Modalities Differentiation of Pain Perception Following Ischemic Stroke: Decreased Pressure Pain Perception

Background/Objectives: Ischemic stroke frequently leads to somatosensory impairments and abnormal pain perception. Meanwhile, pain perception can be evoked through multiple somatosensory modalities, each mediated by distinct neural pathways. Despite this understanding, current research investigating stroke-induced alterations in pain perception across different modalities of noxious stimulation remains insufficient, particularly concerning responses to varying stimulus intensities (including both sub-threshold and supra-threshold levels). Methods: In this study (March 2023 to July 2024), we enrolled 30 ischemic stroke patients and 35 matched controls and employed two modalities of noxious stimuli (e.g., heat stimuli were delivered using the Medoc CHEPS and pressure stimuli were administered via an MRI-Compatible Foot-Sole Stimulator) to systematically evaluate post-stroke changes in pain perception through two experiments. We compared self-reported pain sensitivity, somatosensory thresholds (i.e., warmth and pressure), and pain thresholds (i.e., heat and pressure pain) between ischemic stroke patients and healthy controls in Experiment 1. We focused on pain perception when participants simultaneously experienced heat and pressure in Experiment 2. Results: Experiment 1 showed an absence of a significant correlation between heat and pressure pain thresholds in stroke patients, but this correlation could be observed in healthy controls. Notably, stroke patients had an impairment in pain perception of pressure stimulation at supra-threshold intensities. Experiment 2 observed a similar facilitative pain integration in patients as healthy controls when they perceived heat and pressure stimuli jointly and simultaneously. Conclusions: These findings provide valuable insights into pain perception following a stroke, highlighting the need for tailored evaluation strategies considering the differences in somatosensory modality damage.