Swollen tibial nerve and medial plantar nerve

[Xue Heng]

Hi, Steve. Nice to meet you again on the forum.
I have a case here.
71F, left tibial region swelling with palpable mass for over 4 months, accompanying great and 2nd toe tingling, numbness, and “walking on sand” sensation, gradually extending proximally to plantar forefoot. Patient has less walking tolerance (can only walk 2 blocks before having to rest) Motor function normal. No trauma history or clear precipitating factor. Patient had been using foot message machine(motion and heat), and recalled possible mechanical issue 10/2023, with left foot tightly squeezed (mediolaterally) for several second, with subsequent edema the next day.
Do you have some suggestion on that case?
Looking forward to your reply, thank you for your answer.

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[Stephen Bird]

Hi Xue,

So nice to see your excellent work again,

The video did not load up as the file was too large,

If you email it to me I can compress it and upload it for you, or you can do it yourself if it is easier.

Despite this the still images are really beautiful and make the case.

that tibial nerve is massively swollen.

I assume it was proximal to the bifurcation into the medial and lateral plantar nerves.

The symptoms seem to be medial plantar nerve related as this is the sensory neural provider for the first and second toes exclusively, with the 3rd toe being shared with the medial and lateral plantar nerves.

It is worth looking at the muscles of the foot for atrophy changes. The medial plantar nerve motor drives the Abductor Hallucis and the Flexor Digitorum Brevis muscles, while the Quadratus Plantae and the Abductor Digits Minimi are lateral plantar nerve driven. So it would be interesting to see if there was any subtle atrophy changes in the muscles and which muscles are involved.

As for the cause of the neural oedema. It does not look like a nerve sheath tumour as the fascicles are still intact, although swollen. So what would cause such dramatic neural oedema? In the tarsal tunnel any space occupying lesion could be a cause and a subtalar joint ganglion is the most common, however I can see no evidence of this.
I suspect the foot massage machine is unfairly compressing and irritating the nerve and perhaps the footwear of the patient also requires some assessment.

I will add more once I have seen the video.

Steve.

[Xue Heng]

Hi, Steve. I have compressed the videos and upload them. Thank you for your timely and detailed answer.
I did not scan the muscles of the foot for atrophy changes, becasue they cannot suggest the causes of neural oedema.
The neural oedema is so dramatic that I have never seen such findings before.
Four months have passed since the compressing of the foot massage machine, but the degree of oedema does not change at all. That really confuse me.

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[Stephen Bird]

Hi Xue,

The videos help a lot.

You can see the division of the tibial nerve into the medial and lateral plantar nerves and your long axis image of the swollen nerve is the medial plantar nerve branch, which likely explains why most of the symptoms are involving the great toe and the second toe.

BUT the lateral plantar nerve is also abnormal, but with a different pattern.

The lateral plantar nerve just has a couple of fascicles that are really enormous.

The medial plantar nerve also has a hypo echoic halo around it in a localised area, which I am uncertain about.

I don’t think I have ever seen such dramatic neural oedema in this location.

OK, how about a systemic cause.

We are getting exotic now, but lets consider the possibility of one of these conditions:

Leprosy

Guillain-Barré syndrome

chronic inflammatory demyelinating polyneuropathy

Charcot-Marie-Tooth disease

Amyloidosis

I am heading down this path, as I have never seen such neural oedema in this area.

The other thing I would do is look at some other nerves in the same patient. The other tarsal tunnel, both carpal tunnels, both brachial plexus. If you can find other neural oedema, then you know it is a systemic condition.

I did think for a minute about an intra-neural ganglion, but it does not have the typical appearance.

If I saw this in the upper limb I would also consider Parsonage Turner Syndrome (Neuralgic Amyotropy) , but I don’t know ow if you can get a similar condition outside of the brachial plexus distribution.

What a case!

Does anyone else have an idea as to what this is?

Keep us posted Xue.

Steve

[Stephen Bird]

Hi Xue,

This makes me think about a case I had a couple of years ago.

The patient had no neural symptoms at all, but while performing a MSK scan for non neural symptoms it struck me that EVERY nerve in his body was like a big rope.

Global neural enlargement.

If anyone has a diagnosis for me I would be grateful!

Remember, he was a completely asymptomatic early 20’s male.

I will upload some videos.

Steve.

Steve.

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[Stephen Bird]

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