Epidural steroid injection, as the name implies, is a technique of injecting a steroid into the epidural space for relieving pain in the neck, arm, back, and leg, caused by inflamed spinal nerves due to spinal stenosis or disc herniation.
An epidural steroid injection typically includes both a corticosteroid like methyl-prednisolone, dexamethasone or other and an anesthetic agent like lidocaine or bupivacaine. The drugs are mixed and delivered into the epidural space of the spine[ space between the bone of the vertebra and the outermost covering surrounding the spinal nerves and spinal cord.]. The drugs then percolate to the site of inflammation to take the effect.
Epidural steroid injections are considered an integral part of the nonsurgical management of radicular pain, especially from lumbar spine disorders.
Steroid injections can reduce inflammation and are effective for pain relief when delivered to the painful site.
But the relief is temporary and can last from days to months.
How does Epidural Steroid Injection Work?
Radicular pain often is the result of nerve root inflammation with or without mechanical irritation.
Mechanical compression of the nerves, per se, causes only motor deficits and altered sensation but not the pain.
The inflammation is caused by
- Leakage of disc material
- Compression of the blood supply of nerve root vasculature
- Irritation of dorsal root ganglia from spinal stenosis
In addition to this, the chronic nerve root compression can induce axon ischemia, decrease venous return, promote plasma protein extravasation, and cause local inflammation.
Steroids in the epidural space cause anti-inflammatory effect. This anti-inflammatory effect is brought out by inhibition of nerve impulses in C fibers which are pain receiving fibers. Moreover, steroids cause a reduction of capillary permeability leading to a decreased outflow of fluid.
Indications for Epidural Steroid Injections
- Radicular pain associated with a herniated nucleus pulposus [primary indication]
- Spinal stenosis with radicular pain
- Central canal stenosis
- Foraminal stenosis
- Lateral recess stenosis
- Compression fracture of the lumbar spine with radicular pain
- Facet or nerve root cyst with radicular pain
- Postherpetic neuralgia
The relief of pain is typically short-term and does not affect the course of disease or abate need for surgery.
When to Apply Epidural Steroid Injection
The optimal timing of epidural injection is unknown.
If the patient does not respond to treatment by relative rest or activity modification, medication, physical therapy, and/or manual therapy, epidural injection is indicated for pain control.
Early use of epidural steroid injections can be considered in patients with severe radicular pain severely interfering with sleep habits and daily functioning.
Earlier use of epidural steroid injections has been reported to be more efficacious than delayed use.
While an injection within three months of symptoms has a 90% success rate, after 6 months this reduces to 70% and after one year, it becomes 50%.
Contraindications for Epidural Steroid Injections
- Systemic or local [at the site of injection] infection
- Bleeding disorder
- Patient on anticoagulants
- History of significant allergic reactions to injected solutions (eg, contrast, anesthetic, corticosteroid)
- Acute spinal cord compression
Fluoroscopy should not be used in epidural injections in pregnant women.
Procedure of Epidural Steroid Injection
Approaches for Epidural Steroid Injections
Cervical and thoracic epidural injections can be carried out using interlaminar and transforaminal approaches. Lumbar epidural injections can be performed using transforaminal, interlaminar, and caudal.
Interlaminar epidural injections
The pace is approached through the area between laminae.
The injection can be performed through paramedian or midline approaches. The epidural needle penetrates the skin, subcutaneous tissue, paraspinal muscles or interspinous ligament (midline approach) and ligamentum flavum
Transforaminal epidural injections
The transforaminal approach is performed by placing the needle under the pedicle in the neuroforamen, superior and ventral to the dorsal root ganglion and exiting nerve root.
Caudal epidural injections
Caudal lumbar epidural injections may be performed by inserting a needle through the sacral hiatus into epidural space at the sacral canal.
- Patient examination in detail for the history of illness and medications she is taking
- Any allergies to medication should be noted.
- The patient is instructed to eat a light meal about 6-8 hour prior to the procedure and nothing by mouth thereafter.
- The patient should take normal medications except those who had been stopped by the doctor
- Obtain a consent for the procedure
- An intravenous line is secured after the patient arrives. Some patients may require anxiolytic drugs to reduce the anxiety of the procedure.
The patient should know that the procedure would take about 30-60 minutes and the patient would require to spend a few hours under observation in recovery for monitoring after that.
Procedure of Epidural Injection
- The patient can be in prone [lie on stomach] or lateral [on side] position on a translucent table
- The skin in the low back area [or intended space] is cleaned and then infiltrated with a local anesthetic.
- Using fluoroscopy, a needle is inserted into the skin and directed toward the epidural space.
- Once the needle is in the desired position, contrast is injected to confirm the needle location.
- Not all surgeons use contrast
- The epidural steroid solution is then injected.
- Steroids mixed with local anesthetics
- Steroids commonly used are – dexamethasone, triamcinolone, betamethasone, and methylprednisolone.
- Anesthetic agents are lidocaine or bupivacaine
- More than one injection can be given as per the need
For patients with a suspected allergy to contrast medium, antihistamines and corticosteroids prior to the procedure should be given.
Following the injection, the patient is monitored for 15 to 20 minutes before being shifter to recovery.
Sedatives are rarely necessary.
Most patients can walk around immediately after the procedure.
However, the patient is monitored for some time before discharging.
The patient is cautioned against driving for the day as temporary leg weakness or numbness can occur.
Tenderness at the needle insertion site can occur for a few hours after the procedure and can be managed by applying an ice pack for 10 to 15 minutes once or twice an hour.
For initial 2-3 days, there might be a slight increase in pain, numbness, or weakness but goes away after that as corticosteroids start to take effect.
Patients are usually asked to rest for the day on and begin normal activities from the next day.
Many studies show that about 50% of patients are benefited.
In case there is no relief from the first injection, a second one should be given.
In case of partial relief, is exhibited, a series of three injections in two weeks may be performed.
As the relief is for short-term, repeated injections may be given.
The general consensus is about 3 injections per year
If a patient does not experience any back pain or leg pain relief from the first epidural injection, further injections may not be beneficial.
Complications of Epidural Injections
- Postural puncture headache [epidural headache]
- Nausea, vomiting, dizziness, and vasovagal reaction
- Bleeding including epidural hematoma
- Nerve root injury
- Anterior cord syndrome [injury to the artery of Adamkiewicz]
- Subdural space puncture leading to spinal block and hypotension
Complications are lesser by using
- Fluoroscopic guidance
- Contrast enhancement to avoid vascular uptake
- Nonparticulate corticosteroid
- Transforaminal approach to avoid injury to the vessel or nerve root.
Factors affecting the efficacy are the clinician’s training and duration of symptoms. Disc herniation responds better pain from lumbar disc herniation responds more than lumbar spinal stenosis. Fluoroscopy is associated with better results.