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  Treatment       Epidural Injections      
 
 
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Introduction
  • Epidural steroid injections are used in the pain clinic to improve sciatica pain where the cause is thought to be due to a pinched or trapped nerve within the spine. The usual indications are nerve root irritation caused by:-
  • Epidural steroid injections can be performed at the following levels:-
    • Caudal - for nerve root irritation between L4 and S4 (Sciatica = Lumbar and Sacral Radiculopathy ).
    • Lumbar - for nerve root irritation between L1 and L5 (Sciatica = Lumbar Radiculopathy ).
    • Thoracic - for nerve root irritation between T2 and T12 (Thoracic Radiculopathy).
    • Cervical - for nerve root irritation between C3 and T1 (Brachialgia = Cervical Radiculopathy ).
  • Injecting steroid drugs epidurally at the site nerve root irritation can reduce the degree of nerve inflammation and relieve the nerve root irritation symptoms (pain, numbness, tingling, mild weakness). They do not affect the rate of healing of an annular tear or a disc protrusion - this is controlled by healing processes in the body.
  • The aim of the treatment is pain relief through the reduction of nerve root inflammation. Minor disc disruptions and annular tears can heal naturally in about 6 months, and a series of 2 -3 epidural injections can greatly reduce sciatic pain, allowing rehabilitation to proceed more easily.
  • The best results with epidural steroid injections are seen in those patients with annular tears and small disc protrusions. Roughly 66% of "surgical virgins" will obtain good relief lasting 6 -8 weeks for each epidural performed, with a overall trend of general improvement over several months, and staying better long term.
  • If the series of epidurals helps the nerve root pain, but the spinal pain persists, it may be worth considering Spinal Manipulation as the next step.
  • Large disc protrusions which are causing moderate to severe nerve root compression, weakness, spinal cord compression or bladder / bowel dysfunction need an urgent surgical opinion for spinal decompression. I would not advise having an epidural injection in this situation.
  • Epidural injections are often used after disc surgery for residual nerve root symptoms. The success rate is often lower than in "surgical virgins", but it may be worth while trying one if the cause of the pain is thought to be due to continuing nerve root irritation (See Non Nerve Root causes of nerve root pain).
  • There is less convincing evidence for the use of epidurals in Spinal Stenosis. Some practitioners suggest that if spinal stenosis is associated sciatic symptoms rather than just back ache, that it may be worth trying a series of epidural injections.
  • Nerve Root Blocks may be more useful for Foraminal Stenosis.
Caudal Epidurals
  • Technique - Used for nerve root irritation between L4 and S4. Injecting through the sacral hiatus is the least complicated way to access the epidural space, and may be performed as a day case without the need for admission. The patient is usually positioned face down with a pillow under the hips for comfort . The buttocks and sacral area are cleansed using anti-septic, and then the needle insertion point is frozen with some local anaesthetic. A small needle is inserted through the sacral membrane into the epidural space. (N.B. the needle normally used is a lot smaller in length and diameter than those shown in the diagrams). Most practitioners use the Minimal Entry Technique with the needle at position "1" in the diagram. Advancing the needle to position "2" increases the chance of injecting the solution into the spinal fluid. The epidural injection is injected 1-2 ml at a time with a short pause in between each bolus, usually taking about 5 minutes to perform. Most patients feel a sensation of mild pressure which builds during the injection, and falls during the short pauses. Some people have reproduction of the sciatica pain down the leg during the injection, which subsides when the local anaesthetic begins to work inside the epidural space.
