LESI LESI Techniques and Approaches 1 — Questions and Answers
Question 1: The interlaminar epidural approach at lumbar levels is typically performed with the patient in what position?
- Prone with a pillow under the abdomen to flex the lumbar spine (Correct answer)
- Lateral decubitus with knees drawn to chest
- Supine with knees elevated on a bolster
- Sitting upright leaning forward over a pillow
Correct answer: Prone with a pillow under the abdomen to flex the lumbar spine
The prone position with an abdominal pillow flexes the lumbar spine, widening the interlaminar space and facilitating needle entry into the epidural space.
Question 2: Which method is considered the most reliable for confirming correct epidural needle placement during a lumbar ESI?
- Loss of resistance to saline
- Loss of resistance to air
- Aspiration for blood or cerebrospinal fluid
- Fluoroscopic contrast injection (Correct answer)
Correct answer: Fluoroscopic contrast injection
Fluoroscopic contrast injection provides real-time visual confirmation of injectate spread within the epidural space and can detect intravascular or intrathecal misplacement.
Question 3: In the transforaminal LESI approach, where is the needle tip ideally positioned under fluoroscopic guidance?
- At the 6 o'clock position of the neural foramen
- In the superior-anterior quadrant (safe triangle) of the neural foramen (Correct answer)
- At the medial border of the pedicle on the AP view
- Adjacent to the spinous process in the midline
Correct answer: In the superior-anterior quadrant (safe triangle) of the neural foramen
The safe triangle (Kambin's triangle) in the superior-anterior foramen positions the needle near the nerve root sleeve while avoiding the exiting nerve and major radicular vessels.
Question 4: The caudal epidural approach accesses the epidural space through which anatomical opening?
- The interlaminar space at L5-S1
- The sacral hiatus at the base of the sacrum (Correct answer)
- The S1 neural foramen
- The posterior sacral foramina at S2-S4
Correct answer: The sacral hiatus at the base of the sacrum
The sacral hiatus is a midline opening at the inferior end of the sacral canal formed by non-fusion of the S4-S5 laminae and is the entry point for the caudal approach.
Question 5: Which epidural approach provides the most targeted steroid delivery to a specific spinal nerve root?
- Midline interlaminar approach
- Caudal approach via sacral hiatus
- Transforaminal approach (Correct answer)
- Paramedian interlaminar approach
Correct answer: Transforaminal approach
The transforaminal approach deposits steroid directly at the ventral epidural space adjacent to the target nerve root's sleeve, providing site-specific delivery.
Question 6: The 'loss of resistance' technique during epidural needle advancement detects the transition from which structure into the epidural space?
- Subcutaneous fat to paraspinal muscle
- Paraspinal muscle to interspinous ligament
- Ligamentum flavum to epidural space (Correct answer)
- Dura mater to subarachnoid space
Correct answer: Ligamentum flavum to epidural space
The ligamentum flavum is a dense, resistant structure; as the needle tip exits it into the low-pressure epidural space, resistance to syringe plunger pressure suddenly drops.
Question 7: Which needle type is most commonly used for interlaminar lumbar epidural steroid injections?
- Quincke (cutting bevel) spinal needle
- Tuohy (curved bevel) epidural needle (Correct answer)
- Sprotte (pencil-point) spinal needle
- Chiba (thin-wall) needle
Correct answer: Tuohy (curved bevel) epidural needle
The Tuohy needle's curved tip helps direct flow and reduces the risk of dural puncture compared to cutting-bevel needles, making it the standard choice for interlaminar epidural access.
LESI LESI Techniques and Approaches 1
The interlaminar epidural approach at lumbar levels is typically performed with the patient in what position?