Diagnostic neuroinjection X-rays, CT scans and MRIs provide quality images of a variety of spinal disorders. However, these images do not allow for the examination of pain. Spinal nerve injections, which are generally used for pain control, can also be used diagnostically to identify the site of the pain source. Diagnostic spinal nerve injections include discography, selective nerve root blocks (SNRB), sacral joint injections, and small facet joint injections.
Nerve roots and discs in the spine are common sources of pain. For example, a herniated disc in the lumbar spine may wrap around a nearby nerve and cause pain in the buttocks and thighs. Compression of nerve roots in the cervical spine may cause pain in the shoulder and arm. The choice of the type of diagnostic spinal injection depends on the patient’s medical history, physical and neurological examination, and other findings such as a CT scan.
Intervertebral discography
A discogram can help determine if a particular disc is the source of the pain. This is not a routine test, but may be performed when surgery is being considered.
Under x-ray fluoroscopy (a technique that allows real-time imaging of the patient’s internal anatomy), a contrast agent is injected into the suspected disc. The contrast agent helps to show the anatomical features of the disc. The disc may look normal, or the inner layer of the disc may be ruptured (cracked).
Discography may be uncomfortable for the patient. When the dye is injected, the patient’s typical symptoms may reappear. This is called a positive discogram. The patient’s pain response is important to help diagnose the exact source of pain. If the injection does not reproduce the patient’s pain, the test result is a negative discogram.
Depending on the number of discs to be injected (spinal level), this test takes 30 to 45 minutes. Infection is a potential risk, but very rare. Antibiotics are given before the test or with the contrast to avoid infection.
Selective nerve root block (SNRB)
SNRB is used to identify the specific source of spinal nerve pain. It can help diagnose cervical or lumbar radiculopathy (pain and inflammation of nerve roots in specific areas of the body).
Under the guidance of X-ray fluoroscopy, the specialist injects steroid medication into a specific nerve root. Steroids have a strong anti-inflammatory effect. If the injection reduces or relieves the patient’s symptoms, the doctor can determine the source of the pain. The examination takes 15-30 minutes per spine.
Small facet joint blocks and intermediate blocks
Inflammation of the joints between the bones of the spine may cause back pain. Small facet blocks and intermediate blocks are steroid injections into the joint to determine if the joint is the source of pain. Steroids can reduce inflammation and relieve pain.
A small facet joint block is an injection of a local anesthetic and steroid medication into the joint. Intermediate blocks inject similar medications into the periphery of the joint space near the joint nerve. These injections are performed under fluoroscopic guidance.
If the pain decreases, it may mean that the suspected joint or intermediate nerve is the source of the pain.
Sacral joint injections
The sacrococcygeal joint is the largest joint in the spine. It is located in the lower spine above the coccyx. Inflammation of the sacral joint may cause pain in the lower back and buttocks.
A local anesthetic and steroid medication is injected into the sacral joint using x-ray guidance. If the pain decreases, it may mean that the suspected joint is the source of the pain.
Patient preparation: at home
Patients must follow pre-test precautions so that the results of the diagnostic injection will be accurate. These precautions include
Stop taking blood thinners 2 days before the test Do not take any aspirin-based products 5 days before the test Stop taking anti-inflammatory medications (except VioxxT or CelebrexT) 8 hours before the test Stop taking pain medications 6 hours before the test Do not eat or drink anything Arrange for someone to drive you home
Patient Preparation: At the hospital
The provider will ask the patient about their medical history, condition, daily medications, diet and/or medication allergies and other conditions. The patient changes into a gown and lies in a hospital bed. The patient wears an EKG monitor (to monitor heart function), an automatic blood pressure cuff (to monitor blood pressure), and an oximeter (to monitor blood oxygen levels). These devices allow the healthcare provider to continuously monitor the patient’s vital signs before, during and after treatment. Injections of medications that relax the patient. In some cases, light intravenous sedation may be administered. Diagnostic spinal injections require the patient to remain awake and answer questions from the injection specialist.
What is done during the injection
Injections are performed in a sterile environment similar to an operating room. The injection site is cleaned and covered. Skin anesthetic medication is injected at and around the injection site. Prior to initiation, an x-ray fluoroscopic C-arm is placed over the patient. During injection, the fluoroscope guides the needle into the correct position. After insertion of the injection needle, a contrast agent is injected to improve visualization of the injection site.
Anesthetic dissolved in steroid solution is injected after the contrast agent. The steroid solution may contain antibiotics. The purpose of this test is to reproduce a typical condition (symptom) that is uncomfortable for the patient. The patient may have to bend, turn, walk or sit or stand to reproduce the symptoms. Feedback from the patient is suspicious to help find the cause of the pain.
After the examination
The patient is transported in a wheelchair to the rehabilitation unit, where the health care provider continues to monitor the vital signs. Patients are usually discharged home within 30-60 minutes. Numbness is felt around the injection site. Relief of typical symptoms may last up to six hours after the injection is completed. Steroids may cause side effects including blurred vision, frequent urination, thirst and changes in blood glucose levels, especially in diabetic patients.
If these side effects are intolerable or worsening, you should see your doctor. If high fever, chills, increased pain, weakness, or impaired bowel/bladder function occur, a doctor should be seen immediately. Patients should reach out to their primary care physician for test results.
Possible complications
As with other medical procedures, diagnostic spinal injections carry certain risks. Complications include risk of infection, hypotension, headache, and nerve tissue damage.
Contraindications
For safety reasons, diagnostic spinal nerve injections may not be allowed in certain patients due to the following reasons.
allergy to the contrast medium and/or medication to be injected anemia severe asthma bleeding disorders infected kidney disease pregnancy/lactation severe spinal anomalies
Conclusion
Diagnostic nerve injections can be very useful in identifying the source of a patient’s pain. However, patients often experience discomfort and pain during the examination. We recognize that these exams can be both valuable and discomforting to the patient. Our specialists are committed to making the examination process as comfortable as possible. We also value careful explanation of the procedure to patients, as we have found that exams run more smoothly if patients understand the procedure.