Sciatica and low back pain have been treated with epidural steroid injections (ESIs) since 1952. In recent years, epidural steroid injection has been the choice of treatment prior to surgery. Epidural steroid injection or ESI is an invasive procedure and performed in office or surgical facilities under strict aseptic precautions. Epidural steroid injection is performed to treat nerve or radicular pain in neck, thorax and lumbar epidural space.
Injection is performed as a diagnostic injection or therapeutic injection. Diagnostic injection is performed to evaluate the cause of pain. Radicular pain is caused by nerve pinch within foramina or spinal canal. Nerve is pinched at foramina by bulge or herniated disk protruding in to foramina or stenosis caused by hypertrophic arthritic foramina. Diagnostic epidural is indicated if MRI, CAT scan or EMG studies are normal and the patient is complaining of radicular pain. Diagnostic injection is also performed to rule out psychological pain. Epidural corticosteroid injection is also performed as therapeutic injection. Therapeutic injections are performed to provide pain relief, which may last from 2 to 6 months or any few cases longer. Therapeutic injection is also performed to achieve adequate pain relief, so the patient can continue with physical therapy. Epidural steroid injection is used in combination with a comprehensive rehabilitation program to provide long-term pain relief and also to prevent further disk herniation or disc bulge. Epidural steroid injection is beneficial for a patient during an acute episode of back and leg pain.
Corticosteroids can be given as oral pills, or intramuscular and intravenous injection. Amount of corticosteroid received at the source of pain is less than 1% of oral dosage, less than 6% of intramuscular dosage and less than 20% of intravenous dosage. Therapeutic value of interventional corticosteroids as in epidural steroid injection is 75% to 90% of injected dose, when injected directly at the source of pain. Epidural steroid injection delivers medication near the source of pain generator. Volume injected in epidural space is debated by pain societies and academics. Higher volume spreads wider and helps flush inflammatory chemicals from epidural space.
Anatomy of Epidural Space
Epidural space surrounds dural membrane, which encloses spinal fluid and spinal cord. Boundaries of epidural space are as follows:
- Anteriorly – Anterior boundary of epidural space is occupied by posterior longitudinal ligament.
- Laterally (right and left) – Lateral epidural space is covered by pedicle of vertebrae and spinal nerve entering foramina. Epidural space communicates freely with the paravertebral space through the intervertebral foramina.
- Posteriorly – Epidural space is surrounded by laminae and the ligamentum flava.
- Superior (cephalic) – Epidural space ends superiorly at the foramen magnum.
- Inferior (caudal) – The epidural space ends at the sacral hiatus, which is closed by the sacrococcygeal ligament.
Epidural Space Contains:
- Loose areolar connective tissue
- Adipose tissue – fat lobules
- Lymphatics vessels
- Arteries and arterioles
- Plexus of veins
- Spinal nerve roots.
Radicular Pain: Inflammatory Nerve Pain
Radicular pain is also called sciatica. Characteristics of radicular pain is as follows:
- Radicular pain is directed along the course of spinal nerve.
- Spinal nerve pain is dermatomal pain, felt over the low back and area of the body connected with the pinch nerve.
- Pain is caused by pressure (pinch) over the nerve and/or irritation of nerve by inflammatory chemicals.
- Traumatic disk herniation and bulge disk secretes inflammatory chemicals such as substance P and prostaglandin E2.
- Inflammatory chemical irritates the dorsal nerve resulting in radicular pain and also causes swelling of the nerve.
Causes of Radicular Pain
- Disc Herniation – Nucleus of cervical, thoracic and lumbar disc penetrates through the outer ring (the annulus) of disk causing tear of fibrous coverings and triggers inflammation. Inflammatory chemical causes irritation and swelling of nerve resulting in severe pain.
- Disk Bulge – Nucleus of the disk pushes the outer layer causing disk bulge. Bulge disk presses the nerves within foraminal tunnel and causes swelling of pinch nerve resulting in severe pain.
