Nerve Root Compression

Question 1

Possible levels of nerve root compression?

Answer 1

1. Disc level
2. Lateral recess
3. Foramen
4. Extra foraminal

Question 2

Where are nerves most commonly compressed?

Answer 2

Disc level; mostly by herniated discs (less frequently = spinal stenosis)

Question 3

What is the lateral recess?

Answer 3

Area below disc where nerve runs more laterally towards the foramen

Question 4

What causes narrowing of the lateral recess?

Answer 4

Decreased stability of vertebral column –> facet joint hypertrophy and arthritis, disc bulging, flavum ligament hypertrophy.
Facet arthrosis +/- hypertrophy of ligamentum flavum +/- disc bulge

Question 5

What causes narrowing of the foramen?

Answer 5

• Facet arthrosis
• Spondylolisthesis
• Foraminal disc herniation (usually a migrated disc from a lower level)

Question 6

Cause of extra foraminal compression?

Answer 6

Area lateral to the foramen; uncommon but usu due to laterally herniated disc

Question 7

What is the ligament flavum?

Answer 7

Ligament on interior posterior side of vertebral canal connecting laminae of adjacent vertebrae

Question 8

What causes ligamentum flavum hypertrophy?

Answer 8

Ageing and instability of vert column due to facet arthrosis; more stress on flavum ligament causing hypertrophy and fibrosis

Question 9

What do facet arthritis and ligamentum flavum hypertrophy both produce?

Answer 9

Stenosis of the lateral recess; if bilateral = spinal stenosis

Question 10

What is epidural fat?

Answer 10

fat surrounding the dural sac (contains nerves).

Question 11

When is epidural fat increased?

Answer 11

• steroid therapy
• extreme obesity
• rare = idiopathic

Question 12

Approach to MRI for ?spinal stenosis (protocol)?

Answer 12

Sagittal T1 and T2 with correlation on transverse sections (T2) at level of suspected pathology

Question 13

Interpretation of ?spinal stenosis MRI?

Answer 13

Sag T1:
1. Prevert soft tissue (aorta)
2. Bone marrow / end plates
3. Four levels of compression
Correlate with Tra T2

Question 14

What is disc herniation?

Answer 14

Displacement of disc material (nucleus pulposus, annulus fibrosus, cartilage) beyond limits of IV disc space

Question 15

What are the types of disc herniation? (related to size)

Answer 15

-Focal 180)

Question 16

Protrusion v extrusion of disc?

Answer 16

Protrusion: distance between edges herniation

Question 17

When are synovial cysts commonly seen?

Answer 17

In combo with facet arthrosis

Question 18

What do synovial cysts most commonly cause?

Answer 18

• Stenosis of the lateral facet

- if XL can cause foraminal stenosis

Question 19

What are the most common causes of spinal stenosis?

Answer 19

Bilateral facet arthrosis in combination with bulging of the disc and hypertrophy of ligamentum flavum

Question 20

Less common causes of spinal stenosis?

Answer 20

• Congenital narrowing with short pedicles
• Spinal injury and epidural haematoma
• Bone tumours
• Spondylodiscitis or epidural abscess
• Spondylolisthesis

Question 21

What is epidural lipomatosis?

Answer 21

Excessive fat within the epidural space compressing thecal sac. Presents with CFx of spinal canal stenosis.

Question 22

What is spondylolisthesis?

Answer 22

One vertebra slips forward over the one below it (usu L4 on L5).

Question 23

What is spondylolysis?

Answer 23

Stress fracture of the pars interarticularis

Question 24

Annular tear v disc herniation

Answer 24

Tear: =annular fissure. Separations of annual fibres, avulsion from their vert insertions or breaks in annular lamellae
Herniation: displacement of disc material beyond limits of iv disc space

Question 25

Bulging disc?

Answer 25

Circumferential disc tissue (180-360”) beyond edge of ring apophyses; not considered form of herniation. NP covered by intact AF

Question 26

Migration v sequestration?

Answer 26

Migration: displacement of disc material away from site of extrusion
Sequestration: displaced material has completely lost continuity with parent disc

Question 27

Descriptions of axial localisation herniated discs (midline to lateral)?

Answer 27

i) Central
ii) Paramedian/-central
iii) Foraminal
iv) Extraforaminal / lateral

Question 28

Where and why are discs herniations most common?

Answer 28

Paramedian: PLL (posterior longitudinal ligament) is thinner in this region