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Diagnostic tests? MRI, NCV, EMG

Posted by lara on 8/07/03 at 10:19 (126469)

Several people have recently posted that their TTS was diagnosed by one of the above mentioned tests (or at least that the test was part of the picture the doctor considered when diagnosing things. My understanding was that the NCV test is the 'gold standard' (such as it is, with many false negatives but few false positives) for TTS (although the doctors may have been ruling out other things rather than trying to rule in TTS when ordering the tests), and the the MRI was useful if going in for surgery to see WHY there is a problem, and I'm not sure what an EMG would show?

How do each of these tests help with diagnosing various foot problems.

It seems to me that given the number of people on this board who have been misdiagnosed, it would be important to get a clear understanding of what tests are appropriate to learn what information.

Am I right? wrong? muddled? confused?

Re: Diagnostic tests? MRI, NCV, EMG

chrisb on 8/08/03 at 11:12 (126570)

Just a request for clarification - NCV is the nerve conduction test, right? I've had one, and it was negative with only slight latency -- they told me of course that a negative result doesn't necessarily rule out TTS.
But what is the EMG? And what does it measure?
Thanks

Re: Diagnostic tests? MRI, NCV, EMG

Sharon W on 8/08/03 at 14:26 (126585)

No, the EMG and the NCV are separate tests. The EMG measures the ability of your nerves to activate your muscles. The NCV measures how fast an impulse is conducted down a nerve. Of course, when these tests are done they are often both done together and the doctor usually measures several nerves, and/or measures the nerve in different areas.

It IS kind of confusing...

Sharon
:-/

Re: Diagnostic tests? MRI, NCV, EMG

lara on 8/08/03 at 14:33 (126586)

Good point Chris. I did a couple of quick searches and found the following:

EMG = ELECTROMYOGRAM: A device which displays a graph which corresponds to the electrical currents in muscles. (I didn't know this one so looked it up in a dictionary - sounds similar to an NCV - see below for some sense of the relationship of the two)
(http://www.jklcompany.com/e.html)

NCV= nerve conduction velocity. Nerve conduction velocity (NCV) is a test of the speed of conduction of impulses through a nerve.
The resulting electrical activity is recorded by the other electrodes. The distance between electrodes and the time it takes for electrical impulses to travel between electrodes are used to calculate the nerve conduction velocity.
Electromyography is often done at the same time as the NCV test.
(http://www.nlm.nih.gov/medlineplus/ency/article/003927.htm)
My understanding is the same as yours - a negative result doesn't rule out TTS, but positive is pretty reliable.

MRI - Magnetic Resonance Imaging - My understanding this is good at 'seeing' things that might be causing the problem, but doesn't actually tell you if the nerve is impinged.

Re: Diagnostic tests? MRI, NCV, EMG

lara on 8/08/03 at 14:34 (126587)

Sharon wrote her response while I was on my response. :~ I think her answer is better - and easier to understand.

Re: Diagnostic tests? MRI, NCV, EMG

cindyp on 8/08/03 at 18:54 (126609)

i don't know about any other tests. i just had a mri and the dr. took one look and said you need tts surgery .