Lumbar cistern

Lumbar cistern (a.k.a. spinal subarachnoid cistern) refers to the large subarachnoid space or cistern located between L1 and S2 vertebrae.

During the development of the central nervous system, it is observed that the spinal cord in an adult does not extend fully into the vertebral canal. Instead, it terminates at the L1-L2 vertebral level. Below this point, the spinal arachnoid mater continues to descend until it reaches the S2 vertebral level. This results in the creation of a significant subarachnoid space called the lumbar cistern, which is situated between L1 and S2 vertebrae.

The lumbar cistern contains important structures such as the filum terminale and a collection of lower lumbar and sacral spinal nerves known as the cauda equina. Since the lumbar cistern does not contain the spinal cord, the safest approach to drain and collect the cerebrospinal fluid through a spinal tap (or lumbar puncture) is to introduce the needle into the lumbar cistern, well below the level at which spinal cord terminates. Typically, lumbar punctures are performed at the L3 vertebral level or in the space between the L3 and L4 vertebrae.