (ET) dysfunction (n = 6). The MEM contraction or ET dysfunction could be evoked by acoustic stimulation (n = 3), somatic maneuvers (n = 3), or pressure changes in the ear canal (n = 3). Spontaneous TTM contraction (n = 1) or ET opening (n = 1) could also be observed. Finally, voluntary contraction of MEM was also reported (n = 5). On the other hand, tonic contraction of the TTM could not be observed in any patient. The implications of these results for the mechanisms of TTTS are discussed.

[New discovery and short-term effect analysis of tensor tympani muscle tenotomy for Meniere's disease under otoscope].

Objective: To explore the feasibility and short-term effect of tensor tympani muscle Tenotomy in the treatment of Meniere's disease under otoscope. The possible pathogenesis was discussed and our views were put forward. Methods: The clinical data of 9 cases of Meniere's disease treated by otoscopic Tenotomy were analyzed retrospectively, including 2 males, 7 females, 5 right ones, 2 left ones and 2 bilateral ones. The average age was (56.33± 10.56) years, ranging from 38 to 75 years. We evaluated intraoperative findings and short-term postoperative efficacy, respectively evaluated postoperative aural fullness, tinnitus and hearing recovery, and evaluated postoperative vertigo attack in a short time. Results: Nine patients were completed the operation under general anaesthesia and otoscopy, and no serious complications occurred. We found new pathological changes in tympanic cavity in some cases during operation. There were rupture of round window membrane in 1 case, severe fibrous hyperplasia near the round window membrane and vestibular window and adhesion with ossicular chain in 1 case, fibrous cord and membranous hyperplasia near vestibular window and round window membrane in 1 case, fibrous hyperplasia and adhesion near the round window membrane in 2 cases, membranous hyperplasia and adhesion around vestibular window in 1 case. No fibrous hyperplasia was found in 3 cases in the tympanic cavity. The round window membrane can be exposed in 4 cases and failed in 5 cases. After 3 months of follow-up, we found that we found that 5/5 cases of aural fullness disappeared, 2/2 cases of earache disappeared, 3/8 cases of tinnitus improved, 5/8 cases presented with improvement and no aggravation, 3/3 cases of hearing allergy improved, 4/9 cases of hearing improved, and 5/9 cases showed no improvement or decrease. 9 patients were followed up for 3 months, of whom 8 patients had no vertigo, one patient suffered from vertigo twice within 3 months after operation, and the patient suffered from rupture of round window membrane. Conclusions: Endoscopic Tenotomy for Meniere's disease has obvious curative effect and quick recovery after operation. During the operation, we find that most of Meniere's patients have fibrous cord hyperplasia near the inner ear window membrane, which may be the pathological manifestation after repeated rupture and repair of the inner ear window membrane. The vertigo of Meniere's disease may be related to the destruction and repair of inner ear membrane structure caused by improper contraction or spasm of tympanic tensor muscle.

Contraction of the stapedius and tensor tympani muscles explored by tympanometry and pressure measurement in the external auditory canal.

It has been suggested that tensor tympani muscle (TTM) contraction may be involved in the development of ear-related pathologies such as tinnitus, hyperacusis and otalgia, called the tonic tensor tympani syndrome (TTTS). However, as there is no precise measure of TTM function under normal and pathological states, its involvement remains speculative. When the TTM or the stapedius muscle (SM) contracts, they both generate an increase of middle ear stiffness that can be measured through middle ear admittance. However, this technique cannot differentiate the contraction between the two muscles. On the other hand, the air pressure measured in a sealed external auditory canal can provide a measure of the eardrum displacement that may be able to differentiate SM from TTM contraction. TTM is attached to the malleus, and its contraction causes a retraction of the eardrum inside the middle ear cavity, while SM can have a small but reversed effect on TTM displacement. To investigate this issue, we compared the middle ear admittance and air pressure in a sealed external ear canal upon auditory stimulation (sMEMC) and voluntary middle ear muscle contraction (vMEMC). In addition, we assessed the perceptual effect of vMEMC, including pitch and loudness matching of the fluttering noise produced by vMEMC and the threshold shifts, were measured. Out of the 14 ears tested, sMEMC was associated with a decrease of admittance in 93% (mean peak average: -0.06 ml, SD:0.04) and an increase of air pressure in 29% of ears (mean peak average: 8.1 Pa, SD:5.1). No decrease in air pressure was found upon sMEMC. For vMEMC (n = 8 ears), decreases were found for both admittance and air pressure in 100% and 88%, with a mean peak average of -0.38 ml, SD: 0.54 and -149 Pa, SD:156, for admittance and pressure respectively. These results suggest that SM and TTM are involved in sMEMC and vMEMC, respectively. In addition, vMEMC was associated with perceptual effects including a low-frequency sound, pitch-matched at ∼30 Hz (>15 dB SL), and a low-frequency hearing loss of at least 10 dB between 20 and 200 Hz. In conclusion, admittance and air pressure recordings provide useful and complementary information on middle ear muscle contraction and can be used to explore the middle ear function.

