Low back pain, radicular pain, radiculopathy and lumbago have been treated with epidural steroid injections (ESIs) since 1952. In recent years, the epidural steroid or corticosteroid injection has been the choice of treatment prior to back surgery for diagnosis of cause of pain. It is an invasive procedure and performed in office or surgical facilities under strict aseptic precautions. Epidural corticosteroid injection is performed to treat radicular pain caused by irritation of nerve in neck, thorax and lumbar dermatome. 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. Epidural corticosteroid injection is beneficial for a patient during an acute episode of back and leg pain.
Epidural steroid injection is invasive procedure and performed either at outpatient surgical center, hospital surgery center or at physician’s clinic. Interventional pain specialists as well as rehab physician, orthopedic surgeon or neurosurgeon performs procedure. Physicians who may be qualified to perform epidural injection are anesthesiologist, radiologist, neurologist, physiatrist, and surgeon.
Anatomy of Epidural Space
Anatomy of epidural space in upper back (neck), middle back (thorax) and lower back (lumbar) spinal segment differs in diameter and thickness. Cervical epidural space is thinner and lumbar epidural space is wider. Three fibrous membranes surround spinal cord. Outer membrane or mater is called dura, middle membrane is arachnoid and inner membrane is pia mater. Pia mater is closely attached to spinal cord and arachnoid membrane. There is no space between pia and arachnoid membrane. There is space between arachnoid and dura mater known as subdural space. Subdural space contains cerebrospinal fluid. Space outside the dura is known as epidural space.
Boundaries of Epidural Space Are As Follows:
- Anterior– Anterior boundary is occupied by posterior longitudinal ligament.
- Lateral (right and left)– Lateral space is covered by pedicle of vertebrae and spinal nerve entering foramina. Epidural space is connected to the paravertebral space through the intervertebral foramina.
- Posterior– Epidural space is surrounded by lamina and the ligamentum flava posteriorly.
- Superior (cephalic)– Epidural space ends superiorly at the foramen magnum.
- Inferior (caudal)–The epidural space ends at the sacral hiatus continuous as sacrococcygeal ligament.
Contents of Cervical, Thoracic and Lumbar Epidural Space
- Loose Areolar Connective Tissue
- Adipose Tissue And Fat Lobules
- Lymphatics Vessels
- Arteries And Arterioles
- Plexus of Veins
- Spinal Nerve Roots And Nerves
Indication for Epidural Corticosteroid Injection: Level- Cervical, Thoracic or Lumbar
Epidural route of corticosteroid injection is indicated as alternative therapy to oral pills, intramuscular injection, or intravenous injection. Amount of corticosteroid received at the source of pain near spinal canal is less than 1% of oral dosage, less than 6% of intramuscular dosage, and less than 20% of intravenous dosage. Therapeutic value of epidural steroid injection is 75% to 90% of injected dose when injected in epidural space. Epidural steroid injection delivers corticosteroid near the source of pain generator.
- Anti-Inflammatory-Corticosteroid is an effective anti-inflammatory medication. Corticosteroid reduces inflammation. Inflammation causes increased secretions of inflammatory chemicals. Inflammatory chemicals like prostaglandin causes irritation of spinal nerve resulting in severe pain. Epidural corticosteroid injection results in decreased secretion of inflammatory chemicals.
- Nerve Swelling-Inflammation of the disc or epidural soft tissue causes secretions of inflammatory chemicals, which produces nerve edema and swelling. Swollen and edematous nerve triggers severe intractable pain. Corticosteroid decreases nerve edema and swelling resulting in pain relief.
- Immune Response-Reduces immune response caused by disk trauma or nerve injuries.
- Diagnostic Injection-Diagnostic epidural injection is performed to evaluate the cause of pain. Diagnostic injection is also performed to rule out psychological pain. Diagnostic epidural corticosteroid injection is indicated if MRI, CAT scan or EMG studies are normal and patient is complaining of radicular pain not responding to conservative treatment.
