New onset foot drop

[pastafan]

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57 yo female presents with 5 week history of left foot drop no pain. No trauma, recent surgeries, unremarkable PMH. Symptoms preceded a long cross country flight. Seen by PMD and w/u including brain MRI (-) plus EMG. EMG report:

This is an abnormal electrodiagnostic study of the left lower extremity. Although there is no evidence of focal slowing in the peroneal across fibular head segment, the absent superficial peroneal response and borderline low peroneal motor amplitudes associated with evidence of acute denervation changes are concerning for a common peroneal neuropathy distal to the take-off of the branch innervating the short head of the biceps femoris. A L5 radiculopathy is considered much less likely given the paucity of denervation changes in other sampled L5 innervated muscles. Similarly, a lumbosacral plexopathy is not considered likely. There is no evidence of an additional mononeuropathy or more diffuse polyneuropathy involving the left lower extremity on this study.

I ordered Lumbar MRI but it looks ok. Disc bulge L4-5 and small central herniation L5-S1 w/o neural impingement.

Have you seen isolated superficial perineal insult w/o history of trauma to nerve/stirrups/etc? What would be your next move?

 

[SSdoc33]

57 yo female presents with 5 week history of left foot drop no pain. No trauma, recent surgeries, unremarkable PMH. Symptoms preceded a long cross country flight. Seen by PMD and w/u including brain MRI (-) plus EMG. EMG report:

This is an abnormal electrodiagnostic study of the left lower extremity. Although there is no evidence of focal slowing in the peroneal across fibular head segment, the absent superficial peroneal response and borderline low peroneal motor amplitudes associated with evidence of acute denervation changes are concerning for a common peroneal neuropathy distal to the take-off of the branch innervating the short head of the biceps femoris. A L5 radiculopathy is considered much less likely given the paucity of denervation changes in other sampled L5 innervated muscles. Similarly, a lumbosacral plexopathy is not considered likely. There is no evidence of an additional mononeuropathy or more diffuse polyneuropathy involving the left lower extremity on this study.

I ordered Lumbar MRI but it looks ok. Disc bulge L4-5 and small central herniation L5-S1 w/o neural impingement.

Have you seen isolated superficial perineal insult w/o history of trauma to nerve/stirrups/etc? What would be your next move?

the EMG write-up/report is actually pretty good. i usually dont trust results, but just by the language alone, i think the electromyographer was good.

if the MRI doesnt show L5 compression, there is not all that much to be done other than PT with funcitonal E-stim, +/- AFO. id hold off on the AFO for now.

it doesnt really matter if the compression is at the fibular head, or below it. this sounds like conduction block from crossing her leg for 5 hours or direct compression on the side of her leg. it should come back. the fact that there is still a good peroneal motor amplitude is a good sign. this is when it helps to be a physiatrist. 😉

 

[pastafan]

Foot drop preceded long plane trip.

This is when being a member of this forum is a good thing. ;-)

 

[Ducttape]

did she have any compressive condition (ie surgery, prolonged time in lithotomy position) for any reason prior to her cross country trip?

prolonged immobilization? is she very thin, anorectic, alcoholic, at risk for autoimmune diseases?

 

[pastafan]

did she have any compressive condition (ie surgery, prolonged time in lithotomy position) for any reason prior to her cross country trip?

prolonged immobilization? is she very thin, anorectic, alcoholic, at risk for autoimmune diseases?

No compression history before trip. 5'7 203 lb, not an alcoholic.

 

[Orin]

No compression history before trip. 5'7 203 lb, not an alcoholic.

How much longer before the trip? Was it in her sitting/packing/planning stage?

Based on that EMG, I would do an ultrasound based exam of the region and trial a steroid injection if you really were crazy enough to to stick a needle in it. It does sound like a good case for functional electrical stimulation to help with rehab though.

 

[lobelsteve]

Emg book by bashir katirji has excellent case study on peroneal neuropathy.

 

[Ducttape]

How much longer before the trip? Was it in her sitting/packing/planning stage?

Based on that EMG, I would do an ultrasound based exam of the region and trial a steroid injection if you really were crazy enough to to stick a needle in it. It does sound like a good case for functional electrical stimulation to help with rehab though.

what would be the purpose of an injection if there is probable already established neuropathy and weakness?

if anything, channeling my inner drusso, a PRP injection would seem more logical, right?

 

[lonelobo]

I have never seen an Injection improve a foot drop

 

[painfree23]

I tell patients all the time. I don’t do injections for weakness relief, I do it for pain relief

 

[MD87]

When you say foot drop, are we talking 0/5 ankle dorsiflexion? 4/5? Does she has any sensory loss? Weakness less than 3/5 is pretty much never radiculopathy, regardless of what the MRI shows, due to dual innervation of all the lower extremity muscles that are tested regularly during a pain physical exam. In the absence of a significant drop in amplitude over the fibular head, I think it's hard to chalk it up to conduction block, though if she is already improving, resolving peroneal neuropathy is the likely culprit.

