Comparative study of the volume and fiber of frontal lobe in amnestic mild cognitive impairment

Objective To detect the fiber structure and volume differences in frontal lobe between patients with amnestic mild cognitive impairment (aMCI) and normal control. Methods T1-weighted magnetic resonance imaging and diffusion tensor imaging were obtained in 28 aMCI patients and 25 normal controls. Volumes, fiber fractional anisotropy (FA), fiber apparent diffusion coefficient (ADC), fiber number, and average fiber length of frontal lobe in the two groups were measured. Results Volumes of left frontal lobe ((337.35±20.45)cm3) in aMCI group were smaller than control ((358.54±27.26)cm3) (t=-3.223, P=0.002). Numbers of short range fiber in left frontal lobe (16985±892) were significantly increased relative to control (16387±752); while numbers of long range fiber (3214±185) were reduced compared with control (3425±277), and ADC values increased (t=2.621, P=0.012; t=-3.714, P=0.001; t=17.595, P=0.000). In aMCI group, numbers of long range fiber in right frontal lobe were reduced (2895±343 vs. 3451±230, t=-7.011, P=0.000), and ADC values were increased (t=4.443, P=0.000). In aMCI group, numbers of long range fiber in left frontal lobe were positively correlated with scores of mini-mental state examination (MMSE) (r=0.457, P=0.015), while ADC values of long range fiber in left frontal lobe were negatively correlated with scores of MMSE (r=-0.415, P=0.028). Conclusion The structure and fiber connectivity are affected in aMCI patients and the lesion of connectivity in left frontal lobe are related to the severity of symptom. Key words: Amnestic mild cognitive impairment; Magnetic resonance imaging; Fiber tractography