Sciatica : Symptoms, Causes, Therapy and Prognosis

Sciatica is the term given to pain down the leg, which is caused by irritation of the main nerve into the leg, the sciatic nerve. This pain tends to be caused where the nerves pass through and emerge from the lower bones of the spine (lumbar vertebrae). Much of the advice regarding this condition is the same as that for low back pain.

In sciatica, there is a pain down into the leg, which travels below the knee, and may involve the foot. There may be numbness and there may be weakness of the lower leg muscles.

These symptoms may come on their own, but are often combined with low back pain. The order in which the symptoms appear may vary. Sometimes the back pain comes before the sciatica, and sometimes will follow.

As with low back pain, there is a group of features which doctors use to highlight the need to act more quickly, because they may suggest a problem which is not as straightforward as simple back pain or sciatica. If you fit into one of these groups or are concerned, you should see your doctor soon:

·             You are younger than 20 or older than 55 when you get the problem for the first time.

·             The pain follows a violent injury, such as a road traffic accident.

·             The pain is constant and getting worse.

·             The pain is in the back of the chest.

·             You have had cancer in the past or at present.

·             You are on steroids.

·             You are a drug abuser, or have HIV.

·             You are generally unwell in yourself.

·             You have lost significant weight recently.

·             You continue to have great difficulty bending forwards.

·             You have developed a number of problems in your nervous system (eg numbness, loss of power, etc).

·             You have developed an obvious structural deformity of your spine.

Anyway, it is probably wise to see your doctor if you develop sciatica. Certainly you should consult him or her if you are not able to adequately control the pain with simple painkillers and/or anti-inflammatory drugs, or if the pain carries on for more than two weeks.

The most common cause of true sciatica is a "slipped disc". The discs (or inter-vertebral discs) are the cushions which separate the bones of the spine (vertebrae). Your doctor may refer to a slipped disc as a prolapsed intervertebral disc (PID) or a herniated nucleus pulposus.

The intervertebral disc looks a bit like a draughts/checkers piece in shape. The ring around the outside is tough and fibrous, and the centre is rather more like the consistency of a chewy sweet. These discs allow for some flexibility between the bones of the spine, and also act as shock absorbers.

The pressures within the discs can reach high levels when we bend or twist, even without carrying a heavy load. If we add to that a heavy load, especially held out at arms' length, the pressures rise even higher.

If part of the fibrous outer ring of the disc is rather weaker than the rest, the softer centre (nucleus pulposus) may push its way through, bulging outwards. If this bulge presses against a nerve which is running from the main, central nervous system to one of the legs, it causes symptoms in that leg.

Sciatica occurs when the herniated disc presses against the nerves which go to make up the sciatic nerve. This is more likely to cause problems when the nerve is squashed by this, usually between the disc and an adjacent bone.

Nerves have many functions, transmitting messages around the body, rather like a telephone system. They allow us to feel things that happen to us, such as things we touch or that touch us, hot and cold, and pain, and they cause our body to do things, eg making your leg muscles contract when you want to walk. Thus, when a nerve is squashed, it may malfunction, and we might feel pain, numbness, pins and needles, and we might find our limbs do not work in the way they should.

Other things can cause irritation of or pressure on a nerve in the spine. Sometimes this may be a rough and enlarged part of one of the vertebrae, brought about by ageing, and sometimes rarer conditions, infections and tumours are to blame. Most times the cause is nothing too serious, but one of the reasons for seeing your doctor if the pain persists, is to make sure that serious and treatable causes have been ruled out.

If you still have sciatica after a few weeks, it is likely that your doctor will arrange for you to have a CT (Computerised Tomography) or MRI (Magnetic Resonance Imaging) scan. These show up the soft structures in the spine, as well as the bones, and will thus show whether a nerve is being squeezed by a disc, or whether something else is causing irritation of the nerve.

Really the main reason for doing such a scan is to see whether an operation will help to cure the sciatica.

The key points about most back pain and sciatica are:

·             Do not worry - it will usually get better on its own, within a few days, or possibly a few weeks.

