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.

[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.

An Integrative Model Accounting for the Symptom Cluster Triggered After an Acoustic Shock.

Acoustic shocks and traumas sometimes result in a cluster of debilitating symptoms, including tinnitus, hyperacusis, ear fullness and tension, dizziness, and pain in and outside the ear. The mechanisms underlying this large variety of symptoms remain elusive. In this article, we elaborate on the hypothesis that the tensor tympani muscle (TTM), the trigeminal nerve (TGN), and the trigeminal cervical complex (TCC) play a central role in generating these symptoms. We argue that TTM overuse (due to the acoustic shock), TTM overload (due to muscle tension), and ultimately, TTM injury (due to hypoxia and "energy crisis") lead to inflammation, thereby activating the TGN, TCC, and cortex. The TCC is a crossroad structure integrating sensory inputs coming from the head-neck complex (including the middle ear) and projecting back to it. The multimodal integration of the TCC may then account for referred pain outside the ear when the middle ear is inflamed and activates the TGN. We believe that our model proposes a synthetic and explanatory framework to explain the phenomena occurring postacoustic shock and potentially also after other nonauditory causes. Indeed, due to the bidirectional properties of the TCC, musculoskeletal disorders in the region of the head-neck complex, including neck injury due to whiplash or temporomandibular disorders, may impact the middle ear, thereby leading to otic symptoms. This previously unavailable model type is experimentally testable and must be taken as a starting point for identifying the mechanisms responsible for this particular subtype of tinnitus and its associated symptoms.

Development of digastric muscles in human foetuses: a review and findings in the flexor digitorum superficialis muscle.

The digastricus and omohyoideus muscles are digastric muscles with two muscle bellies. An insertion tendon of the posterior belly becomes an intermediate tendon in digastricus muscles, whereas a single band-like muscle in omohyoideus muscles may later be interrupted by an intermediate tendon, possibly due to muscle cell death caused by mechanical stress. In human foetuses, an intermediate tendon provides the temporal origins of the tensor veli palatini and tensor tympani muscles. Some reptiles, including snakes, carry multiple series of digastric-like axial muscles, in which each intersegmental septum is likely to become an intermediate tendon. These findings indicate that many pathways are involved in the development of digastric muscles. A review of these morphologies suggested that the flexor digi-torum superficialis (FDS) muscle was a digastric muscle, although the intermediate tendon may not be visible in the surface view in adults. The present observations support the hypothesis that the proximal anlage at the elbow develops into a deep muscle slip to a limited finger, while the distal anlage at the wrist develops into the other slips. The findings suggest that, in the FDS muscle, the proximal and distal bellies of the embryonic digastric muscle fuse together to form a laminar structure, in which muscle slips accumulate from the palmar to the deep side of the forearm. (Folia Morphol 2018; 77, 2: 362-370).

Fetal Tendinous Connection Between the Tensor Tympani and Tensor Veli Palatini Muscles: A Single Digastric Muscle Acting for Morphogenesis of the Cranial Base.

Some researchers contend that in adults the tensor tympani muscle (TT) connects with the tensor veli palatini muscle (TVP) by an intermediate tendon, in disagreement with the other researchers. To resolve this controversy, we examined serial sections of 50 human embryos and fetuses at 6-17 weeks of development. At 6 weeks, in the first pharyngeal arch, a mesenchymal connection was found first to divide a single anlage into the TT and TVP. At and after 7 weeks, the TT was connected continuously with the TVP by a definite tendinous tissue mediolaterally crossing the pharyngotympanic tube. At 11 weeks another fascia was visible covering the cranial and lateral sides of the tube. This "gonial fascia" had two thickened borders: the superior one corresponded to a part of the connecting tendon between the TT and TVP; the inferior one was a fibrous band ending at the os goniale near the lateral end of the TVP. In association with the gonial fascia, the fetal TT and TVP seemed to provide a functional complex. The TT-TVP complex might first help elevate the palatal shelves in association with the developing tongue. Next, the tubal passage, maintained by contraction of the muscle complex, seems to facilitate the removal of loose mesenchymal tissues from the tympanic cavity. Third, the muscle complex most likely determined the final morphology of the pterygoid process. Consequently, despite the controversial morphologies in adults, the TT and TVP seemed to make a single digastric muscle acting for the morphogenesis of the cranial base.