- Therapeutic Injection-Radicular pain1 is caused by nerve pinched within foramina or spinal canal. Nerve is pinched within spinal canal or foramina by bulge or herniated disk that protrudes in to spinal canal or foramina. Series of 3 to 4 therapeutic injections are performed to provide radicular pain relief, which may last from 2 to 6 months or in few cases longer.
- Assist Physical Therapy and Rehab-Therapeutic injection is indicated to achieve adequate pain relief so patient can continue with physical therapy and rehab therapy.
Contraindication for Cervical, Thoracic and Lumbar Epidural Corticosteroid Injection
Epidural Corticosteroid Injection Is Contraindicated In Following Diseases-
- Systemic Infection
- Skin infection and lesions over injection site
- Epidural abscess or epidural bleeding
- Bleeding disorder like hemophilia
- Patient taking blood thinners (Coumadin).
- Use of high dose aspirin.
- Use of anti-platelet drugs (e.g. Ticlid, Plavix).
- Spinal tumor
Pre-Op Evaluation for Epidural Corticosteroid Injection
- Informed Consent-Pre-op evaluation involves an interview by a pain specialist and anesthesiologist. Pain specialist will discuss details of present illness, past illnesses, procedure, complications, alternative treatments and risk of procedure in details. Anesthesiologist will discuss history and examination, choice and risk of anesthesia. Anesthesia is very safe because of close monitoring and reliable anesthetic medications.
- I.V. Access-Intravenous (I.V.) access is necessary to give anesthetics for sedations. Preop sedation is also given to patient exhibiting anxiety prior to patient taken to surgical room. Anxious patient may develop serious vaso-vagal response induced by fear, apprehension and needle phobia. Sedation is essential during procedure to prevent sudden involuntary or deliberate movement of patient during critical phase of procedure. Insurance providers because of additional cost often deny sedation.
Procedure: Cervical, Thoracic or Lumbar Epidural Corticosteroid Injection
- Sedation-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 and movements during critical phase of procedure, which may cause minor or serious nerve injury. Vasovagal shock is a fainting often seen in apprehensive, claustrophobic and in patient afraid of needles. Several patient prefer not to have any sedation and procedure is performed under local anesthesia. Post procedure discharge to home is sooner when procedure is done under local anesthesia. Patient may have to stay in recovery room for 30 to 60 minutes if procedure is performed under sedation. An epidural steroid injection usually takes between 15 to 30 minutes.
- Position-Patient is advised to lie in prone (face facing operating table) or lateral (lie on side) positions on X-ray compatible surgical table. Flex prone or lateral position is maintained by placing pillow under abdomen. If the patient is unable lie prone, surgical area where needle is going to be inserted is identified by clinical AO tolerate flex prone position then procedure is performed in curled lateral position.
- Skin Preparation-Surgical area where needle is going to be inserted is identified by clinical and X-Ray examinations. Skin area where needle will be penetrating is marked with marking pen. The skin around the surgical area is prepped with antiseptic solution.
- Epidural Space-Procedure is performed under X-Ray or image intensifier. Cervical (upper back), Thoracic (mid back) or Lumbar (lower back) interspinous space is selected for epidural injection. Level is confirmed by clinical and X-Ray examination.
- Numbing of Skin and Subcutaneous Tissue-Two adjacent spinal processes are identified at selected level in cervical (neck), thoracic (chest) or lumbar (lower back) segment of the vertebral column.The skin and subcutaneous tissue is anesthetized using 0.5% lidocaine a short acting local anesthesia. Amount injected is 0.5 cc to 3 cc.
Epidural Corticosteroid Injection Approach
Four Different Approaches of Epidural Corticosteroid Injection
There are four different approaches used for epidural injection. Approach depends on preference of pain specialist and indication for procedures.
Once the patient is prepared for needle penetration, one of the following four approaches is used to inject cortisone in epidural space.
