The new grading system of neuropathic pain
32 slide(s) – 00:24:55– English –2010-09-26
Neuropathic pain has been defined by the International Association for the Study of Pain (IASP) as pain initiated or caused by a primary lesion, dysfunction or transitory perturbation in the peripheral or central nervous system. With this definition a variety of conditions such as fibromyalgia, chronic low back pain, chronic regional pain syndrome (CRPS) and whiplash associated disorder may share features with neuropathic pain, which may be difficult to distinguish from proper neuropathic pain. As a consequence of this unclarity a new and more distinct definition of neuropathic pain has been proposed.According to this neuropathic pain is now defined as: pain arising as a direct consequence of a lesion or disease affecting the somatosensory system (Neurology 2008). Without a gold standard for what constitutes neuropathic pain it is necessary to introduce a grading system with increasing evidence of neuropathic pain. In the new proposal it is suggested that neuropathic pain is graded into 3 categories: possible, probable and definite neuropathic pain. Neuropathic pain is not a single condition but a heterogeneous group of etiological different disorders ranging from axonal neuropathies, injuries to radices to pain following stroke. A multitude of pain-generating mechanisms have been shown to contribute and if these pathophysiological mechanisms can be identified it is assumed that a better treatment can be offered to patients suffering from neuropathic pain. Neuropathic pain can be: stimulus dependent and stimulus independent. The stimulus dependent types of pains include mechanical, thermal and chemical evoked pains, while the stimulus independent types are characterised by spontaneous, ongoing types of pain. In the individual patient the various types of pain may coexist in different combinations and contribute to the heterogeneity of the clinical picture. Neuropathic types of pain have irrespectively of underlying pathology certain essential characteristics: 1) sensory deficit in the painful area, 2) allodynia or hyperalgesia in the painful area, 3) aftersensations, 4) gradual increase of pain following repetitive stimulation, and 5) paroxysms of pain. In particular two paradoxical clinical features: loss of sensation and increased sensation are met by most neuropathic pain conditions and reflect deafferentation or lost input to the CNS together with the presence of neuronal hyperexcitability. In this talk the advantages and limitations of the 2008 proposed definition of neuropathic pain will be presented.