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Wrist anatomy, Guillain's Canal,

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and the anterior aspect of the wrist.

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The place that houses the ulnar nerve, otherwise

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known as the syndrome of Guillain's Canal.

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Let's scroll, shall we?

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In the right-hand corner, wearing the

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blue trunks, heavily water weighted.

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In the left-hand corner, wearing the red

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trunks, T2, spin echo, somewhat water weighted.

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And in the middle, the anatomy, T1 weighted image.

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The first thing I find as a

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landmark is the ulnar artery arch.

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There it is as a circumferential,

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laminated, lamellated structure.

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It's got a little white from slow flow; it's

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got a little dark in the middle from fast flow.

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The slow flow being from turbulence or drag.

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And then the periphery is the wall.

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This dark arc around the outside.

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On the heavily water weighted image, vessels

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are going to be a bit brighter than, say, nerves.

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So here is our artery, and it is surrounded

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by a group or a clump of veins on either side.

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But it's most easy to identify the

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artery with this laminated signal on the

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T1, as well as the T2 weighted image.

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Now let's scroll a little bit more distally.

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And let's follow that ulnar artery.

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There it is.

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It's nice and bright, and

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there are some veins around it.

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They're not quite as bright.

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Sometimes it's the opposite.

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Sometimes the veins will be a

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little brighter than the artery.

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But never should the nerves

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be brighter than the vessels.

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And there are the nerves off to the side.

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Now this case is unique because there's very

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early branching of the ulnar nerve into a

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more superficial group of sensory branches.

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There are two of them right there.

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In fact, I'm going to make them even bigger.

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Let's make them a little bit bigger.

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So here are the sensory nerves.

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Sensory nerves.

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Sensory nerves.

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And here's the motor nerve.

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So you could have a sensory

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syndrome or a motor syndrome.

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Now let's scroll and follow them.

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Oh, look how beautiful they are.

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They're gorgeous.

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Motor nerve.

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Sensory nerves.

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Let's keep going.

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Sensory nerves.

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Motor nerve.

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Now let's keep following them to the hamate.

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And they start to scooch along the

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tip of the hamulus of the hamate.

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Here they are, motor deep, sensory superficial,

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artery, sorry, artery, and a vein right next door.

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And then you'll see them scooch

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all the way to the outside.

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Now when people with hypothenar hammer syndrome,

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who are doing karate, or martial arts, or

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they're constantly impacting this, such as bike

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riders or golfers, this may impact against the

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motor and sensory divisions of the ulnar nerve

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and produce the syndrome of Guillain's Canal.

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Some have said that this space is analogous to a

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triangle, and it sort of is, with the superficial

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boundary, although not well developed in this

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patient, formed by a continuation of the flexor

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retinaculum, known as the ligamentum palmari.

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Only, in this case, somewhat

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attritional developmentally.

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Guillain's Canal with artery, veins, and two key

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nerves that have branched on a common ulnar nerves.