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 / 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.