A Non-invasive Method to Assess Tensor Tympani Muscle Contraction in Response to Tactile Stimulation.

BACKGROUND: The function of the tensor tympani muscle and its effects, as well as a universal testing procedure, is not yet known. The purpose of this study is to investigate the effect of tactile stimulation on the tensor tympani muscle activity in an attempt to evaluate the functional status of the muscle. METHODS: In this study, 20 healthy adults aged between 18 and 30 years were included. All participants had their history taken, as well as the evaluation of otoscopy, audiometry, and tympanometry. A modified reflex decay paradigm was used to evaluate the tensor tympani muscle activity, in both humans and a fresh-frozen cadaver. The tactile stimulation was applied by thumb tappings on different forehead areas. RESULTS: Reflex decay responses were in the form of the absence of a response or either a positive or negative waveform. Tactile stimulation had no impact on reflex decay recordings obtained from the cadaver. There was no significant difference between the waveforms obtained from both ears, at different stimulation frequencies, tactile stimulation areas, or the 3 successive stimuli for 1 individual in 1 ear (P > .05). Changes observed in the reflex decay test upon tactile stimulation seem to be due to tensor tympani muscle activity as supported by the previous findings in the literature. CONCLUSION: The application of a tactile stimulus on the forehead is a non-invasive test method to assess tensor tympani muscle contraction. Understanding the function of the tensor tympani muscle using a non-invasive method will be helpful during the decision-making process in the practice of otology.

The Tensor Tympani Tendon: A Hypothetical Site of Origin of Congenital Cholesteatoma.

Multiple theories have been discussed about the etiopathogenesis of congenital middle ear cholesteatoma (CMEC) and its specific site of origin. The intraoperative identification of the precise location of the keratinous mass is important to guarantee its complete removal, in order to reduce the risk of recurrence. This study proposes the tensor tympani tendon (TTT) as a possible site of origin of CMEC. All CMECs treated between 2013 and 2019 were reviewed. Only Potsic stage I lesions were included. Preoperative radiologic images were compared to intraoperative findings. Three removed TTT were sent for histologic evaluation. Seven patients were included (M:F = 3:4). Preoperative CT images were classified as type A in 2 cases (28.6%) and type B in 5 cases (71.4%). At intraoperative evaluation all CMEC sacs were found pedunculated on the TTT. The histologic examinations confirmed the connection between the cholesteatomatous sac and the TTT. According to the correlation of imaging, intraoperative findings and histology, we proposed that the TTT could be the primary site from which CMEC originates.

[Postoperative hearing in tympanoplasty preserving the manubrium of malleus and tensor tympani muscle tendon].

Objective:To study the effect of retaining the manubrium of malleus and tensor tympani muscle tendon （TT） on postoperative hearing reconstruction in tympanoplasty. Methods:Ninety-seven patients underwent tympanoplasty and ossiculoplasty in Peking University Third Hospital from January 2012 to December 2017, their postoperative results of audiometry were analyzed and compared with the preoperative results. The patients were divided into two groups according to retaining the manubrium of malleus and TT or not during the operation. Retention group include the cases with the manubrium of malleus and TT retained, resection group include the cases with TT resected with the manubrium retained or resected. T test was used to analyze and compare the differences of air conduction threshold air-bone gap （ABG） and the postoperative improvement between the two groups. Results:One year after operation, the air conduction thresholds and ABG were lower in retention group （n= 44） than those in resection group （n= 53） at each frequency, and there were differences with statistically significant at 0.25, 0.5 and 1.0 kHz （P<0.05）; the postoperative improvement of hearing thresholds and ABG at above frequencies in retention group was better than that in resection group. In cases with canal-wall-up operations or partial ossicular prostheses implanted, the above differences still existed between the two groups with statistical significance （P<0.05）; while in cases with canal-wall-down operations or total ossicular prostheses implanted, there were no significant differences between the two groups （P>0.05）. Conclusion:The preservation of the manubrium of malleus and TT is significant for postoperative hearing improvement in tympanoplasty, especially in the canal-wall-up operation with partial ossicular prostheses.

