The covering over the nerve roots in the spine is called the dura. The sleeve-like space surrounding the dura is called the epidural space. Nerves travel through the epidural space before they move into your legs. The nerves leave the spine from small nerve holes. These nerves may become inflamed due to irritation from a damaged disc or contact with a bone spur. Inflammation of these nerves may cause pain in your low back, hip, buttock, and legs.
An epidural injection places anti-inflammatory medicine (cortisone) into the epidural space to reduce nerve inflammation and hopefully, reduce your symptoms. By stopping or limiting nerve inflammation, we may promote healing, and speed up "mother nature," thereby decreasing your pain. Although not always helpful, epidural injections reduce pain and improve symptoms in most people within 3-7 days. They may provide permanent relief or provide a period of pain relief that will allow other treatments like physical therapy to be more productive.
Your doctor may order up to three epidural injections spaced approximately 2-4 weeks apart. Performing a repeat injection depends on your response to the prior injection. If you obtain excellent relief from an epidural, you do not need to have it repeated. If you have a partial sustained benefit (>35% relief) the epidural can be repeated for possible additive benefit. If an epidural injection provides minimal benefit (<35 % relief), the physician may choose another injection to be performed with a change in technique and cortisone used.