Introduction
Sciatica – radiating pain along the pathway of the sciatic nerve – is a symptom caused by nerve root compression, but also by injury to the sciatic nerve along the peripheral pathway of the nerve. Nerve root compression is usually caused by a herniated disc, but can also be caused by a tumour, spondylarthrosis or spondylolisthesis, for example.
Back pain which radiates down to the leg is not always sciatica.
The pain could, for example, be caused by hip arthritis. The course of the radiation is usually less typical in such cases, in other words it does not radiate down to a specific dermatome. This is known as pseudoradicular pain.
If, based on the history-taking, you suspect that your patient may have a compressed nerve root (leg pain radiating to a dermatome which increases upon, or can be provoked by, coughing, sneezing or bearing down), you should carry out the following examination to test your hypothesis.
Procedure
Inspection of the back
Ask the patient to undress down to their underwear. Stand behind the patient and assess the position of the spinal column.
- Look in particular for scoliosis and/or deep lumbar lordosis. This abnormal position of the spinal column can develop secondarily to nerve root compression.
Examination of spinal movement
- Ask the patient to bend over, keeping their knees stretched and then to bend backwards and lean to the left and right.
- Assess whether these movements can be carried out without provoking the symptom.
Kemp’s test
- Stand behind the patient and place your hands on their shoulders. Have the patient bend backwards slightly while leaning to the painful side. If the patient does not yet indicate being in pain, apply light pressure to the vertebral column [Figures 119, 120].
- While carrying out the test keep asking whether the patient is experiencing pain, where the pain is located, whether there is any radiating pain and to where the radiating pain can be felt.
Figure 119
Figure 120
Palpation of the back
- Using your thumbs, for example, palpate paravertebrally at the site where the nerve roots exit and at the Valleix points along the course of the sciatic nerve.
- Inquire whether this elicits any pain (location, radiating).
Examination of muscle strength
- A quick impression of the strength of the relevant leg muscles can be obtained by having the patient walk on their heels and toes and bend deeply at the knees, or by asking the patient to step up onto the foot stool a few times. This will clearly reveal an obvious loss of strength.
- It is also possible to examine the strength of the leg muscles of a supine patient, as described in the sectio ‘Motor function’.
- Next examine bilaterally the quadriceps muscle, the hamstrings, the anterior tibial muscle and extensor digitorum muscles, the extensor hallucis longus muscle, the flexor hallucis longus muscle, and the gastrocnemius muscle.
Examination of sensory function
As described in the section ‘Coordination and diadochokinesis’, examine the spinothalamic and dorsal column sensory functions in the L4 through to S2 dermatomes.
Examination of the reflexes
Examine the knee tendon and Achilles tendon reflexes as described the section ‘Reflexes’.
The nerve root irritation tests
Palpation of the Valleix points and Kemp’s test are also nerve root irritation tests. The aim of these tests, and those described below, is to provoke the symptom described by the patient during the history-taking. If the symptom does not occur or worsen with these tests, nerve root irritation is less likely.
Lasègue sign
- The patient should lie on the examination table.
- Raise the patient’s outstretched leg [Figure 121].
- Look carefully at the patient’s face and ask whether it hurts. If so, ask the patient to indicate precisely where it is painful. Pain caused by nerve root irritation is generally so severe that raising the leg further leads to reflex tension of the hip muscles, causing you to tip the patient to one side.
- Note the angle between the leg and the underlying surface at the point where the pain arises. This will not help you in establishing the diagnosis, but will help when evaluating treatment.
Figure 121
Braggard’s test
Braggard’s test can be carried out immediately after Lasègue’s sign.
- The outstretched leg should be raised to the point where the patient indicates feeling pain.
- Allow the ankle to drop a few degrees to the point where the patient no longer feels any pain and then place the foot in dorsal flexion. If the pain returns, Braggard’s test is positive.
The crossed Lasègue’s sign
- The patient should lie on the examination table [Figure 122].
- Raise the patient’s outstretched symptom-free leg. If this evokes sciatic pain in the other leg, it constitutes a positive crossed Lasègue’s sign.
- Note the angle between the leg and the underlying surface at the point that the pain occurred.
Figure 122
The reversed Lasègue’s sign
If there is nerve root irritation at L4, the pain will radiate to the front of the upper leg.
In this case, the reversed Lasègue’s sign may be positive rather than the Lasègue’s sign itself.
- The patient lies in prone position or on the pain-free side.
- Extend the patient’s painful leg at the hip.
- Assess whether this manoeuvre evokes the patient’s symptom [Figure 123].
Figure 123
Femoral nerve pain upon palpation
If there is nerve root irritation at L4, the pain will radiate via the femoral nerve.
- Palpate this nerve in the groin.
- Assess whether this evokes the patient’s symptom.
Interpretation
Positive nerve root irritation tests, loss of sensory function in one of the L4-S2 dermatomes, reflex differences and loss of leg muscle strength can indicate lumbar nerve root compression.
If you find:
- tingling and/or sensory deficit in the S1 dermatome
- loss of strength, possibly atrophy of the triceps surae muscle and the peroneal muscles, weakened Achilles tendon reflex, it indicates an S1 syndrome usually caused by a herniated disc between L5 and S1.
If you find:
- tingling and/or sensory deficit in the L5 dermatome
- loss of strength and possibly atrophy in the extensor hallucis longus muscle and the extensor digitorum brevis muscle, it indicates an L5 syndrome usually caused by a herniated disc between L4 and L5.
Far less frequently found:
- tingling and/or sensory deficit in the L3 or L4 dermatomes
- loss of strength or atrophy of the femoral quadriceps muscle
- weakened knee tendon reflex, indicating an L3 or L4 syndrome.
In addition to the above-mentioned findings, there is usually also radicular pain both spontaneous and with the nerve root irritation tests. If the following are present as well as radicular pain:
- saddle anaesthesia (S2- S5 dermatome)
- incontinence
- impotence
- loss of anal reflex,
it indicates the presence of cauda equina syndrome, which may be caused by a dorsomedial prolapsed lumbar disc.
The cauda equina syndrome and loss of strength in the case of the other syndromes both justify rapid follow-up with specialised diagnostic examinations, possibly followed by surgery.