What do evoked potentials do and how is it done?

[wizardsmom6]

I need some advice, I am having an evoked potential test on my spine on Thursday, I wondered if any one could tell me about how this is done and what they are looking for.

Thanks!

[22cyclist]

Evoked potentials are a set of three tests.

1. the visual evoked potential. you will be wired up with electrodes like when patients have seizures, only less. You will also have two close to your eyes. Then, you will be placed in front of a TV screen. They will monitor your your eye movement as you watch a red dot projected onto a screen the uses a reverse pattern black box test. All this means is that there is a checkerboard in there that moves backwards, it looks like it moves forward, at least to me, but all of this checks for the latency of the optic nerve.

The latency means the time it takes for the signal to leave the optic chiasm and reach the eye surface down the optic nerve.

;
2. The second test is called the BAER or bear. This test determines if there is a lesion hiding out in your brainstem, or if it is a simple ear problem that you have. You keep your lovely hair piece on and they add a few more probes to your ears and around your facial area. When they are done, you will be given earphones to listen to for pings. The examiner will then control the rate and placement of these pings. You don't have to do anything but let it record. Just lie there and look happy. The pings make no sense so don't try to make anything out of them. Like I said they are testing both your hearing, and your brain.

3. SSEP (Somatosensory evoked potential): This one is for the legs and the arms. You will keep your lovely headwear, and gain some more electrodes on your arms and legs. During this time they usually give you some low dose valium to keep you calm and sleepy during the test. After you are wired up, they will get you comfortable in the bed and they are ready to start the test. This test can be painful, you arms and legs can jerk everywhere.

At the end of the test they are looking for is a latency in the time of the trigger (when they sent out the shock), to the response. If that time is delayed you may need an MRI.

Good luck. Bring a driver.

Lisa

[poohb3ar]

wow, lisa gave you a great detailed answer.
i've had lots of evoks but don't remember all that detail.

i remember the computer one is pretty fun, except when i almost fell out of my chair from dizziness!

i don't remember ever having a SSEP. i have had where needles are poked into me on legs, arms,etc. then electric current (very small, but a bit painful) runs through to see how well your body is transmitting messages to the brain. but i believe that is called a nerve conductive test. i've had several and depending on the dr. they're not too bad.

you will be worn out after all the tests, so have somebody with you.

praying that all goes well for you!

take care & GOd bless ya!

[wizardsmom6]

Wow

Thank you! That was very detailed and I understood what you said! (cognitive problems ). I really appreciate it.

Thanks again!

[piper]

Why does a doctor order an Evoked Potentials Test? Is there a symptom that causes a doctor to want to order them?

[22cyclist]

Sometimes evoked potentials are ordered before an MRI when looking for MS just to detect any abnormalities. It is cheaper than an MRI and is actually more sensitive. Some order them after an MRI if the MRI is negative to check and see if there are any abnormalities that the MRI didn't pick up, like a very small lesion that can not yet be seen on MRI.

Lisa