  • Epidural Mixture - 20 ml of solution is injected containing 40 mg triamcinolone, a long acting depot steroid lasting 21 days, mixed with 0.5% lignocaine. The triamcinolone exerts the anti-inflammatory effect, whilst the lignocaine (lidocaine) helps to make the procedure more comfortable. Some practitioners prefer not to use lignocaine in the mixture, to avoid any leg numbness afterwards. In my experience 0.5% lignocaine produces mild numbness in the buttocks and legs for up to 2 hours, but does not cause any leg weakness that interferes with walking.Commonly used steroids include:-
    • Triamcinolone (Kenalog )
    • Methylprednisolone (Depo-medrone )
  • Aftercare - you will be asked to lie down on the treatment couch for 10 - 15 minutes afterwards. You may be observed for a longer period according to frailty, and other medical conditions. Vital signs measurements will be performed where necessary. Leg strength and walking ability will be assessed prior to discharge. You must not drive that day, and you must be accompanied home by a responsible adult. 
  • See Side Effects and Complications for more information.
  • - Information Leaflet.
Lumbar Epidurals
  • Technique - Used for nerve root irritation between L1 and L5. Performed using X-ray screening, with the patient positioned left lateral. An intravenous cannula is usually inserted and intravenous sedation used. The skin and needle track are numbed with local anaesthetic, and the epidural needle inserted between the spinous processes until it reaches the epidural space . The space is identified by loss of resistance to an air-filled syringe, with the average depth being 5 cm (Range  3 cm to 11 cm). After confirmation of correct needle position with an Epidurogram , the epidural solution is slowly injected. Injection may provoke the usual nerve root pain due to volume effects within the epidural space - this is usually short lived and not severe if the injection is performed slowly. Afterwards the patient is positioned affected side down for 2 hours to encourage spread of the epidural mixture to the correct nerve root.
  • Epidural Mixture - as for Caudal Epidurals above.
  • Aftercare - A lumbar epidural injection is more likely to drop blood pressure than the caudal version, but with the mixture described above, this is very unusual. Vital signs observation are performed, and leg strength checked before standing. Usually done as a day case, but may need an overnight stay at UHCW Hospital (NHS) or BMI The Meriden Hospital (Private) depending on frailty or concurrent medical conditions.
  • See Side Effects and Complications for more information.
  • - Information Leaflet.
Thoracic Epidurals
  • Technique - usually performed for nerve root irritation between T1 and T12. As for lumbar epidurals, the injection is performed in the left lateral position, under X-ray screening, using local anaesthesia and intravenous sedation . The mid thoracic levels are the most difficult to perform because of the steep angulation of the vertebral spinous processes. Average depth is longer being between 6 and 11 cm. After confirmation of correct needle position with an epidurogram, the epidural solution is slowly injected. Injection may provoke the usual nerve root pain due to volume effects within the epidural space - this is usually short lived and not severe if the injection is performed slowly. Afterwards the patient is positioned affected side down for 2 hours to encourage spread of the epidural mixture to the correct nerve root.
  • Epidural Mixture - as for Caudal Epidurals above.
  • Aftercare - as for Lumbar Epidurals above.
  • See Side Effects and Complications for more information.
  • - Information Leaflet.
Cervical Epidurals
  • Technique - usually performed for nerve root irritation between C3 and C8. As for lumbar epidurals, the injection is performed in the left lateral position, under X-ray screening, using local anaesthesia and intravenous sedation . The injection is usually performed at the C6/7 or C7/T1 level, as the other cervical levels are too close together to allow the epidural needle to pass. Technically cervical epidurals are easier to perform than at the thoracic level because the spinous processes are widely spaced and horizontal. Average depth is between 4 and 7 cm. After confirmation of correct needle position with an epidurogram, the epidural solution is slowly injected. Injection may provoke the usual nerve root pain due to volume effects within the epidural space - this is usually short lived and not severe if the injection is performed slowly. Afterwards the patient is positioned affected side down with 10 degrees head down tilt for 2 hours to encourage spread of the epidural mixture to the correct nerve root.
  • Epidural Mixture - as for Caudal Epidurals above.
  • Aftercare - as for Lumbar Epidurals above.
  • See Side Effects and Complications for more information.
  • - Information Leaflet.
