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Focal Dystonia EHL and EDL

Discussion in 'General Issues and Discussion Forum' started by Mart, May 29, 2012.

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  1. Mart

    Mart Well-Known Member


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    Hi all

    I had a consult today with a healthy 11 yo male; normal reported developmental milestones. chief complaint was mild persistent right side episodic inner longitudinal arch pain - worsened with increased activity, improved with rest. Also concern regarding mother noticing abnormal foot alignment. Pediatrician reported as unconcerned.

    I observed: There was no tenderness to palpation at any of foot joints, tendons, muscles, fascia or ligaments, no pain with active resistance testing of foot intrinsic and extrinsic flexors/extensors, invertors/evertors, dorsiflexors/plantar flexors, or with passive range of motion of ankle or joints distally. No remarkable joint stiffness or contractures.

    right foot relaxed calcaneal stance position was everted ++

    Observing gait whilst walking barefoot in the corridor I noted; he had no pain, right foot only constant firing of extensor hallucis longus and brevis through swing and stance with subsequent supinated postion. Otherwise normal gait progression, clearance and ankle dorsiflexion.

    When resting there was no muscle spasm.

    I was unable to find any extrinsic/instrinsic weakness

    Any comments regarding how to further evaluate this?

    My impression was that he likely has primary focal dystonia.

    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
     
  2. fronny

    fronny Active Member

    Your diagnosis seems logical. Does the spasm happen at any other times or just during gait? I am surprised that the paediatrician is not concerned as I believe that a focal dystonia in children can a sign of worse to come.
     
  3. Mart

    Mart Well-Known Member

    There is spasm in relaxed calcaneal stance position (mostly) but this stops when non weight-bearing. I'll post a bit of video for anyone interested. I have asked the pediatrician to take another look.

    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
     
  4. Mart

    Mart Well-Known Member

  5. fronny

    fronny Active Member

    The left foot appears adducted ?? What are your observations of the tibia - not possible to see in the video?
     
  6. Mart

    Mart Well-Known Member

    I believe that the adducted foot alignment compared to line of progression is result of femoral/tibial torsion. Not too concerned regarding this since left side is asymptomatic and can't really do anything useful about that anyway.

    Because right foot behavior likely has neurological origin I wanted to be as clear as possible regarding understanding this.

    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
     
  7. fronny

    fronny Active Member

    Should confess I have an interest in this post because I walked in a similar way as a child. Internal femoral torsion caused my right foot to adduct, left foot also adducted slightly, as a result I was constantly tripping over my own feet, was labelled clumsy (my mother even wondered if I'd suffered some brain damage at birth!). At some point I seem to have learned to avoid this by extreme supination of the right foot, extending the hallux to achieve contact at toe off. I stopped falling over my feet but developed a lot of sprained ankles! Its a bit of a long shot but is there is any chance its whats happening here?
     
  8. Mart

    Mart Well-Known Member

    If you look at the video you can see that there is quite abnormal firing of the digital extensors which causes the foot to grossly invert throughout entire gait cycle. This is also occurring in relaxed calcaneal stance position too causing right foot invertion (not everted as I stated earlier - typo).

    Having thought about your own strategy I am a bit puzzled because firing of EHL and Tib anterior would I assume to internally rotate and adduct foot more. Someone please correct me if I am missing something here. I can't see in this case why this phenomenon might be caused by internal torsion therefore especially since this activity is asymmetric. I did attempt to have patient consciously relax his extensors during gait but he was unable to.

    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
     
  9. efuller

    efuller MVP

    It looks like a gait where the person is avoiding medial forefoot loading. It looks like a pain avoidance gait of someone whose medial arch hurts. The gait can cause the pain or the pain can cause the gait.

    Eric
     
  10. Mart

    Mart Well-Known Member

    Thanks Eric

    I agree that this might be one interpretation of the video.

    However there was no pain during this exam and patient had been put on treadmill for approximately15 minutes prior to stress feet to elicit any symptoms and observe any variation in foot motion.

