Lumbar cistern

Subarachnoid cisterns
Diagram showing the positions of the three principal subarachnoid cisterns.
Details
Latin	cisterna
Dorlands /Elsevier	c_37/12241802
Anatomical terminology []

The subarachnoid cisterns are spaces formed by openings, where the arachnoid mater and the pia mater are separated, in the subarachnoid space of the brain. These cisterns are filled with cerebrospinal fluid.

Although the pia mater adheres to the surface of the brain, closely following the contours of its gyri and sulci, the arachnoid covers only its superficial surface. It follows from this that in certain areas around the brain the pia and arachnoid are separated widely; in such regions cavities are formed called the subarachnoid cisterns.

Although they are often described as distinct compartments, the subarachnoid cisterns are not truly anatomically distinct. Rather, these subarachnoid spaces are separated from each other by a trabeculated porous wall with various-sized openings.

There are many cisterns in the brain with several especially large, notable ones each with their own name.

Some major subarachnoid cisterns:

It is of clinical significance that cerebral arteries, veins and cranial nerves must pass through the subarachnoid space, and these structures maintain their meningeal investment until around their point of exit from the skull.