AQP4 and Parkinson disease: The keyword co-occurrence network (453 nodes, 1,808 links; Figure 4D) identified high-frequency and high-centrality terms (Table 8), including “Alzheimer’s disease” (399), “glymphatic system” (308), “cerebrospinal fluid,” “interstitial fluid,” “Aβ clearance,” “amyloid beta,” “blood–brain barrier,” “aquaporin-4,” and “cognitive function.” Cluster analysis grouped keywords into 11 thematic clusters (Figure 4E), such as #0 Parkinson’s disease, #1 cerebrospinal fluid, and #4 glymphatic system.