Laminar Anteroposterior Epidural Steroid Injection (LESI)
This approach is useful to perform epidural steroid injection in upper, middle or lower back. 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.
Steps of Procedures for Laminar Epidural Steroid Injection
- After local anesthesia epidural needle is advanced anteriorly (from back to front direction) between upper and lower spinous process. Epidural needle is carefully advanced while passing through inter-spinous ligament and ligamentum flavum in to epidural space. Epidural space is identified with loss of resistance technique using air or normal saline.
- Dye is injected in epidural space. Spread of dye is examined under X-Ray 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 cc.
- Observed for any side effects or complication before patient is transferred to recovery room.
Transformational Epidural Steroid Injection (TESI)2
This approach is useful to perform epidural steroid injection in upper, middle or lower back. Transformational epidural injection is specifically targeted to block the nerve on one side. Procedure is used for selective nerve root block. Pain relief is diagnostic to diagnose unilateral radicular pain from a particular nerve suspected to be pinched. Procedure is frequently performed at more than one nerve and sometimes bilateral as indicated. Diagnostic injection is often performed on one side and at one nerve. If pain is involving multiple nerves and bilateral, diagnostic injection may be multiple procedures. Therapeutic injections are performed at multiple nerves and bilateral at the same time so as to prevent patient coming back multiple time for procedure. Patient suffering with pain caused by irritation of multiple nerves will never get adequate and optimum pain relief if all the nerve involved is not treated simultaneously.
Steps of Procedures for Transformational Epidural Steroid Injection
- Procedure is performed with minimum or just adequate sedation.
- Procedure is performed using image intensifier. (X-Ray).
- Needle entry point is about 3 to 5 inch lateral from midline depending on patient’s size and weight. Needle is passed towards foramina in oblique direction to the side of vertebrae and placed at the rim of spinal foramina. Needle tip is carefully placed at posterior superior portion of neural foramen and advanced in epidural space.
- Dye is injected to confirm position of needle in epidural space. Dye study is important to rule out needle placement in blood vessels or spinal fluid. Needle tip could be accidentally placed in blood vessel or CSF.
- Corticosteroid particles may accumulate and cause venous or arterial embolism if needle tip is in blood vessels.
- Needle placement in subarachnoid space may cause spread of local anesthesia through cerebrospinal fluid. Procedure may result in total spinal anesthesia if local anesthesia is used with corticosteroid.
- Diagnostic block is performed using local anesthetic 1 to 2 cc with or without corticosteroids. Therapeutic injection is performed by injecting corticosteroid with or without local anesthetics. Volume injected at each level is 1.5 to 2 cc of solution. Multiple nerve injection is performed at same time to prevent patient coming frequently for injection.
Caudal Epidural Steroid Injection
This approach is useful to perform epidural steroid injection in lower back only. Caudal epidural steroid or corticosteroid injection is specifically targeted to block the lumbar and sacral nerves. Pain relief is diagnostic or therapeutic. Procedure results in treatment of multiple bilateral nerves. Diagnostic caudal injection is often performed if pain is unilateral or bilateral. Caudal epidural procedure is safer than trans-foraminal and laminar (antero-posterior) approach.
Steps of Procedure for Caudal Epidural Steroid Injection
- X-Ray is used for procedure.
- Sacrum and sacral hiatus is identified using X-Ray (image intensifier).
- Epidural needle is passed through sacral opening in to sacral hiatus. Needle position in epidural space is confirmed by using 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 suggests needle is in appropriate space and position.
- Medications are injected through the needle. Medications spread through sacral epidural space to lumbar epidural space. Large volume between 10 to 20 cc containing corticosteroids, normal saline and local anesthetics are injected. Most of the pain specialists prefer not to inject local anesthetics to prevent accidental spinal anesthesia.
- Procedure is less traumatic and has least complications.