Forces Required for Isolated Malleus Shaft Fractures.

BACKGROUND AND HYPOTHESIS: Isolated malleus shaft fractures are rare cases. A commonly reported cause is a finger pulled out from a wet outer ear canal after a shower or bath. The objective was to investigate experimentally the mechanism and forces needed to establish an isolated malleus shaft fracture. METHODS: Ten fresh-frozen human temporal bones were adapted to allow visual inspection of the structures involved while negative pressure trauma was applied. Thirty malleus bones were broken and the required forces were measured. Measurements from 60 adult test subjects were used to create mathematical and physical models to calculate and measure the forces necessary for generating trauma. To calculate the maximum muscle force developed by the tensor tympani muscle, the muscle area and fiber type composition were determined. RESULTS: The temporal bone experiments showed that applied negative pressure in a wet ear canal could not fracture the malleus shaft with only passive counterforce from supporting structures, although the forces exceeded what was required for a malleus shaft fracture. When adding calculated counteracting forces from the tensor tympani muscles, which consisted of 87% type II fibers, we estimate that a sufficient force is generated to cause a malleus fracture. CONCLUSION: The combination of a negative pressure created by a finger pulling outward in a wet ear canal and a simultaneous counteracting reflexive force by the tensor tympani muscle were found to be sufficient to cause an isolated malleus fracture with an intact tympanic membrane.

Acoustic reflex preshoot: A sign of contraction of the tensor tympani muscle?

Two tiny muscles are attached to the ossicles of the middle ear: the stapedius, whose role as a protector of the inner ear against loud noise has been widely accepted, and the tensor tympani, which remains a mystery since no valid method of detecting its contraction has yet been developed. However, tonic contraction of the tensor tympani has been associated with a number of otological conditions including fullness, tinnitus, slight hearing loss, and Menière-like findings. Our hypothesis is that an easily recognizable sign in the acoustic immittance testing that is part of almost every basic audiological evaluation indicates the contraction of the tensor tympani. During acoustic reflex assessment, a loud stimulus causes a bilateral contraction of the stapedial muscles and an increase in impedance which appears as a deflection in the tracing of the immittance test results. In the case of a contracted tensor tympani, when an intense sound is sent to provoke the acoustic reflex, the stapedius must overcome its resistance which would otherwise have the opposite effect on the footplate. This effort can be seen as a small peak or "preshoot" preceding the greater negative deflection of the impedance. We report the cases of ten patients with unilateral aural symptoms such as tinnitus, impaired noise tolerance, fullness, ear pressure and/or ear discomfort during chewing; the preshoot was present only in the symptomatic ear. If further studies confirm our hypothesis, this could give rise to new therapeutical strategies aimed at reducing contraction of the tensor tympani and balancing its function.

Time-domain and frequency-domain effects of tensor tympani contraction on middle ear sound transmission in gerbil.

The middle ear is a high-fidelity, broadband impedance transformer that transmits acoustic stimuli at the eardrum to the inner ear. It is home to the two smallest muscles in mammalian species, which modulate middle ear transmission. Of this pair, the function of the tensor tympani muscle (TTM) has remained obscure. We investigated the acoustic effects of this muscle in young adult gerbils. We measured changes in middle ear vibration produced by pulse-train-elicited TTM contraction - in the time-domain with a click stimulus and in the frequency-domain with multitone zwuis stimuli. In our click experiments, there was generally a small reduction in the primary peak of the response and a slight increase in the subsequent ringing, but there was essentially no change in the delay of the click response at the umbo (less than 1 µs change). In our multitone experiments, there were consistent patterns of attenuation and enhancement in the velocity responses at the umbo and ossicles. TTM contraction produced a narrow band of enhancement around 6 kHz (maximally ~5 dB) that can be modeled with an increased stiffness of an overdamped spring-mass resonance. At frequencies below 2 kHz and above 35 kHz, TTM contraction attenuated middle ear vibrations by as much as fivefold.

A Novel Technique for the Diagnosis and Management of Middle Ear Myoclonus.

A novel technique for the diagnosis and management of middle ear myoclonus is described. A patient with middle ear myoclonus underwent a trans-canal microscopic middle ear exploration with injection of botulinum toxin into the stapedius and tensor tympani muscles. Postoperatively, the patient noted complete resolution of symptoms. This is the first report of the use of botulinum toxin directly applied to the middle ear musculature via a trans-canal approach for the management of middle ear myoclonus. This approach is both a useful diagnostic and therapeutic tool that allows for temporary muscle paralysis prior to offering definitive surgical management. Laryngoscope, 131:E248-E249, 2021.