Side Effects
  • Mild numbness and tingling - usually lasts for 2 hours or less, and is due to the local anaesthetic effect. Severe leg numbness and weakness requires urgent medical assessment and referral to hospital.
  • Pain exacerbation - some patients experience an exacerbation of their sciatica for 24 hours after the injection when the local anaesthetic wears off. This is usually followed by a period of very much improved pain relief, and so it is worth sitting it out.
  • Urinary difficulties - some patients may experience difficulty passing urine for a short time. This occurs in about 1:200 cases and is more common with pre-existing bladder difficulties (pelvic floor control, cerebral palsy, very large disc prolapses). If you are not able to pass urine 6 hours post-procedure then medical assessment is necessary.
  • Menstrual Irregularity - high doses of depot steroids can cause menstrual irregularity due to interference with hormonal systems. Post-menopausal bleeding may unexpectedly occur, but is usually short lived. This is very unusual with triamcinolone 40 mg, but quite common with triamcinolone 80 mg. The national average dose of triamcinolone is 40 mg at present.
  • Don't be a hero - it is important to remember that the epidural produces pain relief and is not a cure for the disc problem. If you have a known disc prolapse, then heavy lifting must be avoided even if you feel wonderful afterwards, to prevent increasing the size of the disc protrusion. Sensible exercise like walking and swimming is advised.
Complications

Epidural complications are very rare, but when they do occur they can be serious.

Early Complications (during or just after the injection)

  • Post Dural Puncture Headache (PDPH) - if the epidural needle accidentally enters the space containing the cerebro-spinal fluid (CSF) during the procedure this is called a dural tap . If this is picked up at the time, then the procedure is usually postponed. CSF can leak out of the hole in the dura made by the epidural needle causing a severe headache. The headache occurs because the CSF around the spinal cord communicates with the CSF around the brain. A leak in the system causes the pressure to drop, with increased tension on the supporting membranes of the brain. The headache is usually worse with sitting and standing, whilst being relieved by lying flat. When the hole in the dura closes, the fluid leak slows, and the headache resolves, usually between 1 -2 weeks.
  • Dural puncture rates have been quoted as between 1 - 3% of all epidurals performed. There is a higher risk in obstetrics due to maternal movement during contractions. The risk is much lower for caudal epidurals as the needle is further away from the dura when using the minimal-entry technique. Dural puncture rates are higher for lumbar, thoracic and cervical epidurals as the needle is much closer to the dural membrane. My personal dural puncture rate for lumbar, thoracic and cervical epidurals is 1/1000, and zero for caudal epidurals.
  • The recommended treatment for PDPH is :-
    • Oral analgesics - paracetamol / codeine / NSAIDs.
    • Oral or IV fluid rehydration - dehydration makes the spinal fluid pressure lower and increases the headache.
    • Anti-emetics - sometimes the headache can cause nausea and vomiting, and therefore anti-emetics help to maintain hydration and minimise the headache.
    • Intravenous caffeine - caffeine sodium benzoate (500 mg) can be given intravenously every 8 hours to help the headache. It is thought to work by causing constriction of the cerebral blood vessels. Strong oral caffeine taken in the usual way may also be useful, but should not be taken at the same time as the intravenous version.
    • Epidural blood patch is used when PDPH fails to resolve with conservative treatment and time. About 20 ml of the patients own blood is collected aseptically, and injected into the epidural space, usually one level above or below the original injection level. A different level is used to avoid a possible second dural tap caused by pre-existing epidural anatomical abnormalities (this may be why the dural tap occurred in the first place). As this blood coagulates, it forms a plug to prevent further CSF leakage, helping the PDPH to resolve fairly quickly. Occasionally a second blood patch is required should the PDPH fail to resolve. Epidural blood patches are contra-indicated in the presence of suspected infection e.g. pyrexia, raised white blood cell count, or known source of infection elsewhere in the body. Blood cultures are usually sent to the lab at the same time as performing a blood patch, so that if infection does occur (epidural abscess), the organism will be discovered and treated sooner.
