Visual Evoked Responses or VER's is a painless test used to detect plaques in
optic nerves, chiasm or tracts. Electrodes are placed on the scalp along the
vertex and the cortex lobes. You sit in front of a computer-like monitor and
watch a strobe light flash or a reversible checkerboard pattern flash on the
screen. This provides the visual stimulus to the eye and causes an
electrical response in the occipital region of your brain that can be
recorded with electrodes similar to an EKG or EEG. Electricity passes only
from your brain to the machine. The machine then records the length of time
it takes the signal to go from your eye to the occipital area. Abnormal
responses are found in 85 to 90% of those with definite MS and 58% of those
with probable MS - no stats on TM were mentioned.
Auditory Brainstem Evoked Potentials or ABEP's is a painless procedure most
useful in detecting suspected lesions in the cochlear divisions of the 8th
(vestibulocochlear) nerve, the auditory pathways of the brainstem.
Electrodes are placed on the scalp along the vertex and on each earlobe. Ear
phones are placed on the patient and a series of clicking noises or tone
bursts are played. The test is performed on both ears to detect lesions in
the auditory pathway. There are abnormal responses in 67% of patients with
definite MS and 41% of those with probable MS - no stats on TM patients
mentioned.
Somatosensory Evoked Responses or SER's is not a painful test however it may
be slightly uncomfortable. It is useful to detect sensory abnormalities.
Small electrodes are placed on the scalp, each wrist (medial nerve) and the
knees (peroneal nerve) or ankles. It takes about 30 minutes. Electrical
stimuli is applied via the electrodes and the time it takes the current to
travel along the nerve to the cortex of the brain is measured. The current
is small. Abnormalities are seen in 77% of patients with definite MS and 67%
of patients with probable MS - no stats on TM patients mentioned.
Your Doctor may order 1 or all 3 of the above - I had all 3 which took
approx. 2 hours start to finish - none of it was painful but you look like
Frankenstein by the time you're finished because they need to cleanse the
area on the scalp where they will affix the electrodes and then they apply
some "goop" to make the electrodes stick and conduct the current. Once it's
all done they try to do a good job in cleaning most of the stuff from your
scalp but
you come out looking a bit different than when you went in. You're supposed
to have freshly washed hair with no gel, mousse or hairspray on it and I was
advised to wear shorts and a short-sleeved T-shirt. The results are printed
and analysed by a Neuro and the results sent to your Dr. - my results took
about 2 weeks.
Good luck - and remember, there's no pain involved!
Ginny
Toronto, Ontario
Canada