Amyotrophic Lateral Sclerosis (ALS) / Motor Neuron Disease (MND) - Part I

Motor Amplitude  in ALS                                                                                  top

Question

What is the motor amplitude? Is it pathologically higher or lower than normal in ALS/MND?

Answer 1

The motor unit potential (MUP) gets higher in MND. While the compound muscle action potential (CMAP) is normal initially, but in advanced disease gets lower (even absent) due to severe loss of axons.

Answer 2

SNAPS or sensory nerve action potentials should be characteristically normal in ALS as the disease affects the anterior horn cell, (Amyotrophy) a motor neuron disease. If the SNAP is abnormal consider a concomitant neuropathy of different etiology or revise your diagnosis to something other than ALS

Abnormal motor units in ALS                                                     top

Question

I have read there is a connection (in ALS) between abnormal motor units (large amplitude) and the appearance of fasciculations- which means if there are ALS fasciculations - there will also be abnormal units - Is that true? And if not, how much time would it take for abnormal units to appear if there are already ALS fasciculations? (Weeks, months..)?

Answer

Fasciculations (at least Motor Neuron fascics) are a sign of ongoing reinnervation and can actually begin distally in regenerated nerve fibers. By the time fascics develop in ALS, you should see a good deal of neurogenic potentials

Comment

What do you mean by neurogenic potentials? Do you mean neurogenic units - the abnormal motor units (amplitude etc.)? Second, so according to your answer if a person fasciculates for months and It is due to ALS (malignant fasciculations)- His motor units should be abnormal (huge amplitude and so on)? How much time on average does it take from the beginning of ALS fasciculations to the appearance of abnormal motor units (neurogenic units)

* I am asking it because I have read that abnormal motor units (huge amplitude.) are more common with chronic long standing denervation

Answer

Yes neurogenic units means polyphasic units, later on with high amplitude. In my experience, I see the neurogenic units before I see the fascics, or very close to them in time

Are there 2 types of fasciculations in ALS?                                              top

Question

I know that fasciculations in ALS are due to nerve irritation (the same as in benign fasciculations?)- However in one of the posts it was said that fasciculations are due to ongoing reinnervation (the ones seen in EMG) are there two types of fasciculations in als??

Answer

No, in ALS (even normal or other conditions), it is one kind of fasciculation. Clinically this refers to visible twitching of the muscle and are seen in the EMG needle examination as fasciculation potentials. Fasciculations may mimic normal or abnormal motor unit potentials (MUPs) as seen in on-going reinnervation. There is no "infallible" way to tell whether the fasciculating discharge by itself is benign or malignant. The decision is made by what kind of company they keep. In a study in 1993, a total of 121 patients with benign fasciculations were followed up to 32 years, none developed ALS (Blexrud et al, in Ann Neurol 1993;34:622-625).

Comment

Referring to your answer: in ALS - Do you find fasciculations only when there is on going reinnervation? Isn't it possible to find/have them during denervation - before reinnervation starts?

And if so, I know It is common for people with ALS to have them as a very very early sign - does it mean that when they feel/notice them- they are already in the reinnervation phase (after denervation)? And if so, how come fasciculations are an early sign of ALS (as reinnervation takes place much later)

Answer

Yes, I agree that patients with ALS may present with fasciculation. In one report (letter), 6.7% of ALS patients had fasciculations as an isolated, initial manifestation of the disease (Eisen and Stewart. Ann Neurol 1994;35:375-376). Practically, all the patients I have seen got the fasciculation (if present) with other signs of denervation and neurogenic MUPs of variable degree. About your point do fascics specifically occur before or after the onset of reinnervation in ALS, I do not know. However, the single fiber EMG jitter reveals that reinnervation could be detected in the fourth week (increased jitter) after muscle transplant in healthy nerve and muscle fibers.

Interference pattern in ALS                                                      top

Question

In anterior horn cell disease, there is a reduced recruitment (not full interference pattern) does it matter how long does it take for a person to build the full interference pattern (by increasing exertion)? Because I read somewhere that ALS patients just cannot build the full interference pattern, even after a lot of time because they lack these motor units. So, FOR ALS DIAGNOSIS, does it matter how long does it take to reach it? I mean, Is it true to say that if a person has anterior horn cell degeneration - he will never be able to reach a full interference pattern, even after minutes?

