LESI Cheat Sheet 2026

The 30 highest-yield LESI facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Before performing LESI, a patient should be screened for allergy to which class of medications? → Local anesthetics, corticosteroids, and iodinated contrast
2. A disc herniation at L5-S1 most commonly compresses which nerve root? → S1 nerve root
3. Which structure must be pierced just before entering the epidural space during a loss-of-resistance technique? → Ligamentum flavum
4. Which artery, if inadvertently injected during LESI, can cause catastrophic spinal cord ischemia? → Artery of Adamkiewicz
5. According to ASRA guidelines, what INR threshold generally requires postponement of ESI? → INR > 1.5
6. Which lumbar interspace is most commonly used for a caudal epidural steroid injection approach? → Sacral hiatus (S4-S5 level)
7. Which needle type is most commonly used for interlaminar lumbar epidural steroid injections? → Tuohy (curved bevel) epidural needle
8. Post-procedural instructions for LESI patients should include which specific warning sign to monitor? → Report any signs of infection: progressive back pain, fever, or neurological worsening
9. In fluoroscopic interlaminar LESI, the AP (anteroposterior) view is used primarily to: → Verify midline or paramedian needle position between the laminae
10. During transforaminal LESI setup, the C-arm is obliqued ipsilaterally until which classic landmark is visualized? → The 'Scotty dog' silhouette of the vertebra with the pedicle as the eye
11. The 'loss of resistance' technique during epidural needle advancement detects the transition from which structure into the epidural space? → Ligamentum flavum to epidural space
12. Where do preganglionic fibers of the parasympathetic nervous system end? → In the organ they innervate
13. Why is preservative-free formulation required for epidural steroid injections? → Preservatives (e.g., benzyl alcohol) are neurotoxic and can cause arachnoiditis
14. Which structure forms the anterior boundary of the lumbar epidural space? → Posterior longitudinal ligament
15. What is the FDA's current regulatory status of corticosteroid use for epidural injection? → Off-label use — not approved for epidural administration
16. Real-time fluoroscopy during contrast injection during LESI serves what critical safety purpose beyond confirming epidural placement? → Detecting intravascular injection by identifying rapid vascular contrast washout patterns
17. Which condition is an ABSOLUTE contraindication to lumbar ESI? → Active systemic infection or local infection at the injection site
18. Which comorbidity requires informing the patient that ESI may cause a prolonged elevation of blood pressure? → All of the above require this counseling
19. Which corticosteroid is particulate and therefore associated with higher risk of embolic complications in transforaminal LESI? → Methylprednisolone acetate (Depo-Medrol)
20. Which local anesthetic is preferred for LESI in patients with a documented allergy to amide anesthetics? → Chloroprocaine (ester anesthetic)
21. Intravascular injection during transforaminal LESI is best detected in real time by which method? → Digital subtraction angiography (DSA) or real-time fluoroscopy with contrast injection
22. Patients should be instructed to avoid which activity for 24 hours following LESI? → Driving or operating heavy machinery
23. The Lumbar vertebrae are larger and stronger than the other vertebral segments. → True
24. Which outcome measure is most commonly used to assess pain relief following LESI in clinical practice? → Numerical Rating Scale (NRS) or Visual Analog Scale (VAS) for pain intensity
25. What is the primary neurotransmitter of the parasympathetic nervous system? → Acetylcholine
26. An epidural hematoma after LESI is most likely to occur in patients who: → Are taking anticoagulant or antiplatelet medications
27. What is the characteristic feature of postdural puncture headache that distinguishes it from other headaches? → Positional — worse when upright, relieved when supine
28. What is the recommended treatment for a confirmed postdural puncture headache that fails conservative management? → Epidural blood patch
29. 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
30. An epidural abscess following LESI most commonly presents with which triad of symptoms? → Back pain, fever, and neurological deficits