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Failing to see the usefulness of vibration testing for feet which demonstrate no LOPS with 10g Monof

Discussion in 'Diabetic Foot & Wound Management' started by LaFilleAustralienne, Jul 4, 2011.


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    Hello fellow podiatrists,

    I'm trying to set out a meaningful diabetes assessment form. I've heard those articles which suggest that loss of vibration perception accompanies early peripheral neuropathy.

    However...

    Would you ever commit to a diagnosis based on loss of vibration perception alone (in the absence of insensate 10g Monofilament sites)?

    Is there a confounding argument that the loss of vibration perception may also be related to the normal aging process? And at that rate should we be using it as part of a falls risk assessment?

    I have no problems following this scenario if others agree:
    1. always test vibration after LOPS with 10g Monofilament is found to assist or support the diagnosis of peripheral neuropathy
    2. never use vibration testing on it's own for diagnosis of PN

    ANY THOUGHTS OUT THERE???

    :pigs:
     
  2. LuckyLisfranc

    LuckyLisfranc Well-Known Member

    LaFille

    Would suggest going back to your basic neurology studies, and consider the different types of nerves fibres that transmit sensory information. And also consider that the diagnosis of diabetic peripheral neuropathy, is a clinical diagnosis after exclusion of other causes.

    Vibration perception is usually the first to go in most causes of polyneuropathy, because these fibres are not only extremely long, but heavily myelinated and are subject to heavy metabolic demands. As are deep tendon reflexes. Soon after is pain, temperature, light touch, and much later proprioception and finally motor effects (intrinsic atrophy).

    We could talk at length about the various receptors and fibres, but this is basic nerve physiology which I am sure you were taight at undergraduate level.

    So to answer your questions;
    * monofilament is a useful, cheap reliable test to diagnose large fibre neuropathy. It will adequately determine established LOPS, but not necessarily detect more subtle presentations of neuropathy.
    * adding more tests improves the reliability of your diagnosis - eg vibration, deep tendon reflexes, nerve conduction, skin biopsy et al - they may not be necessary for all people, but adds weight to your diagnosis
    * there is nothing actually wrong with using vibration perception alone to diagnose large fibre neuropathy (eg >25V)
    * the incidence of polyneuropathy does increase with age, so this always needs to be taken in context with other relevant comorbidities
    * small fibre neuropathy is another beast altogether...

    Would suggest some googling to refresh on the topic?

    LL
     
  3. Certainly I agree with all that you say. Perhaps I'll re-qualify my concern:

    -Recently I posed the question to myself: how reliable is reduced vibration perception in isolation in a diabetic with well-contolled BGL's in 1, 2 or even 3 out of 6 sites (apex of hallux, styloid process, med. malleolus)? Especially if it's on an 86 yo patient?

    -There's a myriad of critique out there about using it in isolation for a clinical diagnosis of diabetic polyneuropathy.

    -There is also suggestion in the literature that vibration assists with balance. I thought perhaps for this 86 yo with good BGLs that the loss of vibration (3/6 sites <25V).. I thought maybe it would be indicating a higher clinical suspicion of age-related deterioration leading to increased falls risk. If the assumption that vibration/small changes detected by brain are truely proprioceptive in their function & have simply been affected by age-related change in this patient with no absent reflexes (or even if they were absent???). I find it difficult to justify the cost of additional nerve conduction studies if this is the case.

    I'm only a new graduate so I'm familiar with things but also could be guilty of over-thinking it or even looking at research into vibration which may not be deemed all that reliable in its own right (of the stuff that I've looked at it's mostly prospective, etc.). Just thought I'd put it out there as a question?
     
  4. I'm not sure you can "over think" something like this. Its good to question what we think we know. The only stupid question is the one which does not get asked!

    I'm a heretic. I too question what information a negative vibration test gives you and how it changes your advice / treatment.

    But then...

    I also question how a monofilament changes your advice / treatment.

    There is a case study I've posted before of a heel ulcer in which someone has poked a set of forceps (painlessly) up to the hilt. Massive tracking. A neuropathic ulcer. And yet that patient has intact 10g monofilament sensation.

    So a positive (can feel) 10g test does not prove neuropathy DOESN'T exist.

    And I've seen more than a few feet with diminished monofilament sensation who hit the roof when I debride a corn or cut a toenail.

