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post-polio syndrome? EMGs

      Re: Re: Re: post-polio syndrome? EMGs

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Posted by CCF Neuro MD on January 05, 1998 at 16:29:40:

In Reply to: Re: Re: post-polio syndrome? EMGs posted by Ruth Bridgens on January 05, 1998 at 13:54:23:

: : : 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?
  : ==========================================================================
  : 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."
  Thank you for your quick reply. In the Bromberg article you mentioned,
  he concluded the patient had an illness in childhood which had led to
  their weakness and, in some cases, breathing problems, even though their
  EMGs were normal. They had had a polio-loke illness in childhood and
  subsequent weakness in some cases. Several did have abnormal SF-EMGs.
   What diagnosis could they have and what is this weakness that doesn't
   show up on EMG? Many neurologists would say there was nothing wrong,
   as the SF-EMG is not done on such patients. Thanks for your help.
It is really not possible to comment on the specific cases cited by
Bromberg beyond the information in his article, you might benefit from
writing to him directly regarding his thoiughts on this issue.
The conventional wisdom on this issue, which I would consider entirely logical
is that polio always leaves clear abnormalities  on subsequent EMG studies.
As regards weakness which is not detected on EMG this could be
because the weakness is minimal in degree and therefore does not show-up
or because it arises from a disorder of the upper motor nerves
which connect the cerebral cortex to the spinal cord.
The lower motor nerves in turn carry impulses from the cord to the muscles,
disorders of these nerves are more likely to cause EMG changes.
Upper motor neurons are involved in brain or spinal cord diseases,
like stroke, ALS, tumors or cysts of the cord or brainstem.

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