- acquisition of cerebrospinal fluid for analysis.
- CSF drainage and pressure reduction, e.g. in communicating hydrocephalus/CSF fistula.
1. Correct positioning of the patient is essential. Open the vertebral laminae by drawing the knees up to the chest and flexing the neck. Ensure the back is perpendicular to the bed to avoid rotation of the spinal column.
2. Identify the site. The L3/4 space lies level with the iliac crests and this is most often used, but since the spinal cord ends at LI any space from L2/L3 to L5/S1 provides a safe approach. ^_
3. Clean the area and insert a few millilitres of local anaesthetic.
4. Ensure the stylet of a 20G lumbar puncture needle is fully home (22G for children) and insert at a slight angle towards the head, so that it parallels the spinous processes. Some resistance is felt as the needle passes through the ligamentum flavum, the dura and arachnoid layers.
5. Withdraw the stylet and collect the CSF. If bone is encountered, withdraw the needle and reinsert at a different angle. If the position appears correct yet no CSF appears, rotate the needle to free obstructive nerve roots.
A similar technique employing a TUOHY needle allows insertion of intra- or epidural cannula (for CSF drainage or drug instillation) or stimulating electrodes (for pain management).
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