Foot-Drop is a common problem for people with MS and is a very common cause of falls. It can be caused by different mechanisms.
This is usually caused by damage to the nerve that innervates the muscle that lifts the foot up, bending the ankle. The muscle is called the Anterior Tibialis. To locate this muscle, sit in a chair with your foot flat on the floor. Locate the muscle that runs just along the outside of the shin bone on that leg. Keep your fingers on it. Now, keeping your heel on the floor, lift your forefoot up, bringing the toes up toward the knee. You will feel the muscle contract to pull the forefoot up. That is the Tibialis Anterior.
If the nerve to that muscle is damaged it will show up as being unable to bring the toe up or to do it very weakly and slowly.
Now, why is this important? Being able to lift the toes (the forefoot) up is crucial to being able to walk smoothly and safely. As we stride forward we pull up the toes to clear the ground as the foot swings forward. If we can't pull them up enough, then they will drag against the ground and often cause us to stub them on the ground and trip us up. We can compensate by lifting the knee much higher to pull the foot up so that it clears the ground even though the toes can't pull up. The we tend to place the foot back down with a "plop". This is called an absolute foot-drop.
If we can pull up the toes just a little we can usually walk on even ground, but will trip over the slightest irregularity. Area rugs are killers as are cracks in sidewalks or any other small rise in the ground.
This type of Foot-Drop is present as long as the nerve is damaged. The damage can arise up in the central nervous system, as in MS, and is usually a spinal lesion. As we know MS lesions sometimes heal and if this happens, the foot-drop can resolve. Damage can also happen to the peripheral nerve, the Tibialis anterior. This would be a peripheral neuropathy. Peripheral nerves can also sometimes heal. If healing occurs the Foot-Drop will disappear.
A little historical note here. In the depression or any time alcoholics can get drinking alcohol, they sometimes drank either methanol (a neurotoxin) or a medicinal called Jamaican Ginger which bootleggers adulterized by adding a substance that was later discovered to be a neurotoxin. This caused all sorts of peripheral neuropathy, especially to the nerve going to the tibialis anterior muscle. They walked with this gait in which they lifted the leg high to bring it forward and plopped it down, toe first. The condition was referred to as "Jake Leg".
In the second type foot-drop is caused by spasticity and not by a weakness of the tibialis anterior muscle. If a person has "extensor spasticity" they will have the tendency to have their foot pull downwards via the contraction of the calf which has a higher tone in it. When these people do the test trying to lift their forefoot while the heel is on the ground, they will often be able to do it quite easily if they raise the toes slowly. However, during the act of walking the spasticity of the calf will activate and pull the foot downward, even though the person is trying to raise the foot to clear the ground during the stride forward. So, they trip anyway. This is called a "functional" foot-drop.
I have this second probem. When I am sitting I can easily bend my ankle up to bring up my foot. But when I walk the toe drags the ground. I also cannot lift the leg higher to compensate for this as I also have hip flexor weakness. I drag the foot so much that I have a deep, thick callus on the side of the great toe.
Many of us have observed that spasticity can vary thoughtout the day or day-to-day. I find that I have almost no spasticity after a long rest and my first 50ft or so of walking I may have a perfectly normal stride. But, the muscles fatigue quickly, and soon I am dragging my foot.
The standard treatment for both types of foot-drop is a brace called an AFO - Ankle Foot Orthotic - which holds the foot in the same position as if you were just standing on the ground - the foot is at right angles to the lower leg.
Another part of the treatment is to frequently stretch the Achilles' tendon so that it does not shorten permanently either from the persistent droop of the foot or from the pull of spasticity. Also if the person is able to lift the foot, exercises to strengthen the muscle should be done to increase or maintain what strength is there.
There are also electrical biomechanical devices that can be programmed so that the device will deliver a signal to make the tibialis anteroir contract (pulling up the foot) at the right moment as we walk, instead of using a brace. There are several of these. A few are called the Walkaid, the ODSF - Odstock Foot Drop Stimulator, and the Ness H200 or Bioness. The generic term for this type of devise is FES Functional - Electrical Stimulator.
I looked into one of these at one time. It would have been $6000 out of pocket, and I had to pass. But, some insurances might help pay for such a device.
During a neuro exam, what are they looking for when one is asked to place the heel of one foot on the opposing knee and drag it down the shin?
I know that I did not do well with this one yesterday and had to repeat it several times for the doc. She finally had me repeat it not from the knee, but from mid shin down with my right leg over the left leg. I do have more problems on the right side of my body than the left.
I also told her that I noticed that I have been walking more flat or slap footed over the past month.
I worked with someone years ago who had MS and he definitely had drop foot. From what you describe, I don't have drop foot, but probably something else.
The Heel-down-the-Shin test is a test of smooth coordination and tests each side of the cerebellum. In cerebellar damage (lesion) the heel cannot move smoothly in a straight line down the shin. It wavers from one side to the other.
Weakness in certain muscle groups can make the test hard to perform.
My first sign that I was developing foot-drop was going up carpeted stairs. I could see that the toe of the right foot would touch the edge of the stair and leave a mark against the nap of the carpet. As the weeks went by the mark got wider and deeper and eventually I could feel the brush against the edge of the step even through my shoe.
Then I started tripping.
the "slap-footed" walk sounds suspiciously like drop foot. Try walking through firm sand and see if there is a mark where the toe drags.
I recently started PT and I do have foot drop on the left side where I have most of my issues. My foot will lock up both ways...I can't bring it all the way downward (away from me & straight out) and I can't bring it up towards me (point my foot and toes up ).
I do see some improvement after PT for a few hours if I have a muscle relaxer on board with bringing my foot in a downward position & straight out, but so far, I still can't bring my foot up towards me. It stops like my foot is flat on the ground and won't budge past that point.
The improvement I do see is short lived..it will lock back up within a few hours after PT and I trip over runners on the floor. If I try to do the neuro test where you walk on your heels..I fail on the left side..always. There is no lift.
Is my problem with bringing my foot all the way downward and straight out..is that a foot drop problem as well? They started to put me on a slant board at PT and I did get a little of a response with bringing my foot all the way down..just nothing with bringing the foot all the way up towards me. I guess this all takes time? Maybe I need an AFO?
Quix, thanks for your (as usual) very helpful explanation.
I meant to post this before, but I am so far behind on everything in my life at the moment...
Anyway, I got a letter from the Bioness people and they're having a half off sale on refurbished L300 foot drop systems--only $2900. I got this a while ago so they may be out by now, but if you're interested, call them at 1-800-211-9136 option 2.
Best description I've heard, and also the one that makes it most clear to me that I did indeed have this, the first type, with the foot slapping down like I was wearing a flipper, back when I was having all my other symptoms. Also, I know even more surely that the superneuro so-called MS expert who did my 3rd neurological exam was evidently paying little attention, as my drag-the-heel-along-the-shin line looked like the Great Wall of China, among other things. His notes contradict what I saw with my own eyes.
I'm not sure if I have the "I" or "II" type, as you describe. Have had it off and on for years, though. That anterior tibialis muscle is weak on me, and often it spasms, as well. And sometimes during that spasm, I'll have fasciculations near the insertion of that muscle (as opposed to the origin). But my calves spasm more often, and more powerfully.
I fail the tandem walking (I know, cerebellar cr@p), but then my neuro asks me to walk on my toes (I'm good at that), and then on just my heels. I simply can't do that. I can't lift my feet up, let alone walk on my heels.
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