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Neurology (Expert Forum)
EMG - fasciculations/fibrillations/PSWs
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EMG - fasciculations/fibrillations/PSWs
by Ico, Aug 23, 2006 12:00AM
Hello,
I am writing to enquire about EMG findings. I am primarily concerned with the timing of fibrillations and positive sharp waves (PSWs) in MND/ALS. In the interest of clarity I will set out my questions separately.
1. Do fasciculations appear before the point when any fibs/PSWs would show up on an EMG or would you expect fibs/PSWs to be present before fasciculations? (I have had fasciculations for 4-6 months now but no fibs/PSWs appeared)
2. Is the appearance of fasciculations accompanied by occasional runs of complex repetitive discharges (CRDs) anything to be concerned with? (Specifically in the left EDB (Deep Peroneal L5 s1))
3. What is the significance of polyphasic units and low recruitment patterns? If the amplitude is normal in all muscles is slightly low recruitment (seemingly concentrated in left leg) anything to worry about?
4. If polyphasic units and low recruitment patterns are found along with CRDs is this a cause for concern even if they are not outside normal limits?
5. Although not related to the EMG, can benign fasciculations cause fatigue/weakness in particular muscles?
I look forward to hearing your responses and I thank you for your time.
Kind Regards
I am writing to enquire about EMG findings. I am primarily concerned with the timing of fibrillations and positive sharp waves (PSWs) in MND/ALS. In the interest of clarity I will set out my questions separately.
1. Do fasciculations appear before the point when any fibs/PSWs would show up on an EMG or would you expect fibs/PSWs to be present before fasciculations? (I have had fasciculations for 4-6 months now but no fibs/PSWs appeared)
2. Is the appearance of fasciculations accompanied by occasional runs of complex repetitive discharges (CRDs) anything to be concerned with? (Specifically in the left EDB (Deep Peroneal L5 s1))
3. What is the significance of polyphasic units and low recruitment patterns? If the amplitude is normal in all muscles is slightly low recruitment (seemingly concentrated in left leg) anything to worry about?
4. If polyphasic units and low recruitment patterns are found along with CRDs is this a cause for concern even if they are not outside normal limits?
5. Although not related to the EMG, can benign fasciculations cause fatigue/weakness in particular muscles?
I look forward to hearing your responses and I thank you for your time.
Kind Regards
Doctor's Answer
by CCF-Neuro-M.D.-SH, Aug 26, 2006 12:00AM
First of all, keep in mind that I am unable to diagnose you because I am unable to examine you, this forum is for educational purposes.
The questions you raise are common concerns of patients that present with fasiculations (you will find many similar posts on this forum).
1. When patients present with ALS it is generally with weakness and atrophy in a distal upper and/or lower extremity (hand or foot). This is most commonly in the form of hand atrophy/weakness or foot drop. The EMG even in early disease has frequent spontaneous activity (fibrillations and positive sharp waves). It is very important to rule out other conditions that can cause this same picture clinically and on EMG such as multifocal motor neuropathy with conduction block and inclusion body myositis.
Fasiculations on the other hand, are NOT an early finding that then leads to ALS. They can appear at any time in ALS and are a symptom of the lower motor neuron processes(the weakness and atrophy), but can also be found in other myopathic conditions (muscle diseases), after viral infections, after excessive exercise and in normal people. Thus fasiculations are only trouble "by the company that they keep", they do not mean anything towards ALS without weakness and atrophy.
2.CRDs are not a feature of ALS and the EDB is often dennervated by non-neurological processes such as tight shoes. CRDs can be seen in other metabolic diseases, but are often without significance.
3. Polyphasic units with low amplitude is called the "myopathic unit" and is found in muscle diseases. Decreased recruitment is found in ALS because there is less motor units able to respond due to the dying alpha motor neurons (in the spine). The measuring of motor recruitment is subjective and can easily be misinterpreted. I can not see your EMG, but ALS does usually present asymmetrically as mentioned earlier. If you only have decreased recruitment without any other features, this could reflect other spinal cord disorders, old polio, etc, and your EMG should be evaluated by an ALS expert.
4.Not for ALS, as above.
5. People with benign fasiculation syndrome do often complain of fatigue, cramps and exercise intolerance. In studies, these people do NOT go on to develop ALS.
ALS is a clinical diagnosis that is supported by EMG findings with the 2 key features to be concerned about, weakness and atrophy, and even with these symtoms it can be many other things. Neurologist in general work very hard to find another diagnosis than ALS, since there is no treatment, and the average survival after diagnosis is 3 years (although some varients can live longer 10-20 years).
The questions you raise are common concerns of patients that present with fasiculations (you will find many similar posts on this forum).
1. When patients present with ALS it is generally with weakness and atrophy in a distal upper and/or lower extremity (hand or foot). This is most commonly in the form of hand atrophy/weakness or foot drop. The EMG even in early disease has frequent spontaneous activity (fibrillations and positive sharp waves). It is very important to rule out other conditions that can cause this same picture clinically and on EMG such as multifocal motor neuropathy with conduction block and inclusion body myositis.
Fasiculations on the other hand, are NOT an early finding that then leads to ALS. They can appear at any time in ALS and are a symptom of the lower motor neuron processes(the weakness and atrophy), but can also be found in other myopathic conditions (muscle diseases), after viral infections, after excessive exercise and in normal people. Thus fasiculations are only trouble "by the company that they keep", they do not mean anything towards ALS without weakness and atrophy.
2.CRDs are not a feature of ALS and the EDB is often dennervated by non-neurological processes such as tight shoes. CRDs can be seen in other metabolic diseases, but are often without significance.
3. Polyphasic units with low amplitude is called the "myopathic unit" and is found in muscle diseases. Decreased recruitment is found in ALS because there is less motor units able to respond due to the dying alpha motor neurons (in the spine). The measuring of motor recruitment is subjective and can easily be misinterpreted. I can not see your EMG, but ALS does usually present asymmetrically as mentioned earlier. If you only have decreased recruitment without any other features, this could reflect other spinal cord disorders, old polio, etc, and your EMG should be evaluated by an ALS expert.
4.Not for ALS, as above.
5. People with benign fasiculation syndrome do often complain of fatigue, cramps and exercise intolerance. In studies, these people do NOT go on to develop ALS.
ALS is a clinical diagnosis that is supported by EMG findings with the 2 key features to be concerned about, weakness and atrophy, and even with these symtoms it can be many other things. Neurologist in general work very hard to find another diagnosis than ALS, since there is no treatment, and the average survival after diagnosis is 3 years (although some varients can live longer 10-20 years).
