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Leg pain in neuropathic postural tachycardia syndrome is associated with altered muscle membrane properties, 2021, Rodriguez et al

Discussion in ''Conditions related to ME/CFS' news and research' started by Ryan31337, Nov 14, 2021.

  1. Ryan31337

    Ryan31337 Senior Member (Voting Rights)

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    Leg pain in neuropathic postural tachycardia syndrome is associated with altered muscle membrane properties, 2021, Rodriguez et al

    Abstract
    Purpose
    In neuropathic postural tachycardia syndrome, peripheral sympathetic dysfunction leads to excessive venous blood pooling during orthostasis. Up to 84% of patients report leg pain and weakness in the upright position. To explore possible pathophysiological processes underlying these symptoms, the present study examined muscle excitability depending on body position in patients with neuropathic postural tachycardia syndrome and healthy subjects.

    Methods
    In ten patients with neuropathic postural tachycardia syndrome and ten healthy subjects, muscle excitability measurements were performed repeatedly: in the supine position, during 10 min of head-up tilt and during 6 min thereafter. Additionally, lower leg circumference was measured and subjective leg pain levels were assessed.

    Results
    In patients with neuropathic postural tachycardia syndrome, muscle excitability was increased in the supine position, decreased progressively during tilt, continued to decrease after being returned to the supine position, and did not completely recover to baseline values after 6 min of supine rest. The reduction in muscle excitability during tilt was paralleled by an increase in lower leg circumference as well as leg pain levels. No such changes were observed in healthy subjects.

    Conclusions
    This study provides evidence for the occurrence of orthostatic changes in muscle excitability in patients with neuropathic postural tachycardia syndrome and that these may be associated with inadequate perfusion of the lower extremities. Insufficient perfusion as a consequence of blood stasis may cause misery perfusion of the muscles, which could explain the occurrence of orthostatic leg pain in neuropathic postural tachycardia syndrome.

    Open access, https://link.springer.com/article/10.1007/s10286-021-00830-5
     
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  2. Sean

    Sean Senior Member (Voting Rights)

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    "misery perfusion"

    ???
     
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  3. Hutan

    Hutan Moderator Staff Member

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    We've talked about misery perfusion before (in the brain). Looks as though any part of the body can have it.
     
    Last edited: Nov 16, 2021
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  4. Hutan

    Hutan Moderator Staff Member

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    I think this is an interesting study; I think they found real differences! Yes, I have allowed myself an exclamation mark. The leg pain and increase in leg circumference upon standing fit with what happens to me; I do have postural orthostatic tachycardia, especially on bad days.

    @Snow Leopard

    See in Figure 3, the muscle relative refractory period is shorter in the POTS people before and during the tilt test, and slower after the tilt test. (The bars showing the measurements during the tilt test are in the section with the grey background.)

    Screen Shot 2021-11-15 at 7.26.27 PM.png
    The authors say that the results they found before the tilt test look like what they found in people who had been training hard for two weeks. They think it's an adaptation to repeated ischaemia.
    Another finding was present the whole time, regardless of body position - lowered late supernormality. The authors say they saw this in healthy subjects with muscle fatigue.
    The authors are hypothesising that the leg circumference increase is due to 'impaired vasoconstriction caused by the peripheral sympathetic dysfunction'.
    They think this explains muscle weakness and exercise intolerance:
    Unfortunately, they then go on to suggest exercise as a treatment. I don't understand their point about increasing hyper polarisation - because muscles of people with POTS had already adapted to be hyper polarised, and it wasn't preventing the problems. Certainly, it doesn't seem likely that exercise will cure the problem.
     
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  5. Ryan31337

    Ryan31337 Senior Member (Voting Rights)

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    Useful summary & comments, @Hutan, thank you.

    Interesting study for me as lower leg pain was one of my primary complaints at on-set, long before other more overt POTS signs & symptoms started.

    I thought it interesting to note that the patients did not actually meet POTS heart rate criteria at the time of HUT.

    In this study the patients were allowed to continue with most of the usual POTS medications and eat/drink normally - its fairly well recognised that HUT sensitivity for diagnosing POTS is influenced by these factors, as well as time of day, so this isn't surprising and the authors came to the same conclusion. Can't help but wonder how much of the misery perfusion is still happening in patients without the significant heart rate increase, for whatever reasons. Much like what we've seen from CBF measurements in CFS patients with & without clinical POTS.
     
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  6. Ryan31337

    Ryan31337 Senior Member (Voting Rights)

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    Would be interested to know if anyone here has an understanding of this point made in the paper.

    Specifically how that might relate to David Systrom's theories of Pyridostigmine action in SFN/POTS.
     
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  7. Snow Leopard

    Snow Leopard Senior Member (Voting Rights)

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    But perhaps the sympathetic response is itself a response to dysregulated perfusion of blood in the muscle capillaries?

    Pooling and shunting (as observed post-exercise by Systrom et al) could be a result of trying to maintain blood flow across the capillary bed.
     
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  8. Mithriel

    Mithriel Senior Member (Voting Rights)

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    I cant follow the science very well but one of the strange symptoms of my ME is pain in my lower leg which is relieved by my husband squeezing it tightly with both hands starting at the ankle then working towards my knee.
     
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  9. Blueskytoo

    Blueskytoo Senior Member (Voting Rights)

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    Me too, and my daughter who has POTS as well also struggles with this. We’ve both found lower leg compression stockings help with the pain immensely, although they’re an absolute bugger to get on and off (especially if you have extremely high arches on your feet…).
     
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  10. Mithriel

    Mithriel Senior Member (Voting Rights)

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    I'd forgotten. Years ago I kept a pair from when I was in hospital and they worked great until they fell apart!

    My daughter got a fancy pair of compression stockings to wear as all the other nurses on her ward use them to stop aching legs. Maybe Santa will bring me some :)
     
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