For a lumbar puncture, the needle is inserted in the midline at the level of the intercristal (supracristal) plane. This plane corresponds to which intervertebral space in most adults?
- A L3–L4 (occasionally L4–L5) ✓
- B L1–L2
- C L2–L3
- D L5–S1
Correct answer: A. L3–L4 (occasionally L4–L5)
Explanation
Tuffier's (intercristal) line is drawn between the highest points of the iliac crests and intersects the spine at the L4 vertebral body or L3–L4 interspace (commonly, though in up to 30% of individuals it may be at L4–L5). LP is performed at L3–L4 or L4–L5 because the spinal cord ends at L1–L2 (conus medullaris) in adults, making these levels safe below the cord. Inserting above L2 risks cord damage.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.