Epidurolysis Using Spring Loaded Catheter
This approach is useful to perform epidural steroid injection in upper, middle or lower back. Spring-loaded catheter is placed through epidural needle in epidural space. Procedure is preferably done for lower back pain. Procedure is used for selective nerve root block or therapeutic bilateral nerve block. Catheter can be navigated under X-Ray guidance to selected nerve for diagnostic block. Procedure is mostly performed for therapeutic reason. Epidural scar tissue often causes severe pinched of spinal nerve. Epidural scarring follows back surgery and injury of back. Epidural scar tissue causes irritation and pinch of spinal nerve in epidural space. 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. Softening or separation of scar tissue adhering to spinal nerve is difficult with caudal or inter-laminar epidural injection. Spring loaded catheter helps to break and separate scar tissue from nerve. Catheter is carefully navigated through scar tissue and placed near selected nerve. Micro shearing effect of spring located at tip of the catheter and volume of medications injected helps to break and separate scar tissue from nerve. Procedure may need to be repeated 2 to 3 times in sequence to obtain optimum results. Pain relief may last for 4 to 6 months.
Steps of Procedures for Epidurolysis Using Spring Loaded Catheter
- Catheter is passed through epidural needle into epidural space of neck, thorax or lumbar segment. Procedure is also performed by inserting epidural needle in sacral epidural space. Catheter is navigated under X-Ray image to specific nerve or nerves. Catheter tip is carefully moved several times in all directions with gentle force to prevent dural tear. Surgeon will aspirate the catheter to make sure catheter is not in cerebrospinal fluid before injection of medications.
- Dye is injected in epidural space. Spread of dye is examined under X-Ray 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 cc.
- Patient is observed for any side effects or complication before being transferred to recovery room.
- 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.
Medication Injected in Epidural Space
One of the following three corticosteroids are used for procedures.
- Triamcinolone Acetonide
- Methylprednisolone Acetate
Following Are the Choices of Local Anesthetics Used For Epidural Injection
- 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 prolonged 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.
Discharge Plan Following Epidural Corticosteroid Injection Procedure
- Post-Op Observation-After procedure, the 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 the end of surgery. Initial pain is not felt because of effects of local anesthesia. Patient can use cold pack if pain continues after 3 to 4 hours.
- Resume Normal Activities-Whether the patient has received sedation or not, 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 procedure was performed under sedation. 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 procedure or he has withdrawal symptoms. Patient is advised to see pain physician if experiencing withdrawal symptoms.
Efficacy of Epidural Corticosteroid Injection
- Use of X-Ray (Image Intensifier) Machine– Use of X-ray machine has reduced complications and procedure is much safer than in the past.
- Short-Term Benefits of ESI– Single cortisone injection may give 2 to 6 week of pain relief.
- Long-Term Benefits of ESI– Multiple injections between 3 to 5 injections with frequency of every 2 to 4 weeks may give 3 to 6 month of pain relief.
- Satisfaction of Pain Relief– Patient’s satisfaction of pain relief is measured by decrease of visual analogue pain score.Pain relief over 50% or more is considered satisfactory pain relief.
- Effectiveness (Efficacy) of Lumbar Epidural Steroid Injections– Continues to be a topic of debate since guidelines of diagnostic and therapeutic injection are not very clear.
- Radicular Pain– Pain relief following series of 3 to 4 therapeutic epidural is more often satisfactory and over 50% last more than 4 to 6 months.
- Radiculopathy– Cortisone injection improves chronic pain but tingling, numbness, and muscle weakness may continue.
- Multiple Pain Generator– Pain caused by multiple pain generator like pinched nerve, facet joint disease and muscular illnesses do not respond to only epidural injection. Epidural steroid injection treatment fails if multiple pain generators are treated with only epidural injection. Epidural injection relieves radicular pain but facet and muscular pain continues with same intensity.
