Hi all
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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
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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.
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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 -
illustrative video clip
View attachment FD.pdf -
The left foot appears adducted ?? What are your observations of the tibia - not possible to see in the video?
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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 -
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?
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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 -
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 -
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?
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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