Applied epidural anatomy

Question 1

Where does the interlaminar approach enter?

Answer 1

The posterior epidural space

Question 2

Where is the hanging drop technique useful?

Answer 2

In the cervical region, of no value in the lumbar region. It’s a drop of saline at the end of the needle which is sucked in when you reach the epidural space due to the lower pressure of the epidural space.

Question 3

What approach should be used for an epidural in the T5-6 space?

Answer 3

A paramedian approach - almost impossible to use any other route

Question 4

Is piercing the sacrococcygeal ligament a reliable method of providing lumbo-sacral anaesthesia in the adult?

Answer 4

No

Question 5

Is piercing the sacrococcygeal ligament a reliable method of providing lumbo-sacral anaesthesia in the adult?

Answer 5

No - you need to make sure that this is what has been achieved

Question 6

With respect to the anatomy of the epidural space: what is the inferior limit?

Answer 6

The sacrococcygeal ligament

Question 7

Where is the posterior venous plexus generally largest?

Answer 7

Largest in the thoracic and cervical areas.

Question 8

With respect to the anatomy of the epidural space: what is the present laterally?

Answer 8

Laterally is the pedicle of the vertebra and the intervertebral foramen.

Question 9

Where does the spinal cord end?

Answer 9

Lower border of L1, but beware, it can be lower.

Question 10

How does the dural sac end?

Answer 10

The dural sac generally ends at the lower border of S2 below which it continues as the filum terminale.

Question 11

What is the first ‘recognizably typical’ vertebra?

Answer 11

C3

Question 12

Where does cervical spinal nerve C7 exit the spinal canal?

Answer 12

In the intervertebral foramen between C6 and C7. Spinal nerves are named after the vertebra above, except in the cervical region, where they are named after the vertebra below.

Question 13

What does a transforaminal approach in the thoracic region require?

Answer 13

It is dangerous without proper training and an image intensifier.

Question 14

What does a typical vertebrae look like?

Answer 14

They have a recognizable anterior body, posterolateral pedicles, transverse processes and posterior laminae, which fuse to form the spinous processes.

Question 15

What does the dural sac contain?

Answer 15

The dural sac contains the anterior and posterior spinal nerve roots, collectively know as the cauda equina.

Question 16

Where does the C8 spinal nerve exit?

Answer 16

Leaves between vertebra C7 and T1.

Question 17

What is the superior boundary of the epidural space?

Answer 17

Fusion of the spinal and periosteal layers of dura mater at the foramen magnum

Question 18

What is the posterior boundary of the epidural space?

Answer 18

Ligamentum flavum, capsule of facet joints and laminae

Question 19

What is the lateral boundary of the epidural space?

Answer 19

Pedicles and intervertebral foraminae

Question 20

What is the anterior boundary of the epidural space?

Answer 20

Posterior longitudinal ligament, vertebral bodies and discs

Question 21

What is the inferior boundary of the epidural space?

Answer 21

Sacrococcygeal membrane

Question 22

What does the epidural space contain?

Answer 22

Fat, the dural sac, spinal nerves, blood vessels and connective tissue

Question 23

What is the nerve supply of the spinal canal?

Answer 23

The anterior dura is heavily innervated, fortunately for spinal anaesthesia, the posterior dura is sparsely supplied

The nerve supply of the spinal canal is via direct branches from the sympathetic chain and via the sinu-vertebral nerves that originate from the rami communicantes.

Question 24

What congenital abnormalities cause difficulties for epidural anaesthesia?

Answer 24

• Achondroplasia
• congenital adolescent scoliosis
• spina bifida

Question 25

Why should epidurals not be used in someone with spina bifida?

Answer 25

As spina bifida is frequently associated with a meningocoele, which may be close to the surface, and with the failure of fusion of the laminae with attendant ligamentum flavum abnormalities, epidural location should not be attempted

Question 26

What acquired abnormalities make epidural anaesthesia difficult?

Answer 26

• ligamentum flavum hypertrophy, often contributing to spinal stenosis
• foraminal stenosis
• disc prolapse

The latter two are not contraindications, but could make satisfactory entry or catheterization difficult. X-ray guidance may be of help.