Thread by @zach_london

1/11
Time for a #tweetorial on one of my favorite topics: Wrist Drop. @AANMember @NMatch2022 #neurology #futureneurologist #neurotwitter #neurotwitternetwork @AANEMorg #meded @KoriPoRodri

The first thing you should think of when you see a patient with weak wrist extension is…

2/11
This. Compression of the radial nerve at spiral groove. And usually, we think of it as being caused by...

3/11
This. And by the way, if you’re ever curious about the surprising origins of the term “Saturday Night Palsy,” read this article. pubmed.ncbi.nlm.nih.gov/12188953/

But I digress. The spiral groove (aka radial groove) is not the only peripheral localization for wrist drop.

4/11
This chart shows you who you can distinguish five peripheral localizations by only testing four other muscles. (How is that even mathematically possible?)

5/11
But when a patient shows up in the ED with a wrist drop that wasn’t there the night before, you are really thinking of the 2 most likely things:
1. Radial mononeuropathy at the spiral groove
2. Stroke. (In the infamous hand knob!)
How do you tell them apart without imaging?

6/11
The brachioradialis may be particularly helpful. It is supplied by the radial nerve, but it is a FLEXOR. It flexes the elbow with the thumb pointing up. CNS lesions often affect extensors more, so the brachioradialis (both the muscle and reflex) may be spared in stroke.

7/11
And patients with radial neuropathy can’t extend the wrist at all. Patients with a stroke may have trouble extending it volitionally, but (and I just learned this!) they may be able to extend it when they try to make a fist, because of synkinetic activation of the extensors.

8/11
So a patient with a radial mononeuropathy trying to make a fist would look like this.

9/11
While a patient with a cortical wrist drop trying to make a fist might be able to do this.

10/11
Localization take homes:
1. Check the brachioradialis and compare sides. If weak, you may not need imaging.
2. Have the patient make a fist. If they extend, it's probably a brain problem.
3. Still not sure? Go look at that chart to figure out all the less common things!

11/11
The last point I wanted to make is what to do if you think it's a radial neuropathy.
1. Order OT and get them a cock up wrist splint.
2. Refer for an EMG in 3-4 weeks and tell them to cancel the appt if they are better. And guess what... they almost always are by then!