Re: post-polio syndrome? EMGs

Posted By CCF Neuro MD *!* on January 03, 1998 at 14:41:27:

In Reply to: post-polio syndrome? EMGs posted by Ruth Bridgens on January 03, 1998 at 10:13:32:







: I have had slight weakness in arms and legs since age 2(1950). I have become gradually much weaker over the past 12 years (I can only walk about 20 feet before I get sciatica and stiff legs) and thought I might have had polio even though I had a normal muscle biopsy and EMG in one hand in 1987. I had EMGs in my legs this year which I was told were normal but the technique seemed very different from last time; I was told to move the muscles as little as possible instead of as much as possible. Can these two approaches lead to the same results? What is a normal or abnormal result in an EMG? I have read research (Bromberg) that some people who have had polio have normal EMGs. Is there a kind of weakness that does not cause abnormal EMGs?



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The techniques you describe for EMG recording yield essentially
the same information, some workers in the area like to progress
to full contraction whereas others and this includes the author
of a one of the major textbooks in EMG say it is seldom necessary, the
basic information obtained is the same.
The fact that you have had normal EMG's by both techniques suggests
that there areno electrically significant abnormalities.
An abnormal EMG shows spontaneous electrical activity when the
muscle is relaxed, normal muscle is electrically silent.
During contraction the number of muscle fibres firing is represented by
waves on the screen. These can be abnormal in terns of their
frequency, duration, amplitude, shape/ configuration and recruitment.
Old polio should be manifest by increased spontaneous activity
hile the muscle is at rest.
I have reviewed several papers by Bromberg in the last 12 years, there
is one where he refers to possibly normal EMG studies in polio, his conclusion
is  "the lack of clear evidence for previous denervation after
extensive electrodiagnostic testing is a valid means for excluding
the diagnosis of post-poliomyelitis syndrome."