As discussed in our page on the structure of the spine, the spinal cord passes down the spine and is encased in a layer of membranes called the dural sac (or "dura" or "theca"). This sac contains the fluid, called cerebrospinal fluid or CSF, which bathes the spinal cord and the nerves emerging from it. Outside the dura and within the bony structures of the vertebrae is a very narrow space called the epidural space.
At each level in the spinal column a pair of nerves, called the spinal nerves, emerge from gaps at the side (foramina) between the vertebrae and pass through the epidural space, and these then travel on to supply the various parts of the body. Each part of the body surface is supplied by a particular spinal nerve, these areas being called dermatomes.
A video linked here gives a good explanation of the procedure.
(Please see general comments on the Procedures page)
The Trust's information sheet on Epidural Injections can be downloaded here
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Pain Service Website, Gloucestershire Hospitals NHS Foundation Trust
Webmaster Dr J G de Courcy, Consultant in Pain Medicine and Anaesthesia
Page updated 22/6/2016