Evoked potentials and their clinical application

Electrical activity evoked in a sensory pathway by an external stimulus is termed an evoked potential (EP). EPs are one class of investigations within electrophysiology which also includes areas such as electromyography and electroencephalography. The methodology of recording an EP is well-documented and primarily relies on techniques to detect and extract small responses from a somewhat noisier background signal. The activity being recorded from suitably sited electrodes, typically surface scalp electrodes. The three main modes of stimulation in clinical practice are auditory, visual and somatosensory and each provides a valuable, objective means of investigating the functioning of their respective pathways and diagnosis of pathology. EPs also play a major part in the intraoperative monitoring of surgical procedures. The practical application of EPs will be discussed both in their diagnostic role and as monitoring tools in the operating theatre.