Pathophysiology of pain: from theory to clinical evidence

Following damage to the nociceptive signalling system or sustained activation of this a series of plastic changes occur. These changes includes development of increased responses to a noxious stimulus (hyperalgesia), pain evoked by low‐intensity normally innocuous stimuli (allodynia), persistence after cessation of stimulation (aftersensations), spread of pain to surrounding non‐damaged areas and an increase of pain after repetitive stimulation. The nociceptive system serves a warning role in acute pain states, which is necessary for survival. But in chronic pain conditions the noceiceptive system serves no purpose at all. Basic studies have shown a cascade of neurobiological events underlying the plastic changes but there is still a gap in how these molecular and cellular translate into clinical manifestations as they are seen in three fundamental different forms of chronic pain: inflammatory, neuropathic and generalized types of pain