Merck Manual

Please confirm that you are a health care professional

honeypot link

Measurement of Evoked Responses (Potentials)


Michael C. Levin

, MD, College of Medicine, University of Saskatchewan

Last full review/revision Jul 2021| Content last modified Jul 2021
Click here for Patient Education

Visual, auditory, or tactile stimuli are used to activate corresponding areas of the cerebral cortex, resulting in focal cortical electrical activity. Ordinarily, these small potentials are lost in EEG background noise, but computer processing cancels out the noise to reveal a waveform. Latency, duration, and amplitude of the evoked responses indicate whether the tested sensory pathway is intact.

Evoked responses are particularly useful for the following:

When integrity of the brain stem is in question, brain stem auditory evoked responses is an objective test.

Somatosensory evoked responses may pinpoint the physiologic disturbance when a structural disorder (eg, metastatic carcinoma that invades the plexus and spinal cord) affects multiple levels of the neuraxis.

Somatosensory evoked responses can also help predict the prognosis of patients in a coma, particularly those with hypothermia, when the usual bedside indicators are unclear.

Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read
Test your knowledge
Thiamine Deficiency
Thiamin deficiency causes beriberi. It is most common among patients with alcoholism and people subsisting on white rice or highly refined carbohydrates. Early symptoms of all types of beriberi are nonspecific and include fatigue, poor memory, anorexia, and abdominal discomfort. As beriberi progresses, different forms of this condition cause different symptoms. Of these symptoms, which of the following is most indicative of dry beriberi?
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest