Baik M W, Branston N M, Bentivoglio P, Symon L
Department of Neurological Surgery, Institute of Neurology, Queen Square, London, U.K.
Electroencephalogr Clin Neurophysiol. 1990 May;75(5):433-43. doi: 10.1016/0013-4694(90)90088-2.
We related intracranial auditory brain-stem evoked potentials (BAEPs) to the surface BAEP using a model of focal brain-stem ischaemia. In 17 baboons anaesthetised with alpha-chloralose, BAEPs were recorded bilaterally at the mastoids and in the caudal lateral lemniscus (LL) and inferior colliculus (IC), in response to monaural click stimulation. Electrodes at these sites were each connected to the positive input of a differential amplifier, and one other electrode, placed at the vertex, was connected to all the negative inputs. Measurements of local cerebral blood flow (CBF) by hydrogen clearance were made at the LL and IC sites. The LL wave form contained 5-7 positive peaks, the second (B wave) being dominant and coinciding with the negative wave II of the surface BAEP. Following graded ischaemia, produced by basilar artery occlusion and controlled hypotension, the latency changes of these two peaks were significantly correlated, as were those of the third wave (C wave) of the LL response and the surface wave III. In the IC, the contralateral wave form contained 4 positive waves (A-D) and a later, dominant, slow negative wave; changes in its peak latency and those of the slow negative surface wave were similarly correlated. The thresholds of local CBF for increases in latency of waves B and C in the LL were similar (12-15 ml/100 g/min), but in the IC the thresholds were 20, 30-35 and 20-24 ml/100 g/min for the B, C and slow negative waves, respectively. Our data indicate that a gradient of sensitivity to ischaemia is present along the brain-stem auditory pathways; this could explain the earlier change of the late, rather than early, BAEP components as reported in clinical cases involving brain-stem lesions.
我们使用局灶性脑干缺血模型，将颅内听觉脑干诱发电位（BAEPs）与表面BAEP进行关联研究。在17只用α-氯醛糖麻醉的狒狒中，通过单耳短声刺激，双侧记录乳突、尾侧外侧丘系（LL）和下丘（IC）的BAEPs。这些部位的电极分别连接到差分放大器的正输入端，另一个置于头顶的电极连接到所有负输入端。通过氢清除法在LL和IC部位测量局部脑血流量（CBF）。LL波形包含5 - 7个正峰，第二个峰（B波）为主峰，与表面BAEP的负波II相对应。在基底动脉闭塞和控制性低血压导致的分级缺血后，这两个峰的潜伏期变化显著相关，LL反应的第三个波（C波）和表面波III的潜伏期变化也显著相关。在IC中，对侧波形包含4个正波（A - D）和一个较晚出现的、占主导的慢负波；其峰潜伏期变化与表面慢负波的潜伏期变化同样相关。LL中波B和波C潜伏期增加的局部CBF阈值相似（12 - 15 ml/100 g/min），但在IC中，波B、波C和慢负波的阈值分别为20、30 - 35和20 - 24 ml/100 g/min。我们的数据表明，沿脑干听觉通路存在对缺血敏感性的梯度变化；这可以解释在涉及脑干病变的临床病例中所报道的BAEP晚期成分而非早期成分更早出现变化的现象。
