Medial and lateral antebrachial sensory cutaneous stimulation

[gecko]

For r/o brachialplexopathies, i've been adding these studies, however, I find it hard to get consistent wave forms.

For medial antebrach sensory, I'm stimulating just proximal and ventral to the medial epicondyle, and active site is 14 cm distal on a line drawn from the stim site to the distal ulnar head. Ref site is 4 cm distal to that on that same line. The lateral antebrach sensory, I'm stim just lateral to the bicep tendon in the cubital fossa, and active site is 14 cm on a line drawn to the distal radial head. Again reference site is 4 cm distal to that.

This was taken directly from Shapiro's test.

Any suggestions? Are most of you using these sensory tests on your brachialplexopathy studies?

Also, is there a typical set of muscles you screen for to help localize the lesion?

Thanks for any advice.

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[SSdoc33]

i think the reason you are discovering that it is hard to find consistent waveforms is because IT IS hard to find consistent waveforms for those smaller sensory nerves. same with lat fem cut, saphenous, m/l plantar, even sural. im sure the purists who consider themselves EMG wizards will tell you that they always get great waveforms, bit i have similar difficulties. btw, i usually go above proximal to the elbow for MABC.

 

[PMR 4 MSK]

I also have a lot of difficulty with these. My advice is whenever you can, practice on yourself and anyone else you can find. Offer to buy them lunch if they'll let you do a few stimulations on them!

You're doing it the correct way otherwise. I do find myself occasionally "fishing" with both the stim and pickup sites, to see if I can find the waveform. I'm betting there's more variability to their position than we realize.

 

[tchoupdoc]

In residency, with Nicolet Viking IV's, three certified techs, and residents able to take all the time needed, I never saw MABC's, LABC's, or LFC responses.

 

[caedmon]

Although we have techs do most of our NCVs, we routinely get responses with MAC and LAC and do typically use them if a brachial plexopathy is suspected. Set up is similar, but we use 12 cm distal for G1 on both and stimulate just medial to the biceps tendon for MAC and just lateral to the biceps for LAC. Frequently it does require a little fishing around with G1 and stim. We don’t even do LFCN studies due to poor reliability from test to test.

For a muscle screen I usually start with a general radiculopathy screen: FDI, APB or opponens or FPL, pronator, biceps, triceps and deltoid. Then cervical paraspinals and possibly EIP to confirm a lower trunk or posterior cord, brachioradialis can be helpful for upper trunk or posterior cord, and rhomboids if normal can help rule in an upper trunk.

 

[gecko]

Thanks...this is all great advice, and I really appreciate the help. I've been getting quite a few referrals for r/o brachialplexopathies recently, and feel a need to catch up on my diagnostic skills here.