What procedure involves the injection of a hypodermic needle into the lumbar subarachnoid space?

The procedure that involves the injection of a hypodermic needle into the lumbar subarachnoid space is known as a lumbar puncture (LP). This is a diagnostic and therapeutic procedure that allows for the collection of cerebrospinal fluid (CSF) for analysis, which can provide valuable information about neurological conditions.

During the lumbar puncture, the needle is inserted into the lower back, specifically targeting the subarachnoid space where the CSF is located. This space is safe for access because the spinal cord typically ends at the level of the first or second lumbar vertebra, and the needle can be placed below this level without the risk of damaging the cord.

While terms like "spinal tap" and "intrathecal injection" are often used interchangeably or in related contexts, they represent different aspects of accessing the spinal area. The term "spinal tap" typically refers to the same procedure as lumbar puncture but is more colloquial. An "intrathecal injection," on the other hand, refers specifically to the administration of medication directly into the CSF, which may occur during or as a result of a lumbar puncture but is not the defining feature of the procedure itself. Myelography involves the injection of