During an epidural steroid injection, the steroid is delivered directly into the spine’s epidural space. The epidural space consists of a dural sac that is filled with fat and small blood vessels. It surrounds the spinal cord and nerve roots, as well as the cerebrospinal fluid that bathes the nerve roots. Local anesthetic or normal saline solution is also typically used in order to flush away any inflammatory mediators that are causing pain in the area. Inflammation is the most common component of various low back conditions and reducing such inflammation can significantly reduce pain.
Steroids that may be used include Triamcinolone acetonide, Dexamethasone, and Methylprednisolone acetate. For temporary pain relief, a fast acting local anesthetic Lidocaine or Xylocaine is often used. Bupivacaine may also be used if longer lasting medication is needed. Aside from pain relief, these local anesthetics also flush out the chemical or immunological agents that cause inflammation.
How epidural steroid injections control inflammation
Epidural injections are usually performed to treat sciatica, where pain is radiated from a pinched nerve in the low back. Sciatica pain can also spread to the back of the leg or into the foot. These other common back problems that stem from such inflammatory chemicals and immunological mediators can also benefit from epidural steroid injection:
- Lumbar disc herniation – when the disc nucleus pushes through the annulus (outer ring) and into the spinal canal
- Degenerative disc disease – when a disc collapses and impinges on the lower back nerves
- Lumbar spinal stenosis – when the spinal canal narrows and chokes off the spinal cord and nerves
- Compression fractures in vertebra – when a section of the vertebra collapses due to a trauma or a weakened vertebra
- Cysts – when a facet joint or nerve root expands and squeezes spine structures
- Annular tear – when an outer layer of the disc tears
Steroids can inhibit the inflammatory response from these sources of pain. It can also reduce the immune system’s reaction to the nerve or tissue inflammation. In a typical scenario, our body’s immunity generates white blood cells to protect against infection, bacteria, and viruses. Steroids inhibit the immune response in order to reduce any pain associated with the inflammation.
