EVOKED POTENTIALS

The nervous system uses electrical energy to carry messages smoothly along nerve cells to the brain. Systems of nerves which send messages to the brain are called sensory nerve pathways. Damage to the nervous system can affect how well sensory nerves send messages to the brain.

ABOUT THE EVOKED POTENTIALS (EP) TEST

Evoked Potentials (EP) tests check the condition of sensory nerve pathways. These computerized tests help locate the site of nerve damage and help evaluate the patient's condition. There are three types of EP tests. Each uses a mild stimulus to cause the nerves to react and send a message to the brain. Electrodes record how the brain and spinal cord respond. These electrodes are placed on the skin or scalp by a paste which easily washes or shampoos off. The responses are analyzed by a computer and printed as a wave pattern. This pattern may reveal certain problems and show where any damage is along the nerve pathway.

BRAINSTEM AUDITORY EVOKED POTENTIAL (BAEP)

The BAEP evaluates the nerve pathways from the ears to the brain. Electrodes are attached to your scalp and earlobes. Earphones are placed over your ears and you will hear rapid clicking noises. The test takes approximately 20-30 minutes.

VISUAL EVOKED POTENTIAL (VEP)

The VEP evaluates the visual nervous system from the eyes to the brain. Electrodes are attached to your scalp and you are asked to stare at a pattern on a video screen. Each eye is tested separately. The test takes approximately 15 minutes.

SOMATOSENSORY EVOKED POTENTIAL (SSEP)

The SSEP assesses the pathways from the nerves in the arms or legs through the spinal cord to the brain. Electrodes are placed on your scalp and along the spine, and a small electrical current is applied to the skin near nerves on arms or legs. This current creates a tingling sensation, but is not painful. Each leg or arm is tested separately. The test takes approximately 45-60 minutes.

ELECTROCOCHLEOGRAPHY (ECoG)

ECoG measures the electrical responses generated in the inner ear in response to sound stimulation.