A Study on the changes of latency and amplitude of brainstem auditory evoked potentials due to cochlear nerve injury: an analysis of their correlations

脑干听觉诱发电位（BAEP）在手术中的监测已被广泛应用，以减少术后听力障碍的发生率，由于小脑脑桥角的操作。脑干听觉诱发电位V波延长常作为提示外科医生调整手术策略的依据。然而，目前尚不清楚是否所有的神经病理学变化，如果BAEP潜伏期术中恢复到基线水平，或一些神经病理学变化“悄悄”发生，即使BAEP正常化。本研究的目的是通过实验阐明这一点，这将是重要的长期预后患者的hearing.The小脑脑桥角部分的听觉神经定量压缩大鼠和可逆性延长BAEP潜伏期再现，就像它发生在手术中的人。压迫24 h后取听神经行β-APP免疫组化染色，观察轴索损伤程度。本研究的结果表明，轴突损伤甚至发生在延长的IV波（相当于人类的V波）潜伏期的术中正常化的情况下。因此，仅根据BAEP潜伏期的延长来解释BAEP的变化不足以阻止听神经发生形态学改变。BAEP V波振幅的变化比潜伏期的变化更能反映听神经轴索损伤的程度。

Intraoperative monitoring of brainstem auditory evoked potentials (BAEP) has been widely utilized to reduce the incidence of postoperative hearing disturbance due to cerebellopontine angle manipulations. The prolongation of wave V of BAEP is usually used as a criterion to warn the surgeons to modify their surgical maneuvers. However, it is not known whether all neuropathological changes are avoided if BAEP latency intraoperatively returns to the baseline level or some neuropathological changes "silently" occur even if BAEP normalizes. The aim of this study was to experimentally clarify this point that would be important for the long-term prognosis of patients' hearing.The cerebellopontine angle portion of the auditory nerve was quantitatively compressed in the rats and reversible prolongation of BAEP latency was reproduced just as it occurs during surgery in humans. Twenty-four hours after the compression, the auditory nerve was removed for β-APP immunostaining to investigate the degree of axonal injury. The results of the present study disclosed that axonal injury occurred even in the cases where the intraoperative normalization of prolonged wave IV (equivalent to wave V in humans) latency had been obtained. Therefore, the interpretation of BAEP changes based only on the prolongation of the latency of BAEP was not enough to prevent the auditory nerve from developing morphological changes. Changes in the amplitude of wave V of BAEP appears to be more sensitive than its latency change as an intraoperative indicator for axonal injury in the auditory nerve.