- Degenerative Disc Disease – Disk become thinner by degeneration and narrows the foramina causing foraminal stenosis. Foraminal stenosis secondary to collapse of the disc impinges the spinal nerve in foramina causing irritation of nerve and swelling resulting in severe pain.
Lumbar Spinal Stenosis – Spinal cord and spinal nerves lies in spinal canal. Narrowing of the spinal canal is called spinal stenosis. Spinal stenosis strangles spinal cord and spinal nerves. Inflammatory spinal stenosis caused by trauma or arthritis causes secretion of inflammatory neurotransmitters and also swelling of nerve by inducing pressure.
Synovial cysts can cause pressure over facet joint and spinal nerves resulting in severe radicular pain and facet pain.
- Foraminal Stenosis – Spinal nerve passes through the foramina into visceral tissues. Foramina are narrowed by disk shrinkage or traumatic injury to vertebral body. Disk is narrowed by degenerative diseases, old age and trauma such as work accident or auto accident. Vertebral body fracture may occur with degenerative diseases, osteoporosis and traumatic whiplash injury. Foraminal stenosis associated by inflammatory arthritic disease and traumatic injury causes pressure on spinal nerve within the foramina and also irritation by inflammatory chemicals.
Mechanism of Action of Corticosteroid
- Corticosteroid reduces the secretions of inflammatory chemicals.
- Decreases the nerve swelling.
- Reduces immune response to inflammatory changes caused by disk trauma or nerve injuries.
Who Should Avoid Epidural Steroid Injections or ESI?
Epidural corticosteroid injection is contraindicated and avoided if following illnesses or diseases are present at the time of procedures:
- Skin Infection
- Systemic Infection
- Epidural abscess or epidural bleeding
- Bleeding Disorder- Epidural should be avoided if patient has an increased bleeding tendency. Bleeding time and clotting time is measured prior to procedure if necessary. Bleeding tendency is higher in following conditions:
- Patient taking blood thinners (Coumadin).
- History of hemophilia.
- Use of high dose aspirin.
- Use of anti-platelet drugs (e.g. Ticlid, Plavix).
- Spinal tumor
How is Epidural Steroid Injection Procedure or ESI Procedure Done?
Epidural steroid injection is invasive procedure and performed either at surgery center, hospital or a physician’s clinic. Interventional pain physician most often performs this ESI procedure. Physicians who may be qualified to perform epidural injection are anesthesiologist, radiologist, neurologist, physiatrist, and surgeon.
Epidural steroid injection is performed with or without sedations. Apprehensive and anxious patient does better with sedation than without sedation. Sedation is avoided in diagnostic injection. Sedations are preferred by many physicians for therapeutic injection to prevent vasovagal shock, which may happen frequently in apprehensive and claustrophobic patients. An epidural steroid injection procedure usually takes between 15 to 30 minutes.
Pre-Op Evaluation Prior To Epidural Steroid Injection
- Paperwork – Patient is registered at front desk and all necessary paper work are done before patient is taken into surgical area.
- Surgical Gown – Gown is provided if Epidural steroid injection procedure is performed at surgical center. Clothing fabrics may get dirty and stained with iodine during the surgical procedure. Surgical gown also makes it easy to access surgical site.
- Informed Consent – Patient is interviewed by specialist performing procedure and anesthesiologist before being given any sedation or taken into operating or procedure room. Procedure, complications, alternative treatments, precautions and detailed history of present and past illness is discussed in detail if it is not done already in prior preop evaluation.
- I.V. Access – Intravenous (I.V.) access is necessary since Epidural steroid injection procedure is performed in prone position. Also patient may request sedation during pre-op evaluation or in middle of procedure in such situation I.V. access is important to use for sedations. Patient may develop serious vasovagal response to fear if procedure is continued in spite of patient being extremely apprehensive. Sedation may be denied because some insurance companies deny and prohibit anesthesia. In such cases I.V. access can be life saving.
