What is the mechanism of action by which epidural steroid injections work?

What is the mechanism of action by which epidural steroid injections work?

Radicular pain is caused by nerve inflammation from direct impingement or chemical irritation. Steroids injected into the epidural space produce anti-inflammatory effects on the nerve roots. A series of up to three injections is traditionally performed every 2 weeks as needed. A steroid such as methylprednisolone 80 mg, with or without local anesthetic, is diluted to a volume of 10 mL and injected into the epidural space. Success rates of greater than 80% have been reported in the treatment of radicular lower back pain of less than 6 months duration.

Large series have supported the relative safety of this procedure. Recognized complications include dural punc-ture, salt and water retention, congestive heart failure, hyperglycemia, epidural abscess, and hemorrhage.

If the radicular pain is in a specific dermatomal distri-bution, selective nerve root blocks of individual nerves, with local anesthetic and steroids, can be performed under fluoroscopic guidance.