From which location is cerebrospinal fluid (CSF) extracted?

Cerebrospinal fluid (CSF) is most commonly extracted from the subarachnoid space, particularly at the level of the L3/L4 interspace, during a procedure known as a lumbar puncture. This location is chosen due to its safety; the spinal cord typically terminates at the level of L1/L2 in adults, allowing for a safer access point to collect CSF without the risk of damaging the spinal cord.

The technique involves inserting a needle into the subarachnoid space between the vertebrae, where CSF flows freely. This fluid can then be analyzed for various conditions, including infections, hemorrhages, and other neurologic diseases. The selection of the L3/L4 interspace or similar lower lumbar levels is critical to ensure both effective CSF collection and patient safety.

While other locations for CSF extraction exist, such as the lumbar cistern, which is deeper within the subarachnoid space, the most standard and recognized procedure involves the L3/L4 interspace to avoid any complications. The other options, including extraction from the epidural space or lateral ventricles, represent different techniques or anatomical areas that are not typically associated with the standard lumbar puncture for CSF analysis.