Inflammation of nerve roots can be caused by direct compression of nerves causing sciatica or a mechanical radiculopathy. This leads to symptoms of leg pain, numbness, tingling and weakness. Tears in the disc can trigger an inflammatory response that irritates nearby nerves causing a chemical radiculopathy (as opposed to a mechanical radiculopathy from direct compression of the nerves).
Epidural steroid injections are performed under x-ray to help the physician place the needle and a very small amount of steroid and local anesthestic into the spinal canal and around the specific nerves that are inflamed.
Epidural steroid injections typically only take minutes to perform and can last for months or years. One may be all you need. If more are required you can have up to 3 to 4 per year.
Not all patients and procedures are the same. The above is an example of what the typical patient can expect from some minimally invasive procedures.