Is it necessary to retain the tensor tympani tendon in tympanoplasty?

OBJECTIVES/HYPOTHESIS: To evaluate the acoustic effect after canal wall-down tympanoplasty with sectioning of the tensor tympani muscle (TTM) tendon in patients with chronic otitis media. STUDY DESIGN: Prospective, controlled clinical trial. METHODS: From January 2010 to April 2014, 212 patients underwent canal wall-down tympanoplasty with ossicular chain reconstruction in one-stage surgery. For this study, the patients were assigned to two groups. In group 1 (107 patients), the TTM tensor would be removed during the surgery, whereas it would be retained in group 2 (105 patients). Pre- and postoperative air conduction and bone conduction thresholds at 0.5, 1, 2, and 4 kHz were reported, and the air-bone gaps (ABGs) were measured. RESULTS: Mean postoperative ABG was 16.0 dB in group 1 and 17.0 dB in group 2 and the ABG closure was 11.9 ± 8.5 in group 1 and 11.8 ± 9.7 in group 2. Both were not statistically different (P = .2381 and P = .9625). Overall, 84.1% of patients in group 1 and 75.2% of patients in group 2 attained a postoperative ABG of 20 dB or less. Success rate in group 1 is slightly higher than group 2, but not significant (P = .1255). CONCLUSIONS: The section of the tensor tympani muscle tendon in canal wall-down tympanoplasty with ossiculoplasty had no statistically significant influence on sound transmission and can be a safe maneuver in middle ear surgery. LEVEL OF EVIDENCE: 4

Phylogenic Oto-stomatognathic Connection of the Mammalian Jaw: A Novel Hypothesis for Tensor Tympani Muscle and TMD-related Otologic Symptoms / 체질인류학회지

Otologic complaints, including otalgia, tinnitus, vertigo, and hearing loss, are known to be related to temporomandibular disorders (TMDs). There have been several hypotheses regarding the clinical correlation between otologic complaints and TMDs, based on clinical phenomena with corresponding symptoms, the close neurological relationship between otic and masticatory structures, and anatomical features of the tympanic cavity and jaw joint. Function of the tensor tympani muscle seems to be crucial to understanding TMD-related otologic symptoms. The tensor tympani inserts into the handle of the malleus and it modulates sound transduction in situations of excessive noise. This muscle is innervated by the trigeminal nerve, like the masticatory muscles. Voluntary eardrum movement by pathological tensor tympani contraction results in various otologic symptoms. Thus, co-contraction of the tensor tympani with the masticatory muscle could be a possible cause of TMD-related otologic symptoms. The tensor tympani is rather unrelated to the acoustic reflex, in which the stapedius is strongly involved. The tensor tympani seem to be controlled by proprioceptive information from the trigeminal sensory nucleus. The peripheral innervation pattern of the tensor tympani and masticatory muscles is also supposed to be interconnected. The middle ear structure, including the malleus, incus, and tensor tympani, of mammals had been adapted for acoustic function and lacks the masticatory role seen in non-mammalian jawed vertebrates. The tensor tympani in non-mammals is one of the masticatory muscles and plays a role in the modulation of sound transduction and mastication. After the functional differentiation of the mammalian middle ear, the nervous connection of the tensor tympani with other masticatory apparatus still remains. Through this oto-stomatognathic vestige, the tensor tympani seems to contract unnecessarily in some pathological conditions of the TMD in which the masticatory muscles contract excessively. We hypothesized that the phylogenic relationship between the tensor tympani and masticatory apparatus is a significant and logical reason for TMD-related otologic complaints.

The Effects of Tensor Tympani MuscIe on the Hearing Reconstruction Outcome / 听力学及言语疾病杂志

