Topological properties of brain networks in patients with hemiplegic shoulder pain: a functional magnetic resonance imaging study

Hemiplegic shoulder pain (HSP), a common complication of stroke, has a reported incidence of 34%-85% and a complex pathophysiology. This study aimed to explore differences in brain network topological properties between patients with and without HSP after stroke using resting-state functional magnetic resonance imaging.

Fifty patients with hemiplegia after stroke were recruited and divided into two groups based on the presence of HSP. Resting-state functional magnetic resonance imaging data were acquired, and GRETNA was applied to calculate both global and regional network topological properties. Group differences were assessed between patients with and without HSP.

At the global network level, both groups demonstrated a clear small-world organization (small-worldness index > 1). Compared with the non-pain group, patients with HSP showed significantly lower global efficiency (0.1733 ± 0.0047 vs. 0.1765 ± 0.0044; P = 0.02) and higher characteristic path length (0.3224 ± 0.0152 vs. 0.3170 ± 0.0089; P = 0.001). At the regional network level, patients with HSP showed reduced nodal degree centrality and nodal local efficiency in the opercular part of the right inferior frontal gyrus and in the orbital gyrus (P < 0.05). They also exhibited decreased nodal betweenness centrality in the right pallidum, left dorsolateral superior frontal gyrus, triangular part of the left inferior gyrus, and left Rolandic operculum (P < 0.05). Conversely, nodal betweenness centrality was increased in the left thalamus, right parahippocampal gyrus, left inferior occipital gyrus, and left angular gyrus (P < 0.05).

The topological properties of brain networks in patients with HSP have shifted toward a weaker small-world organization. Nodal alterations were primarily concentrated in the executive control network, default mode network, basal ganglia, and language network, regions associated with pain processing and emotional regulation. These findings provide new insights into the central mechanisms of HSP after stroke and suggest potential neural targets for future research and therapeutic intervention.