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G'day all,

I've got a patient who I'm managing with CMT with peroneal atrophy. She is 30 years old, and has had it for about 10 years or so, but feels it is progressively getting worse. She exhibits all classical features of peroneal atrophy associated with CMT, with still good range of motion in rear and midfoot, forefoot is significantly plantarflexed on rearfoot, and digits quite signuificantly retracted into claw position. Any suggestions that may assist with my clinical resioning with regardsa to orthotic therapy would be much appriciated. :)

-Adrian

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Related threads:
CMT- Treating ankle weakness/ instability
Charcot Marie Tooth Disease

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Hi Adrian:
CMT is difficult to treat, as you are finding out.
First, since you state she is a female, be sure she knows that because CMT is an Auto. Dominant trait she has a 50/50 chance of passing this along to her children (if she has not already).

My approach to CMT (the classic type) is first and foremost to retain muscle strength and ROM. Of course the patient is going to loose both as time passes, but a Physical Therapy program, either at home or at a PT Department, is crucial. Since the resulting deformity of CMT may vary, you will need to appraise each patient and structure the therapy accordingly.

Foot orthotic or AFO use is assessed for each individual depending on your clinical findings. It sounds as though your patient is developing a TEV. ALong with the usual sub 1st and 5th Metahead pain, these patients often develop lateral ankle instability and midfoot arthritic pain along with contraction of the MTPJ and IPJs.

Surgical procedures are available but I find I limit them to symptomatic relief only.

Hope that helps.

Steve

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Hi Adrian,

CMT is the most common genetic nerve disorder in humans (1 in 2500). There are over 50 types and only some are autosomal dominant. All advice regarding genetics, particularly an exact diagnosis, should be referred to a neurologist and/or a geneticist. Similarly multidisciplinary management is essential to not only address foot and ankle manifestations, but also hand dysfunction, hip dysplasia, etc.

Orthotic management in CMT is tricky. I have published a paper describing a device for pes cavus foot pain in CMT (Burns J, Crosbie J, Ouvrier R, Hunt A. Effective orthotic therapy for the painful cavus foot: A randomized controlled trial. Journal of the American Podiatric Medical Association 2006;96(3):205-211). However, there are many other problems with the CMT foot such as foot drop, ankle instability, plantar callosities, stress fractures (esp. styloid process), sensory disturbances, cramps and toe deformities not entirely addressed by an in-shoe custom device. There is also a subset with pes planus and profound foot drop requiring AFO intervention.

It is unclear if muscle strengthening is effective since it is a nerve disorder and not a muscle disorder i.e. muscles are fine but the nerve messages are not getting to their destination due to demyelination and axonal loss. Maintaining range of ankle joint motion is very important. I am involved in several trials in CMT looking at increasing ankle range, strengthening muscles, cavus foot surgery, botulinum toxin for muscle imbalance and even vitamin C as a potential cure for CMT type 1A and curcumin (tumeric) for CMT type 3 (Dejerine Sottas).

So try to link in to a network of health care providers dealing with CMT and see if you can help improve her quality of life.

Kind regards

Joshua Burns PhD, B App Sc (Pod) Hons
NHMRC Australian Clinical Research Fellow
Institute for Neuromuscular Research, The Children's Hospital at Westmead
Locked Bag 4001, Westmead NSW 2145 Australia

Conjoint Senior Lecturer, Discipline of Paediatrics and Child Health
Faculty of Medicine, The University of Sydney, Australia

In addition to Josh Burns excellent post, I would do a thorough muscle strength and gait exam. Often it's more than just the peroneals that are weak. When you have weak foot muscles the natural tendency of the foot in response to ground reaction force is accentuated. A laterally deviated STJ axis foot will tend to have increased supination and a medially deviated STJ axis foot will tend to have increased pronation. Examine the gait in terms of muscle strength to figure out what you want your orthotic (in shoe orthtic, AFO, guantlet etc.) to do to maintain safe ambulation.

Regards,

Eric

Dear Josh

I have a female patient who recently came to me with laterally weak ankle. I suspected neuropathy. She has very weak peroneals and sufferes foot drop and inversion during swing thru with a toe first foot strike and a tendency to inversion sprain the ankle during weight bearing activities. I have made her orthoses which she admits substantially improve the foot stability and get her back to a heel toe action. She is not keen on having an AFO.

History is: onset 2 years ago, seen GP refered to neurologists has had various tests including nerve conduction and MRI brainscan but she has been discharged with no negative neurological findings. I find this odd since she has no noticable wasting of the peroneals just severe weakness. Also cavus foot and retracted toes. Recently she has moved to this area and has a new GP. I have refered her to her new GP for further evaluation and referal. She appears reluctant to attened her GP tho. Admits no history of contacts or ingestion of heavy metals . She is not on any medication including phsyciatric drugs like lithium.

