El espacio epidural (también llamado espacio extradural o peridural). Es un espacio que está fuera de la duramadre (meninge más superficial que envuelve la médula) siendo ocupado por tejido conjuntivo laxo, grasa peridural y por el plexo venoso vertebral interno.
https://es.wikipedia.org/wiki/Espacio_epidural

In the spine, the epidural space (from Ancient Greek ἐπί, "on, upon" + dura mater also known as "epidural cavity", "extradural space" or "peridural space") is an anatomic space that is the outermost part of the spinal canal. It is the space within the canal (formed by the surrounding vertebrae) lying outside the dura mater (which encloses the arachnoid mater, subarachnoid space, the cerebrospinal fluid, and the spinal cord). In humans the **epidural space** contains lymphatics, spinal nerve roots, loose connective tissue, **fatty tissue**, small arteries, and a network of internal vertebral venous.
https://en.wikipedia.org/wiki/Epidural_space

Epidural fat is not evenly distributed. At cervical level fat is absent while in the lumbar region, fat in the anterior and posterior aspects of the epidural space forms .
https://www.ncbi.nlm.nih.gov/pubmed/19459550