When treating patients with pain, it is important to at least try to understand what pain is. This first article in a series on chronic pain covers some general aspects of pain and its taxonomy, in particular the differences between acute and chronic pain, and between nociceptive and neurogenic pain. The next article will explore the psychology of pain, and in particular the relationships between pain, anxiety and depression. A follow-up article will be devoted to some of the thorny issues of pain measurement. The references given should be useful as a starting point for anyone embarking on their own exploration of the literature on chronic pain.

Keywords
Acute, chronic, neurogenic, nociceptive, psychosomatic and somatopsychic pain, pain dimensions, laterality, TENS, transcutaneous spinal electroanalgesia (TSE), acupuncture, electroacupuncture.

I. THE VARIETIES OF CHRONIC PAIN

‘Now this, monks, is the Noble Truth of Suffering:
birth is suffering, decay is suffering,
disease is suffering, death is suffering;
to be conjoined with things which one dislikes is suffering;
to be separated from things which one likes is suffering;
not to get what one wants, that is also suffering.
In short, these five aggregates, which are the objects of grasping, are suffering.’
Gautama Buddha: The First Noble Truth

Introduction
The polarity of pleasure and pain is basic to life. One we seek, the other we seek to avoid. Pain is ever-present, and particularly for the practitioner - in personal life, and in daily encounters with patients. Whether physical, mental or spiritual, it cannot be escaped or forgotten, but is always there to be wrestled with, ultimately unconquerable and yet ever challenging us to respond to its presence.

Groping towards understanding pain in its seemingly endless variety can give at least some sense of control over it. Illusory this may be, but for what it is worth, I would like to share some of what I have found from my readings on chronic pain.

I have written this series of articles to provide some pointers for acupuncturists towards (a) understanding chronic pain, primarily from a Western point of view, and (b) how to assess the extent to which a patient may benefit from a particular treatment method, without readers having to endure the almost total immersion in the pain literature that I have imposed upon myself for the last two years. While I have enjoyed wading through the morass of books and papers that exists on chronic pain and allied subjects, others may not!
 
I should say that my impetus for gathering all this information came from an interest in simple electrotherapy treatments for patient self-care, many of which can be used to advantage as adjunctive treatments in a TCM practice. The topics I have covered are therefore those I have considered of particular relevance to such treatments, although of course also important for acupuncture.

These articles are in fact spin-offs from designing a small pilot study (hopefully also to be published in EJOM at some future date) to determine the effectiveness of one such novel device for the treatment of chronic pain, the TSE ‘Pain 2000’ device, created by Dr Alexander Macdonald, one of the founders of the British Medical Acupuncture Society (80).

TSE (Transcutaneous Spinal Electroanalgesia) differs usefully from TENS (Transcutaneous Electrical Nerve Stimulation), as it produces a virtually subthreshold electrical stimulus, applied to standard locations on the skin via self-adhesive electrodes, and is extremely simple to use. It has two different outputs, supposedly for nociceptive and neurogenic pain, respectively. It is not helpful for acute or acute on chronic pain.

On first reading terms like ‘nociceptive,’ ‘neurogenic,’ or ‘acute on chronic,’ I felt very much at sea. Because it is useful to know what these mean, and how they are relevant to clinical practice, much of this first article concerns the labelling of pain, its taxonomy. Other topics are also included because of their relevance to practice, and to the use of TSE in particular.

For instance, TSE is not the only device using subthreshold signals. Others have been developed that also produce low or subthreshold signals, applied at similar locations, and have been used with some success for many years in the treatment of anxiety, depression, insomnia and drug withdrawal (140). I therefore thought it would be useful to see if TSE affected these as well as pain, and so have included an account of pain in its relation to anxiety and depression in the next article in this series. There are also some claims that these other devices may affect the electrical balance between the two brain hemispheres. Therefore, because there is a possible link between negative affect (such as depression), hemispheric specialisation and pain laterality, I have included some information on the relationship between pain and laterality.

