Evoked Potentials

Evoked potentials provide a noninvasive, sensitive, and quantitative way to assess the functional integrity of the somatosensory, auditory, and visual pathways. The basic principle of evoked potentials is to apply a stimulus (sensory, auditory, or visual) in a controlled manner to create a volley of depolarization and repolarization. This stimulus volley ascends through the peripheral and central sensory, auditory, or visual pathways and can be recorded as the signals pass underneath recording electrodes. The generated evoked potential waveforms can represent either a traveling wave of depolarization in white matter or a stationary depolarization within gray matter. The use of somatosensory and brainstem auditory evoked potentials for outpatients has decreased in the past decades as the quality and availability of neuroimaging have improved; however, their use has had a resurgence in electrophysiologic monitoring and mapping of surgical cases involving the spine, posterior fossa, and supratentorial lesions, for which they are now a part of the standard of care.