Epidural steroid injection, as the name implies, is a technique of injecting steroid into the epidural space for relieving pain.
Epidural steroid injections is considered integral part of nonsurgical management of radicular pain especially from lumbar spine disorders
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.
In case of disc herniation, inflammation within the epidural space and nerve roots is a significant factor in causing radicular pain. The inflammation is caused by leakage of disc material, compression of the nerve root vasculature, and/or irritation of dorsal root ganglia from spinal stenosis.
In case of spinal stenosis, there is probable inhibition of normal nerve root vascular flow leading to nerve root edema and dysfunction.
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, inhibition neural transmission in nociceptive C fibers and reduction of capillary permeability
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.
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.
- Factors affecting the efficacy
- Clinician’s experience and training
- Patient selection
- Duration of symptoms
- < 3 months, 90% response rate
- <6 months, 70% response rate
- >1 year, 50% reposnse
- Underlying pathophysiology
- Pain from lumbar disc herniation responds more than lumbar spinal stenosis.
- Post surgery pain less responsive
- Whether fluoroscopy and contrast used
- 30-40% of needle misplacement without fluoroscopy
- Vocational status
- Approach used for epidural steroid injections
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 space 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.
An epidural steroid injection usually takes between 15 and 30 minutes.The patient can be in prone or lateral position.
The skin in the low back area 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 desired position, contrast is injected to confirm the needle location.
The epidural steroid solution is then injected.
For patients with a suspected allergy to contrast medium, antihistamines and corticosteroids prior to the procedure should be given.
Steroids which are usually used are dexamethasone, triamcinolone, betamethasone, and methylprednisolone.
Following the injection, the patient is monitored for 15 to 20 minutes before being discharged.
Sedatives are rarely necessary.
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.
Patients are usually asked to rest for the day on and begin normal activities from the next day.
To provide immediate relief anesthetic agent can be mixed with steroids.
As the relief is for short term, repeated injections may be given.
The general consensus is about 3 injections per year
. Some doctors will space the injections out evenly over a year whereas others give two or three epidural steroid injections at 2-4 week intervals.
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
- Nausea, vomiting, dizziness, and vasovagal reaction
- Bleeding including epidural hematoma
- Nerve root injury has been reported.
- Anterior cord syndrome [injury to the artery of Adamkiewicz]
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.