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Old 02-22-2010, 11:53 AM   #1 (permalink)
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Default Re: Rhythman Update

One comment on EMG, weakness and atrophy. ALS is a disease of the motor nerves that carry signals to muscles. One of the first things that happens as the nerve cells weaken is that they withdraw connections from the muscle fibers. However initially this does not cause weakness, because other nerve cells sprout new branches at the end (similar to how a tree limb can sprout new branches) and these re-connect to the muscle fibers. This process is called denervation and re-innervation. It actually shows up on EMG even before muscle weakness occurs.

Later as the disease gets worse the re-innervation process cannot keep up with denervation. Too many nerve cells are dying and there is a limit to how many new branches the remaining ones can send out. At this point some of the muscle fibers lose connections and can no longer contract. This is when weakness first begins. However many people do not notice weakness even in this stage, for a few reasons. First, we never use the full strength of our muscles. Always we have some fibers firing while others rest. So losing a few percent of muscle fibers still lets them work at full strength, just using a greater percentage of their total capacity. Also, even when this gets worse and a substantial part of the muscle fibers are not working, even then people may unconsciously switch to using other muscles to compensate. They may change their posture, gait, or patterns of movement without realizing it, to spare their weakened muscles. I have read that often as much as 50% of the muscle fibers will have lost nerve connections before people notice.

Finally atrophy happens when the muscle fibers are not being used. The body automatically sends resources where they are needed. A muscle which is used hard will get more resources and will grow. A muscle which is not being used will be broken down and the components sent elsewhere in the body, or just metabolized for energy. The rate varies from person to person and also with nutritional status. This is one reason people are advised to keep their weight up; if you are losing weight your body will be more aggressive about eliminating unused muscle.

This is why in ALS you typically see first a bad EMG, then weakness, then atrophy. If you have weakness and/or atrophy with a clean EMG then that would not be caused by ALS. (Well actually as Wright says, upper motor neuron failure can also cause some weakness, but that produces other symptoms that are very noticeable.) Note that other things can cause atrophy, including simple disuse of the muscle. If it is sore or feels bad and you are not using it, it is natural to have atrophy, especially if you are not eating well. A body builder at the gym gets big, but if he stops his workouts and supplements his muscles will shrink, and that is atrophy.

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Old 02-22-2010, 12:40 PM   #2 (permalink)
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Default Re: EMG weakness and atrophy

Hal, you are super helpful. Thank you for this easy to understand explanation, and for your general help in this section of the boards.

Cheers,

Andy
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Old 02-22-2010, 02:21 PM   #3 (permalink)
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Default Re: EMG weakness and atrophy

Thanks Hal Very helpful
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Old 02-22-2010, 04:25 PM   #4 (permalink)
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Default Re: EMG weakness and atrophy

Hi.

I just wanted to add a comment on this, to ease the mind of many people like me, that are in fear of als because of our symptoms.

- On Weakness and atrophy: Clinical weakness is measured with precision through an EMG test, which also shows the denervation/innervation process typical of a Motor Neuron Disease.

- Take in account that an abnormal EMG can be caused by: Peripheral Neuropathy, Guillan Barre Syndrome, and ALS(jut to name three), in a very basic comparison, they have THE SAME symptoms, or almost the same, and they share nerve damage. Depending of the intensity, and onset of the symptoms they could "look ad feel" pretty much the same. They all can cause weakness, and atrophy, where the PN can be self-limited, just as GBS, with the difference that the second one is usually more aggressive, both in intensity and progression, but in both cases you can recover from both conditions, as opposed to ALS.

- One great truth that's been said in here: Clear EMG equals NO ALS. Period. You can have an abnormal EMG with the two(and many other) conditions I've described before(PN and GBS), both are, in terms of a treatment, incurable, but both are, self-limited in their own particular way. ALS keeps on going, that's the real deal, but they all share this common ground where, it's really easy to mix them up, specially for the not medically instructed people, like most of us.

Kudos for all the Warriors of light, that are here, sharing their knowledge from their own experience.

I can't wait for the day that someone finds a cure for this conditions, I wish you all the very best.
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Old 03-18-2010, 07:05 PM   #5 (permalink)
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Default Re: EMG weakness and atrophy

This is SO interesting! Great post!

So (I hope this is not a stupid question) I dont want to get bashed again, but why then does it take SO long for so many people do get a diagnosis?

