by Nicole Berardoni M.D, Tory McJunkin M.D, and Paul Lynch M.D
Anatomy of the Spine
Understanding the anatomy and physiology of the lower back is key in evaluating a person with lower back pain. The bony spine is positioned so that individual vertebrae (bones of the spine) provide a flexible support structure while also protecting the spinal cord. Certain conditions that can produce chronic pain affecting the vertebrae include spinal stenosis, vertebral body fractures, osteoporosis, osteoarthritis, spondylolisthesis, neoplasms (primary vs. metastatic lesions), and infections.
Separating each individual vertebrae are discs that act as cushions to minimize the impact that the spinal column receives. Since the discs are designed to be soft and provide support, they have a tendency to herniate backwards through the outer disc segment and ligaments. This can cause irritation to the spinal cord and adjacent nerves. Disc disease may be acute, herniation resulting from trauma, or more commonly, chronic degenerative disc disease. Degenerative disc disease is a process due to a thinning and degeneration of the discs over time that can lead to a disrupted spinal function, nerve impingement, and peripheral nerve irritation.
Spinal Ligaments and Muscles
There are ligaments that attach to each vertebrae and provide strength and mobility to the spine as well as the many groups of muscles that are responsible for the movement of the spine. The nerves are attached to the spinal cord and exit the spine to innervate the skin, muscles, and surrounding structures of the back and lower extremities. These muscles and ligaments have a tendency to become strained and irritated during strenuous lifting and excessive exercise and cause local nerve irritation.
PathologyIn spinal stenosis, symptoms are due to complications from the narrowing of the spinal canal where the spinal cord is located. This constriction produces symptoms of impingement on the spinal cord, spinal vasculature, and surrounding peripheral nerves. Disc bulging and herniation as well as arthritic changes of the vertebrae can cause narrowing of the canal. The pain and decreased mobility that is produced by this condition may cause a disability that can significantly impair a patient’s lifestyle (Boswell 2007).
Another common complication of chronic pain due to spinal stenosis is central sensitization. This is a development involving both the peripheral nervous system (PNS) and the central nervous system (CNS). Local tissue injury and inflammation activate the PNS, which sends signals through the spinal cord to the brain. Central sensitization occurs when there is an increase in the excitability of neurons within the CNS at the level of the spinal cord and higher. Eventually normal inputs from the PNS begin to produce abnormal responses. Low-threshold sensory fibers activated by very light touch of the skin activate neurons in the spinal cord that normally only respond to painful stimuli. As a result, an input that would normally produce a harmless sensation now produces significant pain. Symptoms of progressive and serious complications of severe progressive spinal stenosis are nerve involvement characterized by bladder or bowel incontinence, lower extremity weakness, or loss of sensation. These symptoms can be a medical emergency and require immediate evaluation.
Diagnosis of spinal stenosis is most often done clinically by a physician. The physician performs a physical examination demonstrating tenderness over certain areas of the spine as well as assessing the various limitations in movement of the lower extremity. The physician most likely will order radiological imaging, such as a CT scan or MRI, to visualize the level of stenosis. Currently MRIs are the standard of care to visualize chronic back pain and are especially useful before any procedures are undertaken.
Treatment for Spinal Stenosis
- Medications: NSAIDs (ibuprofen-like drugs), membrane stabilizing drugs, and other analgesics are often used in the management of pain associated with spinal stenosis. In the past few years, there has been an abundance of research surrounding non-surgical and non-pharmacological procedures and their effectiveness in treating spinal stenosis.
- Epidural steroid injections: This procedure involves injecting a medication into the epidural space, where irritated nerve roots are located. This injection includes both a long-lasting steroid and a local anesthetic (lidocaine, bupivacaine). The steroid reduces the inflammation and irritation and the anesthetic works to interrupt the pain-spasm cycle and nociceptor (pain signal) transmission (Boswell 2007). The combination medicine then spreads to other levels and portions of the spine, reducing inflammation and irritation. The entire procedure usually takes less than 15 minutes. The most important and greatest success achieved with the use of epidural steroid injections (ESI) is the rapid relief of symptoms that allows patients to experience enough relief to become active again. With this, they regain the ability to resume their normal daily activities. Studies with patients suffering from spinal stenosis showed positive results for short- and long-term pain relief while receiving multiple caudal epidural injections (Boswell 2007).
- Percutaneous adhesiolysis: The procedure, also known as the Racz procedure, has proven effective in removing excessive scar tissue in the epidural space. Scar tissue originates from inflammation, irritation, and often surgery. A needle is inserted into the caudal epidural space (by the tailbone) and a catheter is advanced into the epidural space under fluoroscopy guidance. Corticosteroid, local anesthetic, wydase, and hypertonic saline are injected to aid in lysing (or breaking) the adhesions (scar tissue). Clinical research evaluating the effectiveness of spinal adhesiolysis in spinal stenosis shows good short- and long-term improvement (Boswell 2007).
- Spinal cord stimulation: A third procedure that is also offered at Arizona Pain Specialists is spinal cord stimulation, which has been successful in treating spinal stenosis. A study on people with spinal stenosis who received spinal cord stimulation showed a 67% improvement rate, based on verbal pain scores, narcotic (pain medication) intake, and function (Chandler 2003). SCS involves implanting an electrical device that decreases the perception of pain by confusing the spinal cord and brain pain processing centers. Initially a trial is done to see if this device will help you long-term. In the initial trial, a small electrical lead is placed in the epidural space by your pain physician. Painful signals are replaced by tingling electrical signals. If you have success in your trial, you may decide to have a permanent SCS device implanted.
- Alternative treatments: There is adequate proof that acupuncture is more effective in treating neck and back pain than inactive treatments (Trinh 2007).
- Surgical treatments: When all conservative measures have been exhausted and the symptoms continue to be severe, a more invasive surgical laminectomy or foraminotomy may be necessary to take pressure off the spinal cord and surrounding nerves. Often surgical decompression is recommended in acute spinal stenosis and especially in patients who rapidly develop loss of bladder/bowel function, weakness, and decreased sensation.
- Interventional Techniques: Evidence-based Practice Guidelines in the Management of Chronic Spinal Pain. Boswell et. All. Pain Physician 2007; 10:7-111
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- Dorsal column stimulation for lumbar spinal stenosis. Chandler GS 3rd, Nixon B, Stewart LT, Love J. Pain Physician. 2003 Jan;6(1):113-8 PMID: 16878166
- Acupuncture for neck disorders. Spine. 2007 Jan 15;32(2):236-43. Trinh K, Graham N, Gross A, Goldsmith C, Wang E, Cameron I, Kay T. PMID: 17224820