- Position – Patient is advised to lie in prone positions on X-ray surgical table. Flex prone position is maintained by placing pillow under abdomen. If the Patient is unable to tolerate flex prone position then Epidural steroid injection procedure is performed in curled lateral position.
- Skin Preparation – Surgical area where needle is going to be inserted is identified by clinical examination or some time by using X-ray image. Skin area where needle will be penetrating is marked with marking pain. The skin is prep with antiseptic solution suggested by surgical center and joint commission.
- Numbing of skin and subcutaneous tissue – The skin area that was marked for needle penetration is anesthetized to numb with a local anesthetic. Local anesthetics used are lidocaine 0.5% or 1%.
Epidural Steroid Injection Procedure Approaches
There are four different approaches used for epidural steroid injection or ESI. Once the patient is prepared for needle penetration, one of the following four approaches is used to inject cortisone in epidural space.
- Laminar Epidural Steroid Injection (LESI) – Procedure is performed after skin and subcutaneous tissue is anesthetized. Image intensifier (X-Ray) is used to identify the spinous process and spinal canal surrounded by lamina in the cervical, thoracic or lumber vertebral column. Image intensifier is used to identify spinal canal and lamina between upper and lower vertebral spinous process. Epidural needle is inserted through skin and subcutaneous tissue into inter-spinous ligament. Needle is advanced in to epidural space with loss of resistance technique using air or normal saline. Dye is injected to confirm the needle is in epidural space. Solution of corticosteroid, local anesthetics and saline is carefully injected in epidural space. Volume injected is between 8 to 10 ccs. Laminar epidural injection accesses large epidural space and treats several spinal nerves on both sides as well as facet joint nerve. Procedure does not target a specific nerve or specific side. Laminar epidural steroid injection is useful as a therapeutic injection and not diagnostic procedure though almost all physicians use the procedure as diagnostic procedure as well as therapeutic injection.
- Transformational Epidural Steroid Injection (TESI) – Procedure is performed using image intensifier. Needle is passed in oblique direction to the side of vertebrae. Needle tip is carefully placed at posterior superior portion of neural foramen. Dye is injected to confirm position of needle in epidural space. Dye study is important to diagnose needle placement in blood vessels or spinal fluid to prevent injection of cortisone and other medication in to arterial system or spinal fluid. Transformational epidural injection is specifically targeted to nerve block on one side. Pain relief is diagnostic to diagnose unilateral radicular pain from a particular nerve suspected to be pinch. Procedure frequently performed at more than one nerve and some time bilateral as diagnostically indicated. Patient may receive injection at one nerve on each side or just one nerve at one side for diagnostic procedure. Therapeutic injection of 1.5 to 2 ccs of solution containing local anesthetics, corticosteroids and saline is injected at multiple nerves on both sides. Multiple nerve injection is performed at same time to prevent patient coming frequently for injection.
- Caudal Epidural Steroid Injection – Sacral hiatus is identified by clinical examination and x-ray image. Epidural needle is passed through sacral opening in to sacral hiatus. Needle position in epidural space is confirmed by antero-posterior and lateral view of x-ray. Once the needle is in position in caudal epidural space, dye is injected. Dye spread is examined, linear normal cephalic spread of dye suggest needle is in appropriate space and position. Medications are injected through the needle. Medication has to spread through sacral epidural space to lumbar epidural space. Large volume up to 20 cc of medication is needed to spread from caudal epidural space to lumbar epidural space. Procedure is less traumatic and has least complications like dural tear or epidural hematoma.
