Which of the following statements about the epidural space is correct?

Explanation

## Anatomy of the Epidural Space **Key Point:** The epidural space is a true potential space located between the dura mater (anteriorly) and the ligamentum flavum (posteriorly), containing loose areolar tissue, epidural fat, blood vessels, and spinal nerve roots. **High-Yield:** The epidural space is NOT a true anatomical space but rather a potential space created by the separation of the dura mater from the vertebral canal structures. It is continuous throughout the entire neuraxis—from the foramen magnum cranially to the sacral hiatus caudally. ## Boundaries of the Epidural Space | Boundary | Structure | |----------|----------| | **Anterior** | Posterior longitudinal ligament and dura mater | | **Posterior** | Ligamentum flavum and laminae | | **Lateral** | Intervertebral foramina and pedicles | | **Superior** | Foramen magnum | | **Inferior** | Sacral hiatus | **Clinical Pearl:** The epidural space contains: - **Epidural fat** (loose areolar tissue) - **Epidural veins** (Batson's venous plexus) — important for understanding spread of infection and metastases - **Spinal nerve roots** in their dural sleeves - **Lymphatic vessels** **Mnemonic:** **FVNL** = Fat, Veins, Nerve roots, Ligamentum flavum (contents and posterior boundary of epidural space). ## Distinction from Subarachnoid Space | Feature | Epidural Space | Subarachnoid Space | |---------|-----------------|-------------------| | **Location** | Between dura and ligamentum flavum | Between dura and arachnoid | | **Contents** | Fat, vessels, nerve roots | CSF, spinal nerves | | **Continuity** | Entire neuraxis (foramen magnum to sacral hiatus) | Entire neuraxis | | **Pressure** | Atmospheric or slightly negative | CSF pressure (5–15 cm H₂O) | [cite:Gupta Textbook of Regional Anesthesia Ch 7]