·             Stay active, and if at all possible, stay at work.

·             The pain may force you to rest, but this is a result of the pain, and not a good treatment for back pain and sciatica. If you have to take to your bed, limit it, if possible, to a week or two at the most.

·             Use simple pain killers, such as paracetamol or ibuprofen if necessary.

·             Avoid activities likely to put unnecessary strain on your back.

·             See your doctor if you think you are in one of the red flag categories, or are worried about how you are doing.

·             If it seems to be lasting more than a few days, consider seeing a physiotherapist, chiropractor or osteopath. You may wish to consult your doctor prior to this.

·             If you do have to be off work, keep this to a minimum, and do not expect to be pain free before you go back.

·             If the pain is severe and very disabling, and you cannot control it with simple pain killers and/or anti-inflammatory medication, your doctor may suggest you have an epidural injection, which is an injection into the spine, which soothes the nerves that are causing the pain.

·             In a minority of cases, the sciatica does not settle, or complications arise. This may lead your doctor to recommend surgery, which will involve trimming back bone or disc material which is pressing on the nerve or nerves. This is not undertaken lightly, and will be guided by the results of a CT or MRI scan.

Sciatica—pain along the large sciatic nerve that runs from the lower back down the back of each leg—is a relatively common form of low back pain and leg pain. This pain along the sciatic nerve can be caused when a root that helps form the sciatic nerve is pinched or irritated.

Sciatica is usually caused by pressure on the sciatic nerve from a herniated disc (also referred to as a ruptured disc, pinched nerve, slipped disk, etc.). The problem is often diagnosed as a "radiculopathy", meaning that a disc has protruded from its normal position in the vertebral column and is putting pressure on the radicular nerve (nerve root) in the lower back, which forms part of the sciatic nerve.

Sciatica occurs most frequently in people between 30 and 50 years of age. Often a particular event or injury does not cause sciatica, but rather it may develop as a result of general wear and tear on the structures of the lower spine. The vast majority of people who experience sciatica get better with time (usually a few weeks or months) and find pain relief with non-surgical treatments.

Understanding sciatica pain
For some people, the pain from sciatica can be severe and debilitating. For others, the pain from sciatica might be infrequent and irritating, but has the potential to get worse. Usually, sciatica only affects one side of the lower body, and the pain often radiates from the lower back all the way through the back of the thigh and down through the leg. Depending on where the sciatic nerve is affected, the pain may also radiate to the foot or toes.

One or more of the following sensations may occur as a result of sciatica:

·         Pain in the rear or leg that is worse when sitting

·         Burning or tingling down the leg

·         Weakness, numbness or difficulty moving the leg or foot

·         A constant pain on one side of the rear

·         A shooting pain that makes it difficult to stand up

·         Low back pain may be present along with the leg pain, but usually the low back pain is less severe than the leg pain

While sciatica can be very painful, it is rare that permanent nerve damage (tissue damage) will result. Most sciatica pain syndromes result from inflammation and will get better within two weeks to a few months. Also, because the spinal cord is not present in the lower (lumbar) spine, a herniated disc in this area of the anatomy does not present a danger of paralysis.

Symptoms that may constitute a medical emergency include progressive weakness in the leg or bladder/bowel incontinence. Patients with these symptoms may have cauda equina syndrome and should seek immediate medical attention.

Any condition that causes irritation or impingement on the sciatic nerve can cause the pain associated with sciatica. The most common cause is a lumbar herniated disc. Other common causes of sciatica include lumbar spinal stenosis, degenerative disc disease, or isthmic spondylolisthesis.

To clarify medical terminology, the term sciatica is often used very broadly to describe any form of pain that radiates into the leg.  However, this is not technically correct. True sciatica occurs when the sciatic nerve is pinched or irritated and the pain along the sciatic nerve is caused by this nerve (radicular pain). When the pain is referred to the leg from a joint problem (called referred pain), using the term sciatica is not technically correct. This type of referred pain (e.g. from arthritis or other joint problems) is quite common.