- Epidurolysis Using Spring Loaded Catheter – Epidurolysis is a procedure performed for breakage of epidural scar tissue within epidural space by using spring loaded tip of catheter. Catheter was invented and widely used by Dr. Racz. Back surgery and back injury can cause epidural scar tissue. Surgical trauma of epidural space during back surgery result in healing by forming scar tissue within epidural soft tissue. Back injuries after fall, work accident or auto accident causes epidural bleeding and injuries. Healing of injured tissue result into scar tissue. Epidural scar tissue can cause severe radicular pain by tugging and confining the nerves in epidural space and at entrance of spinal foramina. Catheter is expensive compared to epidural needle and procedure takes longer time than other epidural injections. Catheter can be navigated to spinal nerves near foramina and soft lysis can be done without causing nerve injury. Therapeutic results after performing procedure depends on training and experience.
Preference, pros and cons of selection of one of these epidural steroid injection procedure depends on experience, level of comfort doing procedure, time necessary to complete the procedure and cost of providing services.
Which Medication is Injected in Epidural Space During Epidural Steroid Injection?
One of the following three corticosteroids is used for ESI procedures.
- Triamcinolone acetonide
- Methylprednisolone acetate
Local Anesthetic Used in Epidural Steroid Injection Procedure
- Lidocaine (Xylocaine) is a fast-acting local anesthetic used for temporary pain relief. Lidocaine is used for numbing skin and subcutaneous tissue, as well as injected in epidural space with corticosteroid and saline. Epidural corticosteroid and saline can be very painful for first hour because of nerve irritation. Lidocaine prevents the initial pain which may be caused by irritation of nerve by corticosteroid or saline. Quantity injected could be 1 to 4 cc mixed with corticosteroid and saline.
- Bupivacaine – A longer lasting local anesthetic medication. Used in lower concentration of 0.25% or 0.5%. Quantity injected could be 1 to 4 cc mixed with corticosteroid and saline.
- Saline is used to dilute the local anesthetics. If only local anesthetics are used with corticosteroids then patient may get prolong nerve block from local anesthesia. Nerve block may result in numbness and weakness, in few cases may result in bladder and bowel incontinence. Saline is also used as ‘flushing’ agent to dilute the chemical or immunologic agents that cause inflammation.
Efficacy of Epidural Steroid Injections
- Short-Term Benefits of Epidural Steroid Injection- Single cortisone injection may give 2 to 6 week of pain relief.
- Long-term Benefits of Epidural Steroid Injection – Multiple injections between 3 to 5 injection with frequency of every 2 to 4 weeks may give 3 to 6 month of pain relief.
Pain relief of 50% or more is considered satisfactory.
Effectiveness of lumbar epidural steroid injections continues to be a topic of debate since guidelines of diagnostic and therapeutic injection are not very clear. If patient has multiple pain generator like pinch nerve, facet joint pain and muscular pain then just epidural steroid injection will not be beneficial. Guideline does not clearly suggest if multiple pain generators should be treated separately or together. Insurance companies pick and choose depending on cost of treatment and many time multiple pain generators are treated with only epidural steroid injection. Obviously treatment fails since patient gets pain relief in nerve pain only and joint or muscles pain continuous at same intensity. Some treating physicians do argue suggesting epidural injection do help in blocking nerves to joint and muscles. Question is how long? May be as long as local anesthesia is blocking the nerve.
- Research and Literature – Most of the literature has criteria’s of patient selection. Epidural injection when performed in patients with nerve pain gives over 50 to 75% pain reliefs. Research or literature does not clearly suggest if only epidural steroid injection provides long term pain relief in multi pain generator.
- Epidural steroid injection using fluoroscopy has eliminated several minor and major complications in recent years.
Complications or Side Effects of Epidural Steroid Injections or ESI
Following symptoms if observed after Epidural steroid injection procedure or ESI must be further investigated to prevent permanent damage or serious outcome:
- Fever – 100 F or over for 24 hours is sign of infection.
- Tingling and numbness after epidural injection suggest either nerve is blocked by local anesthetics or epidural bleeding causing hematoma. If numbness continues over 12 to 24 hours, CAT scan or MRI is indicated to rule out epidural bleeding.