*I know that in muscle fatigue, there is a full interference pattern, however it takes much more time to reach it - is that true?

Answer

Yes, in ALS there is motor units loss, therefore, those patients have a reduced interference pattern or reduced recruitment. Whatever they do, they do not reach the full recruitment pattern. This is very much noticeable if there is significant motor units loss. As a matter of fact this is also true for other neuropathic conditions, for instance, peripheral neuropathy. So, reduced recruitment is not specific for ALS.

Fasciculations and ALS                                                           top

Question

A couple of questions:

1) I have at least a thousand fasciculations a day. How come during the 3 EMG's (2 partials, 1 full) no fasciculations were detected? Seems impossible.

2) Besides random fasciculations, I frequently have fasciculations right after moving a muscle. Is this more problematic than a "random" fasciculation?

3) Is it likely that twitching can occur for six months without loss of strength and still get diagnosed with ALS???

Answer

Actually it is not always surprising if the concept of EMG needle recording is understood. If the tip (or the recording pick up area) is far from fasciculating potential, then you do not see any fasciculations on the screen. For the second question, yes it is possible, and that is why a follow up EMG is usually needed. Regarding time period after onset of twitching without weakness or an abnormal EMG, it is difficult to be absolutely precise in time. But several months are usually acceptable by the time fasciculation is seen, but provided no other clinical/EMG findings.

Thoracic paraspinals EMG Specificity in ALS                                     top

Question

Is it true that in ALS there is a specificity of the thoracic paraspinals and that they are almost the first ones to show prominent denervation (PSW, fibs etc..) - my neuro told me that if I had ALS, He would have seen that immediately when sticking the needle there. What is your experience in this specificity (thoracic paraspinals show denervation FIRST and most profound one). HAVE you seen any ALS patients who had denervation in limb muscles but had completely clear thoracic paraspinals then (in your long experience).

Answer

If you look at the WFN El Escorial criteria for diagnosis of ALS; as follows: 1. LMN signs (by clinical, electrophysiological, or neuropathological exam) in 1 or more of 4 regions (bulbar, cervical, thoracic and lumbosacral) 2. UMN signs (by clinical exam) in 1 or more of the 4 regions. AND Progression of signs within a region and progression to involve other regions. Therefore, from item one we cannot say that thoracic paraspinal abnormal EMG is specific for ALS, otherwise we do not need other factors to diagnose the disease, and may have false positive diagnosis. However, let me address this point in a different way, they are very useful muscles when a cervical or lumbosacral radiculopathy is a strong consideration, then an abnormal EMG in the thoracic paraspinals would indicate a more widespread neurogenic involvement in favor of ALS, as radicular thoracic lesions are uncommon or rare by comparison to cervical or lumbosacral lesions.

Comment

So, Isn't it true that there is some specificity for the thoracic paraspinals in ALS denervation?

Answer

I too have read about the specificity of the paraspinals, and probably know where you saw it.

However, at the MDA clinic my EMG was overseen by well known author, who has written some of the standard texts on EMG and disease processes and he said this was just a "neurological wives tale." In addition, in one study I found on about 750 PALS, only about 50% showed denervation in the thoracic paraspinal muscles vs. 90%+ showing denervation in their arms.

Fibrillations and Fasciculations in ALS                                           top

Question

In a previous post, I brought a citation from "Cecil" textbook of medicine which claimed that in the course of lower motor neuron injury (ALS and related conditions), fibrillations appear first and later fasciculations. Is this true??? Have you seen such pattern with your ALS (or other lower motor neuron) patients?

