Neuropathic pain: an updated grading system for research and clinical practice

Abstract

The redefinition of neuropathic pain as "pain arising as a direct consequence of a lesion or disease affecting the somatosensory system," which was suggested by the International Association for the Study of Pain (IASP) Special Interest Group on Neuropathic Pain (NeuPSIG) in 2008, has been widely accepted. In contrast, the proposed grading system of possible, probable, and definite neuropathic pain from 2008 has been used to a lesser extent. Here, we report a citation analysis of the original NeuPSIG grading paper of 2008, followed by an analysis of its use by an expert panel and recommendations for an improved grading system. As of February, 2015, 608 eligible articles in Scopus cited the paper, 414 of which cited the neuropathic pain definition. Of 220 clinical studies citing the paper, 56 had used the grading system. The percentage using the grading system increased from 5% in 2009 to 30% in 2014. Obstacles to a wider use of the grading system were identified, including (1) questions about the relative significance of confirmatory tests, (2) the role of screening tools, and (3) uncertainties about what is considered a neuroanatomically plausible pain distribution. Here, we present a revised grading system with an adjusted order, better reflecting clinical practice, improvements in the specifications, and a word of caution that even the "definite" level of neuropathic pain does not always indicate causality. In addition, we add a table illustrating the area of pain and sensory abnormalities in common neuropathic pain conditions and propose areas for further research.

Conflict of interest statement

Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.

Figures

Figure 1.

Summary of how the citations of the neuropathic pain grading paper were used. The figure indicates the percentage of 608 publications that cited the original grading paper for defining neuropathic pain and the number of clinical studies that used the grading system for identifying neuropathic pain. The insert indicates the total number of clinical studies and the number of studies using the grading system for identifying neuropathic pain per year.

Figure 2.

Flow chart of updated grading system for neuropathic pain. aHistory, including pain descriptors, the presence of nonpainful sensory symptoms, and aggravating and alleviating factors, suggestive of pain being related to a neurological lesion and not other causes such as inflammation or non-neural tissue damage. The suspected lesion or disease is reported to be associated with neuropathic pain, including a temporal and spatial relationship representative of the condition; includes paroxysmal pain in trigeminal neuralgia. bThe pain distribution reported by the patient is consistent with the suspected lesion or disease (Table 1). cThe area of sensory changes may extend beyond, be within, or overlap with the area of pain. Sensory loss is generally required but touch-evoked or thermal allodynia may be the only finding at bedside examination. Trigger phenomena in trigeminal neuralgia may be counted as sensory signs. In some cases, sensory signs may be difficult to demonstrate although the nature of the lesion or disease is confirmed; for these cases the level “probable” continues to be appropriate, if a diagnostic test confirms the lesion or disease of the somatosensory nervous system. dThe term “definite” in this context means “probable neuropathic pain with confirmatory tests” because the location and nature of the lesion or disease have been confirmed to be able to explain the pain. “Definite” neuropathic pain is a pain that is fully compatible with neuropathic pain, but it does not necessarily establish causality.