The basics - Sciatica

Sciatica is a common condition, but acquiring specific statistics about sciatica as opposed to back pain in general is difficult.

1. Sciatica or simple backache?
Sciatica needs to be differentiated from simple backache. The pain of simple backache originates in the lumbosacral region and may radiate to the buttocks and thighs but not below the knee, and varies with activity and time.

Sciatica is due to pressure on a nerve root, usually from a prolapsed intervertebral disc, and presents as unilateral leg pain that radiates below the knee to the foot or toes.

It may be accompanied by low back pain, but this is less severe than the leg pain. When taking the history, question the patient about whether the problem has occurred before, when it started, if anything triggered it, how sudden the onset was and the extent of radiation of the pain.

Ask about aggravating or relieving factors, and about the patient's occupation and sporting activities. The past medical history may indicate the possibility of prolonged steroid use or a previous malignancy that may metastasise to bone.

The diagnosis of sciatica is usually straightforward, with the symptoms and signs of nerve compression generally limited to one nerve root, and there may be numbness and paraesthesia in the same distribution. Straight-leg raising aggravates the leg pain and sometimes the nerve compression symptoms.

Exclude serious pathology by assessing for red flags (see box).

2. Differential diagnosis
Other conditions to consider when assessing sciatica include ankylosing spondylitis; piriformis syndrome (where the sciatic nerve is compressed or irritated by the piriformis muscle); spinal claudication (bilateral calf pain, paraesthesia, or numbness on walking) and nerve entrapment at the fibular head (peroneal palsy). Cauda equina syndrome occurs when these nerves are compressed.

An examination of the hips, knees, and trochanteric bursae will suggest or reveal most of the conditions with symptoms similar to sciatica.

There is no indication for routine imaging in acute presentations earlier than six weeks unless there are red flags, and then MRI is likely to be the most useful investigation.

3. Management
Sciatica is a physical problem, but psychological state affects how well patients cope with the pain. In most cases the pain settles within six to 12 weeks, but it may persist for months.

Patients should be advised that the situation is temporary, with encouragement to mobilise as soon as possible followed by a return to work. Bed rest should be brief.

Techniques such as using a small cushion between the knees when sleeping on the side, or pillows propping up the knees when lying on the back, may ease symptoms.

It is not necessary to wait until the pain has completely gone before resuming usual activities and work, although activity should be graduated, and adjustments may need to be made at work until the patient is pain-free.

Only if the symptoms are persistent and severe should a specialist referral be made, and this should be urgent if the patient develops foot drop or bowel or bladder dysfunction, as this may need surgical intervention.

The patient should be encouraged to maintain a positive attitude, and analgesia prescribed to minimise pain and encourage activity. Paracetamol or an NSAID are first-line treatments, used alone or in combination.

A weak opioid, such as codeine, dihydrocodeine or tramadol, can be used if further pain relief is required.

In more persistent severe pain, a short course of a strong opioid, such as morphine, could be considered, but if this is ineffective or prolonged, referral should be made to a pain clinic.

Paraspinal muscle spasm can be a problem that may be eased by the use of hot packs or a short course of a benzodiazepine. A trial of amitriptyline or gabapentin may be worthwhile, and if progress is slow, consider physiotherapy.

Some physiotherapy departments run courses of graduated exercises to aid rehabilitation.

• Dr Barnard is a former GP from Fareham, Hampshire