Diagnosis and management of chronic
neuropathic pain are challenging, leading to current efforts to characterize 'objective'
biomarkers of
pain using imaging or neurophysiological techniques, such as electroencephalography (EEG). A systematic literature review was conducted in PubMed-Medline and Web-of-Science until October 2021 to identify EEG
biomarkers of chronic
neuropathic pain in humans. The risk of bias was assessed by the Newcastle-Ottawa-Scale. Experimental, provoked, or chronic non-
neuropathic pain studies were excluded. We identified 14 studies, in which resting-state EEG spectral analysis was compared between patients with
pain related to a neurological disease and patients with the same disease but without
pain or healthy controls. From these heterogeneous exploratory studies, some conclusions can be drawn, even if they must be weighted by the fact that confounding factors, such as medication and association with anxio-
depressive disorders, are generally not taken into account. Overall, EEG signal power was increased in the θ band (4-7Hz) and possibly in the high-β band (20-30Hz), but decreased in the high-α-low-β band (10-20Hz) in the presence of ongoing
neuropathic pain, while increased γ band oscillations were not evidenced, unlike in experimental
pain. Consequently, the dominant peak frequency was decreased in the θ-α band and increased in the whole-β band in
neuropathic pain patients. Disappointingly,
pain intensity correlated with various EEG changes across studies, with no consistent trend. This review also discusses the location of regional
pain-related EEG changes in the
pain connectome, as the perspectives offered by advanced techniques of EEG signal analysis (source location, connectivity, or classification methods based on artificial intelligence). The
biomarkers provided by resting-state EEG are of particular interest for optimizing the treatment of chronic
neuropathic pain by neuromodulation techniques, such as
transcranial alternating current stimulation or
neurofeedback procedures.