The epidural space is the area between the dura mater (a membrane) and the vertebral wall, containing fat and small blood vessels. The space is located just outside the dural sac which surrounds the nerve roots and is filled with cerebrospinal fluid.
Epidural steroid injections are delivered to the epidural space in order to deliver analgesics to the immediate site of pain. The epidural space is vulnerable to developing epidural abscesses, infections that can impair neurological function.