Neurophysiological Study on Onset Mechanism of Ear Symptoms in Temporomandibular Disorders

耳鸣、耳痛等耳部症状常见于颞下颌关节紊乱病患者。本研究的目的是通过记录听性脑干反应(ABR)来评价口面部感觉输入对听神经传导的影响。豚鼠用戊巴比妥钠(25 mg/kg)腹腔注射麻醉并用于实验。动物安装在立体定位仪上，将带小扬声器的耳钉插入右侧外耳道。诱发ABR的声刺激由扬声器以卡答声(频率：9赫兹)提供。ABR记录电极安装在皮肤下方正中顶(Cz)和左、右乳突(A1，A2)处。枕部放置参比电极。声刺激的声压在实验开始时为100分贝，然后降低5分贝，直到ABR的所有反应都减弱。每一次S…上的ABR波对100次以上的声压级进行平均，并估计ABR的平均波形。对口面部施加单个和连续的矩形恒流脉冲(持续时间：1mec)进行电刺激。皮下注射辣椒素(100 mg/10μL)作为化学疼痛刺激。对犬的牙周韧带、口腔粘膜和咬肌进行电刺激和化学刺激，刺激前记录ABR作为对照。在注射30μ1辣椒素后记录ABR。刺激前，在记录的ABR中可明显观察到I、II、III、IV、V、VI波，这些反应的潜伏期随着声压的降低而缩短。应用化学刺激法后，ABR反应无明显变化。电刺激后的结果与化学刺激后的结果相同。也就是说，短暂的电或化学疼痛刺激不能引起ABR的改变。这些结果表明，对口腔面部的短暂伤害性刺激不会引起诸如颞下颌关节紊乱病患者的耳朵症状之类的耳功能障碍。因此，有必要进行慢性模型动物实验，用人工错牙合方法制作颞下颌关节紊乱病动物模型。在这些实验中，应观察口面部症状与耳功能障碍的关系。较少

Ear symptoms, such as tinnitus and earache, are observed frequently in the patients of temporomandibular disorders. The aim of this study was to evaluate the influence of sensory inputs from the orofacial area on the auditory neural conduction by means of recording auditory brainstem response (ABR).Guinea-pigs were anesthetized with pentobarbital sodium (25mg/kg) intraperitoneally and used for the experiment. Animals were mounted on the stereotaxic apparatus and were inserted a earbur with a small speaker into right external auditory canal. Sonic stimulation for eliciting ABR was supplied as click sound (frequency : 9 Hz) from the speaker. Recording electrodes of ABR were attached beneath the skin at the median vertex (Cz) and the Ieft and right mastoid (Al, A2). A reference electrode was placed at occiput. Sound pressure of the sonic stimuli was 100 dB at the beginnings of the experiment and then reduced by 5 dB until all of the responses in ABR were diminished. Waves of ABR at each s … More ound pressure level were averaged 100 times and averaged waveforms of ABR were estimated.Single and train rectangle constant current pulses (duration : lmec) were applied for electrical stimulation to the orofacial regions. Subcutaneus injection of Capsicin (100mg/10 μl) was used as chemical pain stimulation. Electrical and chemical stimulation were applied to the periodontal ligaments of canine, oral mucosa and masseter muscles.Before applying stimulation, ABR was recorded as a control. ABRs were also recorded after injection of 30 μ1 of capsicin. Before stimulation, six responses ( Wave I, II, III, IV, V, VI) were obviously obserbed in recorded ABR and the latency of these responses were reduced as reducing the sound pressure. After applying the chemical stimllation, the responses of ABR were not changed. The results after applying the electrical stimulation were the same as the results of the chemical stimulation. Namely, transient electrical or chemical pain stimulation could not induce the change of ABR.These results suggest that transient noxious stimulation to the orofacial region does not cause the ear dysfunction such as ear symptoms observed in temporomandibular disorders patients. Therefore, it suggests the need of chronic model animal experiment, in which model animal with temporomandibular disorders would be made by artificial malocclusion. The relation of orofacial symptoms and ear dysfunction should be observed in thoese experiments. Less