Answer

Yes, I have seen such pattern of appearance of fibrillation first. It is however the combination of findings that is the usual pattern

Peripheral neuropathy versus ALS/MND                                        top

Question

I know there are theoretical ways to distinguish (in EMG) peripheral neuropathy (where there is a damage to the peripheral nerves) and ALS (where there is a primary damage to anterior horn cells (CNS). however I know fibs and positive sharp waves as well as reduced recruitment are features of both. So how is the distinction and later the diagnosis made by EMG and NCV - How can you know where is the source of the damage to nerves (central or peripheral) because in both conditions there are exact signs of denervation?

* My question refers to peripheral neuropathy of the kind, which is predominantly motor (so you cannot distinguish by lack/presence of sensory signs) and is quite widespread. How the distinctions are made?

I refer in my question to AXNONAL neuropathy with actual damage to the axons (NOT demyelination where it is obvious due to very slow velocities.)

Answer

In ALS or peripheral neuropathy the diagnosis depends on the history and clinical presentation. Some points to differentiate: the reflexes are brisk in ALS while they are absent in neuropathy. In EMG, in axonal neuropathy and ALS you may have the same findings. But the examination of sensory nerve action potentials is important. They are normal in ALS but they are affected in neuropathy.

Motor neuropathy and ALS                                                       top

Question

You said that ALS and axonal neuropathy cannot be distinguished by EMG due to similar findings but what about nerve conduction velocity - I read that in ALS they are normal (not slowed) aren't they ALWAYS slowed in motor axonal neuropathy? (Is it possible to have motor neuropathy of axonal type with normal velocities)??? The question is about the velocities because as far as I am concerned the CMAP (amplitude of motor nerves) is very reduced early in both conditions so you cannot rely on that. (Correct??)

Answer

Yes, the MCV may be normal or slightly slow in either conditions because of the low motor amplitudes in both. But the sensory nerve response is normal in ALS but affected in neuropathy.

Comment

About these distinctions you mentioned:

1. ARE THE SENSORY POTENTIALS ALWAYS ABNORMAL IN NEUROPATHIES? ALSO IN PURELY MOTOR NEUROPATHIES (or there is not such a thing purely motor neuropathies???) * are there any neuropathies with motor symptoms only and motor emg abnormalities only?

2.and what about fasciculations - are they present also in motor neuropathies (because if not it can be one distinction) what is the percentage of patients with motor neuropathies who have fasciculations?

Answer

Thank you. To clarify myself, the ALS/MND require certain criteria for diagnosis; presence of Lower Motor Neuron (LMN) findings in at least 2 limbs, Upper Motor Neuron findings in at least 1 limb and progression. Now, going to your point about the SNAP, it is always normal in ALS but it may be normal in neuropathies including motor neuropathies. Therefore, if it is normal then it cannot be used in that case to differentiate. About the fasciculation, it is characteristically present in ALS but it is not the only condition they are present in. So it is not a distinction criterion. Last point I am not sure about the frequency of fasciculation in motor neuropathy.

The electrophysiologic diagnosis of ALS                                         top

Question

My symptoms are fasciculations and minor cramps I read somewhere that a clean EMG after 6 months of symptoms rules out almost completely the diagnosis of ALS –

1.Does it fit with your clinical experience?

2.Is it possible in your experience that after 6 months of fasciculation the EMG will show nothing but fasciculation (no fibs and positive waves) but later would show ALS (fibs and positive sharp waves or psw) 3. when you say that somebody with fasciculations has inconclusive EMG what do you mean? Does the definition of "inconclusive" in relation to possible diagnosis of ALS includes actual fibrillations and psw or anything else - what would be inconclusive in relation to a person with fasciculations and suspected ALS?

Answer

ALS is an elimination diagnosis, that is that we only make it after having ruled out other (and there are many) conditions which can mimic it. Unfortunately, frequently fasciculations have been the only thing identified with ALS. So the short answer to your question is do not mind so much the EMG as much as you should mind what your neurologist tells you and if you don't think you're getting the right answers, by all means seek a second opinion.

Comment

So do you mean that frequently ALS patients do not exhibit PSW or fibrillations in their EMG exam?

Answer

No, on the contrary, the fibs and PSW are frequently seen in combination with fasciculation in ALS patients. If the EMG is free from fibs and PSW it is reassuring.

