Epidural space

The anatomy term "epidural space" has its origin in the Ancient Greek language; ἐπί, "on, upon" + dura mater also known as "epidural cavity", "extradural space" or "peridural space". In humans the epidural space contains lymphatics, spinal nerve roots, loose connective tissue, adipose tissue, small arteries, dural venous sinuses and a network of internal vertebral venous plexuses.

Cranial epidural space

In the skull, the periosteal layer of the dura mater adheres to the inner surface of the skull bones while the meningeal layer lays over the arachnoid mater. Between them is the epidural space. The two layers of the dura mater separate at several places, with the meningeal layer projecting deeper into the brain parenchyma forming fibrous septa that compartmentalize the brain tissue. At these sites, the epidural space is wide enough to house the epidural venous sinuses.

There are four fibrous septa:

1. Falx cerebri, that separates the left and right hemispheres of the cerebrum. It contains the superior sagittal sinus and inferior sagittal sinus.
2. Tentorium cerebelli, which separates the cerebrum from cerebellum and contains the transverse sinus, straight sinus and superior petrosal sinus.
3. Diaphragma sellae, that encloses the hypophyseal fossa from the superior side, cushioning the pituitary gland. It contains the anterior and posterior intercavernous sinuses.
4. Falx cerebelli, which separates the left and right cerebellar hemispheres and contains the occipital sinus.

In pathological conditions fluid such as blood can fill this space. For example a torn meningeal artery (often the middle meningeal artery) or dural venous sinus (rarely) may bleed into this potential space and result in an epidural hematoma.