If the Dr sees weekness in a limb & performs an Emg, if its negative, doesnt that mean its not als? If thats the case, this should be read by everyone that first comes here. Ive read thru the posts & the majority of them are asking if Emg was clean, do I have als?

Why Not just make a Sticky that says just that, "If ya had an Emg & it was Negative, ya dont got Als"

Is that right? I dont wanna go & twist words around.
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Old 03-19-2010, 12:53 AM   #6 (permalink)
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Default Re: EMG weakness and atrophy

We tell people this all the time "CONGRATS a clean EMG, no ALS," but they do not believe us.
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Old 03-19-2010, 02:23 PM   #7 (permalink)
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Default Re: EMG weakness and atrophy

Quote:
Originally Posted by SilverLining View Post

Why Not just make a Sticky that says just that, "If ya had an Emg & it was Negative, ya dont got Als"

Is that right? I dont wanna go & twist words around.
SilverLining... you mean like the statement in the last paragraph of halfin's excellent explanation? "If you have weakness and/or atrophy with a clean EMG then that would not be caused by ALS. "

So here is very oversimplified summary of this:
1. ALS causes nerves to die.
2. EMG detects effects of nerves dying.
3. For ALS, muscles get weak/atrophy when they lose their nerves (no pun intended).
4. Therefore a weak/atrophied muscle due to ALS will absolutely, positively show up on EMG. Clean EMG = No ALS.

Brian
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Old 04-14-2010, 12:36 PM   #8 (permalink)
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Default Re: EMG weakness and atrophy

I have a question after reading these blogs. If an EMG displays nerves that are dying than why do the nerves continue to feel pain? As I understand ALS patients continue to feel sensations and pain. Are the nerves then communicating with the brain in the same manner as people who experience fantom pain? Or is there a different explanation? Do other people with ALS feel an increase of pain when injured even with minor injuries like stumbing toes? When my cat scatches me and it really hurts.

Could someone explain this to me please?

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Old 04-14-2010, 12:48 PM   #9 (permalink)
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Default Re: EMG weakness and atrophy

Hi Karin - ALS is a disease of the motor nerves that carry signals from the brain to the muscles. It does not affect the sensory nerves or pain nerves that carry signals back to the brain. So it would not be like phantom pain.

I know you are right that many PALS do feel increased pain especially later in the disease. I think most of this is due to inactivity. If the joints and limbs aren't moving very much then they can stiffen up and be more sensitive. Also as muscles atrophy they may no longer be able to hold the joints together properly and that can cause pain. Of course muscle cramps are another source of pain for some people.

I'm not sure what would make you more sensitive to cat scratches. Possibly if you are inactive then your skin may not get as much stimulation as usual and that could make it more sensitive.
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Old 04-14-2010, 08:54 PM   #10 (permalink)
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Default Re: EMG weakness and atrophy

When we first diagnosed, a Neuro told us that ALS is a painless disease. I have seen this Doc a few times at the VA. So glad we have a different Neuro, who understands how it really is! HUGS Lori
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Old 04-21-2010, 12:30 PM   #11 (permalink)
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Default Re: EMG weakness and atrophy

Would that mean that if a neurologist does the emg, ANY muscle will show denervation, (if symptoms of lower motor are already present)?


Just a thought,
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Old 04-21-2010, 08:05 PM   #12 (permalink)
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Default Re: EMG weakness and atrophy

No, only the muscles that have the nerve damage already occurring. AND, they would have to test the right areas. In my husband's case, he has damage in 30 different sites tested on NCT/EMG, but not ALL the nerves in any one area have complete denervated, so the muscles are still functioning-weaker and cramping but still functioning. Hope I explained that clearly...
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Old 04-22-2010, 05:20 AM   #13 (permalink)
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Default Re: EMG weakness and atrophy

what dois this mean? you have to pick the rigth area in the muscle, which shows some damage. or what do you mean by "the right areas"?
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Old 05-06-2010, 12:22 AM   #14 (permalink)
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Default Re: EMG weakness and atrophy

halfin well said
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Old 05-10-2010, 11:27 PM   #15 (permalink)
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Default Re: EMG weakness and atrophy

halfin i was told not to overwork the muscles because there unable to rebuild you qouted that you shoulld yous your muscles to grow.well my phsical therapist also told me they wont get any bigger unable to but to work them out just to keep your srenght. streching is very important for flexability and from keeping the joints from becoming stiff ?

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