WHAT IS PAIN?

‘Pain is what the experiencing patient says it is, and exists when he says it does, and where he says it does.’
Meinhart and McCaffery (85)

Some Statistics
Our society has become in some way ‘allergic’ to pain (20), the most common, and yet one of the least understood symptoms in medicine (127). So much so that two out of three patients attend a practitioner because of pain,54 and perhaps as many as 80% for pain-related problems (143). As living standards and medical techniques have ‘advanced,’ most of us no longer have to face so much acute disease; our society has become one of chronic illness (150), and chronic pain in particular. And so pain becomes expensive in terms of economic loss as well as human suffering. In the US, while one family in three has a member with pain (25), in 1982 chronic pain cost a total of 10% of the US national budget (14). In one Canadian study, nearly a quarter of households had a member with persistent pain (34), while a more recent estimate is that 25-30% of the population of many western countries suffers chronic pain, half to two thirds of this number being either partially or totally disabled for periods ranging from a few days to weeks (15). In the UK, 20 million prescriptions were issued in 1988 for non steroidal anti-inflammatory drugs (NSAIDs) for rheumatism alone, while in 1989/90 the DoH reported 60 million certificated days of incapacity due to back pain and associated conditions (40). Even the pain relief that is offered for acute pain is often insufficient, and little has really changed since Bonica in 1979 wrote that less than half of those with moderate to severe acute postoperative and posttraumatic pain, or the severe pain of myocardial infarction and other acute diseases, receive effective pain relief (14).

Understanding Pain: Definitions and Dimensions
Pain is unsharable, and paradoxical: it cannot be denied, and cannot be confirmed: to have pain is certain, to hear of the pain of another is often (and destructively) to doubt (123). The experience of pain may be hemmed about in words, and yet pain is still a subjective and private sensation which we can only imperfectly communicate (130). In a way, it is the same with our understanding of how pain comes about: many words, and still a lot of uncertainty. It almost seems that the more something lies outside our comprehension, the more desperately we seem to seek to name it and circumscribe it. The many definitions, classifications and disagreements in the pain literature demonstrate just how difficult pain is to define, let alone understand (57).

A generally accepted definition of pain as ‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage’ (70) has been proposed by the International Association for the Study of Pain (IASP), whose journal Pain is a rich resource for those seeking current knowledge on pain and its treatments. The IASP definition recognises that pain is a central percept, not merely a peripheral primary sensory modality (36), not just a physical sensation, but, being unpleasant, with an emotional dimension as well. There is also a cognitive dimension to pain: how we think about pain, what we understand or believe about it, its significance for us, colours our experience of it, and also what we do about it (117,151). And this significance, the meaning of pain, is also a product of the family, cultural/ethnic, work and healthcare contexts in which we live (22): pain may be a universal experience, but our concepts of pain are individual (112).

So, when considering pain, it is necessary to bear in mind its multidimensional nature. In particular, the measurement of pain depends on the dimensions of pain measured. We may at first consider pain simply as a matter of intensity, but it is by no means just a one-dimensional experience, although first studied as a purely sensory modality (31). As Melzack has written, ‘describing pain solely in terms of intensity is like specifying the visual world only in terms of light flux without regard to pattern, colour, texture, and the many other dimensions of visual experience’ (88).

Beecher in 1957 introduced a second dimension to the pain experience, with the concept ‘that pain perception and attitude to pain can be separated, that the reaction component is the important factor from the patient’s point of view, and that suffering is largely dependent on the reaction (attitude) rather than the original sensation’ (29). Thus pain, as Sherrington considered,31 can be seen as ‘sensation plus emotion’ (56), and, as Beecher saw, the emotional component is possibly the most important and disturbing to the pain sufferer (78).

