Sciatica

Sciatica

What is it?

Sciatica is a term to describe pain that radiates from the back or buttock area and down the leg and into the foot or toes. The pain originates in the lower spine where the nerve roots (L4,L5 or S1) that make up the sciatic nerve can be irritated by pressure or inflammation. Although the pathology is in the spine the pain is often worse in the leg along the course of the dermatome for the given nerve root. The medical term is radiculitis or radiculopathy of a specific nerve root and is more precise.

What causes sciatica?

The commonest cause of radiculopathy is acute intervertebral disc prolapse that leads to both pressure on the nerve root as it deviates around the bulging disc and a strong chemical inflammatory reaction that also irritates the nerve root. Other causes of nerve root compression can cause radiculopathy and include facet joint cysts, foraminal stenosis, nerve sheath tumours, and rarely spinal tumour or infection.

How long does it last?

Disc protrusions, the commonest cause of radiculopathy, usually (90%) resolve spontaneously over 6-12 weeks. The pain is often very severe in the first few days and weeks but gradually resolves with the passage of time. Pain in the leg is often accompanied by pins & needles or parasthesia and even numbness in the same area. Sometimes the muscles supplied by the affected nerve root can be weaker than usual. In severe cases there is paralysis of the muscles. The sensory symptoms often resolve but this may be delayed until long after the pain improves. The weakness also often resolves but if there is severe weakness or paralysis then this can be permanent.

In 5- 10% of cases the pain persists beyond the usual timeframes and can lead to significant disability. In these cases it is important to seek a diagnosis and consider surgical management if a reversible cause can be found on imaging.

How is it Diagnosed

In most cases the clinical history and physical examination is enough for your doctor to make the diagnosis. The severity of pain is a poor indicator of the underlying pathology. However, if the pain is difficult to control or does not resolve in an appropriate timeframe or there is severe weakness then imaging is indicated.

Plain X- ray is not generally helpful for diagnosis but may at times give the doctor information that compliments CT or MRI.

Computer Tomography (CT) is also based on X-ray technology but allows cross-sectional and multi planar reconstructions so that the spine structures can be studied in much better detail. CT is useful in diagnosis of sciatica in most cases as the disc prolapse can usually be seen. However, there is increasing concern about the dose of ionizing radiation required to produce a spine CT. In addition, there are circumstances where CT cannot make a definitive diagnosis and many times an MRI is required for the extra information it gives for diagnosis and surgical planning.

Magnetic Resonance Imaging (MRI) is the modality of choice for diagnosis in spinal disorders such as sciatica and gives exquisite detail of the nerves, discs and other soft tissues. It is superior for diagnosis of neural tumours, spinal bone tumors and infections. It can also give detail of disc morphology or disease. The big benefit of MRI is that it does not utilise ionizing radiation and is therefore safer. The downside of MRI is that some patients are unsuitable (eg pacemakers) and MRI is less widely available and acquisition times for scans are longer than CT.

Nuclear Medicine Bone scans are also sometimes used to supplement diagnosis in spinal disorders but typically are not helpful in radiculopathy.

In summary, imaging is not required for most cases of radiculopathy as your doctor can the diagnosis based on the clinical findings and only if the symptoms don’t settle in an appropriate time frame or if the pain pattern is atypical should imaging be ordered.

Treatment

Posture and positioning

Many patients discover that there are positions of relative comfort even when the pain is severe. The positions that are helpful seem to relieve radiculopathy pain by relaxing the nerve or reducing stretch on the nerve. The sciatic nerve runs behind the hip joint and knee joint and bending the legs can reduce the stretch on the nerve. Extension of the back and hips in prone lying can also help some patients for the same reasons. I usually ask my patients to try these positions for themselves and if they help, to use them regularly when the pain is severe.

Massage and gentle manipulation

These modalities can provide some relief in the acute setting but generally only give short-term relief of symptoms. Aggressive manipulation or use of extreme posturing can worsen the situation if the disc prolapse progresses. These techniques are not recommended.

Medication

Analgesics

Often the pain of acute radiculopathy can be severe and even high doses of traditional narcotic-based painkillers are not effective. Simple analgesics such as regular paracetamol and or codeine can play a role and should nevertheless be the first line of treatment because they are safe and have minimal side effects.
Narcotic painkillers are some of the most common used to treat moderate to severe acute pain. They still have their role in treating acute radiculopathy but there are many side effects and the main concern relates to the tolerance and dependence effects if used for more than short-term pain control. In some patients, they also seem to be ineffective.

