ESI is most effective for lumbosacral radiculopathy associated with intervertebral disc herniation, bulging, or degeneration. The main criterion for success is the presence of nerve root inflammation that can be relieved by the steroid. ESI also has been used to treat pain from degenerative joint disease, scoliosis, spondylolysis, spondylolisthesis, postlaminectomy syndrome, facet abnormalities, herpes zoster, and postherpetic neuralgia.
After informed consent is obtained, the patient is placed prone, lateral decubitus, or sitting with the back, hips, and knees flexed. The injection should be performed as close as possible to the bony level of the nerve root irritation. The patient is prepared in a standard aseptic fashion over an area large enough to allow palpation of landmarks, and sterile technique is used throughout the procedure. Local skin anesthesia is provided with 1% to 2% lidocaine. A Tuohy epidural needle is then advanced between the spinous processes in a midline (or paramedian) approach until the needle is well seated in the posterior ligaments. The stylet is then removed and a loss-of-resistance syringe is attached to the hub of the needle. Two to 3 mL of normal saline should be in the syringe. The needle is slowly advanced 1 to 2 mm at a time, with constant checking for loss of resistance by tapping on the plunger of the syringe, or advanced slowly and continuously with light pressure on the plunger. Once a distinct loss of resistance is obtained, the needle is halted, and an attempt is made to aspirate blood or CSF. After negative aspiration, either 40 to 80 mg of methylprednisolone acetate or 6 mg mixture of betamethasone sodium phosphate and betamethasone acetate is injected. The steroids can be injected as is or diluted in 5 to 10 mL of preservative-free normal saline. If multiple levels are involved, dilution will ensure better spread of the steroid. The needle should be flushed with normal saline and the stylet replaced before it is removed from the skin to avoid tracking steroid to the skin. If blood is obtained on aspiration, the needle should be repositioned. If CSF is obtained on aspiration, the procedure can be continued; however, a spinal headache may result from dural puncture, and intrathecal injection is a possibility at this location (Fig. 67-9). The needle can be reintroduced at an adjacent level.
FIGURE 67-9. Lumbar epidural steroid injection. Approach for lumbar epidural steroid injection. A: Midline. Note that insertion is closer to the superior spinous process and with a slight upward angulation. B: Paraspinous (paramedian). Note insertion alongside caudal edge of “inferior” spinous process with 45-degree angulation to long axis of spine below.
A complete evaluation of the pain should be undertaken before ESI to rule out serious neurologic dysfunction or malignancy. Local infection, sepsis, coagulation abnormalities, and patient refusal are contraindications to ESI. Success is higher if the patient has had no previous back surgeries and the pain has been present for less than 6 to 12 months. Methylprednisolone acetate is best used for localized nerve root irritation. Triamcinolone diacetate is water soluble and results in optimal outcome in generalized nerve root irritation such as arachnoiditis. The paraspinous (paramedian) approach may be used if difficulty is encountered with the midline approach. A Tuohy epidural needle is inserted alongside the caudal edge of the inferior spinous process to the bony level of nerve root irritation. The needle is inserted with a 45-degree angulation to the long axis of the spine below and a 10-degree offset from midline and then advanced between the spinous processes until it is well seated in the posterior ligaments.
Inadvertent dural puncture may result in a postdural puncture headache. Risk of dural puncture is increased at sites of prior laminectomy. Intrathecal injection of steroid may result in aseptic meningitis, adhesive arachnoiditis, or conus medullaris syndrome. Each milliliter of methylprednisolone acetate contains about 30 mg of polyethylene glycol, which has been associated with nerve damage in experimental models (35). Epidural steroids can suppress plasma cortisol levels for about 3 to 5 weeks. Iatrogenic Cushing’s syndrome, fluid retention, and elevated serum glucose levels also can occur (36). Infection or bleeding into the closed epidural space also can result in significant neurologic deficits, including quadriplegia. Any complaint of increasing pain or neurologic changes should be investigated immediately. Early recognition can prevent permanent injury.