What are epidural steroid injections?
This type of injection involves injecting glucocorticoids into the epidural space in order to administer antiinflammatory relief to the spine. The objective of this injection is to decrease inflamed nerves that may contribute to pain in conditions of radiculopathy, radiculitis, or spinal stenosis with back pain with neurogenic claudication. Some practitioners will perform injections for nonspecific back pain or discogenic pain (causing localized back pain). There is little research to support the use of epidural injections for spinal stenosis, discogenic pain, or nonspecific back pain. A common indication for epidural steroid injection treatment is for disc herniations causing radicular pain. A high level of phospholipase A2 has been found in herniated disc matter. In animal studies it has been shown that the detection of this substance is associated with demyelinating nerve roots. The intention of injecting glucocorticoids, or “steroids,” into the epidural or transforaminal space would be to inhibit inflammation causing the production of phosphoslipase A2, to inhibit neural transmission of nociceptive C fibers, and to decrease capillary permeability.
Adverse responses from the injection include postural headaches, nausea, dizziness, hyperglycemia, vasovagal syncope, infection, epidural hematoma, nerve injury, and adrenal suppression (though there is limited research on this last adverse response). It is advised that no more than three to four epidurals be performed each year, to minimize steroid exposure.
The epidural can be approached in the interlaminar space between the ligamentum flavum and dura, or approached into the transforaminal space just posterior to the nerve root near the neuroforamina. For the interlaminar approach, the needle must penetrate skin, fat, subcutaneous tissue, supraspinous ligament, interspinous ligament, and ligamentum flavum to get to the epidural fat in the epidural space. This space is on average 5 to 6 mm deep. One must be familiar with spinal anatomy to avoid vascular structures, especially when using the transforaminal approach. These injections can be performed in the cervical, thoracic, and lumbar segments. A caudal epidural also may be approached through the sacral hiatus.