Epidural Steroid Injections
Research studies have shown the benefit of epidural steroid injections for sciatica and back pain caused by spinal disc lesions.
The purpose of the injection is to carry the medicine to the inner part of the back where some of the types of more serious strain affecting the discs, can cause pressure on, or irritation of, the nerves. The solution bathes these structures with anti-inflammatory steroid to reduce swelling and pain.
The solution contains a mixture of local anaesthetic or normal saline and corticosteroid. It may be injected just above the tail-bone (the caudal route) or between the bones in the small of the back (the lumbar route). The injection can be performed safely without the need for overnight stay or general anaesthetic.
In the majority of cases it is not a particularly painful procedure although you may experience some feeling of pressure as the volume of fluid is injected, or your sciatic pain may worsen temporarily. After the procedure you will be expected to rest for a while (20 minutes or longer) before going home.
You may experience some numbness around the pelvis or buttocks, temporary light headedness and slight unsteadiness in the legs if local anaesthetic has been used. For this reason you should not drive a vehicle or operate machinery until the next day. The benefit may appear almost immediately or build up gradually over the next few weeks. It is extremely unlikely that you will experience any other significant side effects.
Because of the corticosteroid component some women develop a facial flush the next day, which lasts 12-24 hours and more rarely some disruption of the menstrual cycle for one or two cycles. Other possible complications are similar to
those of any injection and are very rare, namely infection and allergic reaction which can occur in approximately 1 in 7,000 cases and can be dealt with promptly. There is no clear evidence of any long term complication from epidural steroids.
Caudal Epidural Injection
By feeling just above the tail bone the doctor identifies the lower entrance to the spinal canal at the base of the sacrum.
The needle enters the spinal canal through a ligament. The anaesthetic and steroid solution is then injected slowly over a period of some minutes. The solution spreads up the canal to reach the level of the third lumbar vertebra or higher.
Background to Recent Controversy
In the last few years there have been several adverse reports about the use of steroid epidurals in the media, stimulating unreasonable worry in people's minds. Despite their regular use for over 40 years, injectable steroids have never been officially licensed for use in the epidural space. Although a few isolated case reports of arachnoiditis have appeared there is no evidence of any causal link between epidural steroids and arachnoiditis.
A large number of people have received epidural steroid injections over the years, most of whom have obtained undoubted benefit. On reviewing the medical literature the number of patients in whom arachnoiditis or other chronic spinal condition has occurred in connection with injection of any substance epidurally is very small indeed, probably less than 1 in 20,000 injections. Putting this into perspective: Each year any individual has a risk of dying in a road accident of 1 in 8000,dying in a plane crash of 1 in 20,000 and death on the soccer field of 1 in 25,000.The use of intradural steroids has been stopped since this deeper injection into the spinal fluid has been shown to cause arachnoiditis in some rare cases. Myodil, the oil based dye formerly used for myelograms, (the old method of showing 'slipped discs' with X-rays) was banned in 1975 after some decades of use since it was clearly implicated in the production of arachnoiditis.
Lumbar Epidural Injections
Between one and five percent of attempts at epidural injection given by the lumbar route may penetrate the dural membrane which contains the spinal fluid. This is usually recognised immediately so that no solution is injected. The use of X-ray to control siting of the needle significantly lowers the risk. Epidurals given by the caudal route puncture the dural membrane in less than 1 in 2500 cases. If a dural puncture occurs your doctor will discontinue the procedure and ask you to lie down for 24 hours to avoid a 'spinal headache'. The small puncture of the dura usually seals itself very quickly without causing future problems.
Dr. John Tanner