What would you suggest in terms of possible rehab. Prof Amoud in Dundee UK has had success with electro stimulation of extrinsics to improve foot drop etc. I don't know of anyone in SouthEast UK that does this tho. I have refered her to the Physio at my practice and after a number of sessions she has been discharged with some exercises but there appears to be no improvement in muscle strength after 2 months. The patient reports that the weakness is variable, sometimes feeling a little stronger, but I have not noticed this clinically. On a strength scale of 1 - 10 where 10 is normal she would score 1.

Appreciate your thoughts, cheers Dave Smith

Josh

Just to be a little facetious would a diet of lemon & clostridium Vindaloo be good for these types?

Dave

Dear David,

Interesting case. There are many causes of cavus foot and retracted toes, of which most are termed idiopathic (unfortunately). But to also have marked weakness of peroneals and foot drop suggests neurological pathology. I'm not surprised she is reluctuant to have more tests, particualry nerve conduction studies - they are not fun. But they can be very useful along with needle EMG (muscle pathology) - also not fun.

To enhance management a diagnosis would be useful, especially if it is progressing. If there is a family history, if ankle/knee reflexes are absent or reduced, and/or if babinski is positive, I suggest a second neurology opinion is warranted to clarify upper/lower motor neuron involvement. If still no diagnosis and nerves seems to be functioning normally then Functional Electronic Stimulation through a rehabilitation specialist may be worth considering.

However, I would be really keen to pursue and confirm a diagnosis in this case.

Kind regards
Josh

Treatment for Charcot-Marie-Tooth disease.
Young P, De Jonghe P, Stögbauer F, Butterfass-Bahloul T.
Cochrane Database Syst Rev. 2008 Jan 23;(1):CD006052.

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Charcot-Marie-Tooth (CMT) disease will often manifest itself with weakness of the peroneus brevis muscle more so than the peroneus longus muscle (a common misconception is that it involves both peroneal muscles and I have yet to see a case where the peroneus brevis wasn't the most weak muscle). As a result of this imbalance of peroneus brevis weakness more than peroneus longus weakness, these patient may develop quite significant plantarflexed first ray and forefoot valgus deformities and, as a result, have a greatly reduced capacity to generate internal subtalar joint (STJ) pronation moments during weightbearing activities. These patients, therefore, classically present with cavus feet with lateral instability and sometimes inversion ankle sprains.

In order to treat these patients effectively, one must use a a custom foot orthosis to generate enough external STJ pronation moment to make up for the lack of internal STJ pronation moment that should be coming from the peroneus brevis muscle. These patients will not respond to a foot orthosis that ends at the metatarsal necks and the foot orthosis must extend under the metatarsal heads (normally to the sulcus) with a valgus wedge or the gait pathology and symptoms will persist.

Here is the orthosis prescription I use for patients for CMT disease with peroneus brevis weakness:

1. Negative cast the patient with first ray maximally dorsiflexed to reduce medial longitudinal arch height of cast.
2. Balance positive cast 2-5 degrees everted to increase forefoot valgus correction, raise lateral longitudinal arch height and lower medial longitudinal arch height in resultant orthosis.
3. Use extra thick medial expansion plaster thickness on positive cast to lower medial longitudinal arch height.
4. Use 4-5 mm thick polypropylene shell with a flat rearfoot post.
5. Use a 2-4 mm lateral heel skive.
6. Add a valgus forefoot extension to sulcus of korex/EVA from 2nd to 5th metatarsal heads from 0 mm thickness at medial 2nd metatarsal head to 8 mm thickness at 5th metatarsal head.
7. Add plantar filler to lateral longitudinal arch of orthosis to prevent lateral longitudinal arch deformation of orthosis during gait.
8. Make heel contact points of orthoses 3-4 mm thick.

This type of foot orthosis should greatly aid the patient in walking with less pain, less gait instability and more endurance. However, as the CMT advances, and ankle dorsiflexion weakens, an ankle-foot orthosis may need to be substituted depending on their neurological situation at that point in time. You must remember that CMT is a progressive neurological disease and, as such, these patients should be followed up for routine visits every 6-12 months to keep up with any changes in their foot orthoses or neurological function.

Hope this helps.

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Kevin

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Kevin

That's a great help for clinicians managing this complex and challenging neurological disorder and I concur with your suggestions for foot orthoses. Particularly agree with the follow up regime and re-assesment at the stated intervals.

Kindest.

Mark

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