A great impetus was given to the study of pain in 1965 by the publication of the so-called Gate Control Theory of Pain (GCT) by Melzack and Wall (91,94). Rather like the slightly later fascination with acupuncture analgesia, this seemed to ride in on a zeitgeist, and was rapidly accepted at the time, rather to the surprise of its originators (87). On the basis of this theory, arguably their major contribution to the theory of pain, Melzack and his co-workers contributed importantly to the taxonomy of pain by expanding Beecher’s two-dimensional model to the three-dimensional one mentioned above, with its sensory-discriminative, motivational-affective and cognitive-evaluatory axes, the first influenced primarily by the rapidly conducting spinal systems, the second subserved by activities in reticular and limbic structures and influenced primarily by more slowly conducting spinal systems, and the latter influenced by neocortical or higher central nervous system processes (93). This way of separating out different aspects of the pain experience, for all its artificiality (42), becomes important when attempting to measure pain.

Although this article is not about pain theories, it is important to emphasise that apart from explaining the pain experience in terms of peripheral nerve mechanisms, the GCT allows for supraspinal modulation, input from the brain, and so gives a role to psychological factors - the emotional and cognitive dimensions of pain - as well as making individual variation in the pain experience more acceptable (62,85). But no one theory ever gives the whole picture, and over the years the GCT has been adapted and modified to take more recent findings into account.

Still though, despite textbooks filled with knowledge about pain impulses travelling from the spine to the dorsal horn and into the spinal cord, the perception of pain is ‘not well understood,’ to use the jargon (25). Chronic pain in particular defies understanding and language. Worse, for all the knowledge and interventions available, there are still many pain conditions for which there is no satisfactory treatment (79,142,145), and this we have to accept, even as acupuncturists with a sometimes almost magical faith in the power of our needles or in the diagnostic spells of TCM (or WM, Western Medicine) we weave about our patients.

Pain: Mind or Body?
When we find our treatment does not help a patient in pain, it is sometimes tempting to blame them for the inadequacy or inappropriateness of the interventions we are using. We may lose our holistic perspective (only for a moment, of course) and become dualists, wondering if their pain is after all ‘all in the mind.’ Sometimes we do this partly because we cannot name it, understand it in terms of the physiological (or acupuncture) language we use, and so we feel all at sea, bewildered in the face of this nameless force that we are unable to control.

Of course pain can come more from the mind (psychogenic pain), or from the body (somatogenic pain). But it is not always easy, or even possible, to differentiate these two categories. As we know, gross degeneration may be evident on X-rays without the patient experiencing any pain; however, failure to demonstrate an organic disease does not rule out the presence of a lesion. Pain is often both somatogenic and psychogenic. Like any illness (64), as Sternbach points out (130), pain is both mental and physical: it’s our way of thinking about it that makes it either/or, and ‘the demon within answers to neither name’ (49). Chronic pain challenges the simplifying Cartesian dichotomies of biomedicine (67).

Overall, as Gamsa writes, ‘A critical analysis of the published literature shows that attempts to distinguish pain of psychological origin from pain due to physical causes have not been successful,’ particularly where chronic pain is concerned (48). In particular, the label ‘psychogenic’ has to be used with caution, as it has specific diagnostic and aetiological implications (95). The term ‘cryptogenic,’ meaning ‘of unknown origin,’ was once proposed to replace it (38), but never caught on, perhaps because it is still easier to consider ‘the failure’ as a ‘bad person or a crazy patient’ (58) rather than looking to our own psychological difficulties with failure (whatever ‘failure’ is).

The dualists, however, would disagree with Gamsa’s conclusion. Leavitt, for example (74, cf 6) sees a need to assess organic and psychological status independently, and finds that ‘neither can be inferred from the presence or absence of the other.’ Supporting this, measures of beta-endorphin in the cerebrospinal fluid have been found to differ if pain is relatively more psycho-, neuro- or somatogenic (2, 58,135,136). [For a contrary view, see Millan (104)] Most of us of course do not have the facilities for such sophisticated tests, and more simply, the way patients describe their pain may indicate if there is some psychological involvement: they may complain more about their pain (100); their pain may appear exaggerated, spatially diffuse, variable in time – e.g. throbbing, as opposed to constant, in the case of headaches (19) - and be described elaborately, with an emphasis on affective discomfort rather than just sensation (74,75). A psychological component may also be more evident in certain types of pain than others - headache as opposed to backache, for instance (19) [The psychology of pain will be explored further in the sequel to this article.]

