A spinal needle inserted for lumbar puncture at L4–L5 passes through which structures in sequence from superficial to deep?
- A Skin → subcutaneous fat → supraspinous ligament → interspinous ligament → ligamentum flavum → epidural space → dura mater → subdural space → arachnoid mater → subarachnoid space ✓
- B Skin → posterior longitudinal ligament → ligamentum flavum → epidural space → dura
- C Skin → anterior longitudinal ligament → supraspinous ligament → dura
- D Skin → interspinous ligament → ligamentum flavum → subarachnoid space directly
Correct answer: A. Skin → subcutaneous fat → supraspinous ligament → interspinous ligament → ligamentum flavum → epidural space → dura mater → subdural space → arachnoid mater → subarachnoid space
Explanation
During lumbar puncture at L4–L5 (below the conus medullaris, which ends at L1–L2 in adults), the needle traverses: skin, subcutaneous fat, supraspinous ligament, interspinous ligament, ligamentum flavum (yellow, elastic, resistance felt then 'give'), epidural space, dura mater, subdural space (potential space), arachnoid mater, and finally the subarachnoid space where CSF is collected. The posterior longitudinal ligament is anterior to the spinal cord and is not traversed during LP.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
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Written and medically reviewed by the StethoPrep medical team.