Evoked Potentials

Assessing the function of neural pathways.

Evoked Potentials (EP) measure the speed and strength of nerve signals in the brain. This is done by testing electrical activity in the brain and the spinal cord in response to stimuli, like visual or somatosensory cues. By recording the time it takes for the brain to respond, we can assess the health and functionality of the neural pathways involved. EPs are used in the diagnosis or exclusion of multiple sclerosis, neuropathy, optic nerve disease and nerve tumours.

Electrodes are applied to the surface of the scalp or skin over the spine, which record the impulses as they pass underneath. Each has a different function and pathway, so the means of stimulating impulses to be recorded will differ.

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Up to 120 minutes.

This measures the electrical activity of the visual pathway, from eye to brain, in response to a visual stimulus, like a flashing light — we use a reversing checkerboard.

How to prepare.

Have clean, dry, oil and product-free hair.
Consume caffeine as you normally would (no need to fast or avoid caffeine).
Get a good sleep the night before as you will need to be alert for this test.
If you wear prescription glasses, bring them with you.

Up to 120 minutes.

This test studies the electrical activity in the brain and spinal cord in response to stimulation of the nerves in the limbs — often the median and ulnar nerves at the wrist or tibial nerve at the ankle.

The stimulation applied to these nerves evaluates how well sensory information travels along them and through the spinal cord to the brain.