It may be worth checking an ultrasound to track the nerve, as the nerve could have been compressed at a site that isn't easily tested during EMG/NCS. Additionally (especially if you don't trust the electromyographer), it may be worth a neurology referral. Painless weakness is something scary until proven otherwise (ALS?)

 

[SommeRiver]

There's nothing to do here other than PT and time. Compression neuropathy gets better.

 

[oreosandsake]

u

57 yo female presents with 5 week history of left foot drop no pain. No trauma, recent surgeries, unremarkable PMH. Symptoms preceded a long cross country flight. Seen by PMD and w/u including brain MRI (-) plus EMG. EMG report:

This is an abnormal electrodiagnostic study of the left lower extremity. Although there is no evidence of focal slowing in the peroneal across fibular head segment, the absent superficial peroneal response and borderline low peroneal motor amplitudes associated with evidence of acute denervation changes are concerning for a common peroneal neuropathy distal to the take-off of the branch innervating the short head of the biceps femoris. A L5 radiculopathy is considered much less likely given the paucity of denervation changes in other sampled L5 innervated muscles. Similarly, a lumbosacral plexopathy is not considered likely. There is no evidence of an additional mononeuropathy or more diffuse polyneuropathy involving the left lower extremity on this study.

I ordered Lumbar MRI but it looks ok. Disc bulge L4-5 and small central herniation L5-S1 w/o neural impingement.

Have you seen isolated superficial perineal insult w/o history of trauma to nerve/stirrups/etc? What would be your next move?

Agree on the thought out Edx results write up. this isn't a cut and paste answer.


I pull out the ultrasound. it's not hard to follow the course of the nerve. typically nerves are swollen just distal to the actual entrapment point. you find all sorts of interesting things that cause focal nerve impingement including cysts, osteophytes, thickened fascia, etc. if it's a cyst, it's an easy fix as long as it doesn't come back.

it's easy to find the sciatic near the popliteal fossa. then trace it distally to see where the two branches diverge into tibial/C peroneal. you can also hydro-release the nerve once you find the entrapment point. it's essentially a higher volume nerve blocks AT the entrapment site.

 

[pastafan]

When you say foot drop, are we talking 0/5 ankle dorsiflexion? 4/5? Does she has any sensory loss? Weakness less than 3/5 is pretty much never radiculopathy, regardless of what the MRI shows, due to dual innervation of all the lower extremity muscles that are tested regularly during a pain physical exam. In the absence of a significant drop in amplitude over the fibular head, I think it's hard to chalk it up to conduction block, though if she is already improving, resolving peroneal neuropathy is the likely culprit.

It may be worth checking an ultrasound to track the nerve, as the nerve could have been compressed at a site that isn't easily tested during EMG/NCS. Additionally (especially if you don't trust the electromyographer), it may be worth a neurology referral. Painless weakness is something scary until proven otherwise (ALS?)

Motor is 0/5. She does have sensory deficit. Decreased sensation to pinprick L4,L5,S1 of leg and L5,S1 foot. Saw her back yesterday and ordered PT/Astim

 

[Taus]

Motor is 0/5. She does have sensory deficit. Decreased sensation to pinprick L4,L5,S1 of leg and L5,S1 foot. Saw her back yesterday and ordered PT/Astim

That weak without clear reason I’d suggest Neuro consult.

 

[oreosandsake]

0/5 warrants imaging.

A stim??

 

[MD87]

S1 dermaotme not supplied by peroneal. Just because someone put thought into the NCS report doesn’t mean it’s correct. Dense weakness like that should have significant amplitude drop and not be a borderline study. Neurology referral is warranted.

 

[SSdoc33]

[

S1 dermaotme not supplied by peroneal. Just because someone put thought into the NCS report doesn’t mean it’s correct. Dense weakness like that should have significant amplitude drop and not be a borderline study. Neurology referral is warranted.

you dont know your electromyography. you can have significant weakness with conduction block WITHOUT an amplitude drop. i suspect that is the case here.

who said anything about S1? ALS?

not a bad idea to track the nerve under u/s if you can find anyone around you who can do it.....

SMH.....

 

[lonelobo]

[


you dont know your electromyography. you can have significant weakness with conduction block WITHOUT an amplitude drop. i suspect that is the case here.

who said anything about S1? ALS?

not a bad idea to track the nerve under u/s if you can find anyone around you who can do it.....

SMH.....

Are there surgeons using US to determine surgical releases for peroneal nerve entrapment?

 

[SSdoc33]

Are there surgeons using US to determine surgical releases for peroneal nerve entrapment?

im sure someone out there is. i can see oreosandsake's point. if there is a mass or something, then removal could help. i think that's unlikely, but direct visualization could confirm what the EMG says, especially if you see nerve swelling.

i would probably wait on it myself and see if it comes back, which i would expect it to.....

 

[pastafan]

Neuro consult scheduled but it will be a month or so. Astim ordered. I don't know anyone around to do ultrasound study for her.

