Which of the following is the correct order of layers pierced during a lumbar puncture?
1. Skin
2. Epidural space
3. Supraspinous ligament
4. Interspinous ligament
5. Pia mater
6. Subcutaneous tissue
7. Dura mater
8. Subarachnoid space
9. Ligamentum flavum

Question

Question

This question was previously asked in

AIIMS NORCET 8 Prelims Memory Based Paper 2025

Attempt Online

Answer 1

Correct Answer: 1, 6, 3, 4, 9, 2, 7, 8, 5

Rationale:

A lumbar puncture is a medical procedure performed to collect cerebrospinal fluid (CSF) for diagnostic or therapeutic purposes. It involves inserting a needle into the subarachnoid space of the lumbar region of the spine. Understanding the correct order of layers pierced during the procedure is crucial to avoid complications and ensure accuracy.
The correct sequence of layers pierced during a lumbar puncture is as follows:

Key Points:

1. Skin: The outermost layer that covers the body and serves as a protective barrier. It is the first layer pierced by the needle.
2. Subcutaneous Tissue: The layer beneath the skin, consisting of fat and connective tissue. This layer provides insulation and cushioning.
3. Supraspinous Ligament: A ligament that runs along the tips of the spinous processes of the vertebrae. It provides stability to the spine and is the next structure encountered.
4. Interspinous Ligament: Located between the spinous processes, this ligament adds stability to the spine. The needle pierces this layer after the supraspinous ligament.
5. Ligamentum Flavum: A tough, elastic ligament that connects the laminae of adjacent vertebrae. It is a key landmark during the procedure and is felt as a slight "pop" when the needle passes through.
6. Epidural Space: A space containing fat and blood vessels located outside the dura mater. The needle enters this space after piercing the ligamentum flavum.
7. Dura Mater: The tough outermost layer of the meninges that surround the spinal cord and brain. Piercing this layer is necessary to access the CSF.
8. Subarachnoid Space: The space between the arachnoid mater and pia mater that contains cerebrospinal fluid. The needle enters this space to collect CSF.
9. Pia Mater: The delicate innermost layer of the meninges that directly covers the spinal cord. The needle does not typically pierce the pia mater during a lumbar puncture.

Explanation of Other Options:

Option 1: 1, 4, 2, 6, 5, 9, 8, 7, 3

Rationale: This sequence is incorrect because it places the subcutaneous tissue (6) after the dura mater (7) and the pia mater (5) before the subarachnoid space (8). This does not align with the anatomy of the lumbar region.

Option 2: 6, 5, 3, 1, 4, 8, 7, 2, 9

Rationale: This sequence incorrectly places the pia mater (5) before the supraspinous ligament (3) and the dura mater (7) after the subarachnoid space (8), which is anatomically incorrect.

Option 3: 9, 7, 8, 5, 6, 1, 3, 4, 2

Rationale: This sequence starts with the ligamentum flavum (9) and dura mater (7), which is not correct. The skin (1) and subcutaneous tissue (6) must be pierced first.

Conclusion:

The correct order of layers pierced during a lumbar puncture is 1 (Skin), 6 (Subcutaneous tissue), 3 (Supraspinous ligament), 4 (Interspinous ligament), 9 (Ligamentum flavum), 2 (Epidural space), 7 (Dura mater), 8 (Subarachnoid space), and 5 (Pia mater). This sequence ensures proper understanding of the anatomical layers involved in the procedure, reducing the risk of complications.