Neuropathic pain: proposal of a mechanism-based treatment

Neuropathic pain, defined by the International Association for the Study of Pain as “pain caused by a lesion or disease of the somatosensory system”, has an estimated prevalence of 7–9.2% in the general population and is associated with poorer health-related quality of life than other types of pain. Diagnosis can be improved by the use of diagnostic algorithms, but treatment remains rather unsatisfactory, with only 30–40% of patients achieving an acceptable response. Some authors have suggested that the poor results in the treatment of neuropathic pain may be related to the different mechanisms present in each patient and have tried to correlate them with clinical characteristics in order to evaluate possible targeted treatments. This approach has been used in some studies evaluating the response to specific pharmacotherapies in clusters of patients, with encouraging results but still limited applicability to clinical practice. In this narrative review, we attempt to analyse the literature suggesting possible pathogenetic mechanisms manifested along the nociceptive pathway due to a lesion or disease of the nervous system; aware of the limitations of exploring such a wide field, we look for conditions that could be targeted by the available pharmacological or interventional treatment options. Functional changes may occur in the nociceptive system from the periphery to the cerebral cortex, in particular in the nociceptive terminals, along the first-order neuron and the dorsal root ganglion, at the first synapses, or at supraspinal levels. Clinical assessment is the first step in the study of anatomical and functional changes; the diagnostic hypothesis should be confirmed, if possible, by instrumental studies or diagnostic blocks or procedures to guide an individualised therapeutic algorithm from less to more invasive treatments.