Sciatica is simply the medical term for pain radiating down the leg due to a trapped nerve in the lumbar (lower) spine. The pain may be continuous or intermittent and there may be certain positions that exacerbate the pain. The cause of the trapped nerve in the lower back that produces the sciatica is either a disc prolapse or more longstanding degenerative changes producing compression on the lumbar nerve root.
Is all sciatica the same?
Sciatica may commonly present with a sudden onset of leg pain which is often, but not invariably, associated with back pain. There are, therefore, effectively 2 groups of people who suffer from sciatica, the first with a sudden onset of leg pain with or without back pain and the second who have rather more long term (chronic) symptoms. In the majority of cases, the sciatica radiates down the back or side of the leg, although the distribution does depend on which nerve is trapped in the lumbar spine and can occasionally be down the front of the thigh and indeed into the shin.
Can sciatica be associated with other symptoms?
Sciatica is not infrequently associated with other neurological symptoms in the leg but may be simply that of isolated pain. Other neurological symptoms most commonly include pins and needles (paraesthesia) and less frequently, numbness. On relatively rare occasions, the severity of the nerve root entrapment means that in addition to pain and sensory disturbance, there is loss of motor function (power to the leg). Given that the cause of the sciatica is usually entrapment of a single nerve, the motor deficit tends to be equally precisely located and is most commonly manifest by a weakness either of standing on tiptoe or lifting up the foot. In the most severe cases this can produce a foot drop such that the toes of the affected foot drag along the ground during walking as the sufferer is unable to lift the toes away from the floor.
What causes sciatica?
As has been described, the cause of sciatica is usually a trapped nerve and is most commonly in just one leg rather than both. In rare cases, the underlying condition causing the trapped nerve is a large central disc prolapse rather than the more usual one-sided disc prolapse. In such a situation the sciatica can be in both legs, but of greater concern is that there might be an associated threat to the nerves of bladder, bowel and sexual function which also travel centrally within the spinal canal. Whereas one-sided sciatica can be most unpleasant and painful, the indications for treatment are usually based on the severity and duration of the pain rather than any threat to nerve function. However, should you be describing sciatica in both legs, this represents a potential neurosurgical emergency and urgent referral is recommended.
Does sciatica have to be treated with an operation
A large proportion of people with sciatica due to a disc prolapse will get better in time without requiring surgery. The disc prolapse gradually resolves thereby relieving the nerve compression and resulting in a reduction in pain. This process can take some weeks, but for the majority of sufferers, their sciatica has significantly improved within 2 months of initial onset. As a result, the early treatment of sciatica focuses on pain management, for which a variety of techniques are used including medication, physical therapies and epidural steroid injections.
Medications used include simple pain killers such as paracetamol and anti-inflammatory drugs as well as codeine and paracetamol. Specific nerve pain killers such as gabapentin or pregabalin may be suggested and the possible side-effects of these drugs will be discussed with you.
A lumbar epidural injection will usually help to reduce leg pain. The duration of effect can be variable, but for many patients with acute sciatica, an epidural injection can help them get through the most painful period prior to the disc prolapse settling back down.
Surgery will be considered for sciatica in the following situations:
- If the pain fails to subside within a few weeks of onset despite non-operative treatment
- If the pain is not controlled with medication/steroid epidural injection
- If there is associated progressive muscle weakness
- If there is a threat to bladder or bowel function
What is the surgical treatment for sciatica?
Sciatica is pain radiating down the leg due to a trapped nerve and the surgery is therefore designed to decompress the nerve within the spinal canal by removing whatever is pressing on it. This can either be a disc prolapse (disc bulge, disc rupture, disc herniation) or thickening of the facet joints and ligament lying near the nerve root. In both cases, the operation is similar in that it involves an incision in the lower lumbar spine. The precise position of the incision is based on intra-operative x-ray marking of the appropriate level. The underlying muscle is then stripped away from the vertebra to expose the ligament that spans the space between two adjacent vertebrae (ligament flavum). This is then opened (fenestrated) to enter into the spinal canal. In the case of a disc prolapse, the disc is lying on the far side of the nerve root, in other words in front of it. The surgeon gently retracts the nerve root to expose the lump of disc and physically removes it.
The disc consists of an annulus (annulus fibrosus) and a nucleus (nucleus pulposus). It is the nucleus that has ruptured and a piece of this is pressing on the nerve root and it is this that is removed. In order to try and prevent a recurrence, the surgeon will then remove some more of the remaining nucleus within the disc space. It is commonly asked whether the entire disc is removed and usually it is not the case and the surgeon simply removes the herniated bit of nucleus and attempts to clear out some of the central portion. Therefore, the annulus of the disc remains to provide some structural integrity.
Sometimes the cause of the sciatica is not a disc prolapse but a more generalised narrowing of the spinal canal due to thickening (hypertrophy) of the facet joints and of the ligamentum flavum. If this is the case, then rather than remove the disc prolapse, the surgeon will remove the relevant areas of thickened ligament and may do a partial nibbling of the thickened facet joint (undercutting facetectomy). In both cases (discectomy or flavectomy) the purpose of the surgery is for the surgeon to ensure that at the end of the operation, the nerve root is fully decompressed and this is usually associated with post-operative relief of the sciatica.
After this operation, the patient can usually start walking on the same day and at the very least the day after the operation and is home within a day to two of the surgery. We generally advise 6 weeks off work but it is recognised that many people have busy jobs and are unable to take such a period of time off work. The precise duration of time off will be the subject of a discussion with your surgeon.