The Spinal cord runs within the bony vertebral column and is contained by a membranous sac called the dural sac. This sac contains spinal fluid that bathes the spinal cord and provides it with nourishment. The epidural space is between the outer surface of the dural sac and the bones of the vertebral column.
Nerves from the lower limbs enter the vertebral column and the dural sac to reach the spinal cord. Occasionally, these nerves can become irritated as they enter the vertebral column and cause pain in the lower limbs. This pains is felt as shooting down the lower limb and is referred to as nerve pain, or technically, radicular pain. The common name for this sort of pain is sciatica.
How does an epidural steroid injection work?
The term 'epidural steroid injection' refers to the injection of corticosteroids into the epidural space of the vertebral column as a means of relieving pain caused by irritation of the spinal nerve roots.
There are two theories on how epidural steroid injections work. The first theory is that some leg pain results from the inflammation of one or more of the nerves or their roots in the back. The injection of steroids directly into the epidural space is thought to aid in reducing this inflammation. The other theory is that the injected corticosteroids act like a local anaesthetic and reduce the pain long enough to allow the body to begin the process of repairing itself.
How is an epidural steroid injection administered?
You will be asked to position yourself so that the vertebra in your back are as widely spaced as possible. Local anaesthetic will be injected into the skin and underlying tissues to numb the area around the epidural injection site.
Once the local anaesthetic is working the epidural needle is placed into the epidural space using the bones as landmarks and other technical aids to ensure the the needle is in the right place.
When the needle is in the epidural space, a syringe containing the corticosteroid solution is connected to the needle. The corticosteroid will be injected in a form that may include a saline solution and/or a local anaesthetic. After making sure that the needle is properly positioned, the doctor injects the solution slowly.
What are the risks of an epidural steroid injection?
With any injection procedure, there are risks but in the case of epidural injections, these risks are small. There a variety of side effects and complications that rarely occur, most of which relate not to the steroid itself, but to the way the injection is given.
The most common side effect is a temporary increase in pain. It occurs in about 1% of epidural steroid injections and appears to be related to the volume of substance injected into the epidural space.
Headache, another complication with an incidence of 1% may be related to the accidental puncture of the innermost membrane, which surrounds the spinal cord. The headache is caused either by a leakage of the fluid surrounding the spine, or as a result of an accidental injection of air into the spinal fluid. In most cases, the headache subsudes within a few hours, but sometimes it can persist for days, rarely for longer.
If you are allergic to one fo the additives in the steroid solution you may experience a hot flush or develop a rash. However, this should get better within a few hours or days.
As with any injection through the skin, it is possible for bacteria to gain entry causing an infection. The risk of this with an epidural injection is very small.
It is also theoretically possible that a nerve could be damaged. In the procedure, the needle is inserted very slowly, and if the lining around the nerve is touched, there will be pain in the leg. The doctor will then change the position of the needle slightly to avoid any risk of damage to the nerve.
Important Information
Please DO NOT stop taking your blood pressure, insulin or cardiac medications.
If you are diabetic, steroids may affect your blood sugar, please contact your physician
Stop taking anti-inflammatory medications 72 hours prior to a lumbar/joint injection--resume any anti-inflammatory meds after your injection or as instructed.
Advise your doctor if you are currently being treated for an infection
If you are taking "blood thinners" or allergic to medications, notify your doctor