Pain Has Two Hands
There may even be some differences between left- and right-sided pain and whether it is more psychogenic or organic in origin (5,101), although this remains controversial (73, 82, 98,128). Much research points to functional differences between the two halves of the brain in depression, for instance (129,141) which is of interest when considering the relationship between chronic pain and depression (as discussed in the next article). Certainly it seems that the non-dominant side is more sensitive to pain (107,130), something of which many acupuncturists will be aware as they needle.

The Many Influences on Pain
All in all, ‘the perception of pain is as complex as any other perception, as open to the influence of past experience, attention, meaning, and the multitude of other psychological factors that influence all of our perceptions’ (90). This is of great importance when it comes to considering how to measure pain.

For instance, as might be expected, those with a difficult childhood are more likely to have a psychological component to their pain experience (99) while chronic pain patients in general are more likely to have had more negative childhood experiences than those without chronic pain (24). Maybe as part of this, those from large families seem to experience more pain (63).

And, as Izard points out (56), the experience (and reporting) of pain depends on the patient’s ‘schema’ for a particular situation: it is situation-dependent (86). For example, if a spouse or other family member is present, pain (or reported pain) will not be the same as when the patient is alone with a practitioner (10). while the setting in which we see our patients may well also have a bearing on the sort of pain we are dealing with. Patients seen in specialised pain clinics are often more psychologically distressed than those attending GPs (27), for example. In this context, it would be useful to compare patients seen by acupuncturists in NHS settings with those self-referred to acupuncturists in private practice. I do not know of any such studies.

If we automatically call a sensation ‘pain,’ paying attention to it as such, this will alter and even magnify it, as Melzack points out (86): treatment of pain as merely physical, without taking the patient’s total situation into account, can lead to a kind of behavioural ‘iatrogenic reinforcement’ (149), and further suffering. Similarly, family, cultural or ethnic attitudes to pain will affect the level of distress caused by pain (117), although it is important to note that pain intensity may not differ (4,59); the uncomplaining stoical patient may be aware of de qi to the same extent as the voluble complainer.

More basically, the pain experience will vary with, among other factors, time of day (26, 55, 116), of month (116) and of season (128,136), with stress (88), mental fatigue (54), patient’s sex (33, 69), and age (33, 116). Whatever we and our patients may wish to believe, changes in pain may not represent a response to treatment! 

THE TAXONOMY OF PAIN

How a patient in pain responds to treatment depends in part on the sort of pain they are experiencing. Different types of pain respond differently to different types of treatment. It is therefore important to try to separate these out, so that we can be aware of what sort of pain we are dealing with in specific instances.

I. Acute Pain and Chronic Pain
Pain may be acute, chronic, or ‘acute on chronic’ (an acute episode of one pain on a background of another, chronic pain). Chronic pain itself may be periodic (with intermittent attacks of acute pain, as in trigeminal neuralgia), and not necessarily more or less continuous (143). Response to acute pain is often more extreme when someone is already suffering chronic pain, in part maybe because of depleted endorphin levels (152).

Acute pain is an almost universal human experience, whereas chronic pain, thankfully, is not so ubiquitous (68). Arbitrarily (154), chronic pain is usually considered as pain that has lasted at least 3 months, if not 6 months (1), but the difference between acute and chronic pain is not just one of duration, with chronic pain simply a repetition of acute pain (146). One difference is that chronic pain possibly responds better to acupuncture, for instance (118).

