Absent F Waves
AnonymousMarch 18, 2008 at 9:17 am
I took this from Wikipedia:
“In a typical F wave study, a strong electrical stimulus is applied to the skin surface above the distal portion of a nerve so that the impulse travels both distally (towards the muscle fiber) and proximally (back to the motor neurons of the spinal cord). (These directions are also known as orthodromic and antidromic, respectively.) When the orthodromic stimulus reaches the muscle fiber, it elicits a strong M wave indicative of muscle contraction. When the antidromic stimulus reaches the motor neuron cell bodies, the impulse is reflected and travels back down the nerve towards the muscle. This reflected stimulus evokes the second, weaker F wave when it reaches the muscle.”
I also found this:
“Absence of F-wave, or shortest F-wave latency more than 130% of the upper limit of normal, in at least one nerve.” is indicative of CIDP.
So basically, if I’m reading this correctly, in an EMG if the shock wave doesn’t come back to the spot where the shock was originated then the person is considered to have absent F waves.
To answer your question directly…absent F waves mean that the signal goes out to the spinal cord but isn’t getting back down the nerve to the muscle…basically.
Hope that helps (and that I interpreted the info correctly),
AnonymousMarch 18, 2008 at 9:20 am
F waves are the measure of the conduction rate from the point of stimulus back up to the motor neuron cell body and then back down to the point of the stimulus. An absence of a measurable F wave could mean that you have a nerve conduction problem closer to your spinal cord than the point of stimulus. I looked it up because, of course, I went through a period where I had no measurable F waves. We really do seem to have a lot of similar symptoms Kazza! They are at least measurable now though the last time we checked they still weren’t normal.
AnonymousMarch 18, 2008 at 5:26 pm
Kazza, I have absent f waves also. Never been right from the start;) I was told I had nerve damage from some unknown previous injury—just like the unknown major depressive disorder that some drs told me I have—the way I see it is the drs still aren’t educated enough on cidp. Do you have reflexes? I don’t have those either:rolleyes:
AnonymousMarch 18, 2008 at 8:21 pm
Thanks for explaining everyone. My wonderful Neuro does explain things to me – but as soon as I’m out his door I forget! I need to take notes!
Yes, Julie we do have a lot of symptoms that are very similar (lucky us!) especially the cranial nerve problems – which I don’t think are as common in CIDP – as I think it has a propensity for the longer nerves.
Cheryl, No, I haven’t had any reflexes for ages either. I love the little rabbit next to your user name!
Kelly, Yes your info really does help! – thanks for the effort in typing out what you researched.
I have motor involvment as well, but I think its the sensory stuff that is worse overall.
Thank you again,
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