Endoscopic Assessment of the Isthmus Tympanicum and Tensor Tympani Fold and their Relationship with Mastoid Pneumatization in Chronic Otitis Media.

OBJECTIVES: To endoscopically evaluate the patency of the isthmus tympanicum and integrity of the tensor tympani fold as routes of ventilation of the attic and mastoid in chronic otitis media (COM) and to assess their effects on mastoid pneumatization. MATERIALS AND METHODS: Sixty patients with COM were categorized into two groups: (1) Group A: 36 patients with tympanic membrane perforation (2) Group B: 24 patients with limited attic disease of whom 14 patients had attic retraction pockets and 10 with limited attic cholesteatoma. A multislice computed tomography scan of the temporal bone was performed for each patient to assess the degree of mastoid pneumatization. Notably, either myringoplasty or tympanomastoid surgery was performed in all patients. An endoscope was inserted into the middle ear for evaluation of the isthmus tympanicum and tensor fold area. RESULTS: The isthmus tympanicum was patent in most ears (83.3%) of group A, whereas it was blocked in most ears (83.3%) of group B. The tensor fold was complete in 77.8% of ears in group A and 83.3% of ears in group B. It was observed that 94.1% of ears with patent isthmus in both groups had normal mastoid pneumatization and 5.9% of ears had poorly pneumatized mastoid. By contrast, 7.7% of ears with blocked isthmus tympanicum had normal mastoid pneumatization and 92.3% had poor mastoid pneumatization. Normal mastoid pneumatization was observed in 50% of ears in both groups with complete tensor fold, and 83.3% of ears with an incomplete tensor fold. CONCLUSION: A significant correlation was observed between COM with limited attic disease and obstruction of the isthmus tympanicum. Obstruction of isthmus tympanicum was associated with poor mastoid pneumatization. Furthermore, an incomplete tensor fold was associated with well pneumatized mastoid.

[Effect of the stapedius and tensor tympani muscles tenotomy on the quality of life of patients suffering from Ménière's disease]. / A musculus tensor tympani és a musculus stapedius ín átvágásának hatása a Ménière-betegségben szenvedok életminoségére.

Introduction: Tenotomy of the tendon of the stapedius and tensor tympani (TT) muscles is a minimal-invasive surgical therapeutic procedure in Ménière's disease (MD). It has been assumed that the TT medializes the stapes into the oval window, resulting in changes in perilymphatic pressures of the inner ear. By cutting the tendons of both middle ear muscles, they affect the pressure dynamics by not augmenting this pressure even further. Aim: The immediate and long-term investigation of the effect of middle ear muscle tenotomy on the quality of life of patients suffering from Ménière's disease, measured by the Dizziness Handicap Inventory (DHI) and the Tinnitus Handicap Inventory (THI). Method: A follow-up study of 22 patients with definite, unilateral Ménière's disease had undergone tenotomy under general or local anesthesia through an endaural approach. Pre- and postoperative DHI values were compared for all patients. Statistical analysis: The statistical analysis was completed by using the IBM SPSS V24 software. Since the parameters did not show normal distribution, non-parametric test (Mann-Whitney U test) was used. The significance level was specified as p<0.05. Results: A statistically significant reduction of DHI scores was noted in all patients. The tinnitus significantly reduced and all of the patients mentioned improved symptoms of MD. Conclusion: Although the follow-up period is short, and the pathomechanism (decrease of stapes medialization in the oval window) is not exactly clear, tenotomy seems to be a successful promising surgical treatment method with a high reduction of dizziness handicap score in conservative therapy-resistant Ménière's disease. Orv Hetil. 2020; 161(5): 177-182.

Active tympanic tuning facilitates sound localization in animals with internally coupled ears.