Chapman and Syrjala describe acute pain as ‘a transient, continuously changing state that differs radically from normal daily life; it is intimately related to intense emotional arousal, it is linked to tissue pathology, and it is usually characterized by clear, well-focused sensory characteristics. Acute pain states ... can be persistent, lasting weeks or several months until the disease or injury heals. Chronic pain, in contrast, is an enduring condition that has become a stable element in the daily life of the patient. This definition excludes most forms of cancer pain but includes pain associated with chronic muskuloskeletal, neuropathic, visceral, and degenerative disorders and pain problems with behavioral components. Its sensory characteristics are often but not always multifocal and vague, sometimes inappropriate for the organic pathology evident, and relatively constant’ (28).

Thus with chronic pain, not surprisingly, the affective/emotional dimension of pain comes to the fore (144), for whereas acute pain serves a useful biological purpose in warning of localised dysfunction (47), and so may promote survival, chronic pain serves no such function: it is usually destructive physically, psychologically and socially (132) [although it may, paradoxically, contribute to the survival of a species, rather than its individuals (104)].
 
II. Nociceptive and Neurogenic Chronic Pain
Crudely, pain may be somatogenic (organic) or psychogenic, as mentioned above. Chronic somatogenic pain may further be differentiated into nociceptive and neurogenic pain, as well as idiopathic pain which will not be further considered here (diffuse pain that does not conform to any of these categories and resists conventional treatment) (65).

In terms of treatment, there is general consensus that electrical stimulation (TENS or electroacupuncture [EA]) is more effective than manual needling in the management of chronic neurogenic pain (3, 58, 84). There is less agreement on the preferred treatment for nociceptive pain, with some using electrical and others minimal manual needle stimulation (3, 58). When using TENS or EA, it has been suggested that nociceptive pain responds better to ‘conventional TENS’ type parameters, and neurogenic pain, especially with hyperaesthesia, to ‘acupuncture-like TENS’ type parameters (139), although not all would agree (137,138).

Nociceptive pain generally occurs as a result of damage to non-nervous tissue (18), and is ‘pain that occurs as a result of activation of specific peripheral nociceptors in musculoskeletal tissue, in supportive bony-cartilaginous tissue, in the viscera,’ and elsewhere (103), nociceptors being nerve terminals receptive to pain sensation. Nociceptive pain is localised, and will increase with loading (eg, weight-bearing). In origin, it may be somatic (generally aching or throbbing), or visceral (dull aching or cramping, the latter poorly localised) (114).

Neurogenic pain is ‘pain that originates from trauma or injury to the nervous system itself, including the peripheral nerves, spinal roots, spinal cord, and supraspinal structures’ (103). Nerve endings as such are not involved (18).

It is not always easy to differentiate clinically between these two types of pain (103), and they may occur together (3), as when nerves are involved in tumour growth, or subsequent to motorcycle or similar accidents, which often involve the partial avulsion of nerves from the spinal cord, together with limb damage (18). However, nociceptive pain generally responds to analgesics (102), whereas neurogenic or neuropathic pain is often considered as resistant even to opiates (8, 102), but may respond to membrane-stabilising drugs such as carbamazepine, and sometimes to amitriptyline (103) or even anticholinesterase drugs (125).

Neurogenic pain can be particularly unpleasant. It tends to occur in older age groups, and includes post-herpetic and trigeminal neuralgia, as well as painful diabetic neuropathy, causalgia and post-stroke pain (so called ‘thalamic syndrome’) (103). There is characteristically an interval between neural damage and pain onset, with pain intensity increasing gradually to a maximum some weeks or months later (3). Neurogenic pain is usually described as burning and/or shooting, and is very often associated with allodynia [sometimes termed hyperaesthesia (109)], where a normally innocuous temperature or touch stimulus, such as blowing on the skin or moving a hair in the affected area, can produce pain (7), while firm pressure, for example, is not painful (as it would be if the area were merely tender). Hyperalgesia, a painful sensation of abnormal severity following noxious stimulation (7), may also occur. Again, it is not always easy to differentiate between allodynia and hyperalgesia, which are both forms of what has been called hyperpathia. Sometimes an area may exhibit an extreme response to one modality (e.g. touch), and diminished response to another (e.g. temperature), or even such opposite reactions to stimuli of the same modality but of different strengths (77). Referred sensations on electrical stimulation of ear points are also not infrequent with neurogenic pain (61). There are further discussions of these ‘dysaesthesias’ in Nathan (106) and Baldry (3). Their presence is a strong and useful indication that the pain is more neurogenic than nociceptive in origin.

