The inferior extent of the dura-arachnoid sac is at which vertebral level?

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Multiple Choice

The inferior extent of the dura-arachnoid sac is at which vertebral level?

Explanation:
The dural sac ends at the level of the second sacral vertebra (S2). This is where the perineural filum terminale intra-dural continuation reaches the coccygeal end, while the spinal cord itself ends higher up (around L1–L2). So within the dural sac you still have cauda equina roots and CSF down to S2, but below S2 there is no dural sac containing CSF. Clinically, this explains why a lumbar puncture is done below L2–L3 or L4–L5 to access CSF safely in the lumbar cistern without hitting the spinal cord.

The dural sac ends at the level of the second sacral vertebra (S2). This is where the perineural filum terminale intra-dural continuation reaches the coccygeal end, while the spinal cord itself ends higher up (around L1–L2). So within the dural sac you still have cauda equina roots and CSF down to S2, but below S2 there is no dural sac containing CSF. Clinically, this explains why a lumbar puncture is done below L2–L3 or L4–L5 to access CSF safely in the lumbar cistern without hitting the spinal cord.

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