Information On The Types of Evoked Potential Tests

Submitted on March 27, 2012

The evoked potential test is used to diagnose a condition called MS or multiple sclerosis. Multiple sclerosis is a condition that affects the brain and the spinal cord. At its advanced stage, this disease can cause a blockage of communication between the nerves and the brain leading to symptoms such as

  • Disturbances in the vision
  • Muscular weakness
  • Lack of memory
  • Unable to balance and co-ordinate body movements
  • Feeling numb or a prickling sensation at the various parts of the body

Multiple sclerosis, if not treated and diagnosed at an early stage, can lead to total loss of speech, vision, hearing, and movements of the limbs.

The test basically measures the time taken for a response to reach the brain from a nerve point. Analysis of the quality and strength of the response helps a doctor in the analysis of a potential multiple sclerosis condition.

Types of This Tests

There are 3 types of evoked potential tests that are most commonly used. They are called the VER or the visual evoked response, BAEP or the brainstem auditory evoked potential, and SSEP or the somatosensory evoked potential.

All of these tests involve measurement of responses from the scalp of the head. The location of the test changes according to the specific evoked response that is being measured.

Visual evoked response test (VER)

A VER is the most commonly used test that is used to identify multiple sclerosis. An evoked potential test is a relatively short procedure that is completed within a maximum of one hour. To perform this test, the patient is asked to look at a computer screen that flashes checkerboard patterns of different sizes. In some cases, a strobe light is used instead of a flashing checkerboard. One of the patients eyes are closed when the test is performed and the same is repeated with both eyes.

Brainstem auditory evoked potential test (BAEP)

This test is more auditory in nature, and the patient is asked to listen to various test tones. These tones can be clicking sounds, beeps, and various other types of sounds. The patient is given a headphone to listen to these sounds.

Somatosensory evoked potential test (SSEP)

This test involves simulation of the nerves in the arms and legs using an electrical pulse. The electrical pulse is delivered to the skin using small electrodes that are stuck near the knees, elbows, or the wrist. Some may find this test to be uncomfortable as the procedure involves giving a very small electrical shock.

Of all the three tests mentioned, VER provides the most accurate results and is recommended by most doctors.