Facial Biomarkers of Neuropathic Pain: Decoding Neuromicroexpressions with the F-M FACS 5.0

Abstract Neuromicroexpressions have emerged as crucial emotional biomarkers, particularly in the context of neuropathic pain, offering unprecedented insights into the interplay between cerebral activity and facial behavior. Grounded in the theoretical framework developed by Freitas-Magalhães- who classifies pain as a basic emotion - these subtle, involuntary facial movements reflect the deep neural encoding of suffering, often inaccessible to conscious awareness or verbal report. The F-M Facial Action Coding System 5.0 (F-M FACS 5.0), which integrates innovative action units such as AU3 (procerus contraction linked to emotional conflict and pain), provides a scientifically rigorous and clinically validated tool for decoding these expressions. By capturing neuromicroexpressive patterns specific to neuropathic pain, the F-M FACS 5.0 (Freitas-Magalhães, 2024a) enables a more accurate and non-invasive assessment of patient emotional states, bridging neuropsychology, affective neuroscience, and pain medicine. This paradigm shift not only enhances diagnostic precision but also opens new avenues for emotional rehabilitation and empathetic care, consolidating facial expression analysis as a cornerstone in the emerging field of facial neuropsychology.