Objective To study the effects of the integrity of the tensor tympani muscle on the postoperative hearing recovery and the morphology of tympanic membrane,to provide the reference for the handling of the tensor tympani muscle during the operation.Methods A total of 145 cases of chronic tympanitis were grouped by the integ-rity of the tensor tympani muscle and the implanted types of biological auditory ossicles,the clinical data were ana-lyzed retrospectively.There were 80 cases in the tensor tympani muscle intact group,including 45 cases of PORP group and 35 TORP group.The tensor tympani muscle rupture group of 65 cases consisted of 34 cases of PORP group,and 31 cases of TORP group.The postoperative recovery conditions of tympanic membrane morphology, hearing threshold Ac and air-bone gap(ABG)between the tensor tympani muscle intact group and the tensor tym-pani muscle rupture group were compared 1 month or 3 months,and 6 months after the operation.ResuIts One month after the operation,there was no significant difference in tympanic membrane morphology between the two groups.Three months after the operation,the tensor tympani muscle intact group had a higher ratio about the loca-tion and shape of tympanic membrane ,closer to the normal than the tensor tympani muscle rupture group in which the ratio in the intact group was 81.25% (65/80),while in the rupture group it was 52.31% (34/65 ).After 6 months,with the operation of PORP,the tensor tympani muscle intact group of AC value was 27.48±10.02 dB HL, and ABG value was 13.57±6.36 dB,while the rupture group of AC value was 32.36±9.34 dB HL,and ABG value was 25.73±7.44 dB.With the operation of TORP,the tensor tympani muscle intact group of AC value was 28.76± 7.14 dB HL,and ABG value was 21.02±5.48 dB,while the rupture group of AC value was 39.93 ±5.12 dB HL, and ABG value was 31.41±6.25 dB.The postoperative recovery condition of the tensor tympani muscle intact group was better than those of in the rupture group.ConcIusion The tensor tympani muscle can maintain the morphology and location of the postoperative tympanic membrane.The integrity of the tensor tympani muscle may has a positive effect on the improvement of the postoperative hearing.

Initial stage of fetal development of the pharyngotympanic tube cartilage with special reference to muscle attachments to the tube.

Fetal development of the cartilage of the pharyngotympanic tube (PTT) is characterized by its late start. We examined semiserial histological sections of 20 human fetuses at 14-18 weeks of gestation. As controls, we also observed sections of 5 large fetuses at around 30 weeks. At and around 14 weeks, the tubal cartilage first appeared in the posterior side of the pharyngeal opening of the PTT. The levator veli palatini muscle used a mucosal fold containing the initial cartilage for its downward path to the palate. Moreover, the cartilage is a limited hard attachment for the muscle. Therefore, the PTT and its cartilage seemed to play a critical role in early development of levator veli muscle. In contrast, the cartilage developed so that it extended laterally, along a fascia-like structure that connected with the tensor tympani muscle. This muscle appeared to exert mechanical stress on the initial cartilage. The internal carotid artery was exposed to a loose tissue facing the tubal cartilage. In large fetuses, this loose tissue was occupied by an inferior extension of the temporal bone to cover the artery. This later-developing anterior wall of the carotid canal provided the final bony origin of the levator veli palatini muscle. The tubal cartilage seemed to determine the anterior and inferior margins of the canal. Consequently, the tubal cartilage development seemed to be accelerated by a surrounding muscle, and conversely, the cartilage was likely to determine the other muscular and bony structures.

Initial stage of fetal development of the pharyngotympanic tube cartilage with special reference to muscle attachments to the tube / 대한해부학회지

Fetal development of the cartilage of the pharyngotympanic tube (PTT) is characterized by its late start. We examined semiserial histological sections of 20 human fetuses at 14-18 weeks of gestation. As controls, we also observed sections of 5 large fetuses at around 30 weeks. At and around 14 weeks, the tubal cartilage first appeared in the posterior side of the pharyngeal opening of the PTT. The levator veli palatini muscle used a mucosal fold containing the initial cartilage for its downward path to the palate. Moreover, the cartilage is a limited hard attachment for the muscle. Therefore, the PTT and its cartilage seemed to play a critical role in early development of levator veli muscle. In contrast, the cartilage developed so that it extended laterally, along a fascia-like structure that connected with the tensor tympani muscle. This muscle appeared to exert mechanical stress on the initial cartilage. The internal carotid artery was exposed to a loose tissue facing the tubal cartilage. In large fetuses, this loose tissue was occupied by an inferior extension of the temporal bone to cover the artery. This later-developing anterior wall of the carotid canal provided the final bony origin of the levator veli palatini muscle. The tubal cartilage seemed to determine the anterior and inferior margins of the canal. Consequently, the tubal cartilage development seemed to be accelerated by a surrounding muscle, and conversely, the cartilage was likely to determine the other muscular and bony structures.