0:00

The sciatic nerve is the lifeline of the lower extremity.

0:05

It'll supply the motor innervation to the hamstring muscles

0:08

and all sensory and motor function bet below the knee except

0:13

for sensation at the mule leg,

0:15

which is supplied by the sine nerve.

0:17

So the sciatic nerve, uh,

0:21

the nerve roots L four to S3 will, uh,

0:24

join near the inferior aspect of the sacroiliac joint, uh,

0:28

forming the sciatic nerve.

0:30

And then the sciatic nerve will descend, uh, anterior

0:33

to the piriformis muscle

0:35

and will exit the pelvis, uh,

0:38

via the infra piriform portion

0:40

of the greater sciatic foramen.

0:44

So clinically, uh,

0:45

the sciatic nerve can be compressed proximally.

0:49

This will, uh, cause a sciatica, so pain along the, uh,

0:54

posterior aspect of the thigh, uh, pain along, uh,

0:57

in the lower leg laterally and, uh, the entire foot.

1:02

This is a patient who had an injury,

1:04

and you can see there's a large, uh, focus

1:07

of heterotopic ossification just lateral

1:11

to the expected location of the sciatic nerve.

1:14

And when the, uh, compression is proximal, uh,

1:19

it will cause atrophy of the hamstring muscles,

1:22

and it more commonly will affect the common perineal

1:27

division than the tibial division of the sciatic nerve.

1:31

So on ct, the patient had severe atrophy

1:35

of the hamstring muscles, uh,

1:37

because the compression of the sciatic nerve is proximal

1:41

and also severe atrophy of all the muscles below the knee.

1:45

Now, the entrapment

1:46

of the sciatic nerve can occur at the hip region more

1:50

commonly than in the thigh,

1:52

because in the thigh, the nerve is relatively protected

1:55

by it's, it's deep

1:57

and it's protected by the surrounding muscles.

2:00

So at the hip, it can, the entrapment can be caused

2:03

by a hip replacement or,

2:05

or IF of the tta like we have here In this example,

2:09

with some heterotopic acidification,

2:11

the sciatic nerve can be injured

2:13

with a posterior hip dislocation.

2:16

It can be injured by prolonged squatting

2:20

and by, uh, hamstring pathology with scarring

2:23

that can affect the, uh, sciatic nerve,

2:25

given their proximity.

2:28

So this patient, uh, had, uh, uh, surgery

2:32

and you can see here, um, post in the expected location

2:37

of the sciatic nerve, that there's a lot of, uh, scar tissue

2:41

and the sciatic nerve is quite difficult to, uh,

2:45

distinguish, uh, from the, uh, scar tissue.

2:49

So, uh, MR imaging

2:51

of this patient more distally shows denervation changes in

2:55

the hamstring muscles, uh, with some muscle

2:59

Atrophy, more distally.

3:02

Uh, he still had some patchy edema

3:04

and the hamstring, uh, muscles, but below the knee.

3:08

What was interesting is that, uh, the muscles

3:10

that were denervated were the ones supplied

3:13

by the common peral nerve,

3:15

and its spared the tibial division of the, uh,

3:20

of the sciatic nerve.

3:22

So this shows that the, uh, the, uh,

3:25

compression was preferentially, uh,

3:27

affecting the common perineal division of the sciatic nerve.