Dear Editor,

I refer to the article "Clinical management of neuropathic pain" by Dr K F Chin published in your Journal Vol 23 Oct 2001 and would like to congratulate Dr Chin in writing such a good synopsis. I want to highlight a few points for discussion.

1. While most of the acute pain has a noxious stimulus (a stimulus that is capable of producing tissue damage), the relation between psychogenic pain and the noxious stimulus is less well defined. A patient in fear of having cancer of the brain may experience pain (headache). With chronic pain, such as chronic low back pain, patients may experience persistent back pain long after the noxious stimulus has disappeared. In fact, the approach towards chronic pain management nowadays builds from the Biopsychosocial pain model, where the patient's pain is taken as the unpleasant sensory and emotional experience from interactions among the patient's physical, psychological and social domains. This gives family physicians an important role in the management of patients with chronic pain.
   
   
2. The biological response to a noxious stimulus is NOT pain. The biological sensory/discriminative awareness of noxious stimuli is called NOCICEPTION.
   
   
3. In order to accommodate the psychogenic causes of pain into Dr Chin's definition, the International Association of the Study of Pain (IASP) expands the definition of pain as:
   
   "An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage".

Notice that this definition describes pain in three different aspects. The first refers to the physical component (sensory), whereby tissue damage generates sufficient excitation of the special nerve endings in the peripheral nervous system and sends off nerve impulses to the spinal cord or brain stem and thence on the brain i.e. the nociception. The second refers to the psychosocial component (emotional), which centers on the emotional experience of the nociceptive impulses on the body'scognitive and behavioural responses. The third aspect refers to the cause of this nociceptive and emotional experience, which can be "actual", "potential" or even "perceived" as described tissue damages.