Not sure of the source but a friend of mine e-mailed this to me last week as she thought it would be a useful addition to the site

Overview

Epidural injection is the administration of medication into the epidural space. It is used to treat swelling, pain, and inflammation associated with neurological conditions that affect nerve roots, such as a herniated disk and radiculopathy.

Epidural injections may be painful and produce uncertain results. Studies show that epidural injection may provide short-term pain relief for patients when conservative treatments have failed.

Anatomy

The brain is covered by three membranes (dura, arachnoid, and pia), called the meninges that extend through the base of the skull and surround the entire spinal cord. The spinal cord travels down the entire length of the spinal column through the spinal canal. The epidural space is located between the dura and the interior surface of the spinal canal and contains veins, arteries, and fat. Epidural injection is the injection of medication into the epidural space.

Procedure

Epidural injection is usually given in an outpatient setting. An anesthesiologist usually administers the injection, but some neurosurgeons, orthopedic surgeons, and neurologists are also qualified to perform this procedure.

A mild sedative and a local anesthetic may be given prior to the procedure to relax the patient and numb the injection site. Medications, usually an anesthetic such as bupivacaine (Marcaine®) or a muscle relaxant, and a corticosteroid such as methylprednisolone (Medrol®), are injected directly into the epidural space. (The injection is commonly called a cortisone shot.)

Effectiveness

Approximately 30% to 70% of people who receive an epidural injection benefit from it. Some patients notice improvement within hours of the injection; others improve over a number of days; and others experience no improvement with the treatment. In some cases, two or three injections are given over weeks or months.

Complications

Complications resulting from an epidural injection are rare. Possible conditions that may develop following the procedure include infection (e.g., epidural abscess), bleeding into the epidural space, and headache caused by a cerebrospinal fluid leak. Approximately 2% of patients experience side effects from the corticosteroid, such as mild fluid retention.