 

[cowboydoc]

the EMG write-up/report is actually pretty good. i usually dont trust results, but just by the language alone, i think the electromyographer was good.

if the MRI doesnt show L5 compression, there is not all that much to be done other than PT with funcitonal E-stim, +/- AFO. id hold off on the AFO for now.

it doesnt really matter if the compression is at the fibular head, or below it. this sounds like conduction block from crossing her leg for 5 hours or direct compression on the side of her leg. it should come back. the fact that there is still a good peroneal motor amplitude is a good sign. this is when it helps to be a physiatrist. 😉

Not so fast with calling conduction block. First there is no denervation with conduction block. When was the study done? Was there any voluntary motor units?

I'd absolutely put an u/s on this at the lateral knee (maybe a MRI of you can't run an u/s. There probably isn't anything to see, but there might be. I hate the idea of being a neurologist, making a dx and then saying "welp, see you later."

If there isn't anything there, don't inject, but you should look!

 

[MD87]

[


you dont know your electromyography. you can have significant weakness with conduction block WITHOUT an amplitude drop. i suspect that is the case here.

who said anything about S1? ALS?

not a bad idea to track the nerve under u/s if you can find anyone around you who can do it.....

SMH.....

1) Pastafan said that there is decreased sensation to light touch at S1. Please explain how a peroneal neuropathy could cause that.
2) The suggestion of ALS was prior to Pastafan saying the patient had sensory loss. Obviously the sensory loss rules out ALS.
3) I don't know my electromyography? The very definition of conduction block is in fact a drop in amplitude when stimulating proximal to the lesion and return of amplitude when stimulating distal to the lesion. The patient has some axonal loss based on denervation potentials in other L5 muscles, but clearly if the CMAP is mostly preserved, axonal loss is not a huge contributor to the patient's weakness. Please enlighten me as to how someone can have complete paralysis of peroneal musculature due to a conduction block at the fibular head without any significant drop in amplitude across the fibular head. The only conduction block that could explain 0/5 strength is one proximal to where the physician stimulated. And please explain how a peroneal lesion can cause S1 sensory loss. This patient has had complete paralysis for 5 weeks, spontaneously. This cannot be explained by the NCS findings. They need more proximal stimulations performed and/or neurology referral

 

[deleted993114]

u


Agree on the thought out Edx results write up. this isn't a cut and paste answer.


I pull out the ultrasound. it's not hard to follow the course of the nerve. typically nerves are swollen just distal to the actual entrapment point. you find all sorts of interesting things that cause focal nerve impingement including cysts, osteophytes, thickened fascia, etc. if it's a cyst, it's an easy fix as long as it doesn't come back.

it's easy to find the sciatic near the popliteal fossa. then trace it distally to see where the two branches diverge into tibial/C peroneal. you can also hydro-release the nerve once you find the entrapment point. it's essentially a higher volume nerve blocks AT the entrapment site.

Check for peroneal nerve cyst/schwanoma or popliteal artery aneurysm in the absence of trauma to the knee/popliteal fossa.

 

[Bsb2015]

57 yo female presents with 5 week history of left foot drop no pain. No trauma, recent surgeries, unremarkable PMH. Symptoms preceded a long cross country flight. Seen by PMD and w/u including brain MRI (-) plus EMG. EMG report:

This is an abnormal electrodiagnostic study of the left lower extremity. Although there is no evidence of focal slowing in the peroneal across fibular head segment, the absent superficial peroneal response and borderline low peroneal motor amplitudes associated with evidence of acute denervation changes are concerning for a common peroneal neuropathy distal to the take-off of the branch innervating the short head of the biceps femoris. A L5 radiculopathy is considered much less likely given the paucity of denervation changes in other sampled L5 innervated muscles. Similarly, a lumbosacral plexopathy is not considered likely. There is no evidence of an additional mononeuropathy or more diffuse polyneuropathy involving the left lower extremity on this study.

I ordered Lumbar MRI but it looks ok. Disc bulge L4-5 and small central herniation L5-S1 w/o neural impingement.

Have you seen isolated superficial perineal insult w/o history of trauma to nerve/stirrups/etc? What would be your next move?

What was the outcome with your patient?


Sent from my iPhone using SDN

 

[Baron Samedi]

Obviously the sensory loss rules out ALS.

While this is true, there are other motor neuron diseases that can affect sensory nerves -- Progressive muscular atrophy come to mind.

I would agree that abnormal spontaneous activity is not consistent with conduction block and implies axonal loss. If it were conduction block, you would expect normal amplitudes when stimulating distal to the compressed site and based on the limited info, that doesn't appear to be the case. It should still improve with time as reinnervation occurs, but much slower than if it were solely conduction block.

 

[pastafan]

What was the outcome with your patient?


Sent from my iPhone using SDN

Sorry for the late reply. I saw her again after a month of PT and she was having some improvement. Due to insurance issues I lost the patient to follow-up and my call to her asking about status was not returned. I'm also interested and we will reach out to her again.