Space
Lumbar cistern
Cerebrospinal fluid space surrounding the lower descending roots
High-yield
Clinicians commonly access lumbar cerebrospinal fluid at L3–L4 or L4–L5, below the usual cord termination. The levels of the conus and surface landmarks vary, so the anatomy reduces risk without making puncture automatically safe.
Overview
Below the conus, the spinal subarachnoid space widens around the cauda equina and internal filum terminale. This lumbar cistern continues to the lower end of the meningeal sac, usually near S2 in adults.
Reference facts
- Boundaries
- Extends from below the conus, usually around L1–L2, to the end of the arachnoid-lined dural sac near S2; these are approximate adult vertebral levels
- Contents
- Cerebrospinal fluid, descending cauda equina roots and the filum terminale internum
- Communications
- Continuous upward with the spinal and cranial subarachnoid space; arachnoid and dura separate it from the epidural space
Clinical correlation
Lumbar puncture samples fluid from the subarachnoid space. Spinal anesthesia also targets this fluid space, whereas an epidural places medication outside the dura. These locations are separated by meningeal layers and have different clinical effects and risks.
Frequently asked questions
What are the boundaries of the lumbar cistern?
Extends from below the conus, usually around L1–L2, to the end of the arachnoid-lined dural sac near S2; these are approximate adult vertebral levels.
What does the lumbar cistern contain?
The lumbar cistern contains the cerebrospinal fluid, descending cauda equina roots and the filum terminale internum.
What does the lumbar cistern communicate with?
Continuous upward with the spinal and cranial subarachnoid space; arachnoid and dura separate it from the epidural space.