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Evoked Potentials (EPs)

Overview

Evoked potentials (EPs) are tests that measure electrical responses in the brain or nervous system that are elicited by specific stimuli such as sound or touch. EP tests the intactness and conductivity of the sensory conduction pathways (from the eyes, ears, skin, spinal cord, or nerves) from the peripheral receptor organ to the brain. 

EP tests may be recommended for conditions such as:

  • Optic neuritis (inflammation of the optic nerve causing vision problems)
  • Multiple sclerosis (a disease affecting the brain and spinal cord)
  • Head injury or encephalopathy (to check brain pathway functioning)
  • Hearing disorders and nerve injuries
  • Spinal cord disorders (e.g., compression, trauma, demyelination)
  • Paralysis, muscle weakness, or unexplained sensory loss
  • Monitoring during surgery involving the brain or spinal cord
  • Coma and suspected brain death (to assess prognosis)

  • Electrodes are placed on the scalp over specific brain areas.
  • A stimulus is given depending on the type of EP:
    • Visual Evoked Potentials (VEP): visual patterns like flashing checkerboards or lights are shown.
    • Brainstem Auditory Evoked Potentials (BAER/ABR): clicking sounds are delivered through earphones.
    • Somatosensory Evoked Potentials (SSEP): mild electrical pulses are applied to the skin or nerves to mimic touch/pressure.
    • Motor Evoked Potentials (MEP): the brain or spinal cord is stimulated, and the response in muscles is recorded.
  • The brain’s response is recorded from the scalp electrodes and analysed for latency (time taken) and amplitude (strength of response).

The test usually takes 30–90 minutes, depending on the number of pathways being tested.

  • You can return to normal activities immediately after the test.
  • No lasting side effects are expected.

Disclaimer:

The information in this Health Library is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional with any questions about a medical condition or before starting any treatment. Use of this site and its content does not establish a doctor–patient relationship. In case of a medical emergency, call your local emergency number or visit the nearest emergency facility immediately.