INTRACTABLE PAIN AND ITS CONSEQUENCES

Pain Benign and Malign
Chronic noncancerous pain that has lasted for around 6 months may be described as ‘benign’ chronic pain: pain which has continued long after healing of the involved part and cessation of pain for that condition are expected to have occurred. Benign pain can become progressively more difficult to deal with, and the painful areas may increase in size (even if nonmalignant) (85), which in itself can be distressing. The lack of a diagnosis to legitimise the pain can also have considerable emotional impact (48). Certainly the patient may not consider this pain ‘benign’!

Whatever its original cause, in the central nervous system or from peripheral injury, it now has no ongoing known pathological basis in physiology, or anatomy, or nociceptive input (60), although it is often difficult to ascertain if this input has indeed come to an end (65). Chronic pain seems to be centrally maintained (37, 46, 91), whereas acute pain has both peripheral and central components (153). However, a contrary view, particularly important in the context of acupuncture treatment, is that of Rosomoff et al. and Baldry, who point out that chronic intractable pain may have continuing nociceptive peripheral input, from trigger points (3, 120).

In extreme cases, persistent pain is no longer considered benign, even by the experts. The longer it lasts, the more it will affect the patient (119). After a year, it can become ‘intractable’ (60), increasingly the centre of the patient’s life and yet somehow utterly without purpose and meaning (131), especially in our secularised society (11). The patient may no longer feel in control, but helpless in the face of something that seems without end (76). Without meaning in itself, pain becomes a focus for all their projected fears, or even fantasies of punishment (130). Whereas in acute pain, pain is a symptom of disease, in chronic pain, pain is the disease (14). It is no longer something external that can be fought or evaded (92), avoidable if the right (in)action is taken, but it invades and occupies us, and destroys our world (123). ‘It is not any longer a matter of having a body that has a hurt member, but we are a body that is almost entirely pain’ (130). [Indeed, in patients with advanced cancer, sometimes pain has become so much part of life that, if it is taken away suddenly, death can follow quickly after (11).] Wrestling with a life of endless pain exhausts our resources, emotional as well as financial (21). Pain, in an ‘ontological assault’ (111), has taken us over and become self-sustaining.
 
Patients in this state may cease to cope adequately, become socially isolated or otherwise maladjusted, sometimes at odds with their family (96), sometimes with familial rewards for their ‘invalid’ status, especially if other family members derive ‘tertiary gains’ from their pain (22), apart from their own secondary gains that in themselves can create formidable obstacles to change. They may go into a physical decline (often brought on by inactivity), with escalating physical incapacity. Often they will have a history of generally ineffective medical and surgical interventions (each with their own side effects), and sometimes a resulting overuse of drugs (see below). These are the patients that most of us find difficult to treat, unfairly suspecting their condition to be primarily psychogenic.

But even in psychologically healthy patients, ‘physical pain always mimes death’ (123), and anyone dealing with a pain that seems as inescapable as death may go through the same stages of response delineated by Kubler-Ross: depression, anger, denial, bargaining (51). Often worn down by lack of sleep (131), they become discouraged and depressed, and increasingly hopeless and even bitter as they exhaust the resources not just of conventional medicine, but of complementary approaches too. And without hope, what is there? Profoundly demoralised, like my patient with years of back pain who is forever comparing his body and his problem Jaguar car (‘you know before you take it in to the garage that it’s not going to sort the bloody thing’), such patients can in turn demoralise even the sanest practitioner, who may then respond with what has been aptly termed ‘therapeutic mania,’ trying any intervention in desperation that it will do something to help (81). This in itself can be unhelpful, reinforcing unrealistic and passive beliefs of some possible magical cure, while denying the patient the opportunity to develop appropriate coping skills (113).