    So a negative (can't feel) 10g test does not prove neuropathy DOES exist.

    So I have to tell my DM patient that neuropathy MIGHT exist, regardless of my neuro test. Regardless of the test, I must treat them on the basis that they ARE neuropathic.

    I can see the use in terms of tracking progress or referring on (although I would question repeatability) but for a test to determine neuropathy I think both vibration and monofilament are sorely lacking.

    But then I'm a biomechanist, and a heretic, so you almost certainly should not listen to me la fille.
     
  5. Tuckersm

    Tuckersm Well-Known Member

    All the monofilament studies that I have read relate to an increased risk (about 7 times) of ulceration when a 10g filament is not 'felt'.
    Vibration studies have not been as clearly linked to a risk of increased foot pathology, but a couple of studies I read 10 yrs ago, did show an association with loss of VPT and risk of a Charcot # but low powered studies.
     
  6. Tom Galloway

    Tom Galloway Member

    LaFille

    As others have said, the value of 10G monofilament sesitivity testing is not to make the diagnosis of neuropathy - it is to screen for people who are at most high risk of foot ulceration due lacking the protective sensation that stops the rest of us destroying our foot tissue.

    It just so happens that 10G monofilamant is a great cost effective means of screening for this.

    Tom
     
  7. Admin2

    Admin2 Administrator Staff Member

  8. julesrose

    julesrose Member

    From reading La fille's thread I thought she was asking about vibration perception and how lack of vibration perception relates to poor balance and risk of falls. Almost every response has been on monofilament testing.
    She's only repeated her question twice, encore une fois?

    A bientot
     
  9. Silvester

    Silvester Member

    Hi Lafille,

    I am currently doing some research on the biothesiometer, but in RA. I have read a lot around vibration testing. There is definitely evidence to suggest that loss of vibration sensation occurs with aging and with this it increases the variation amongst readings. There is also evidence that has supported the use of the biothesiometer together with the monofilament for diabetic assessments. I think if you have access to both of these tools, it would be better to use them together than only one. With regards to how lack of vibration perception or sensory decline relates to poor balance, there is research that advises that falls patients have got significant sensory loss compared to their control counterparts. The link has not been clarified between sensory loss and falls, but diagnosis of sensory loss should be done with tools that are reliable and valid in an older population. Vibration testing is not considered a reliable tool in older adults. I hope this helps a little bit.

    Thanks
     
  10. Mart

    Mart Well-Known Member

    The initial question for this thread has been answered already.

    For those interested there does seem good evidence that VPT is correlated with normal aging, however this issue can be addressed for use as clincial tool because there is a fairly linear relationship between aging and logV and there doesn't seem to be problem for using VPT as an index when age is degradation is factored in especially for hallux vs medial malleolus. There is also good evidence that pacinian corpuscles degenerate with aging which shows consistency with this finding.

    It seems logical that it would more reliable than a C128 TF (constant energy) and possibly more sensitive for early sensory PN than other measures, there is evidence to support this.

    The problem with using VPT as a solitary measure for evaluation for risk of lower extremity amputation as complication of diabetes mellitus is that the type of fibres damaged with DM are extremely variable and unpredictable between individuals so multiple measures including touch, vibration, temp and pain, perhaps also motor should be factored. This means that any individual measure is likely to lack sensitivity. I think that the holy grail is to have tool(s) which are specific and sensitive enough to be clinically useful BEFORE the irreversible changes occur. Currently our tools are correlated with relative risk for amputation NOT possibility of "tuning" glycaemic control favorably to prevent PN.


    Papers attached for those who might be interested.

    Also attached is a excel page I use within my evaluation for risk of lower extremity amputation as complication of diabetes mellitus MHR which calculates age factoring within 1 SD of normal data, those using VPT may find this useful.

    Cheers

    Martin

    Foot and Ankle Clinic
    1365 Grant Ave.
    Winnipeg Manitoba R3M 1Z8
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     
  11. Mart

    Mart Well-Known Member

    Here's the excel SS VPT calc file I created for anyone interested

    Cheers

    Martin

    Foot and Ankle Clinic
    1365 Grant Ave.
    Winnipeg Manitoba R3M 1Z8
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     

    Attached Files:

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