Evaluation of pressure-induced pain in patients with disorders of consciousness based on functional near infrared spectroscopy.

In patients with disorders of consciousness, acute pressure pain stimulation did not produce significant changes in oxygenated or deoxygenated hemoglobin concentrations across multiple brain regions, indicating minimal activation of pain-related areas. However, functional connectivity between the primary somatosensory cortex, primary motor cortex, and dorsolateral prefrontal cortex significantly increased during stimulation, with correlation coefficients exceeding 0.9. This enhanced coordination among sensory, motor, and cognitive regions suggests that the brain continues to process pain information through altered network connectivity even when regional activation is absent. The findings underscore the potential of functional connectivity measures for evaluating pain processing in patients with disorders of consciousness.

Study at a glance

Abstract

This study aimed to investigate the brain's hemodynamic responses (HRO) and functional connectivity in patients with disorders of consciousness (DoC) in response to acute pressure pain stimulation using near-infrared spectroscopy (NIRS). Patients diagnosed with DoC underwent pressure stimulation while brain activity was measured using NIRS. Changes in oxygenated hemoglobin (HbO) and deoxygenated hemoglobin (HbR) concentrations were monitored across several regions of interest (ROIs), including the primary somatosensory cortex (PSC), primary motor cortex (PMC), dorsolateral prefrontal cortex (dPFC), somatosensory association cortex (SAC), temporal gyrus (TG), and frontopolar area (FPA). Functional connectivity was assessed during pre-stimulation, stimulation, and post-stimulation phases. No significant changes in HbO or HbR concentrations were observed during the stimulation vs. baseline or stimulation vs. post-stimulation comparisons, indicating minimal activation of the targeted brain regions in response to the pressure stimulus. However, functional connectivity between key regions, particularly the PSC, PMC, and dPFC, showed significant enhancement during the stimulation phase (r > 0.9, p < 0.001), suggesting greater coordination among sensory, motor, and cognitive regions. These changes in connectivity were not accompanied by significant activation in pain-related brain areas. Although pain-induced brain activation was minimal in patients with DoC, enhanced functional connectivity during pain stimulation suggests that the brain continues to process pain information through coordinated activity between regions. The findings highlight the importance of assessing functional connectivity as a potential method for evaluating pain processing in patients with DoC.