Monday, May 4, 2009

Low Back Pain Diagnosis

By Jonathan Blood Smyth

The diagnosis of lumbar back pain is difficult and uncertain due to the various conditions which can present with this problem. Effective back pain management depends on identifying what kind of back pain problem is present, and many people have suggested that there are many back pain subtypes which need to be identified before treatment can be well targeted. The variations in diagnoses for low back pain and related symptoms include: postural pain; trigger point pains; nerve root compression; neuropathic pain; facet joint pain; disc related pain and lumbar stenosis.

One of the most important distinctions is between mechanical low back pain, secondary to changes which may have occurred in the discs, joints, ligaments or muscles and neuropathic pain. Neuropathic pain is quite different to tissue based pain and is generated by the nervous system itself, usually after injury or damage. Phantom pain, diabetic neuropathic pain, post shingles pain and pain after nerve root damage are all examples of neuropathic pain. Neuropathic pain is particularly unpleasant and difficult to treat. Diagnosing it correctly from all the other pain types is the first step.

A recent study performed by researchers from Massachusetts General Hospital in Boston and Addenbrooke's Hospital in Cambridge, UK, has investigated this difficulty. They recognised that the assessment by taking a score of pain intensity does not reflect the reality of the complex nature of pain processes by which pain is generated. They set out to design an assessment which would take these complexities into account, allowing the clearer identification of the diagnosis and thereby a potentially more accurate treatment. They developed a standardised tool to use in the assessment of chronic pain with the aim of delineating differing pain subtypes.

The researchers tested fifty-seven patients with typical low back pain and one hundred and thirty with peripheral neuropathic pain were investigated in a repeatable manner by a standardised group of sixteen questions then a physical examination consisting of 23 particular tests. Pain descriptors in terms of a series of words to describe pain were presented to patients who then chose the ones most applicable to their pain. Alteration in the ability to accurately sense pin-prick, light touch and vibration inputs is altered in chronic pain syndromes and the ability to accurately distinguish these modalities is also assessed.

Two subgroups of mechanical pain and 6 subgroups of neuropathic pain were identified by researchers and they were able to narrow down to ten physical tests and six questions which best allowed an accurate delineation of pain subgroups. Once they had this tool they assessed a further 137 patients to test this further and found it discriminated well and was acceptable to the patients who used it. A relatively small number of symptoms and signs could be used to identify a group of subtypes of neuropathic pain, with the symptoms and signs not connected with the underlying pain conditions.

The most discriminating part of the testing was the physical examination and not the symptom recording of types and distributions of pain. The nature and quality of the pain were of lesser importance than often thought and testing by pinprick found to be of greater importance. The pain subtypes were linked by the researchers to the biological mechanisms of the underlying nerve pathways. Spontaneous burning pains were thought to reflect discharges in the pain nerves with heat sensitivity. Pain from brushing the skin was linked to heightened reactivity of the nerve cells in the spinal cord dorsal horn.

Diagnosticians usually classify patients into pain categories which relate to their disease conditions but researchers found that the diseases which the patients exhibited were not linked to the neuropathic pain types found. Patients with the same disease may have a group of different pain generating mechanisms going on at any one time and the same pain generation system may be occurring in patients with various diseases. Over time the pain generating mechanisms may change in one individual. The test was able to tell the difference between nerve root and segmental lumbar pain which is often not very clear due to the subtle deficit in muscle power and sensibility which can occur in nerve root lesions. - 14130

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