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