title: Small world properties changes in mild traumatic brain injury.
abstract: To investigate local and global efficiency changes characterized by small-world properties based on resting-state functional MRI, such as centrality and clustering coefficient, in mild traumatic brain injury (MTBI) patients; and to associate these findings with axonal injury as measured by diffusion tensor imaging (DTI) as well as with post-concussive symptom (PCS).
  
  
  
  Thirty patients (mean age 35 ± 13 years) with clinically defined MTBI and 45 age-matched healthy controls (mean age 37 ± 10 years) participated in the experiments. Resting-state functional MRI was performed using gradient echo planar imaging sequence with 3 Tesla MRI scanner to obtain functional small-world networks. Out of all participants, 20 MTBI patients and 20 controls had available DTI data with three b-values (0, 500, 1000) s/mm2and 30 directions for diffuse axonal injury analyses.
  
  
  
  Compared with controls, MTBI patients showed lower relative betweenness centrality (P = 0.01), but significantly higher clustering coefficient (P = 0.04), and these two metrics correlated negatively in patients (r = -0.77; P < 0.001). Regions with lower betweenness centrality (e.g., frontal and occipital) corresponded with the regions of reduced FA in patients, while global FA reduction correlated with betweenness centrality (r = 0.48; P = 0.03) and clustering coefficient (r = -0.46; P = 0.04) in MTBI patients. In addition, there was significantly higher thalamocortical connectivity that correlated with clustering coefficient (r = 0.39; P = 0.03) in patients. Also, patients with higher clustering coefficient tended to have less PCS score with negative correlation (r = -0.4; P = 0.04).
  
  
  
  Our results demonstrated significant functional small-world properties changes in patients with MTBI, and suggest decreased global efficiency, possibly due to diffuse axonal injury and local network upregulation including increased thalamo-cortical connectivity.
  
  
  
  2 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:518-527.
authors.affiliation: Department of Radiology / Center for Biomedical Imaging, NYU Langone Medical Center, New York, New York.
authors.forename: Yongxia
authors.initials: Y
authors.lastname: Zhou
mesh_terms: D000328:Adult; D001369:Axons / Q000473:pathology; D001921:Brain / Q000503:physiopathology; D001930:Brain Injuries / Q000503:physiopathology; D000070642:Brain Injuries, Traumatic / Q000000981:diagnostic imaging* / Q000503:physiopathology; D016022:Case-Control Studies; D056324:Diffusion Tensor Imaging; D017352:Echo-Planar Imaging; D005260:Female; D015600:Glasgow Coma Scale; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D038223:Post-Concussion Syndrome / Q000000981:diagnostic imaging* / Q000503:physiopathology; D055815:Young Adult
keywords: diffusion tensor imaging; functional connectivity; graph theory; mild traumatic brain injury; postconcussive symptom; small-world property