Complications Following Epidural Corticosteroid Injection
- Dural Puncture– Dural tear may occur secondary to needle penetration through dura or dural laceration while performing epidural steroid injection or epidurolysis using spring catheter. Dural puncture or tear causes following complications-
- Spinal Fluid Leaks (0.4-6%)- Cerebrospinal fluid (CSF) leaks through the dural puncture or tear.3
- Positional Headaches (28%) – Headache is observed in sitting up or standing position. Headache is either relieved or less severe in lying down position. Symptoms if not improved in 3 to 4 days then blood patch may be necessary to alleviate the headache.3
- Air Embolism– Air may be injected in subarachnoid space and CSF causing air embolism.3
- Irritation of Dural Membrane and Epidural Space
- Adhesive Arachnoiditis (6-16%) – Adhesive arachnoiditis is inflammation of arachnoid and dural membrane. Adhesive arachnoiditis is caused by epidural injection of contaminated corticosteroid, local anesthetics or normal saline. Arachnoiditis is also caused by intrathecal bleeding and adverse reactions to chemicals. Inflammation is caused by bacterial or viral infection. Adhesive arachnoiditis is also seen following back surgery. Arachnoiditis causes severe chronic nerve compression resulting in pain.3,4
- Neurological Complications– Recently most of the following neurological complications are avoided by not using local anesthetics.
- Nerve Injury– Nerve may be injured during needle penetration in epidural space. Superficial nerve injury may cause pain from nerve irritation but penetrating nerve injury may cause pain followed by tingling, numbness and muscle weakness suggesting severe nerve damage.
- Tingling and Numbness– Tingling and numbness is caused by either nerve injury during needle placement, pressure from hematoma (blood clot) or partial nerve block by local anesthetics. Hematoma may occur from tear of epidural blood vessels during procedures.
- Stroke– Stroke is secondary to rapid dilatation of blood vessel following epidural injection resulting in low blood pressure. Low blood pressure results in low blood flow to brain, mid brain and spinal cord. Prolonged lack of adequate blood flow causes extensive brainstem (midbrain) and thalamic stroke resulting in infarction.5
- Paralysis– Severe low blood pressure and low blood flow to spinal cord or nerve block of sensory and motor nerve by local anesthesia may cause paralysis. Paralysis caused by low blood pressure may be permanent if not recognized and treated immediately.6
- Seizures– Vasodilatation of lower leg blood vessels causes severe hypotension (decrease blood pressure) resulting in decreased blood supply to brain followed by seizures. Immediate anti-hypotensive treatment will improve blood supply to brain.
- Urinary and Bowel Incontinence (unable to hold) – Patient following epidural injection, occasionally are unable to produce or hold urine or stool. Symptoms are secondary to autonomic nerve block from local anesthetics.
- Blindness– Occasional transient reversible blindness is caused by severe hypotension.3
- Allergic Reactions
- Allergy to corticosteroid and local anesthetic is rare.
- Vascular Injection and Injuries
- Intravascular (in the blood vessels) Injections (7.9-11.6%) 1– Epidural space has abundant network of blood vessels and capillaries. Epidural needle tip may be placed within blood vessels and if aspiration test does not indicate aspiration of blood then medications are directly injected in the blood vessels.
- Bleeding and Hematomas (blood clot) – Epidural bleeding is a rare complication and is more common for patients with underlying bleeding disorders. Tear, injuries or puncture of blood vessels within epidural space can cause bleeding and hematoma (blood clot). Hematoma can cause pinch nerve complications.
- Fever– Fever is sign of infection. Temperature may be above 1010 F. Severe infections are rare, occurring in 0.1% to 0.01% following epidural steroid injections.
- Meningitis– Rare but any contamination of the medications can cause infection of spinal cords and its covering. Recently over 100 cases of bacterial and fungal infection of epidural space and meninges were diagnosed in few patients following epidural injection.
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Department of Neurosurgery, Wellington Regional Hospital, Wellington, New Zealand.
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Divisions of Neurosciences Critical Care, Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
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Department of Neurosurgery, University of Tennessee Health Science Center and Semmes-Murphey Neurologic and Spine Institute, Memphis, Tennessee 38120, USA.