Somatosensory Evoked Potential (SSEP)

It is a test in which we stimulate the nerves in the arm and leg with electrical impulses and record the response from the brain and other parts of the body. The responses are recorded by a computer and the tests interpreted afterwards by a Doctor. It is performed to assess the condition of the nerve pathway. There are no known complications or risks to having an SSEP performed.

Visual Evoked Potential (VEP)

A visual evoked potential is an evoked potential caused by a visual stimulus, such as an alternating checkerboard pattern on a computer screen. Responses are recorded from electrodes which are placed on the back of your head and are observed as a reading on an electroencephalogram (EEG). These responses usually originate from the occipital cortex, the area of the brain involved in receiving and interpreting visual signals. The test is useful for detecting optic nerve problems. It measures the time that it takes for a visual stimulus to travel from the eye to the occipital cortex. The test is also useful because it can be used to check vision in children and adults who are unable to read eye charts. A normal VEP can be fairly sensitive in excluding a lesion of the optic nerve, along its pathways in the anterior part of the brain.

• It is a standardized and reproducible test of optic nerve function.
• It is more sensitive compared to magnetic resonance imaging (MRI) in detecting lesions affecting the visual pathway in front of the optic chiasm (area in the optic pathway where the optic nerve crosses sides).
• It is usually less costly compared to other investigations such as MRI.
• If results of the VEP are negative, this can be useful in excluding certain disorders.