Reduced Interference Pattern (IP) in ALS?                                            top

Question

Is reduced IP seen in the beginning of ALS or only later on? (Is it one of the first things to appear on EMG with ALS patients?)

Answer

I would think that reduced IP is perhaps a "later" EMG sign in ALS. However, it's appearance early or late, on one the hand, does not have a diagnostic value similar to spontaneous activity. On the other hand, a reduced IP may be variable and changes with the patient's cooperation, the strength of the muscle, pain and the presence or absence of disease of the upper motor neuron such as spasticity.

Can we depend only on EMG “without NCV” in diagnosis of ALS?                top

Question

Is it possible to have an EMG test checking for ALS without an NCV? (I understand that by leaving out the NCV part other possibilities may be undetected, but the major concern is ALS)

Answer

I am afraid we cannot do that because a normal sensory nerve conduction studies are essential part in electromyographic findings in ALS.

Abnormal foot movements after EMG & NCV; is it due to the test?               top

Question

I had an EMG and nerve conduction test done for ALS because of some minor fasciculations The EMG found fasciculations, no fibrillations, so the neurologist felt I was clean. But just 4 days after the test my foot, where most of the testing was done on, (at least five separate sets) started vibrating and fasciculating like crazy. It then spread after a month to my other foot. Is this not an uncommon reaction to the test?

Answer

This is not a common reaction to the test; in fact I have never seen it happen. I cannot tell you what this is due to but if you feel that this is way out of the ordinary for you (and it has lasted this long) I would get in touch with your doctor and tell him/her about it.

Time lag before detection of positive sharp waves                                    top

Question

In your quite lucid explanation you make mention that fibrillations cannot be picked up until about 2 months after injury. I was wondering how long a lag exists till the EMG can pick up positive sharp waves. Also, I've seen differing opinions as to whether patients can actually feel the fibrillations and the waves themselves. What is your opinion on this? Thanks very much.

Answer

Fibs and positive waves are seen at about the same time. In fact it's been argued that fibs are positive waves, which are seen from a different vantage point by the needle. People cannot feel either fibs or positive waves, what you are referring to is fasciculations, which are much larger contractions of muscle, and which patients can usually feel.

Fasciculations Frequency “definition”                                            top

Question

I have read in "principles of neurology" that benign fasciculations tend to be more frequent and constant in location than the malignant ones. What do they mean by FREQUENT? 1. More frequent in EMG: once it fires the frequency of each "muscular jump" is higher (shorter intervals between each fasciculation) 2. Or, maybe they mean the clinical way: that the patient gets them more, feels more fasciculations in a given muscle -the frequency of each such "battery" of fasciculations is higher. HE gets more twitches?

What do you think they mean 1 or 2?

Answer

It is 2, referring to frequency in clinical way

Comment

So according to your clinical experience: the random twitchers, those who get them few times a day only and every time in totally different location (a twitch in the calf muscle once every hour or less, for example)- these are the twitchers who should worry more about als? * More than the twitchers who have them continuously in the same muscle?

Answer

Yes, this is true, it is good clinical assumption to follow, but it is not perfect, as surprisingly some patients with ALS are oblivious to their fasciculations.

Contraction fasciculation versus spontaneous ones                             top

Question

I have read there are two types of fasics: spontaneous ones that fire with no relation to contraction of muscles and the contraction ones: which are rhythmic firing of motor unit - observed during weak contraction. The latter are seen in ALS and a compression of nerve root.

My question is: 1. So, are there two kinds of fasics. Both happen in the course of als?? (or the spontaneous happen less) 2.The contraction fasics-How will they be heard electromyographically (rhythmic popping??) I am a bit puzzled because I once read that fasciculation are random pops in EMG while normal motor unit firing are rhythmic popping and that is the way to distinguish fasciculation from normal motor units activity - so How come contraction fascics (malignant!) also produce rhythmic popping?

Answer

You are right, there is something called contraction fasciculations, BUT this has nothing to do with ALS and it is not spontaneous. As a matter of fact we should not confuse it with the usual spontaneous fasciculation. This contraction fasciculation is merely a motor unit contraction visible underneath skin seen initially during a slight voluntary muscle effort.

