Sciatica is pain within the pathway and distribution of the sciatic nerve.
The sciatic nerve is formed by nerves from the spine at the junction of the lumbar and sacral regions. The nerve passes from the spine into the pelvis then into the buttock, posterior (back of) thigh and down below the knee.
Pain that occurs within the sciatic nerve is most frequently due to compression of the nerve within the spinal canal. This most commonly occurs secondary to disc herniation in the middle years between 20 and 60. In older age groups it may occur secondary to the narrowing of the path for the nerve ways as a result of spinal stenosis. However, in practice the most common cause of sciatica is disc herniation.
The discs in the lumbar spine are the soft tissue structures that lie between the vertebrae. A disc consists of an outer casing or annulus, and an inner jelly-like substance or nucleus. The healthy disc has a jelly-like nucleus, but as discs age or have been subject to damage and/or prolapse, the healthy jelly dries out to have more of a consistency of crab meat.
A disc herniation occurs when the wall of the disc or annulus develops a tear or weakness and disc material comprising nucleus and annulus is pushed out through the weakening in the outer annulus. This may be associated with local back pain related to the damage to the annulus.
When the disc herniates or ruptures it frequently puts pressure on the nerve root that passes in close to the disc in the spinal canal. This is where the symptoms of sciatica may occur.
Most discs that rupture develop changes in the disc material consistent with degeneration or wear and tear. It is not entirely clear whether this occurs before the disc ruptures or after it. It seems likely that a variety of possibilities exist. The disc annulus may weaken and develop tears with age, but it also seems likely that injury may have a role.
Newer evidence suggests that some groups of patients may have abnormalities in the tissue makeup of the disc that predispose them to rupture or weakening of the outer annulus or casing. When the nerve passing the disc is exposed to a rupture, the nerve can either be affected by direct pressure of the prolapse or by chemical inflammation caused by the tissue from the disc.
Direct pressure occurs when the nerve is trapped by a prolapse within the nerve canal. This probably accounts for changes in nerve conduction which the patient experiences as altered feeling or muscle weakness. The other effect that the disc prolapse can have is to inflame the nerve.
There is now good evidence that the chemicals from the nucleus can leak out of the prolapse onto the nerve root resulting in inflammation of the nerve, pain within its distribution (sciatica) and also changes of nerve function (again manifested by numbness, pins and needles or weakness).
As stated above, disc herniation and sciatica are very common. Patients may have disc prolapse without symptoms of sciatica. When sciatica does occur, it tends to be associated with an early, intense phase of severe pain which is probably due to both pressure and inflammation secondary to disc herniation. The pain often settles after the first few weeks.
It may resolve completely or plateau at a level less severe than when it was most intense, but still giving ongoing pain. Some have suggested that the early intense pain correlates with inflammation and the latter pain with ongoing pressure.
We believe that many bouts of sciatica resolve without treatment. Treatment may hasten resolution or ameliorate symptoms at the time. If sciatica occurs and has been present for a short duration of time it is more likely to spontaneously resolve. If it has been present for a long period of time it becomes much less likely to resolve.
If it has resolved and recurs particularly more than once, then it is more likely that further recurrences will occur and treatment will eventually be necessary. As a guideline, if the sciatica has been present for less than four weeks there is still a reasonable chance that it may resolve. If it has been present for more than six weeks the likelihood of rapid resolution becomes much less.
Please Contact the doctor urgently if you get any of the following symptoms:
- Low back Pain and leg pain with
- Alteration in Bladder Function – like not being able to feel yourself pass urine, or leaking of urine
- Pain in both legs
- Altered sensation in one or both buttocks
This means you may be developing a cauda equina syndrome, which is a surgical emergency
The cauda equina, which is Latin for “horse’s tail,” is the bundle of nerve fibres inside the lower spinal canal that radiate out to the trunk, pelvis, and lower limbs. Pressure on this bundle of nerves causes distinctive symptoms including low back pain, pain running down the back of both legs, and numbness or tingling between the legs in the area you would contact if you were seated on a saddle.
The pressure can disturb function of the bowels and bladder. You need to raise a flag if you feel the need to urinate, but can’t, or if you lose bowel or bladder control. Cauda equina syndrome is an emergency.
If the pressure isn’t relieved, it can lead to permanent paralysis of the bowels and bladder. Doctors usually recommend immediate surgery to remove pressure from the nerves.
Most patients desire relief from pain when they have severe sciatica. This can be achieved using a number of medications. Simple pain killers and anti-inflammatory medications are most commonly prescribed. These can be used together. Anti-inflammatories can be very useful although care must be taken if there is a history of peptic ulcer disease or other gastrointestinal upset, or any history of poor kidney function.
Stronger pain relievers, some with an opioid base, may be used for more severe and persistent pain. Patients with intense neuralgic or nerve type pain may also respond to medications that specifically act to reduce the sensitivity of the nerves. These include low-dose antidepressants (tricyclics) and other drugs of a sedative nature. During the very severe phase of sciatica rest may be necessary. There is a growing trend to avoid prolonged periods of rest unless absolutely essential.
Many find that it is the only way that the very severest of symptoms can be controlled. Physiotherapy may have a role, although with severe sciatica it can sometimes upset symptoms. Simple interventions such as massage and heat may help relieve symptoms but have not been proven to effect the outcome.
Epidural injections of steroid may also be used. This is a technique where cortisone/steroid preparations are injected around the nerves in the spinal canal. The aim of the injection is to reduce the inflammation around the nerve root. This technique may be very effective but is somewhat unpredictable.
In some patients it is not beneficial. The risks are relatively low. All patients who are being cared for with sciatica should be encouraged to maintain activity. This represents part of the swing away from bed rest mentioned before. It is clearly better if patients can maintain function and employment if possible even when symptoms persist.
Many patients take the view that they should rest and should not overdo it at this stage. The medical evidence does not support extreme activity restriction.
If sciatica has been present for a prolonged period of time (over six weeks) and has failed to respond to conservative care, surgical treatment may have a role. It is imperative that in this situation the patient is investigated with a MRI scan to demonstrate the disc herniation. At this point surgical treatment may be offered.
The common and most effective treatment is partial excision of the disc and is normally referred to as ‘discectomy’. This should only be considered for prolonged pain (greater than six weeks), pain within a sciatic distribution. Below the knee, pain associated with some form of neurological symptom and pain that is exacerbated by stretching the nerve.
In these situations pain can most often be relieved with partial discectomy. Occasionally the surgeon may decide to fuse the disc as well as free the nerve up – if the patient has had back pain for many years before the disc prolapse occurs or if there is marked disc degeneration present at that level.