Electroencephalogram (EEG) and Evoked Potentials (EP)

What is an EEG?

An electroencephalogram (EEG) is a test used to evaluate the electrical activity in the brain. Brain cells communicate with each other through electrical impulses, and an EEG can be used to help detect potential problems associated with this activity.

The EEG test tracks and records brain wave patterns. Small, metal discs called electrodes are attached to the scalp with a specialized conductive cream. The electrodes analyze the electrical impulses in the brain and send signals to a computer, where the results are recorded.

The electrical impulses in an EEG recording look like wavy lines with peaks and valleys. These lines allow neurologists to quickly assess whether there are abnormal patterns. Any irregularities may be a sign of seizures or other brain disorders.

You are being referred for an EEG because your doctor may suspect seizure disorders (such as epilepsy), a head injury, encephalitis (an inflammation of the brain) memory problems, dementia, stroke, a brain tumor or recent behavior changes.

What is an EP?

Evoked potential (EP) tests measure the electrical activity of the brain in response to stimulation of specific sensory nerve pathways. They are able to detect the slowing of electrical conduction caused by damage (demyelination) along these pathways, even when the change is too subtle to be noticed by the person, or too subtle show up on neurologic examination.

Because the diagnosis of MS requires evidence of demyelination in two distinct areas of the central nervous system, EP testing can help confirm the diagnosis by enabling the physician to identify a second demyelinating event that caused no clinical symptoms or was not otherwise apparent.