Comment

1.What exactly are the contraction fasciculation (I read they are rhythmic twitches seen in weak contraction - Is that true?) 2.what is their pathological significance? Are they never consisting a part of ALS or other LMN degeneration? 3. How do you here them in the EMG (rhythmic popping)??

Answer

Practically I do not look for it in ALS and I have not seen among the EMG criteria to diagnose ALS. Historically, it was described by Denny-Brown and Pennybacker in 1938 (Brain 1938;61:311-334) and also by Milner-Brown et al, J. physiology (London)1973,228:285-306.

Fasciculations following muscle activity with normal EMG                      top

Question

I have had muscle twitching all over my body for 3 months now. I have had about 4 normal neuro exams and 2 negative EMG's so far. I have noticed that many of my fasciculations occur directly after applying force to the muscle (i.e. when I lean on my elbow I get a twitch in my elbow, or when I make a muscle in my arm I often follow with a twitch in my bicep). Is this pattern more concerning than fasciculations that occur randomly in a muscle while at rest?

Thanks for your help

Answer

Please be reassured that these kind of twitching or fasciculations are not worrying at all, this is supported by the normal neurological examination and negative EMG on 2 occasions

Sequential appearance of fibrillations and fasciculations in lower motor neuron injury top

Question

There is a point I am quite puzzled about. I would like to hear what is your own opinion on this issue:

1. A citation from "CECIL TEXTBOOK OF MEDICINE": In diseases of the lower motor neuron: Electric signs of denervation, including first fibrillations, and LATER fasciculation, begin within 3 to 4 weeks of injury." So according to this claim, when a patient with ALS presents with various fasciculations, there must be FIBRILLATIONS AS WELL (according to the order mentioned in this book)- according to your clinical experience with ALS patients, how reliable is this claim (FIBRILLATIONS FIRST AND LATER FASCICULATION)? If this claim is correct - Is it true that if a patient presents with fasciculations for long time with no fibrillations on EMG - He has no ALS for sure?

Answer

You are right, you need to see other EMG signs with fasciculations. In my experience, fasciculations by itself does not equal or mean ALS. The description in the textbook is valid point. Namely, fasciculation without other EMG and clinical criteria is insignificant.

Benign fasciculation syndrome (BFS)                                            top

Question

Would you know the answer to this question? I have asked my neurologist, asked the MDA, and looked at a lot of reference material and cannot seem to find the answer. I checked your site, but still no luck. I have been diagnosed with Cramp-fasciculation syndrome/Benign fasciculation syndrome (BFS). On my EMGs, there were positive sharp waves from two different muscles (normal nerve recoupment and no fasciculations noted); my NCVs are all normal. I thought with BFS my EMGs should be normal and my NCVs abnormal? Thank you.

Answer

The term benign fasciculation syndrome (BFS) is used when the patient has fasciculation but no neuromuscular disorder is found. In this case the EMG may show fasciculations only but no positive sharp waves or fibrillations. The nerve conduction study (NCS) is normal, while the Cramp/fasciculation syndrome may have muscle aching, cramps, stiffness, and exercise intolerance. Again in this condition as BFS, the EMG may show fasciculations only, otherwise, no other EMG signs, and the NCS is also normal.

Comment

Thank you, but I am confused. My two EMGs clearly had positive sharp waves in two different muscles. My NCS were all normal. At first my doctors were thinking early signs of ALS. It has now been a year and a half but still no weakness. I have tremors in my hands when I try to hold something; sharp, very localized pains in my arms above and below my elbows and in my hands, fasciculations virtually everywhere from my feet to my face, and have become very exercise intolerant. I can still lift a lot of weight, etc., but just can't do any repetitions. With my EMG findings, how could I have BFS or Cramp/fasciculation syndrome? Thanks in advance.

Answer

May I know what muscles had the positive sharp waves?