- Loss of bowel or bladder control suggests patient is unable to produce or hold urine or stool after the procedure. Symptoms may be secondary to autonomic nerve block from local anesthetics and symptom may last for 8 to 12 hours. If symptoms continue after 12 to 24 hours then CAT scan or MRI performed to rule out epidural hematoma.
- Allergies – History of allergies to steroids and local anesthetics contraindicates the procedure. Allergy to corticosteroid and local anesthetic is rare.
- Nerve Injury – Increased pain following procedure may be caused by nerve injury by sharp needle tip during Epidural steroid injection procedure. Sharp tip of epidural needle can lacerate a nerve if needle placement is not at appropriate anatomical position within epidural space. Complication following Epidural steroid injection procedure is extremely rare with experienced interventional pain specialist, and the use of x-ray while doing procedure has nearly eliminated the nerve injury.
- High blood sugar – Post op hyperglycemia may occur in pre-diabetic and diabetic patients. Blood sugar is checked before and after procedure. Procedure is cancelled or postponed if pre-op blood sugar is higher.
- Dural Puncture –Dural tear can occur with procedure of epidural steroid injection. Any persistent headache after procedure must be evaluated for dural puncture headache. Most of the headache is resolved in 24 hours. Dural Puncture- Painful headache while sitting up or standing:
- Feels better after lying down.
- Improves within a few days.
- Blood patch may be necessary to alleviate the headache.
- Temporary numbness of the bowels and bladder because of autonomic nerve block by local anesthetics is also a known complication or side effect of Epidural Steroid Injection.
- Infection following Epidural Steroid Injection- Severe infections are rare, occurring in 0.1% to 0.01% of injections. But recently there were over 100 patients suffered with fatal and non-fatal fungal meningitis following epidural injection of contaminated corticosteroid.
- Bleeding – Epidural bleeding is a rare complication or side effect of epidural steroid injection and is more common for patients with underlying bleeding disorders.
- Complications of Nerve Damage during Epidural Steroid Injection- Extremely rare, nerve damage can occur from direct trauma from the needle. Nerve damage may occur from pressure necrosis after infection causing epidural abscess or epidural hematoma.
- A side effect from medication – Side effects to corticosteroid and local anesthetics is rare. Skin rash or any symptoms of allergies should be evaluated.
- Facial Flushing.
- A transient decrease in immunity because of the suppressive effect of the steroid.
- Stomach ulcers.
Discharge Plan Following Epidural Steroid Injection
- Postop Observation – After the Epidural steroid Injection procedure or ESI procedure patient is transferred to recovery room. Patient is monitored for vital signs such as heart rate, blood pressure, respiration, temperature and pain score. If necessary blood sugar is also monitored frequently as needed. Patient is monitored for 30 to 45 minutes as suggested by guidelines of surgical center and joint commission.
- Pain at site of needle puncture – Patient is advised that there will be pain at the site of needle puncture for 3 to 4 hours. Pain may be present at the time of discharge or may begin 1 to 2 hours from end of surgery. Initial pain is not felt because of effects of local anesthesia. Patient can use cold pack if pain following Epidural steroid Injection procedure continues after 3 to 4 hours.
- Resuming Normal Activity Following Epidural Steroid Injection – Whether Patient has received sedation or not during ESI procedure, normal activities can be resumed the following day.
- Pain and Other Medications – Patient is advised to discontinue all pain medications, sedatives, antianxiety medications for 24 hours, if Epidural steroid Injection procedure was performed under sedations. If sedation was not given in any form then patient can resume his dosage if pain intensity is same otherwise he is advised to reduce dosage by half until his pain is of same intensity as prior to ESI procedure or he has withdrawal symptoms. Patient is advised to see pain physician if experiencing withdrawal symptoms following Epidural steroid Injection procedure.
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