Abstract

PEDRAJAS NAVAS, José Mª.  and  MOLINO GONZALEZ, Ángel M.. Neuro-medical bases of pain. Clínica y Salud [online]. 2008, vol.19, n.3, pp.277-293. ISSN 2174-0550.

Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such a damage. Pain can be classified by numerous criteria. If pain lasts at least three months, it is considered chronic pain, though the most important feature of chronic pain is its relation with cognitive and behavioural alterations. Nociceptors pick up pain sensations and send them up to the Central Nervous System through several stations. The first station is the dorsal root ganglia, the second station is the dorsal horn of the spinal cord, the third station consists of several subcortical structure (the thalamus being the most important), and finally the fourth station is the cerebral cortex, mainly somatosensorial, cingulus, insula and prefrontal areas. These structures are responsible for the perception of pain, for subconscious activities and for the modulatory, endocrine and emotional answers. The painful experience has three dimentions -sensitive-discriminative, cognitive, and emotional. A careful evaluation of pain is essential before prescribing analgesic drugs. A global planned strategy must be built to manage chronic pain -evaluating before treating, combining different methods of treatment, promoting ensuring therapeutic adherence, preventing adverse effects, working in a multidisciplinary team, gathering information, providing planification, systematically reviewing, and guaranteeing accesability, availability and flexibility. Drug treatment is based on the WHO’s three-step analgesic ladder: the first step consists of non opioids analgesics (acetaminophen, non steroidantiinflamatories), the second consists of weak opioids (plus non opioid agents) and the third step consists of powerful opioids (plus non opioid agents). An adjuvant agent may be added at each step. In chronic pain, other non pharmacologic measures must be used - physical, psychological and other measures such as radiation, surgery or radiofrequency.

Keywords : Chronic pain; Painful experience; Neuromodulation; Analgesic ladder; Adjuvant agents; Opioids.

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