Comment

Sure: Quoting my medical records: May 17: "Right triceps: plus two positive sharp waves with trains of positive sharp waves present demonstrating increased insertional activity. The motor recruitment while having many small motor units, showed no evidence of increased polyphasic motor activity or abnormal recruitment patterns." Left triceps: "plus one positive sharp waves with trains of positive sharp waves present. This demonstrated increased insertional activity. The motor recruitment was normal, with no evidence of increased polyphasic motor activity or abnormal recruitment patterns.

March 26: Triceps, right, 2-3+ positive waves and 1+ fibrillations

March 5: Triceps, right, plus 2 positive sharp waves, motor recruitment normal; - right medial gastrocnemius - one train of positive sharp waves, motor recruitment normal.

I have consistently had increased insertional activity in most muscles tested in each of my 4 EMGs. My last EMG noted no positive sharp waves - just increased insertional activity. In each of the muscles that have had positive sharp waves I have a "stabbing" feeling - in the triceps above the elbow; and the same localized pain in the forearm below the elbow.

I have had a spinal tap to rule out MS; all sorts of blood work to rule out heavy metal poisoning, etc.; brain scan; c-spine MRI (showing a slight stenosis but no impingement of the spine). I am a Persian Gulf Veteran and have tested positive by an DNA PCR test for the mycoplasm fermentans that has been linked to "Gulf War Syndrome" and am on a 1 year course of antibiotics in a study on that.

Comment 2

I'm sorry, I also forgot the following: Feb. 5 - my NCS noted mild slowing for the ulnar motor nerve across the elbow; during exam, very active positive Tinel signs present over the median nerve on the right and the left wrist and over the ulnar nerve over the right and left elbow

- my reflexes are consistently +3 all over; once I was noted as having a Babinski reflex, once a Hoffman reflex

- when I exercise, after a few minutes I get a burning sensation (like if I were lifting weights and got to the point of muscle failure)

- I have a tingling sensation in my 4th and 5th fingers of my right hand, sometimes my right index finger.

In reading about ulnar neuropathies, I seem to have some of the symptoms - the tingling of the 4th and 5th fingers, elbow soreness (about 1 inch above the elbow), there is a history of diabetes in my family, and I used to lean on my elbows alot while I type (I have stopped doing that). Are my EMGs/NCS consistent with ulnar neuropathies?

Again, I have no weakness, no bulbar signs of ALS (occasional slurring of words, but I have always done that when I am tired); lots of fasciculations; and a lot of pain from those very specific parts (feels like someone comes up and stabs me with an ice pick - when it strikes, I will drop what I am holding, etc.).

I am currently on Gabapentin for the tremors (I would pick up something, and sometimes my hand, fingers, etc. would start to tremor, the more I held on, the worse it would get).

Answer

Do you recall the sounds of the sharp positive waves and fibrillations in your EMG, how did they sound like?? How long each has lasted

Comment

It just sounded like a lot of static, no popping or anything, just loud static. That is all I remember; before each EMG I had an NCS, which when I was shocked in my arm, my leg, would fly up, etc. By the time I had the EMGs, all of my nerves were on end, and the EMGs really hurt, a lot!!

Answer

Now that I think of it, the static at times would sound liking rapid popping - no break in between - this would occur on the muscles where the sharp waves were

Answer 2

How did the fibrillation sound like?? You say static. Could you distinguish what it was made of or was it just static sound like a "dead heart" on ECG? Most importantly, about the duration - was it short duration (3,4 seconds) and stopped quickly or was it for a long time??

Comment

I'm sorry; can't remember the exact sound. It continued the entire time the needle was in - it did not stop.

Answer

Here is a link that actually shows videos of fibs, ps waves etc.

http://www.med.ohio-state.edu/physmed/videos/EMGvideos.html

Here is a link to more videos of fibs, ps waves etc:

http://www.casaengineering.com/EMGsampl.htm

Answer 2

Thank you for detailed information about your medical problem. I agree that it cannot be a pure BFS or cramp/fasciculation syndrome or ALS.

Comment

Thank you for your time. I guess I will just have to wait and see what develops. Hopefully I can report back in a few years that it is benign!