Earlier studies have reported that numerous vertebrate taxa have skeletal muscle(s) attaching directly, or indirectly, onto the tympanic membrane. The present study links these prior studies by quantitatively modeling the influence of skeletal muscle contraction on tympanic tension, tympanic dampening, and, ultimately, the fundamental frequency. In this way, the efficacy of these tympanic muscles to dynamically alter the sensory response of the vertebrate ear is quantified. Changing the tension modifies the eardrum's fundamental frequency, a key notion in understanding hearing through internally coupled ears (ICE) as used by the majority of terrestrial vertebrates. Tympanic tension can also be modulated by altering the pressure acting on the deep (medial) surface of the tympanum. Herein we use the monitor lizard Varanus as an example to demonstrate how active modulation of the pharyngeal volume permits tuning of an ICE auditory system. The present contribution offers a behaviorally and biologically realistic perspective on the ICE system, by demonstrating how an organism can dynamically alter its morphology to tune the auditory response. Through quantification of the relationships between tympanic surface tension, damping, membrane fundamental frequency, and auditory cavity volume, it can be shown that an ICE system affords a biologically relevant range of tuning.

Dental occlusion as one cause of tinnitus.

There is large support in literature linking tinnitus to dental occlusion and temporomandibular joint disorders (TMD). However, there is no model to explain such a link. This hypothesis explains how the fusimotor system of the muscles innervated by the trigeminal motor nucleus is affected by inadequacies in the occlusion of the teeth that cause changes in posture and movement of the mandible. Reptile to mammal evolution shows that stomatognathic structures underwent changes related to mastication. Among several changes, there was the appearance of a new articulation between the mandible and skull: the temporomandibular joint. The bones of the old reptile joint, quadrate-articular, have detached from the mandible and are part of the middle ear bone chain. The former becomes the incus and the latter the malleus. This bone change also carried the tensor tympani and its trigeminal motor innervation. Inadequate occlusal contacts give rise to an adapted function of the mandible and the most common compensatory muscular response is hypertonia involving all mandibular muscles, including the tensor tympani. A fundamental clinical feature that demonstrates the involvement of the trigeminal fusimotor system is the characteristic pain by palpation, but no pain on the mandibular movement. Muscle pain is always felt in the dermatome innervated by the mandibular branch of the trigeminal nerve, which carries the motor fibers, reported as tightening, similar to cramp, and has regular behavior in intensity, duration and frequency. In addition, the patient has increased musculature volume, detected by palpation of certain anatomical landmarks, but with loss of functional efficiency. The neuromotor control of the mandibular movements is poor and when asked to make lateral jaw movement touching the teeth, it is common to observe that the patient moves the lips, eyes, and even turns the head in the same direction as the movement. There is also difficulty eating hard foods and talking fast. Tongue biting while chewing is frequent, meaning that these non-physiological events surpass protective reflex circuits. The report of ear pain, tinnitus, blocked ear sensation and sudden hearing loss is common in such patients, compatible with the tonic contraction of the tensor tympani. The fusimotor system hypothesis is able to explain all events related to the symptoms and helps to establish a correct diagnosis for certain types of hearing disorders.

First emerging objective experimental evidence of hearing impairment following subarachnoid haemorrhage; Felix culpa, phonophobia, and elucidation of the role of trigeminal ganglion.

Objective: The exact mechanism of phonophobia induced by subarachnoid hemorrhage (SAH) has not been understood well. This subject was investigated. Material and methods: This study was conducted on 25 rabbits. They divided into three groups: Five as control, five as SHAM, 20 as SAH group. All animals objected to 85 dB impulse noise by daily periods, and their phonophobic score values were examined by daily periods for 20 days. Their brains, trigeminal ganglia were extracted bilaterally. The normal and degenerated neuron densities of trigeminal ganglia were examined by stereological methods and compared with phonophobia scores. Results: Phonophobic score was 19-17, mean live neuron density (LND) of the trigeminal ganglia was 16.321 ± 2.430/mm3, and degenerated neuron density (DND) was 1.15 ± 0.120/mm3 in animals of control groups (n = 5). The phonophobic score was 17-14, LND: 14.345 ± 1.913/mm3, DND of the trigeminal ganglia was 1.150 ± 0.110/mm3 in SHAM group (n = 5). The phonophobic score was 14-8, LND: 12.987 ± 1.966/mm3, mean DND of the trigeminal ganglia was 2.520 ± 510/mm3 in animals with high phonophobia scores (n = 6). The phonophobic score was 7-4, LND: 9.122 ± 1.006, mean DND of the trigeminal ganglia was 5.820 ± 1.610/mm3, in animals with fever phonophobia scores (n = 9). Conclusion: An inverse relationship between DND trigeminal ganglion (TGG) and phonopobic score was found. The paralysis of tensor tympani muscle owing to trigeminal ganglia ischemia may be responsible for phonophobic clinical state in animals with SAH. In addition, there seems to be an important concern for the verbal component of GCS in SAH. These two important findings have not been published previously.