About Herniated Discs
Pain radiating down an arm or leg in the distribution of a nerve originating in the neck or low back is the hallmark of most herniated (also called ruptured) discs. Other nerve symptoms may also be associated such as numbness, tingling, and weakness/paralysis in the distribution of the involved nerve.
In certain more serious cases, some disc herniations in the neck and thoracic area (rib cage region) of the spine can compress the central spinal cord itself. More serious symptoms of generalized weakness, numbness, and balance difficulties can occur. In extreme circumstances, paralysis of the bladder and bowels can cause urinary retention (inability to pass urine) and loss of control of the rectal sphincter (resulting in the inability to hold in stool).
Cause and Anatomy of Herniated Discs
Herniation of a disc is most often part of the evolution of osteoarthritis of the spine. This is the wear and tear type of degenerative arthritis, not the more severe inherited, inflammatory forms of arthritis such as rheumatoid arthritis (RA) and ankylosing spondylitis (AS).
Normally, the discs (shock absorbers of the spine) have a gel-like center called the nucleus which absorbs mechanical stresses from motions of the spine and the application of weight. The nucleus is surrounded, held in place, and mechanically supported by an outer sidewall of interlocking layers of ligaments called the anulus. The anulus is very similar to the structure and function of the sidewall of a car tire.
With degenerative changes in the disc, the gel center gradually loses hydration which translates to less shock absorber capacity. In response, the disc height narrows, and the anulus/sidewall takes on more mechanical stress in a similar manner to the sidewall of a car tire coming under extra stress if the tire is underinflated. As a tire sidewall wears out, it develops cracks and fissures in the sidewall. A worn-out/degenerate disc develops similar cracks and fissures. These are described as anular tears and high-intensity zones (HIZs) on magnetic resonant imaging (MRI) reports.
In a car tire, if one of the cracks and fissures in the sidewall goes completely through the wall, then a flat tire/blowout occurs. In the degenerative disc, if a crack or fissure goes through the sidewall, then a piece of the disc can rupture or herniate out. If the herniated disc is large enough to put pressure on the nerves, then patients experience pain down the nerve being compressed and may have additional neurologic symptoms and physical findings such as numbness, tingling, and muscle weakness/paralysis. Radiating pain originating from the lumbar spine is called sciatica.
Diagnosis of Herniated Discs
The diagnosis of the herniated disc is made by the patient’s history and physical examination with confirmation using diagnostic tests such as magnetic resonance imaging (MRI). The compatible history relates to pain and other neurologic symptoms such as numbness or weakness in the corresponding distribution of a nerve or the spinal cord to the arms or legs. In a similar fashion, the physical examination evaluates muscle strength, sensation and deep tendon reflexes in the extremities. A working diagnosis of the herniated disc is made when the history and physical exam findings correspond to a specific disc level in the spine.
The diagnosis is most often confirmed with a magnetic resonance imaging (MRI) study. In situations such as patients having a non-MRI compatible heart pacemaker, alternative imaging is a computerized tomography (CT) scan or a CT with a myelogram where dye is injected into the spinal fluid around the nerves to see if the dye column is displaced by a herniated disc.
What Are My Options?
It has been estimated that only about 10% of patients having a herniated disc will require surgery. However, patients with acute intractable pain, severe or progressive neurologic deficit and/or bowel or bladder paralysis should be considered for urgent surgery. In the majority of cases, the initial level of treatment will consist of a combination of medications (pain killers, arthritis/anti-inflammatories, nerve stabilizers, muscle relaxants), physiotherapy, and activity modification.
If symptoms persist despite first-level treatments, then interventions that are more invasive are considered. These are generally injection procedures with cortisone (a very strong anti-inflammatory). Using an X-ray fluoroscope to adjust the needle placement into the appropriate area, the cortisone is injected around the nerve and the disc to reduce inflammation in the nerve and potentially shrink the size of the herniated disc. In most cases, non-surgical treatment is sufficient to avoid surgery and return patients to a more functional quality of life with reduced pain, numbness, and weakness.
Nevertheless, there are situations where surgery is a more definite consideration. Clinically, the clear concern is permanent nerve damage. Weakness and/or numbness sufficiently severe to impair function, paired with a corresponding disc herniation on MRI constitute indications to consider surgical intervention. Generally, the best outcomes from surgery occur when significant pressure is on the nerve for less than 3 months. Fortunately, herniated discs in this day and age can be surgically treated by minimally invasive techniques.
In the lumbar spine, a small incision is made in the back and the level of the herniated disc is exposed using a specialized soft tissue retractor or a tube inserted through the small paraspinal muscles for a microdiscectomy. No longer is a large incision or major dissection of the back muscles required. This allows a faster recovery although activity is still restricted for about 3 months to allow the ligaments of the outer cover of the disc anulus to heal thick, tight, and strong. Overzealous mobilization in the first few months can lead to the anulus fibers healing stretched, thin and weak. This leaves a persistent weak area in the anulus and predisposes to recurrent disc herniation.
In the neck, most discectomies are performed via an incision in the front of the throat. The anterior spine is fairly superficial and resides directly behind/posterior to the trachea/windpipe and the esophagus. This makes the disc space much more approachable from the front of the spine in the neck area. The anterior approach also allows the surgeon to avoid irritating the spinal cord versus a posterior approach. In this surgery, the disc must be removed from the front to gain access to the ruptured/herniated disc fragment which is usually encroaching the spinal canal from just behind the posterior edge of the disc. With an extensive anterior cervical discectomy for the surgical approach, the normal shock absorber and motion function of the disc is compromised and the disc must be either fused or an artificial disc inserted.
Frequently Asked Questions
Does a disc arthroplasty in the neck (rather than a fusion) avoid adjacent level problems?
With the long-term data from FDA studies of cervical disc arthroplasty, it appears that the occurrence of adjacent level problems is delayed but not completely eliminated.
After an anterior cervical discectomy and fusion in the neck, what is the incidence of degeneration at the segments above and below from the transfer of mechanical stresses?
At ten years post-op, about one-third of patients have symptoms at an adjacent level but not necessarily sufficiently severe to require additional levels of fusion.
Does microsurgery result in 100% relief of symptoms?
Microsurgery does not cure all the underlying degenerative arthritis in the disc and even microsurgery leaves small amounts of scar tissue around the nerve which may still irritate the nerve long term.
What is the risk of nerve damage or paralysis with microsurgery for a herniated disc?
Very low risk in this day and age. In the last few years, we have been using neural monitoring to avoid irritation to the nerves and spinal cord. Previously, when patients were asleep, we never knew if the surgical procedure was irritating nerve structures which in rare cases would result in nerve damage or paralysis. With neural monitoring, the technician in the operating room and the neurologist monitoring remotely can alert the surgeon when any neural irritation occurs so the surgery can be adjusted intra-operatively to minimize any risk.