LESI LESI Anatomy and Neuroanatomy 1 — Questions and Answers
Question 1: The epidural space in the lumbar region is located between which two structures?
- The dura mater and the ligamentum flavum (Correct answer)
- The arachnoid mater and the pia mater
- The periosteum and the vertebral body
- The anterior longitudinal ligament and the posterior longitudinal ligament
Correct answer: The dura mater and the ligamentum flavum
The lumbar epidural space lies between the dura mater anteriorly and the ligamentum flavum posteriorly.
Question 2: Which lumbar interspace is most commonly used for a caudal epidural steroid injection approach?
- L1-L2
- L3-L4
- L4-L5
- Sacral hiatus (S4-S5 level) (Correct answer)
Correct answer: Sacral hiatus (S4-S5 level)
Caudal epidural injections are performed through the sacral hiatus, which is the caudal opening of the sacral canal.
Question 3: The conus medullaris typically terminates at which vertebral level in adults?
- T10-T11
- L1-L2 (Correct answer)
- L3-L4
- L5-S1
Correct answer: L1-L2
In adults, the spinal cord (conus medullaris) generally ends at the L1-L2 level, making injections below this level safer.
Question 4: Which nerve roots form the sciatic nerve that is commonly implicated in radicular pain treated by LESI?
- L1-L3
- L2-L4
- L4-S3 (Correct answer)
- S1-S4
Correct answer: L4-S3
The sciatic nerve is formed by nerve roots L4 through S3, which are frequently involved in lumbar radiculopathy.
Question 5: The ligamentum flavum, which is traversed during interlaminar LESI, is composed primarily of which tissue?
- Dense irregular collagen
- Elastic fibrocartilage
- Yellow elastic fibers (Correct answer)
- Hyaline cartilage
Correct answer: Yellow elastic fibers
The ligamentum flavum ('yellow ligament') is composed predominantly of yellow elastic fibers, giving it its characteristic color and elasticity.
Question 6: Which structure forms the anterior boundary of the lumbar epidural space?
- Posterior longitudinal ligament (Correct answer)
- Ligamentum flavum
- Supraspinous ligament
- Interspinous ligament
Correct answer: Posterior longitudinal ligament
The posterior longitudinal ligament and the posterior surface of the vertebral bodies form the anterior boundary of the lumbar epidural space.
LESI LESI Anatomy and Neuroanatomy 1
The epidural space in the lumbar region is located between which two structures?