Evoked Potentials

Evoked potentials assess the signal from a peripheral stimulus when the message arrives in the brain. Therefore the entire length of the pathway tested can be assessed for normal function, and with greater sensitivity than that achieved with scans. Nerves convey information via electrical signals. These signals can be recorded by wires placed over the nerves on the surface of the skin, in a procedure called an evoked potential (EP) study. Analysis of the signals can provide information about the condition of nerve pathways, especially those in the brain and spinal cord. Visual, sensory and brainstem auditory evoked potentials are performed.   They can indicate the presence of disease or degeneration, and can help determine the location of nerve lesions. These tests are useful in a wide array of neurological diseases including multiple sclerosis, neuropathy and visual problems.

Reports are generally available within 48 hours of test completion

 

WHY DO I NEED EVOKED POTENTIAL TESTING?

Evoked potentials are important in the diagnosis or exclusion of:

  • Multiple sclerosis
  • Neuropathy (especially proximal forms)
  • Genetic neurological disorders
  • Optic nerve head diseases
  • Diseases of the spine
  • Nerve tumours

 

WHAT TYPES OF EVOKED POTENTIALS ARE PERFORMED?

There are 3 main types of evoked potential tests performed at Sydney Neurology. Please ensure you have a referral requesting a specific test:
Visual evoked potentials are used to diagnose visual losses due to optic nerve damage, especially from multiple sclerosis. During the VEP you will be asked to focus on a red dot in the middle of a checkerboard pattern. Please bring glasses/contact lenses if you wear them. Also ensure that you are well rested and alert when coming for this test.
Auditory evoked potentials are used to diagnose hearing losses. They can distinguish damage to the acoustic nerve (which carries signals from the ear to the brain stem) from damage to the auditory pathways within the brainstem. Most auditory EPs record activity from the brainstem, and are therefore called “brainstem auditory evoked potentials.”
Somatosensory evoked potentials record transmission of nerve impulses from the limbs to the brain, and can be used to diagnose nerve damage or degeneration within the spinal cord or nerve roots from multiple sclerosis, trauma, or other degenerative disease. Somatosensory EPs can be used to distinguish central versus peripheral nerve disease, when combined with results from a nerve conduction velocity test, which measures nerve function in the extremities. Before undergoing a SEP test, tiny electrodes will be placed with a conductive gel on your head, neck, lower back and legs. Please wear comfortable shorts to the test. During the test you will feel a slight electrical “pulse” for a few minutes on your arms and legs.

Please DO NOT apply body lotion or moisturizer to arms or legs. We request that you have clean hair without the addition of hair products.