I noticed no replies to my questions so I did some reading and thought I'd post what I have learned in case it helps someone else.These were questions posed to a neurologist experienced in emg's
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.
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.
Answered my question about fasciculations on contraction of muscles.