0:00

So here this illustrates the, uh, innervation

0:04

of the superficial and deep perineal nerve.

0:07

So here in yellow you have the innervation from the deep

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perineal nerve, which will supply the T ps anterior

0:15

extensor lysis, longus and extensor dig longus muscles

0:20

and it'll course anterior to the anterior iNOS membrane.

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It will also, at the level

0:27

of the foot innervate a single muscle.

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The extensor tissue brevis, uh, muscle

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and the deep peral nerve will supply sensation

0:35

to the dorsal first web space.

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So a very small region at the dorsal foot,

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the superficial perineal nerve will supply the perineals

0:45

longus and brevis muscles,

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and then will, uh, is initially located deep

0:51

to the perineals longus muscle.

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But then as it courses down, it will be located

0:55

between the anterior and lateral compartments,

0:59

and then will become more superficial

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and provide sensation to the distal, uh, two thirds

1:05

of the lateral leg and dorsal aspect of the foot.

1:09

The recurrent articular branch of the common peral nerve

1:14

curves around the fibular neck here.

1:17

And, um, it can communicate

1:19

with the proximal tibial fibrillary joint.

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So when there's retrograde flow from that joint that enters

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that recurrent articular branch, the fluid can, uh,

1:30

travel within the, uh, branch

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and even ascent proximally into the common perineal nerve.

1:37

And that gives you the, an intradural ganglion cyst

1:41

and our on MR imaging.

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You can recognize this as, uh, cystic changes, uh,

1:47

within the, uh, uh, nerve medially

1:50

and laterally to the, uh, fibular neck.

1:53

The horizontal component of the nerve is often not seen

1:58

the superficial perineal nerve, uh,

2:01

so I beset approximately is deep to the perineals longus,

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uh, uh, muscle.

2:07

But then more distally will travel between the anterior

2:10

and lateral compartment, and then approximately, uh, 10

2:15

to 15 centimeters above the ankle, it'll pierce the fascia

2:19

and become superficial.

2:22

So in that location,

2:23

it can become entrapped if there's scar tissue,

2:26

or for example, if there's a muscle herniation.

2:31

Finally, the superficial perineal nerve will become

2:34

subcutaneous at the level of the ankle.

2:36

Here is one of its branches, um,

2:40

and it will supply sensation to the dorsal,

2:43

the majority of the dorsal foot.

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This, uh, drawing illustrates the territory of,

2:51

of the superficial peroneal nerve.

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So the majority of the dorsal foot

2:55

sparing the first dorsal web space, which is supplied

2:59

By the deep perineal nerve.

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And, uh, entrapment

3:03

of the superior perennial nerve will give you, uh,

3:05

focal pain and tenderness often at the site

3:07

where it pierces the fascia.

3:10

And, uh, dorsal foot, uh, edema, uh, pain, sorry,

3:16

uh, thesal nerve here, uh, I will talk about it later.

3:20

It's, it's provides a narrow band

3:23

of innervation along the lateral aspect of the foot.

3:26

The deep perineal nerve, uh,

3:29

s was coursing along the anterior inter ossis membrane,

3:32

but then more distally,

3:34

it will enter the interi tarsal tunnel.

3:37

And so this, uh, anterior tarsal tunnel is a place

3:41

where the deep perineal nerve can become entrapped

3:45

about 1.5 centimeters above the ankle joint.

3:49

It'll then, uh, divide into a medial sensory branch

3:54

that will supply the first dorsal west space,

3:57

and it will, uh, divide, give off.

3:59

A, a motor branch will supply the, uh, um,

4:04

extensor dis and brevis vessel.

4:07

So the deep perennial nerve can become entrapped more

4:10

commonly at the anterior tarsal tunnel,

4:12

where if it's entrapped approximately,

4:15

it'll affect both the motor and sensory branches.

4:19

But if it's, uh, uh,

4:21

entrapped more distally at the dorsal midfoot,

4:24

then only the sensory branch will be involved.

4:28

Here's an example of a normal anti, uh,

4:31

anterior tarsal tunnel.

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So you see the, uh, deep perineal nerve

4:38

along with the artery

4:39

and vein deep to the, um, extensor,

4:42

uh, lysis tendon.

4:44

And here on the right, a patient who had, uh, ankle surgery,

4:48

and there's a lot of scar tissue in that region,

4:51

obscuring the deep perial nerve.

4:54

Here on the, uh, sagittal image,

4:56

you can see the scar tissue corresponding to the port

4:59

of entry at the time of surgery.

5:02

And the patient more distally, uh,

5:04

had some denervation changes involving the extensor de

5:08

degener brevis muscles with denervation, uh, some atrophy

5:12

and edema of the, uh, muscle,

5:16

the deep perennial nerve.

5:18

If it's compressed more distally at the dorsal aspect

5:21

of the first and second tar metatarsal joints, it will, uh,

5:26

cause pain in the dorsal, uh, uh, aspect

5:30

of the first web space.

5:31

It can be, uh, entrapped by

5:34

osteophytes ganglion cyst, uh, tight footwear, for example.

5:39

This is a patient who had, uh, surgery to remove some, uh,

5:43

prominent dorsal osteophytes

5:44

and developed a lot of scar tissue that, uh,

5:48

caused impingement on his, uh, deep perennial nerve,

5:52

the sensory branch.

5:53

Now, at the level of the midfoot like that,

5:56

we focus more on the, uh, cause of the, uh,

6:00

entrapment rather than seeing the nerve itself,

6:02

which is very difficult because it's so small at that level.