  • Total Spinal Injection - if the epidural needle accidentally enters the space containing the cerebro-spinal fluid, and if local anaesthetic is inadvertently injected, then the local anaesthetic can rapidly travel up the spine towards the brain stem and cortex. The local anaesthetic has a much more potent action in this space, and can cause a catastrophic drop in blood pressure, leading to cardio-respiratory arrest, unconsciousness, and total numbness of the head and body. With proper cardio-respiratory support (artificial ventilation, IV fluids, and blood pressure increasing drugs), the total spinal effects are reversible after 1 -2 hours depending on the local anaesthetic used. The incidence of total spinal injections can be greatly reduced by careful minimal entry technique (caudal route), and by aspiration on the needle before and during the injection. Prompt recognition and treatment of the complication can reduce the harmful effects.
  • Seizures - 10% of all epidural injections may be placed into a vein rather than the epidural space. This is because the epidural space has a rich supply of veins. If a large volume of epidural solution is accidentally injected intravenously which contains concentrated local anaesthetic, then an epileptic fit may occur as blood levels of the local anaesthetic rise. This can be prevented by careful aspiration on the needle before and during the injection. Using weak solutions like 0.5% lignocaine and injecting slowly over 5 minutes greatly reduces the risk of having a seizure. Treatment of a seizure involves stopping the injection immediately, controlling the fit with anti-epileptic drugs, and cardio-respiratory support until the fit stops.
  • Anaphylaxis - rarely a massive allergic reaction can occur during or shortly after an epidural injection. It usually causes severe falls in blood pressure, severe wheeze, urticaria (itchy skin rash), and rapid swelling of the face and extremities. This is no more common than after any other type of injection. Allergic reaction to lignocaine is very rare. If you have had a reaction at the dentist's to lignocaine then you should tell your doctor before having the treatment. As steroids are used to treat allergies, it is highly unlikely that you could be allergic to triamcinolone. The treatment of anaphylaxis includes drugs and fluids to support the blood pressure, and drugs to reduce the magnitude of the allergic response (steroids).

Late Complications

  • No Pain Relief - probably the most common late complication. The causes are non-nerve root sciatica, the needle missing the epidural space, or a large disc prolapse causing nerve root compression rather than irritation (surgical assessment advised).
  • Worse Pain - a very small number of patients develop worse sciatic pain which does not resolve spontaneously. The cause of this is unknown, and highlights the fact that all medical treatment carries risks which should be discussed with your doctor before hand.
  • Salt and water retention - depot steroids may occasionally cause salt and water retention. This may cause increased breathlessness in patients with congestive cardiac failure. This may be treated by increasing the dose of your diuretic medication for a short time. Please see your GP for further advice.
  • Spinal Haemorrhage may occur if an epidural vein is inadvertently punctured in the presence of a severe blood coagulation defect. Epidural injections should not be performed in this situation, as an unrecognized clot can compress the spinal cord, producing paralysis and incontinence. Patients with the following should alert their doctor prior to treatment:- warfarin, heparin or clopidogrel therapy, low platelets, severe liver disease, haemophilia, leukaemia and other bone marrow disorders. There is no problem with low dose aspirin therapy for the prevention of strokes. 
  • Spinal Abscess formation may occur if bacteria enter the epidural space during the injection. This can be greatly reduced by proper sterile technique using gloves and anti-septic skin preparation. In some patients the cause of the abscess is due to the formation of an epidural clot which then becomes secondarily infected via the blood route. The caudal route is a potentially more dirty area because of it's proximity to the perineum. Diabetics have a reported greater incidence of staphylococcal abscess formation. Left untreated an abscess can cause paralysis and incontinence. A persistently high temperature, feeling unwell, with increasing back ache may suggest an abscess, and requires urgent spinal surgical investigation and treatment.
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