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Pain is defined as "an unpleasant emotional sensation and experience in response to actual or potential tissue damage."

(International Association for the Study of Pain).

To assess pain, 4 major factors must be taken into account which can generate pain phenomena:

1-Peripheral stimuli: this is the set of nociceptive stimuli which come from all the sensors of the periphery.

They can be divided into two types of pain:

2-nociceptive pain: part of the sensors of all the tissues of the body and is always proportional to the intensity of the stimuli.

This pain can be mechanical (it is triggered by a movement within a given amplitude and disappears outside this amplitude) or chemical (an oedema will attack the nerve cells - the pain is inflammatory).

3-peripheral neurogenic pain: this is pain that starts in the peripheral neuro-vascular chain. In this case there is nerve pain of the compression or stretching type inducing a disturbance in nutrition and vascularisation: this is neural hypoxia.

4- central modulations: each peripheral stimulus arrives at the central nervous system which will interpret and modulate before exchanging with the cerebral centres. In return there will be a motor response. These modulations depend on the biological state of the patient and his environment (stress, living conditions, etc.).

 

If these different mechanisms are not interrupted the pain becomes CHRONIC (more than 3 months) with storage.