0:00

Finally our last nerve about the elbow,

0:02

uh, our ulnar nerve.

0:04

It's one that we see on every elbow MRI.

0:06

So, um, it's one that you can evaluate for

0:08

and kind of get a sense of the normal anatomic course.

0:11

Uh, remember that it really hugs this inner margin

0:14

of the elbow we're just distal, uh, to the,

0:17

to the elbow joint in this instance.

0:18

And then it wraps around the more flexor aspects,

0:22

but stays on that ulnar side of the forearm.

0:24

And so the other residual flexor muscles

0:26

that are not innervated by our median nerve,

0:29

the flexor carpi ulnar

0:30

and the flexor digitorum profundus, uh,

0:32

are really innervated by that ulnar nerve.

0:34

So if you're finding muscle, uh, abnormality

0:37

that's more on the ulnar side of the forearm,

0:39

then you should be suspicious

0:40

for a potential ulnar nerve abnormality.

0:44

So ulnar nerve entrapments,

0:46

the second most common peripheral neuropathy in the upper

0:48

extremity, carpal tunnel being the first, uh, so it's one

0:51

that you'll certainly encounter, uh, and be imaging for.

0:55

One anatomic variant that is, uh, important to be familiar

0:58

with is the ancon trois.

1:00

So remember at the level of your elbow joint,

1:03

you have a normal, an conus, right?

1:05

So normal muscle belly.

1:07

But in the region of the cubital tunnel,

1:09

you should not have a muscle belly.

1:11

So just be aware, if you see kind of a symmetric

1:13

where there's two muscles on both the medial

1:15

and lateral side, uh, you should be raising suspicion

1:18

for an ancon trois.

1:20

It's common, it's present in about 11% of the population.

1:24

Um, the ancon trois isn't the only cause of, uh,

1:28

al neuropathy or cubital tunnel syndrome.

1:29

There are a lot of other small anatomic structures in this

1:32

region that can be abnormal and cause compression.

1:36

And these patients present with involvement of that ring in

1:39

that small finger, um, they kind of lose that grip strength.

1:42

You really rely on that small finger

1:44

for a lot of grip strength.

1:45

And so these patients can have kind of clawing

1:47

of those, of those small finger.

1:49

There. Patients will also have media, um, elbow pain, uh,

1:53

they can have that paraesthesia.

1:54

We've all kind of dinged our own nerve before

1:56

and have experienced that.

1:59

So here's a 52-year-old man.

2:01

He presented with mostly forearm weakness and atrophy.

2:04

So we performed an MRI of his elbow and his forearm.

2:07

We can see on our series of axial proton density sequences

2:10

that he does have some muscle signal abnormality.

2:14

It's predominantly in the ulnar

2:15

aspect of the forearm muscles.

2:17

And when we go back and evaluate the ulnar nerve itself, uh,

2:20

this is, uh, the same image I showed

2:23

before of primary nerve abnormality.

2:25

We can see those enlarged faciles.

2:27

You can just pick out the individual fascial

2:29

of the ulnar nerve, which you can't typically see.

2:32

Um, and they're very bright.

2:33

They're almost fluid intensity signal, um, more similar

2:36

to the adjacent vasculature than they are a similar

2:39

signal to the muscle.

2:41

And this was a case of, of cubital tunnel syndrome.