Chapter 5 Back and related limb neurological problems
5.1 Introduction
History
The aim of history taking and examination relating to any body system is to determine:
Stiffness is a rather vague term that may be related to pain, muscle spasm or deformity. It is the pattern of the stiffness may be more enlightening — early morning stiffness may be more in keeping with an inflammatory arthritis, post-activity stiffness to a degenerative process and continuous stiffness to a bony deformity that impedes motion. Acute deformity may lead one to suspect joint instability or fracture that may be related to an acute process, such as trauma, or a chronic process that destabilises the integrity of the skeletal elements, such as infection or tumour. However, acute painful deformity is also seen in degenative cases.
Examination
Movements of the spine are next observed, beginning with flexion (touching the toes). Most flexion takes place at the lumbar spine. Isolating the precise range of motion in the spine in the various segments of the spine is difficult. Forward flexion is often a combination of movement at the spine and pelvis/hips. Assessment often entails the pelvis being stabilised during the examination process. With the pelvis stabilised, the range of forward lumbar flexion may be assessed. You may measure the change in distance between a fixed point on the sacrum such as the spinous process adjacent to the S2 dimple and the first lumbar vertebra. The patient may show deviation to the painful side on forward flexion. While hip flexion may simulate spinal flexion, the lumbar lordosis will be observed not to unwind, the spine remaining stiff — in this situation the excursion between lumbar spinous processes remains unchanged as flexion proceeds. Whole spine rigidity may be evident in ankylosing spondylitis; this may be associated with a decreased chest expansion during inspiration of less than 2.5 cm.
Examination with the patient supine. A careful neurological examination of the lower limbs is performed, starting with inspection for wasting or other signs, followed by an assessment of tone, then a systematic examination of muscle strength, comparing each side to the other, as well as with your expectation of normal. It is best to start distally, as pain can compound the assessment of proximal strength. Dorsiflexion of the toes is important as this may be reduced in L5 lesions. Inversion and eversion of the ankles should be tested, as well as dorsi and plantar flexion, then flexion and extension at knee and hip. In interpreting these observations, it is essential to be familiar with the myotomes and dermatomes, as outlined in standard anatomy texts.
Subsequently, the straight leg raising (SLR) and flexed leg raising tests are performed. It is best to elevate the flexed leg first to observe the patient’s response, then perform rotation and adduction/abduction of the hip to assess for pathology at the hip/pelvic level. Subsequently, the extended leg is lifted actively by the patient and then by the clinician until pain in the buttock, leg and/or back is felt and the angle at which this occurs is observed. The leg should be raised slowly and the knee kept at full extension during this manoeuvre. At this level, if the knee is flexed the pain of nerve root irritation should abate and, if the ankle is dorsiflexed, the pain is exacerbated. Sudden firm pressure on the tibial nerve in the popliteal fossa may elicit further pain — sometimes known as the bowstring sign — and confirm an underlying organic aetiology. Straight leg raising of the opposite leg giving rise to pain in the affected leg is known as crossover pain, suggesting that the disc lesion is in the axilla of the nerve root or medial to the nerve root (Fig 5.1). Sciatica due to nerve root compression in the lumbar spine will typically cause pain down the back of the leg on the straight leg raise but not with the flexed leg raise. Cadaver studies have shown that the L5 and S1 nerve roots move by 2 cm or more in the spinal canal during the SLR.
Non-organic pathology may also require exclusion with the assistance of a series of signs described by Waddell. Tenderness in such cases is superficial and non-anatomical. Simulated axial loading such as pushing down on the patient’s skull or shoulders is reported as painful in the lumbar spine as is simulated rotation of the lumbar spine by rotating the shoulder and pelvis together. The pain, if present, should not be increased by this manoeuvre. Distraction tests such a extending the knee joint while the patient sits on the edge of the examination couch should produce the same pain as a straight leg raise. If it does not then the pathology may be non-organic. Regional weakness and giving way that cannot be explained on a neurological basis — myotomal/dermatomal or peripheral nerve in their pattern of involvement — should also raise suspicion. Overreaction during the examination process, such as facial expressions, tremor and collapsing, may also be suggestive of non-organic pathology. However, you must also be sensitive to cultural differences that may result in these overreactions. Inconsistency between different phases of the assessment may also be a clue. It is very common for there to be some non-organic overlay to a fundamentally organic situation.