Anti-inflammatory medication(NSAIDs) can be very effective in radiculopathy as often some of the nerve irritation in the early phases is thought to come from the chemicals of acute inflammation. The main side effects of NSAIDs are stomach irritation or ulceration and kidney dysfunction. These side effects preclude their use for some patients but if used as directed can be tolerated by most patients.

Oral steroid medication (cortisone) has also been used successfully to treat acute radiculopathy but there are concerns about routine use as side effects are common and can be devastating. It is best given under close supervision with your doctor.

Muscle relaxants such as diazepam have also been used to relieve the muscle spasm that goes with acute pain. It is advised that these medications be used sparingly and for short terms as the dependence and side effects can be significant.

Nerve membrane stabilsers or neuromodulators have been used more recently with some success to treat acute radicular pain. These drugs have come from the treatment of epilepsy and work by reducing the sensitivity of the pain fibre nerves to send “pain” messages to the brain. The main side effect is drowsiness and slowed thinking (cognition) and for some patients, these effects are unpleasant and prevent achieving an effective dose to relieve pain. In many cases, it can be worth a trial of a medication in this class to see if it helps.

In summary, there are many medications available to treat the pain of acute radiculopathy but all have side effects and some risks and should be taken under the supervision of your doctor. It may be that there is some trial and error to get to the right combination of medication to achieve adequate pain control. Medication should also be regarded as only part of the treatment. In general, patients who keep mobile and only have short periods of rest to relieve pain do better than those who lie down for days on end. Activity does need to be modified according to pain levels in the acute phase but as the severe pain settles it is better to gradually increase activity despite the pain being worse during the activity. This behavior seems to remind the nervous system to revert back to normal by proving to itself that activity can be undertaken without significant consequence.

Why does pain persist in some cases of radiculopathy

The natural healing process after acute disc prolapse is one of acute inflammation, where the body mounts an immune reaction to the disc material with release of chemical mediators that lead to local swelling, pain and recruitment of more immune cells. This acute process lasts 10 days or so and is followed by digestion of the disc by the macrophage immune cells that lasts a few weeks and then fibroblast cells come in to allow healing by scar tissue. This process can go awry at any stage for many different reasons that are not fully understood.

For some patients, the disc prolapse does not fully resolve and there remains persistent stretching of the nerve. In these cases, simple removal of the disc fragment and release of the nerve can lead to rapid resolution of the ‘nerve’ pain.

However, sometimes the pain can persist after nerve release or even when the body’s own healing has followed a ‘normal’ course. This can lead to a condition of chronic or persistent pain. Many patients who develop established persistent or chronic pain were inactive during the acute pain phase and listened to the pain telling them that ” if it hurts don’t do it”. Unfortunately, this strategy can amplify the message that there is still something wrong in the tissues and also leads to physical deconditioning. Sometimes the therapist can reinforce this message by simply giving patients negative messages about their condition eg ” this is a bad case”, or ” you are definitely going to need surgery”, or “you should not do anything that might make it worse”. This could be avoided by giving reassuring messages like “although your pain is severe it is likely to improve in a short time”, or “we know it is safe to stay active and move despite the pain being aggravated in the short term”. If we repeatedly tell ourselves there is something wrong and reinforce these messages with negative thoughts and can see no hope of resolution then the nerves can actually undergo a change in their sensitivity. Scientific studies have shown that the ion channels in the nerve membrane can change and allow the abnormal flow of electrical charge, which can manifest as hypersensitivity of the pain pathways both peripherally and centrally. Negative emotions, anxiety, depression, lack of hope compound the pain problem. The hormones of stress (adrenaline, cortisol) can affect central neurotransmission as can the neurochemicals of depression (dopamine, GABA, noradrenaline). When depression becomes more than just reactive it can become endogenous and need treatment with antidepressants that are designed to reverse these depressive central neurotransmitter chemicals.

However, when pain is the initiator of the negative emotions, surely patients need hope that their pain will improve or that they may be able to control the pain. If there remains no hope then the negative emotions that led to the depression will surely be retriggered when the antidepressants are ceased.