Evoked Potential Studies (BAEP, SEP, and VEP)

All evoked potential tests evaluate the nervous system's pathways. They measure the electrical activity that is initiated or evoked by visual, auditory, or very mild electrical stimulation. Most evoked potentials only record the brains electrical response and do not use direct electrical stimulation to the brain. These three means of eliciting an evoked potential are painless and do not involve significant risk to the patient. The potentials are recorded by the same means as an ENG or EEG with electrodes placed on the head and scalp and on the extremities of the patient. When a potential is recorded the speed is determined and compared to normal values. This helps to determine the health of the nerve pathways or verify multiple sclerosis.

Common Evoked Potential Tests Include:

• (BAEP) Brainstem Auditory Evoked Potential
  BAEP testing evaluates the vestibular system or the pathways from the ear to the brain. The test involves stimulating or eliciting an evoked potential by presenting the patient with auditory stimulation in the form of clicking sounds through earphones. Once the stimulus has evoked a potential the speed of the pathway is determined and a diagnosis may be verified or suggested. AEPs are useful in determining many neurological disorders within the vestibular system, acoustic neuroma, damage or disease in the central nervous system, and multiple sclerosis. Utilizing this test can even evaluate the hearing of an infant by eliciting a response from the brain by an auditory stimulation.
• (SEP) Somato-Sensory Evoked
  SEP testing evaluates the peripheral nerves pathways to the spine and brain. With this test evoked potentials are elicited with very small electrical stimulations (a slight tingle sensation) on the nerves in the arms or legs and the speed of the evoked potential is measured by the electrodes on the scalp. This test is used to detect problems in the spinal cord, nerve roots, effects of trauma causing nerve damage, nerve degeneration, multiple sclerosis, and can be used to differentiate between peripheral nerve disease and central nervous system disease when comparing results of nerve conductive studies (NCVs).
• (VEP) Visual Evoked Potential
  VEP tests examine the pathways involved in sight. To elicit a visual potential the patient is presented with alternating checker board patterns and the potential is measured and quantified. This test can be used in the diagnosis of multiple sclerosis, optic nerve damage, as well as hysterical blindness which is not from nerve damage.

How to Prepare for Evoked Potential Testing
Although, most sedatives should not be taken on the day of the test it is important to discuss any medications with the doctor and whether any need to be discontinued prior to testing.

Hair should be shampooed prior to the test to remove body oils from the scalp and products from the hair. Do not reapply gels, hair sprays, or other hair products.

Hair should be dry and loose not braided or styled with hair pins or jewelry.

Wear loose fitting comfortable clothing.

After the Test
After the test, the technologist will remove the electrodes and clean the scalp of any contacts gels. In some cases the patient may want to shampoo their hair to remove any residual contact gels in their hair left from the electrodes.

There are no residual effects from the test and the patient is free to return to their regular activities.