Space
Extradural (epidural) space
Different relationships in the skull and vertebral canal
High-yield
Cranial epidural: between bone and periosteal dura. Spinal epidural: between the vertebral canal wall and the dural sac, containing fat and the internal vertebral venous plexus.
Overview
Cranial dura normally lies against the skull, so an epidural collection must separate these surfaces. The spinal epidural compartment already contains fat, loose connective tissue and vessels outside the dural sac. This distinction explains why the same term describes a potential cranial space and an occupied spinal compartment.
Reference facts
- Boundaries
- Cranially, inner skull and periosteal dura; spinally, the outer dural sac and the surrounding canal wall, including the posterior longitudinal ligament anteriorly and ligamentum flavum posteriorly
- Contents
- No normally open cranial compartment; spinal contents include fat, connective tissue, blood and lymphatic vessels, and nerve roots with their coverings as they approach the foramina
- Communications
- The spinal compartment extends along the canal and communicates laterally through the intervertebral foramina; its venous plexus connects with veins outside the spine
Clinical correlation
Trauma can tear a meningeal artery or vein and form a cranial epidural hematoma. A middle meningeal arterial injury with a nearby skull fracture is a classic example. The collection is often lens-shaped on CT and usually respects sutures. A lucid interval can occur, but its absence does not exclude the injury.
Frequently asked questions
What are the boundaries of the extradural (epidural) space?
Cranially, inner skull and periosteal dura; spinally, the outer dural sac and the surrounding canal wall, including the posterior longitudinal ligament anteriorly and ligamentum flavum posteriorly.
What does the extradural (epidural) space contain?
No normally open cranial compartment; spinal contents include fat, connective tissue, blood and lymphatic vessels, and nerve roots with their coverings as they approach the foramina.
What does the extradural (epidural) space communicate with?
The spinal compartment extends along the canal and communicates laterally through the intervertebral foramina; its venous plexus connects with veins outside the spine.