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Pt referred for EMG RUE, order reads "R/O Radial tunnel syndrome, Dx - hand numbness."

Umm, ok.

Which resident or med student out there can tell us what's wrong with that order? Attendings can't answer yet...
 

cbest

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Second year medical student here...

Based on my research, radial tunnel syndrome would present with more sharp or 'lancinating' pain over the dorsal forearm and/or lateral elbow, rather than hand numbness.

Looking forward to hearing more about this and other cases!
 

PMR 4 MSK

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Second year medical student here...

Based on my research, radial tunnel syndrome would present with more sharp or 'lancinating' pain over the dorsal forearm and/or lateral elbow, rather than hand numbness.

Looking forward to hearing more about this and other cases!
that's partially true, very good start...
 
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topwise

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I've never seen radial tunnel syndrome personally, but I thought it was a very similar presentation to lateral epicondylitis. Even though the superficial radial nerve does give sensation to the radial aspect of the dorsum of the hand, I believe it's the PIN that's compressed in radial tunnel syndrome, so sensation in the hand shouldn't be affected. Right?
 

PMR 4 MSK

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I've never seen radial tunnel syndrome personally, but I thought it was a very similar presentation to lateral epicondylitis. Even though the superficial radial nerve does give sensation to the radial aspect of the dorsum of the hand, I believe it's the PIN that's compressed in radial tunnel syndrome, so sensation in the hand shouldn't be affected. Right?
Exactly. The presence of tingling in the hand precludes a Dx of RTS. RTS only affects the PIN, and thererfor is purely a motor problem. There can be pain from concominant tendonitis, muscle fatigue or neuritis, but in a pure RTS or PIN syndrome, weakness is the predominating symptom - weakness of extensors.

RTS can be considered on the DDx of wrist drop, but proximal lesions are statistically more common, if only because humeral fracture is one of the most common causes or radial palsy. Since I work with a bunch of orthopods I see proximal radial neuropathy a few times a year. I've only ever seen a few cases of RTS/PIN I would reliably call, and only because of the needle exam.

I'll do radial nerve stimulation, but it is very difficult to do and even harder to measure accurately. It often takes very high stimulations with surface stim which blows the take-off point to hell. It's so deep in the antecubital fossa that I often have to use 400 mcSec stims at 100 mA. Even in the forearm 200 mcSec is often needed. THe distances used are often quite short except in really tall people which brings about more error.

I really only find the radial NCS to be of value in looking for recovery in terms of amplitude, or to see if any fibers reamin after wallerian degeneration should have stopped after proximal lesion.

In the case of this pt, she had normal motor and sensory findings in the median, ulnar and radial nerves and a normal needle exam. She did have a very positive Tinel's over the superficial radial (sensory) nerve in the forearm, with radial-dermatome paresthesias, so I labeled it as EMG-negative radial sensory neuritis.
 
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