Typical sciatica treatments
Nerve pain is caused by a combination of pressure and inflammation on the nerve root, and treatment is centered on relieving both of these factors. Typical sciatica treatments include:

·         Manual treatments for sciatica, including physical therapy and specific stretching and strengthening exercises, and manual manipulation (e.g. osteopathic or chiropractic manipulation) to help relieve the pressure on the nerve root, which is the cause of the pain.

·         Medical treatments for sciatica, including medications such as non-steroidal anti-inflammatory drugs (NSAIDs), oral steroids, or epidural steroid injections to help relieve the inflammation, which is usually a component of the pain.

·         Surgery for sciatica, such as microdiscectomy or lumbar laminectomy and discectomy, to remove the portion of the disc that is irritating the nerve root. This surgery is designed to help relieve both the pressure and inflammation and may be warranted if the sciatic nerve pain is severe and has not been relieved with appropriate manual or medical treatments.

Back problems and the sciatic nerve
The sciatic nerve is the largest nerve in the body and is composed of individual nerve roots that combine to form the “sciatic nerve”. It starts in the low back at lumbar segment 3 (L3). The sciatic nerve roots run through the bony canal in the spine, and at each level in the lower back a pair of nerve roots exits from the spine and then comes together to form the large sciatic nerve that runs all the way down the back of each leg. Portions of the sciatic nerve then branch out in each leg to innervate certain parts of the leg (e.g. the calf, the foot, the toes).

The nerve roots that originate in the lower back are named for the upper vertebral body that they run between (for example, the nerve that exits at L4-L5 in the spine is named L4). The nerve passing to the next level runs over a weak spot in the disc space, which is the reason discs tend to herniate (extrude) right under the sciatic nerve root and can cause sciatica.

The sciatica symptoms (e.g., low back pain, leg pain, numbness, tingling, weakness) are different depending on where the pressure on the nerve occurs. For example, a lumbar segment 5 (L5) nerve impingement can cause weakness in extension of the big toe and potentially in the ankle (foot drop)

Back problems that cause sciatica pain
Common low back problems and other spinal conditions that can cause sciatica - pain along the sciatic nerve - include:

• Lumbar herniated disc. A herniated disc occurs when the soft inner core of the disc (nucleus pulposus) extrudes through the fibrous outer core (annulus) of the disc and the bulge places pressure on the contiguous nerve root as it exits the spine. In general, it is thought that a sudden twisting motion or injury can lead to an eventual disc herniation and sciatica. However, most discs weaken due to repetitive stress and the final result is a herniation. A herniated disc is sometimes referred to as a slipped disk, ruptured disk, bulging disc, protruding disc, or a pinched nerve.
• Lumbar spinal stenosis. This condition commonly causes sciatica due to a narrowing of the spinal canal. It is more common in adults over age 60, and typically results from a combination of one or more of the following: enlarged facet joints, overgrowth of soft tissue and a bulging disc placing pressure on the nerve roots as they exit the spine.
• Degenerative disc disease. While disc degeneration is a natural process that occurs with aging, in some cases one or more degenerated discs can also irritate a nerve root and cause sciatica. Degenerative disc disease is diagnosed when a weakened disc results in excessive micro-motion at the corresponding vertebral level and inflammatory proteins from inside the disc become exposed and irritate the area (including the nerve roots). The term “degenerative disc disease” is an unfortunate one as it is a process, not a disease.
• Isthmic spondylolisthesis. This condition is not that uncommon in adults (approximately 5% to 7% of adults are thought to have it), but it only rarely causes back pain or sciatica pain. Spondylolisthesis occurs when a small stress fracture (most often at the fifth segment) allows the L5 vertebral body to slip forward on the S1 vertebral body. Caused by a combination of disc space collapse, the fracture, and the vertebral body slipping forward, the L5 nerve can get pinched as it exits the spine.
• Piriformis syndrome. The sciatic nerve can also get irritated as it runs under the piriformis muscle in the rear. If the piriformis muscle irritates or pinches a root that comprises the sciatic nerve, it can cause sciatica-type pain. This is not a true radiculopathy, but the pain can feel the same as sciatica caused by a nerve irritation.
• Sacroiliac joint dysfunction. Irritation of the sacroiliac joint at the bottom of the spine can also irritate the L5 nerve, which lies on top of it, and cause sciatica-type pain. This is not a true radiculopathy, but the pain can feel the same as sciatica caused by a nerve irritation.