    He remained pain free and foot behavior was consistent. When he gets pain it is very mild transient inner longitudinal arch pain associated with unshod walking. In this case I an certain there is another explanation for what we are looking at.

    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. efuller

    efuller MVP

    So, you've got some abnormal muscle firing. You don't mention any abnormal neurological tests. I can't think of any abnormal findings that would correlate with this specific of a dystonia.

    Thinking of the neurological wiring on this, It's hard to imagine a neurolgical lesion that would cause just this. It seems that CNS pain avoidance is the best explanation of what your seeing. Did you say that he was able to relax it during the non weight bearing exam?

    One could say, "see how well walking like that prevents the pain." It seems very unlikely that walking like that would cause the medial arch to hurt.

    Eric
     
  12. Mart

    Mart Well-Known Member

    Hi Eric

    Thanks for your thoughts.

    I had a chat to the patient's pediatrician yesterday; he agreed to review for further neurological evaluation. My basic tests for muscle strength and sensory changes were normal; I did not go beyond this because I believe he needs a more expert workup than I can provide to rule out my concerns

    Yes relaxation occurs non weight-bearing.

    Constant tension of FHL, plantar aponeurosis or plantar ligaments caused by EHL contraction might cause mild inner longitudinal arch pain. Although they are plausible mechanisms for potential pain generation I doubt true in this case.

    There are a couple of examples in the literature of EHL focal dystonia treated with botox when causing problems - currently that does seem indicated in this case to me, patient has mild very episodic inner longitudinal arch pain which resolves wearing shoes.

    About wiring; I find the explanation below from wiki helpful and seems to fit the presentation.

    The cause of dystonia is not yet precisely understood. Misfiring of neurons in the sensorimotor cortex, a thin layer of neural tissue covering the brain, is thought to cause contractions. The source of this misfiring may be a result of impaired inhibitory mechanisms during muscle contraction.[2] When the brain tells a given muscle to contract, it simultaneously silences muscles that would oppose the intended movement. In dystonia, it appears that the ability of the brain to inhibit the surrounding muscles is impaired leading to loss of selectivity.[3]

    Furthermore, the sensorimotor cortex is organized as discrete "maps" of the human body. Under normal conditions, each body part (such as individual fingers) occupies a distinct area on these cortical maps.

    In dystonia, these maps lose their distinct borders and overlap occurs.[4]

    Exploration of this initially involved over-training particular finger movements in non-human primates which resulted in the development of focal hand dystonia. Examination of the primary somatosensory cortex in the trained animals showed grossly distorted representations of the maps pertaining to the fingers when compared to the untrained animals.[5] Additionally, these maps in the dystonic animals had lost the distinct borders that were noted in the untrained animals. Imaging studies in humans with focal dystonia have confirmed this finding.[6] Also, synchronous afferent stimulation of peripheral muscles induces organizational changes in motor representations, characterized both by an increase in map size of stimulated muscles and a reduction in map separation, as assessed using transcranial magnetic stimulation.[7]

    The cross-connectivity between areas that are normally segregated in the sensory cortex may prevent normal sensorimotor feedback and so contribute to the observed co-contraction of antagonist muscle groups, and inappropriately timed and sequenced movements that underlie the symptoms of focal dystonia.

    It is hypothesized that a deficit in inhibition caused by a genetically mediated loss of inhibitory interneurons may be the underlying cause of the deficits observed in dystonia.[8]

    While usually painless, in some instances the sustained contraction and abnormal posturing in dystonia may cause pain.

    Focal dystonia is generally "task specific," meaning that it is only problematic during certain activities.


    So to speculate on this

    through swing the extensors are functioning normally

    BUT

    they don't turn off during stance after initial contact as expected - they fire again through swing . .. . . etc

    when resting there is no motor impulse - tone diminishes and foot relaxes

    this is different from an UMN lesion which causes permanent loss of inhibition such as in CVA.

    Does this make diagnosis of Focal dystonia more persuasive now?

    I cant see how you could you test to rule out this phenomena - if that is true then diagnosis would be by ruling other explanations . . . including yours . .. which so far I feel reasonably confident about.

    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
     
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