A case of plexopathy... EMG is king in localization! | Figure 1

Montecristo

A case of plexopathy... EMG is king in localization!

I want to share a nice case to wrap up my EMG rotation...

I've found in EMG localization is supreme, very nice how by testing different nerves and territories, we can come up with specific localizations, in this case, can change management, let's dive into it:

86F, quite healthy for her age and living independently, 2 months ago, while in shower, slipped and fell, had a right anterior shoulder dislocation, reduced in ER, no surgery, sling, and follow up with ortho. however as time passed by, there was no movement on right arm...(no bueno!). Long story short, a previous EMG showed a pan-brachial plexopathy, however as you know, a big part of EMG is the activation of the muscles, since she had no volitional movement, they asked us to repeat EMG now, 2 months out of the injury (that's a fair timeline).

Clinically she is having a bit of movement, specifically elbow flexion, minimal finger abduction, not meaningfully (if anything 2-3/5), 0 movements on shoulder, 0 movements on thumb. Feels numbness throughout her arm, no pain. As they know already the brachial plexus was injured (crushed), their question is if she would be a candidate for tendon transfer (aka, to see if neighboring muscles are intact so they can plan this surgery).

We did NCS and EMG

The first table is the EMG summary, as you can see, lots of PSW (positive sharp waves, seen in blue, remember "positive" is downward, by convention), these are spontaneous activity showing active denervation. Also, I captured a polyphasic discharge (see in the second blue screen), as you can see, this shows a discharge when she activates a muscle, showing the remodeling that has occurred (polyphasic wave). NCS summary shows NR (not recordable) inputs on different nerves, as you can see trapezius was tested (CN 11) and supraspinatus (suprascapular nerve), these too are candidates to share the tendons, and they are working fine. As you see in the diagram, the suprascapular nerve (innervates supraspinatus) comes off of the upper trunk before this will join the posterior chord. This is how this allows us to localize this as a pan-brachial plexopathy, with upper plexus more damaged showing active neurogenic pattern, sparing the suprascapular nerve, hence distal to it.

That's better localization than MRI :)

Diagnosis added by author

Diagnosis: pan plexopathy with more upper trunk involvement, distal to suprascapular nerve