Mental fatigue after mild traumatic brain injury: a 3D-ASL perfusion study.

Our purpose was to evaluate mental fatigue associated with mild traumatic brain injury (MTBI) and investigate the underlying neurological mechanisms. We used a 20-min psychomotor vigilance test (PVT) related ASL-fMRI to evaluate mental fatigue in 25 MTBI patients in acute phase, 21 MTBI patients in chronic phase, and 20 healthy subjects. Mental fatigue in patients in acute phase was more severe than in chronic phase patients and healthy controls. The first 5-min-PVT increased CBF of patients in acute phase in "bottom-up" and "top-down" attention areas, and decreased CBF in default mode network (DMN) areas. Twenty-min-PVT results showed that sustained attention of patients was more fragile than in healthy subjects, while sustained attention in the acute phase was less stable than that in the chronic phase. CBF results showed that in patients in the acute phase, the second, third, and last 5-min-PVT decreased CBF in DMN areas, increased CBF of "bottom-up" and "top-down" areas; in the chronic phase, the third and last 5-min-PVT increased CBF of "bottom-up" and "top-down" cortex, while the second 5-min-PVT only increased CBF of the "top-down" cortex. Mental fatigue of MTBI patients persists for more than 12 months, and can be mitigated partly within the first year after injury. The "bottom-up" and "top-down" deficits result in mental fatigue of MTBI patients.