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.
Mechanical back pain is related to changes which occur in the spinal ligaments, facet joints, muscles and discs. An important distinction in diagnosis is between mechanical pain and neuropathic pain. In mechanical syndromes the pain is generated by the injured or altered tissues but in neuropathic pain it is the nervous system which generates the pain, often secondary to injury of some sort. Neuropathic pain examples are pain after shingles, pain after nerve root damage, pain from diabetic neuropathy and phantom pain. The nature of neuropathic pain is very unpleasant for the patients and is difficult to medically manage.
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.
130 people with peripheral neuropathic pain and 57 people with mechanical low back pain were surveyed and given a standardised assessment. An interview with 16 questions was then applied followed by a specific series of twenty-three physical tests. A list of words applicable to pain descriptions was provided and patients were asked to indicate which ones most accurately described their pain. In chronic pain patients often have an alteration in the ability to feel touch, vibratory and pin prick stimuli so the ability to discriminate these sensibilities is tested.
In neuropathic pain patients it was possible to identify six sub-groups and in non neuropathic patients two further subgroups were noted. Researchers were also able to distinguish the 6 questions and 10 physical tests which were best suited to making the most accurate discrimination between the pain subtypes. Testing this tool on one hundred and thirty seven further patients allowed the researchers to see it worked effectively and that patient acceptability was good. A particular group of neuropathic pain subtypes could be elucidated by a relatively low number of signs and symptoms which were not related to the presenting causative conditions.
Neuropathic pain patients are usually categorised by the disease which is causing their pain but the researchers found that there was no connection between the types of neuropathic pains exhibited and the underlying diseases the patients suffered from. In one disease there may be different pain mechanisms generating pain and in several different diseases the same mechanism of pain production may be active. There may also be a variation in the types of pain production within one individual. The differential diagnosis between mechanical spinal pain and nerve root pain was distinguished by the test, a sometimes difficult task as there can be small changes in the muscle power and skin sensibility.
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.
