Tandon O P
Department of Physiology, University College of Medical Sciences, Shahdar, Delhi.
Indian J Physiol Pharmacol. 1998 Apr;42(2):172-88.
Many clinical neurophysiology laboratories have added average evoked potential studies to their routine procedures as evoked potential recording methods are non invasive, highly objective and informative. Indeed, short latency brainstem auditory evoked potentials as well as short and intermediate latency cortical evoked potentials, lately have proved to be valuable clinical tools for objectively testing afferent functions in patients with neurological and sensory disorders. The averaged evoked potential responses (EPR) have been widely used in clinical practice to record the changes in the electrical potentials that occur within the central nervous system (CNS) of the patient in response to an external stimulus. Two types of evoked potentials are usually recorded. 1-Stimulus related, short latency evoked potentials, which represent an obligate neuronal response to a given stimulus and both the amplitudes and latencies of these depend on the physical characteristics of the eliciting stimulus. In this category brainstem auditory evoked potentials (BAEPs), visual evoked potentials (VEPs) and somatosensory evoked potentials (SEPs), have normal values for latencies, amplitudes of waves and characteristic wave form. Any abnormality of these reflects excitation, conduction block in the specific pathways in the CNS. Certain abnormalities in EPR reflect subclinical involvement of CNS even before the disease clinically manifests. Abnormality in BAEPs can in addition, depict the exact site of lesion in the brainstem auditory pathways. Same is true for SEPs where abnormalities in far-field or near-field components, reflect lesions at the plexus, spinal cord, brainstem or thalamo-cortical regions respectively. 2- The event related potentials (ERPs) can be recorded in response to an external stimulus to which person is attentive or an event requiring cognition, discrimination, or reaction to the target stimulus. P300 is one such ERP, helpful in distinguishing between disorders such as dementia and depression. This first review gives a bird's eyeview of the essentials, methods, interpretation and clinical applications of stimulus evoked short latency (brainstem auditory, visual and somatosensory) responses in human beings.
许多临床神经生理学实验室已将平均诱发电位研究纳入其常规检查程序，因为诱发电位记录方法是非侵入性的，具有高度客观性且信息丰富。事实上，短潜伏期脑干听觉诱发电位以及短和中潜伏期皮质诱发电位，最近已被证明是客观检测神经和感觉障碍患者传入功能的有价值的临床工具。平均诱发电位反应（EPR）已在临床实践中广泛用于记录患者中枢神经系统（CNS）内响应外部刺激而发生的电位变化。通常记录两种类型的诱发电位。1. 与刺激相关的短潜伏期诱发电位，它代表对给定刺激的必然神经元反应，其幅度和潜伏期均取决于引发刺激的物理特征。在这一类别中，脑干听觉诱发电位（BAEP）、视觉诱发电位（VEP）和体感诱发电位（SEP），在潜伏期、波幅和特征波形方面有正常值。这些指标的任何异常都反映了中枢神经系统特定通路中的兴奋、传导阻滞。EPR中的某些异常甚至在疾病临床显现之前就反映了中枢神经系统的亚临床受累情况。此外，BAEP异常可描绘脑干听觉通路中的病变确切部位。SEP也是如此，远场或近场成分的异常分别反映了神经丛、脊髓、脑干或丘脑 - 皮质区域的病变。2. 事件相关电位（ERP）可记录对人所关注的外部刺激或需要对目标刺激进行认知、辨别或反应的事件的反应。P300就是这样一种ERP，有助于区分痴呆和抑郁等疾病。这篇综述首先简要介绍了人类刺激诱发的短潜伏期（脑干听觉、视觉和体感）反应的要点、方法、解读及临床应用。
