median nerve mobility in CTS?

[Mat BR]

Hi Steve, do you assess median nerve mobility in CTS (https://journals.sagepub.com/doi/full/10.1177/0284185118762246)?
A very subjective measure still, but the concept is interesting. Do you find there is an added value?

[Stephen Bird]

Hi Mat,

Good question and it is something I have an open mind about at the moment.

Firstly if you have not read this article please have a look. I think it is an outstanding review of the topic.

https://onlinelibrary.wiley.com/doi/full/10.7863/ultra.15.12014

Assessment for mobility has been talked about for a very long time but I am still to be convinced it makes much of a difference to my diagnostic output.

If you ask the patent to move their fingers while scanning you can see the median nerve freely bobbling about and this gives an impression there is free movement of the structures in the tunnel. The problem I have with the test is that even in cases of severe CTS there is still free movement.

When we inject the median nerve you can often appreciate that it is stuck down to the undersurface of the transverse carpal ligament or the superficial surface of the flexor sheath but I don’t get this information from the dynamic movement prior to injection.

There is also a lumbrical intrusion test where the patient makes a fist while you scan the carpal tunnel. In most people the lumbrical muscles enter the distal tunnel but in people with strong hands (rock climbers etc) the lumbricals can reach the proximal tunnel and significantly displace the nerve. The opposite may also be true with a flexor muscle intrusion test where the bellies of FDS and FDP enter the tunnel with an open hand.
There is also a thenar flexion test where the patient squeezes an object like a roll of hospital tape between their thumb and their index / middle fingers activating the thenar muscles. This may cause compression of the nerve i the tunnel.
I have wondered recently if the craze of gaming and using thumbs / thenar muscles much more may lead to thenar hypertrophy and if this contributes to median nerve compression as the thenar muscles insert onto the transverse carpal ligament (food for thought)

So in summary, I am interested in these types of dynamic assessment and in some cases I think it helps me to understand the cause of the CTS rather than actually making the diagnosis itself.

How is your experience?

Steve.

[Mat BR]

Thanks Steve!
I don’t really use median nerve mobility tests either, because I find them hard to interpret so far and they don’t add that much info to the absolute area, forearm-to-wrist ratio and the longitudinal aspect in&out of the CT.

So far, we still see mostly middle aged people with CTS (as opposed to young “gamers”), but it’ll be interesting to see in a decade or two if there is any change in the incidence of CTS and also 1stCMC / STT OA.

[Stephen Bird]

Watch the tsunami build!

Steve.

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