5.2 Back pain
Special tests in the assessment of spinal pain
1 Chronic lumbar ligamentous strain
A history of pain after lifting at work is common with chronic and recurring back pain. The WorkCover context complicates the situation considerably. Most patients still get better with rest, gentle activity and time. In those cases that pass into chronic pain, the significance of neurosis or malingering in the pathogenesis of this litigation-linked condition can rarely be determined with absolute assurance. True malingering in the sense of complete fabrication of a set of symptoms and signs is uncommon; exaggeration of symptoms and signs in the absence of demonstrable organic disease and persistence of symptoms and signs while litigation is pending is common.
2 Degenerative disc disease, spondylosis and osteoarthritis
With disc degeneration, especially following recurrent disc prolapse, gradual flattening of the disc and displacement of the posterior facet joints occur, eventually gives rise to osteoarthritis in those joints (Fig 5.2). A past history of lumbar pain is common, with subsequent recurrent attacks of pain over a period of several years. The onset of such attacks is often related to exertional trauma, such as repetitive bending or lifting a weight, or strain from sitting in an uncomfortable position during a long journey. Sciatic radiation of the pain to the buttock and sometimes down the backs of the legs, on one or both sides, is common. With the development of osteoarthritis of the facet joints, pain becomes constant and nocturnal. On examination, tender areas may be felt over the spine. There is limitation of all lumbar spine movements and residual neurological signs of disc prolapse, such as an absent ankle jerk, may be present. Most instances of chronic recurring back pain fall into this category; however, it is surprising how many patients have minimal symtoms despite impressive changes on scans.
4 Osteoporosis
This condition is most common in elderly women; gonadal involution is the most important causal factor. Longstanding steroid therapy is an important cause, while nutritional problems may also contribute. Fractures, especially crush fractures of the vertebrae, can occur with minimal trauma. Trabecular bone stiffness varies with the cube of its density — there is almost 50% loss in strength with 30% decrease in the density. Vertebral compression fractures lead to backache, kyphosis and shortening in height. Plain X-ray reveals loss of bone density, wedging or biconcave indentation of vertebrae. Bone densitometry is a more sensitive and effective method of quantifying change in bone mineral density.
5 Secondary carcinoma of the vertebral body
The most common tumours of the vertebral bodies are metastatic lesions arising from tumours of the lung, breast, prostate, thyroid or kidney. The predominant symptom of localised destruction of the vertebral body is constant pain that steadily increases in severity. There may be associated neurological disorders because of involvement of the spinal cord or nerve roots. Plain X-ray may reveal osteolytic or osteosclerotic vertebral destruction by tumour, with preservation of an adjacent normal intervertebral disc (Fig 5.3). Metastases from carcinoma of the prostate are more commonly osteosclerotic. Considerable destruction of bone substance is necessary before radiological signs occur; X-rays are thus commonly negative in the presence of metastases. CT is more sensitive and MRI better again. Bone scans can be diagnostic. Furthermore, focal metastatic deposits can be difficult to differentiate from localised Paget’s disease.
Diagnostic plan
Collapse or destruction of the vertebral body, narrowing of the disc space and soft tissue changes may be assessed on plain X-ray, but this test is relatively insensitive. The most common X-ray features found in the spine are those of chronic disc degeneration, spondylosis, osteoarthritis and sometimes spondylolisthesis. In the case of spondylolisthesis, the early signs of narrowing of the anterior disc space and displacement of the more proximal vertebrae against the one below are seen best on the lateral view. The disc spaces most often involved are those between L4 and L5 and L5 and S1. Later, marginal osteophytes appear at the edge of the disc and there is increased radiolucency of the vertebral body. Lateral and oblique views may show facet joint malalignment and osteoarthritis.