Neurophysiological Study on Onset Mechanism of Ear Symptoms in Temporomandibular Disorders

耳部症状，如耳鸣和耳痛，在颞下颌疾病患者中经常观察到。本研究的目的是通过记录听觉脑干反应（ABR）来评估来自口面区的感觉输入对听觉神经传导的影响。实验用戊巴比妥钠（25mg/kg）腹腔麻醉豚鼠。动物被安置在立体定向装置上，并在右外耳道插入带有小扬声器的耳塞。激发ABR的声音刺激是由扬声器提供的咔嗒声（频率：9 Hz）。ABR记录电极附着于皮肤下正中顶点（Cz）和左右乳突（Al, A2）。在枕部放置参比电极。实验开始时声刺激的声压为100 dB，然后降低5 dB，直到ABR的所有反应都减弱。对各压力水平下ABR波进行100次平均，得到ABR波的平均波形。采用单次和连续矩形恒流脉冲（持续时间：1mec）对面部区域进行电刺激。皮下注射辣椒素（100mg/10 μl）作为化学疼痛刺激。对犬牙周韧带、口腔黏膜和咬肌进行电刺激和化学刺激。在施加刺激之前，记录ABR作为对照。注射辣椒素30 μ1后，记录abr。刺激前，记录的ABR中明显观察到六种反应（波I、波II、波III、波IV、波V、波VI），这些反应的潜伏期随着声压的降低而缩短。施加化学刺激后，ABR的反应没有变化。电刺激后的结果与化学刺激的结果相同。即短暂的电或化学疼痛刺激不能诱导ABR的变化。这些结果表明，对口面部区域的短暂有害刺激不会引起耳部功能障碍，如在颞下颌障碍患者中观察到的耳部症状。因此，提示有必要进行慢性模型动物实验，通过人工错牙合制作颞下颌关节疾病模型动物。在这些实验中应观察口面部症状与耳功能障碍的关系。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