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From the Institute of Physiology and Pathophysiology (R.-D.T.), Johannes Gutenberg University, Mainz, Germany; Department of Neurology (T.S.J.), Aarhus University Hospital, Denmark; Departments of Neurosurgery (J.N.C.) and Neurology (J.W.G.), Johns Hopkins Medical Institutions, Baltimore, MD; Department of Neurology (G.C.), La Sapienza University, Rome, Italy; Department of Physiology (J.O.D.), University of Toronto, Canada; Department of Neurosurgery (P.H.), Pain Center, Karolinska University Hospital, Stockholm, Sweden; Department of Clinical Neuroscience (R.H.), King's College London, UK; Pain Research Institute (T.N.), Division of Neurological Science, University of Liverpool, UK; and Department of Neurology (J.S.), MC Mutual, Barcelona, Spain.
Address correspondence and reprint requests to Dr. Troels S. Jensen, Department of Neurology, Aarhus University Hospital, Norrebrogade 44, 8000 Aarhus C, Denmark tsjensen{at}ki.au.dk.
Pain usually results from activation of nociceptive afferents by actually or potentially tissue-damaging stimuli. Pain may also arise by activity generated within the nervous system without adequate stimulation of its peripheral sensory endings. For this type of pain, the International Association for the Study of Pain introduced the term neuropathic pain, defined as "pain initiated or caused by a primary lesion or dysfunction in the nervous system." While this definition has been useful in distinguishing some characteristics of neuropathic and nociceptive types of pain, it lacks defined boundaries. Since the sensitivity of the nociceptive system is modulated by its adequate activation (e.g., by central sensitization), it has been difficult to distinguish neuropathic dysfunction from physiologic neuroplasticity. We present a more precise definition developed by a group of experts from the neurologic and pain community: pain arising as a direct consequence of a lesion or disease affecting the somatosensory system. This revised definition fits into the nosology of neurologic disorders. The reference to the somatosensory system was derived from a wide range of neuropathic pain conditions ranging from painful neuropathy to central poststroke pain. Because of the lack of a specific diagnostic tool for neuropathic pain, a grading system of definite, probable, and possible neuropathic pain is proposed. The grade possible can only be regarded as a working hypothesis, which does not exclude but does not diagnose neuropathic pain. The grades probable and definite require confirmatory evidence from a neurologic examination. This grading system is proposed for clinical and research purposes.
GLOSSARY: IASP = International Association for the Study of Pain; MS = multiple sclerosis; NeuPSIG = IASP Special Interest Group on Neuropathic Pain.
e-Pub ahead of print on November 14, 2007, at www.neurology.org.
*R.-D. Treede and T.S. Jensen contributed equally to this work.
Supported in part by travel grants from NeuPSIG, the Special Interest Group on Neuropathic Pain of the International Association for the Study of Pain (IASP).
Disclosure: The authors report no conflicts of interest.
Received December 18, 2006. Accepted in final form June 14, 2007.
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