Thus chronic pain patients are, by definition, losers in any health care system (45). All conventional approaches having failed for them (9), they often become examples of what Szasz has termed ‘homo dolorosus’, making such a career of pain that it will be difficult for them to relinquish it unless they decide to become ‘another kind of person’ (66, 134). Their pain has become a pilgrimage, their search for relief an overarching and lifelong goal (21). And, however unfortunate, maybe this piligrimage in itself can give some meaning to their suffering (115).

Cycles of Pain
Finally, the effects of chronic pain on the family should be mentioned. Almost a ‘malefic force,’ it can impose immense emotional, physical and economic stress on family members (154). Not only are the spouses of chronic pain patients likely to be affected (121), and more depressed than controls (30), but the children in the family may be at risk for adjustment problems, particularly if their mother is experiencing chronic pain [and not just chronic illness] (41). 70% of chronic pain patients become divorced (13), and many report poor marital relationships and sexual adjustment (110). Family conflicts tend to be more prevalent in the families of chronic pain patients (43), while if a patient with chronic pain is also depressed, their marriage is more likely to suffer than if they are ‘only’ depressed. Their spouse, as well as other family members, is also likely to have pain problems (105), and children from ‘painful families’ may be less likely to respond to treatment than children from more normal ones (110).

So the effects of chronic pain spread far beyond pain itself (70), and pain breeds more pain: there are not just pain-prone families (32), but even headache families and abdominal pain families (68), with particular similarities between children’s symptoms and their mothers’ (110). Helping to break the cycles of pain is a responsibility, not just to the individual, but to our society and our world as well. It requires patience, and an ability to tolerate relative failure, both on the part of the patient, and on that of the practitioner (97).

Summary and Conclusion
In this article I have attempted to draw out some threads from the vast tapestry of the literature on chronic pain that will be of interest and use to practitioners of TCM. The statistics, definition, dimensions and types of chronic pain have been covered, with particular emphasis on the complex characteristics of neurogenic pain. The laterality of pain has been touched upon, and the difficult topic of psychogenesis versus somatogenesis has been aired. Finally, the distressing and overwhelming individual and social consequences of intractable pain have been described.

Inevitably, I have focused on Western sources, in part because I do not read any oriental languages, but also because most investigations into the nature of pain are Western in origin and approach. I also firmly believe that by familiarising ourselves with Western approaches to acupuncture and the language of pain found in the literature of Western mainstream medicine, as ‘traditional’ acupuncturists we can only gain. This does not mean losing sight of our origins in other traditions, but will help us to become more flexible in our approach, both to patients and to other health professionals. If we do not do this, as Mark Seem pointed out in the last issue of EJOM (124), we may well find ourselves marginalised in the world of pain management.

David Mayor
David Mayor is a Buddhist, acupuncturist and workaholic whose early morning mediations recently seem to have been ousted by bouts of compulsive writing. He has a particular interest in electroacupuncture and forms of treatment (like TSE) that can be used by patients outside the treatment setting.

References
In most fields of human investigation, any initial simplicity soon vanishes under a welter of information and cross-connections that allow for many interpretations of the same findings. More than a decade ago WH Sweet already wrote of the utter impossibility of covering comprehensively the burgeoning literature on pain (133). The uncritical listing of references here and in the following articles is only what I have found (and not all of that!), with my own particular interests and ways of thinking. It has been strip-mined rather haphazardly from publications in English accessed by looking through the journal Pain and searching through references in other publications. I hope it will provide a useful, if unsystematic, resource for others interested in the topic of chronic pain.

Asterisked items have not been consulted directly. Numbers in square brackets refer to other references in this section.