Visual Evoked Potential (VEP), Brainstem Auditory Evoked Response (BAER) and Somatosensory Evoked Potential (SSEP)
What is an evoked potentials study?
Evoked potentials studies measure electrical activity in the brain in response to stimulation of sight, sound, or touch. Stimuli delivered to the brain through each of these senses evoke minute electrical signals. These signals travel along the nerves and through the spinal cord to specific regions of the brain and are picked up by electrodes, amplified, and displayed for a doctor to interpret.
Evoked potentials studies involve three major tests that measure response to visual, auditory, and electrical stimuli.
Visual evoked Potential (VEP) test
This test can diagnose problems with the optic nerves that affect sight. Electrodes are placed along your scalp and the electrical signals are recorded as you watch a checkerboard pattern flash for several minutes on a screen.
VEP provides information regarding conduction in visual pathway from the retina to brain (occipital cortex). VEP is recommended for following diseases:
Impairment of vision due to:
- Multiple Sclerosis
- Optic Neuritis
- Tumours of the brain (pituitary tumours)
- Head injuries
- Drugs which may cause visual impairment
- In children with mental retardation/ delayed development to assess visual status
Brainstem auditory evoked response (BAER) test
This test can diagnose hearing ability and can point to possible brainstem tumors or multiple sclerosis. Electrodes are placed on your scalp and earlobes and auditory stimuli, such as clicking noises and tones, are delivered to one ear. The sound enters ear canal and stimulates auditory nerve. The electrical impulse travels from auditory nerve through the brainstem to auditory cortex. During testing, the patient hears the repetitive click sound through the earphone. BAER is recommended for following diseases:.
- Hearing problem
- Tumours of the Brainstem
- Delayed development in children
- Dizziness/ Vertigo
- Head Injuries
- Jaundice in children.
- Multiple Sclerosis
Somatosensory evoked Potential (SSEP) test
This test can detect problems with the spinal cord as well as numbness and weakness of the extremities. For this test, electrodes are attached to your wrist, the back of your knee, or other locations. A mild electrical stimulus is applied through the electrodes. Electrodes on your scalp then determine the amount of time it takes for the current to travel along the nerves to the brain.
SSEP is recommended for following diseases:
- Numbness/ weakness of arm or leg.
- Diseases of the spinal cord.
- Multiple Sclerosis.