Background: The acute changes that occur in the small-world topology of
the brain in concussion patients remain unclear. Here, we investigated acute
changes in the small-world organization of brain networks in concussion patients
and their influence on persistent post-concussion symptoms. Methods:
Eighteen concussion patients and eighteen age-matched controls were enrolled in
this study. All participants underwent computed tomography, magnetic resonance
imaging (MRI), susceptibility weighted imaging, and blood oxygen level-dependent
functional MRI. A complex network analysis method based on graph theory was used
to calculate the parameters of small-world networks under different degrees of
network sparsity. All subjects were evaluated using the Glasgow Coma Scale and
Rivermead Postconcussion Symptom Questionnaire. Results: Compared with
the controls, the normalized cluster coefficient () of whole brain
networks in patients and the “small-world” index () was slightly
enhanced, whereas the standardized minimum path () was slightly
shorter. Whole brain effect (Eglobal) and local effect (Elocal) changes were not
pronounced. Under the condition of minimum network sparsity (Dmin = 0.13), the
numbers of nodes in the “right intraorbital superior frontal gyrus” (Anatomical Automatic Labeling, AAL26),
right globus pallidus (AAL76), and bilateral temporal transverse gyrus (AAL79,80)
in brain concussion patients were significantly lower. The numbers of nodes in
the left subcapital lobe (AAL61) and left occipital gyrus (AAL51) were
significantly higher, and the normalized cluster coefficients of the right
intraorbital supraphalus (AAL26) and left posterior cingulate gyrus (AAL35) were
significantly increased. The normalized clustering coefficients of the right
triangular subfrontal gyrus (AAL55) (based on the normalized clustering
coefficients of nodes in AAL14) and left sub-parietal lobes (AAL61) were
significantly reduced. The mean local effects of nodes in the right intraorbital
upper frontal gyrus (AAL26), left posterior cingulate gyrus (AAL35), and
bilateral auxiliary motor cortex (AAL19, 20) were enhanced, whereas the mean
local effects of the bilateral triangular inferior frontal gyrus (AAL13,14) and
left insular cap (AAL11) were reduced (p 0.05).
Conclusions: The overall trend of network topology
abnormalities in patients was random, and generalized and local functional
abnormalities were seen. Changes in the function and affective circuitry of the
resting default network were particularly pronounced in these patients, which we
speculate may be one of the main drivers of the cognitive dysfunction and mood
changes seen in concussion patients.