0:01

All right, and here's our next case. This was a 41 year old.

0:06

He had abrupt onset of shoulder and neck pain,

0:09

and then he had some progressive radiation down the arm.

0:13

He had some resultant weakness.

0:15

Just gonna scroll through these images a few times here.

0:19

We have pretty much imaging from the mid humerus through the mid forearm

0:24

in this particular case.

0:31

And I just have these two axial sequences to show you here.

0:34

So hopefully you've had a chance to identify any abnormalities.

0:39

We'll go on to our next polling question here.

0:43

So question number six for case number six,

0:47

abnormalities of the posterior interosseous nerve.

0:49

Present with what physical exam finding.

0:54

So is this a claw hand, a circle sign,

0:57

forearm flexion weakness or finger droop and forearm flexion weakness,

1:01

extensor weakness.

1:05

Have to go back to what those posterior interosseous nerve innervates here.

1:10

Very good. Everybody got that one correct. The, uh, forum extension weakness.

1:16

So a few just notes about radial nerve entrapment and posterior interosseous

1:21

nerve syndrome. Um, again,

1:23

thought to be due to a lot of repetitive supination and pronation.

1:27

Patients have that finger droop,

1:28

and what that means is when they go to hold their fingers in extension,

1:32

they just kind of droop back towards the palm into kind of almost a,

1:36

a fist there. And so that is a very characteristic finding of PIN syndrome. Uh,

1:40

a m G findings are often abnormal in these cases,

1:43

but there's a pretty broad differential, meaning that the nerve all,

1:47

all the way from the central kind of nervous system, uh,

1:50

through the more proximal peripheral nerves can be abnormal and result in

1:55

similar uh, symptomatology. So in this particular case,

1:59

this patient had undergone brachial plexus imaging and cervical spine imaging

2:04

before, uh, kind of this imaging of the extremity was performed.

2:07

So lots of other differential things that can have a similar clinical

2:12

presentation. So let's go back to our case images.

2:15

This is kind of a weird case in its, um,

2:18

what this diagnosis ended up being,

2:21

but the pattern of denervation and the abnormality of the nerves themselves

2:25

should really have tipped you off that this was radial nerve involvement with

2:29

predominantly posterior interosseous nerve involvement.

2:32

So hopefully you picked up on this, um,

2:34

proton density fat sat sequence that there was some edema.

2:38

It's all in these forearm extensors that kind of accounts for why this patient

2:41

was having finger droop.

2:43

And remember the course of our posterior interosseous nerve.

2:46

So maybe there's some increased signal here just posterior to the, um,

2:50

interosseous membrane. But when we get into the super nater,

2:53

it becomes really apparent that this nerve branch is increased in size and

2:58

in signal.

2:59

It almost has the cystic appearance. Uh,

3:01

you can see the muscle abnormality of the supinator itself,

3:05

and then we can see that branch rejoin, uh,

3:08

rejoin the parent nerve here, which is also abnormal in its signal.

3:12

And we can see that along the course of this more proximal radial nerve,

3:16

we also have the corresponding signal abnormality of the, um,

3:21

of the muscles along the radial aspect of the upper arm.

3:24

So this ended up being more of a parsonage, turner's, uh, syndrome picture. Uh,

3:29

this patient had fairly migratory neural symptoms, um,

3:32

that were thought to be idiopathic. And so, uh,

3:35

that's why there's kind of abnormality of both the radial and the posterior

3:38

interosseous nerve. It wasn't thought to be a true impingement case, uh,

3:43

in this particular instance, but the pattern of denervation, um,

3:47

is pretty typical for a posterior interosseous nerve impingement or injury, uh,

3:52

as well as kind of that radial, uh,

3:54

nerve distribution muscle signal abnormality. In, in this particular case,