Editing Evoked potential (section)

== Intraoperative monitoring ==
Somatosensory evoked potentials provide monitoring for the dorsal columns of the spinal cord.  Sensory evoked potentials may also be used during surgeries which place brain structures at risk.  They are effectively used to determine cortical ischemia during carotid endarterectomy surgeries and for mapping the sensory areas of the brain during brain surgery.

Electrical stimulation of the scalp can produce an electric current within the brain that activates the motor pathways of the pyramidal tracts.  This technique is known as transcranial electrical motor potential (TcMEP) monitoring.  This technique effectively evaluates the motor pathways in the central nervous system during surgeries which place these structures at risk.  These motor pathways, including the lateral corticospinal tract, are located in the lateral and ventral funiculi of the spinal cord.  Since the ventral and dorsal spinal cord have separate blood supply with very limited collateral flow, an anterior cord syndrome (paralysis or paresis with some preserved sensory function) is a possible surgical sequela, so it is important to have monitoring specific to the motor tracts as well as dorsal column monitoring.

Transcranial magnetic stimulation versus electrical stimulation is generally regarded as unsuitable for intraoperative monitoring because it is more sensitive to anesthesia.  Electrical stimulation is too painful for clinical use in awake patients.  The two modalities are thus complementary, electrical stimulation being the choice for intraoperative monitoring, and magnetic for clinical applications.