Applied epidural anatomy Flashcards
Where does the interlaminar approach enter?
The posterior epidural space
Where is the hanging drop technique useful?
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.
What approach should be used for an epidural in the T5-6 space?
A paramedian approach - almost impossible to use any other route
Is piercing the sacrococcygeal ligament a reliable method of providing lumbo-sacral anaesthesia in the adult?
No
Is piercing the sacrococcygeal ligament a reliable method of providing lumbo-sacral anaesthesia in the adult?
No - you need to make sure that this is what has been achieved
With respect to the anatomy of the epidural space: what is the inferior limit?
The sacrococcygeal ligament
Where is the posterior venous plexus generally largest?
Largest in the thoracic and cervical areas.
With respect to the anatomy of the epidural space: what is the present laterally?
Laterally is the pedicle of the vertebra and the intervertebral foramen.
Where does the spinal cord end?
Lower border of L1, but beware, it can be lower.
How does the dural sac end?
The dural sac generally ends at the lower border of S2 below which it continues as the filum terminale.
What is the first ‘recognizably typical’ vertebra?
C3
Where does cervical spinal nerve C7 exit the spinal canal?
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.
What does a transforaminal approach in the thoracic region require?
It is dangerous without proper training and an image intensifier.
What does a typical vertebrae look like?
They have a recognizable anterior body, posterolateral pedicles, transverse processes and posterior laminae, which fuse to form the spinous processes.
What does the dural sac contain?
The dural sac contains the anterior and posterior spinal nerve roots, collectively know as the cauda equina.
Where does the C8 spinal nerve exit?
Leaves between vertebra C7 and T1.
What is the superior boundary of the epidural space?
Fusion of the spinal and periosteal layers of dura mater at the foramen magnum
What is the posterior boundary of the epidural space?
Ligamentum flavum, capsule of facet joints and laminae
What is the lateral boundary of the epidural space?
Pedicles and intervertebral foraminae
What is the anterior boundary of the epidural space?
Posterior longitudinal ligament, vertebral bodies and discs
What is the inferior boundary of the epidural space?
Sacrococcygeal membrane
What does the epidural space contain?
Fat, the dural sac, spinal nerves, blood vessels and connective tissue
What is the nerve supply of the spinal canal?
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.
What congenital abnormalities cause difficulties for epidural anaesthesia?
- Achondroplasia
- congenital adolescent scoliosis
- spina bifida
Why should epidurals not be used in someone with spina bifida?
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
What acquired abnormalities make epidural anaesthesia difficult?
- 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.
