Weaknesses in definition of neuropathic pain 

Neuropathic pain in that definition is defined as

“pain initiated or caused by a primary lesion or dysfunction in the nervous system.”

Treede et al sees the upside of this definition, as it has been useful to distinguish between neuropathic and other types of pain, but they state the definition lacks both diagnostic specificity and anatomic precision.

They proceed adressing two key-issues:

1. neuropathic pain needs to be distinguished from pain due to secondary neuroplastic changes in the nociceptive system resulting from sufficiently strong nociceptive stimulation, e.g., inflammatory pain and 
2. neuropathic pain needs to be distinguished from musculoskeletal and other types of pain that arise indirectly in the course of neurologic disorders.

They state that the lack of precision in the definition has prevented further progress in diagnosis, classification, epidemiology, and treatment of neuropathic pain. ^[1]

New step in defining neuropathic pain

There is no specific diagnostic tool which makes an unequivocal diagnosis of neuropathic painpossibled. Therefore, Treede et al developed a grading system with different levels of certainty about the presence of neuropathic pain.

After many discussions within the peergroup of neurologists interested in neuropathic pain, Treede et al proposed to replace the current definition of neuropathic pai by the following wording:

“pain arising as a direct consequence of a lesion or disease affecting the somatosensory system.” Thus the vague term dysfunction has been replaced by the term disease. Furthermore, the restriction to the somatosensory system was felt to be necessary because,

"diseases and lesions of other parts of the nervous system may cause other types of pain that should not be confused with neuropathic pain, such as the pain associated with spasticity and rigidity that is mediated by activation of nociceptive afferents from muscles."

After finetuning the definition the authors introduce an important tool, a grading system to specifically describe the neuropathic pain (see table). This is clearly a major step forward in defining neuropathic pain, and the four questions are highly significant. Each clinician working in this field will directly recognize the relevance of these questions. For instande, how often we see patients complaining of burning pain in regions of the b ody which are not plausibla. However, we need to be careful here, even a neuropathy of the lower intercostal nerves, giving rise to burning pain in the abdomen is possible. It is rare, but you have to know it. Otherwise you might think you are dealing with a pseudoneuropathic syndrome. 

The level of definite neuropathic pain is only acceptable in those cases where there is no reasonable doubt about the presence of a lesion/disease of the somatosensory system and that the pain is directly due to such disorder. 

The authors condense the system in a handy flow chart (see under)

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