The good news for patients is that sciatica usually will get better on its own, and the healing process usually only takes a few days or weeks. Overall, the vast majority of episodes of sciatica pain heal on their own within a six to twelve week time span. However, occasional flare-ups of sciatic nerve pain may be an indication of a condition that should be managed so that it does not get worse over time. For most, readily available pain management techniques and regular exercise will go a long way to remedying the situation. For others, when the pain is severe or does not get better on its own, a more structured pain management program (including specific physical therapy and exercise), and possibly surgery, may offer the best approach to finding pain relief and preventing or minimizing future flare-ups of sciatica.

Conservative care for sciatica
During an episode of sciatica, there are a number of conservative care (non-surgical) options available to help alleviate the sciatic pain and discomfort.

Heat/ice for sciatica
For acute sciatica pain, heat and/or ice packs are most readily available and can help alleviate the pain, especially in the acute phase. Usually ice or heat is applied for approximately 20 minutes, and repeated every two hours. Most people use ice first, but some people find more relief with heat. The two may be alternated to help with sciatica pain relief.

Medications for sciatica
Over-the-counter or prescription medications may also be helpful in relieving sciatica.  Non-steroidal anti-inflammatory drugs (NSAIDs) or oral steroids can be helpful in reducing the inflammation and pain associated with sciatica.

Epidural steroid injections for sciatica
If the sciatica pain is severe, an epidural steroid injection can be performed to reduce the inflammation. An epidural injection is different from oral medications because it injects steroids directly to the painful area around the sciatic nerve to help decrease the inflammation that may be causing the pain. While the effects tend to be temporary (providing pain relief for as little as one week up to a year), an epidural steroid injection can be very effective in providing relief from an acute episode of sciatic pain. Importantly, it can provide sufficient relief to allow a patient to progress with a conditioning program.

Conservative care specialists for sciatica
A visit to a physical therapist, osteopathic physician, chiropractor or physiatrist can be helpful both to alleviate the painful symptoms and to help prevent future recurrences of sciatica. These conservative care professionals can assist in providing pain relief and developing a program to condition the lower back.

Surgical treatments for sciatica
If the sciatica pain is severe and has not gotten better within six to twelve weeks, it is reasonable to consider spine surgery. Depending on the cause and the duration of the sciatica pain, one of two surgical procedures may be considered: a microdecompression (microdiscectomy) or an open decompression (lumbar laminectomy).

Microdiscectomy (microdecompression) for sciatica
In cases where the sciatica pain is due to a disc herniation, a microdiscectomy may be considered after 4 to 6 weeks if the pain is not relieved by conservative means. Urgent surgery is only necessary if there is progressive weakness in the legs, or sudden loss of bowel or bladder control. A microdiscectomy is typically an elective procedure, and the decision to have surgery is based on the amount of pain and dysfunction the patient is experiencing, and the length of time that the pain persists. Approximately 90% to 95% of patients will experience relief from their sciatica pain after this type of surgery.

Lumbar laminectomy (open decompression) for sciatica
Lumbar spinal stenosis often causes sciatica pain that waxes and wanes over many years. Surgery may be offered as an option if the patient’s activity tolerance falls to an unacceptable level. Again, surgery is elective and need only be considered for those patients who have not gotten relief from the sciatica after conservative treatments. After a lumbar laminectomy (open decompression), approximately 70% to 80% of patients experience relief from their sciatic nerve pain.

Compilation Courtesy : Aparna Chatterjee

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