title: Multiparametric and longitudinal MRI characterization of mild traumatic brain injury in rats.
abstract: This study reports T2 and diffusion-tensor magnetic resonance imaging (MRI) studies of a mild open-skull, controlled cortical impact injury in rats (n=6) from 3 h to up to 14 d after traumatic brain injury (TBI). Comparison was made with longitudinal behavioral measurements and end-point histology. The impact was applied over the left primary forelimb somatosensory cortex (S1FL). The major findings were: 1) In the S1FL, T2 increased and fractional anisotropy (FA) decreased at 3 h after TBI and gradually returned toward normal by Day 14; 2) in the S1FL, the apparent diffusion coefficient (ADC) increased at 3 h, peaked on Day 2, and gradually returned toward normal at Day 14; 3) in the corpus callosum underneath the S1FL, FA decreased at 3 h to Day 2 but returned to normal at Day 7 and 14, whereas T2 and ADC were normal throughout; 4) heterogeneous hyperintense and hypointense T2 map intensities likely indicated the presence of hemorrhage but were not independently verified; 5) lesion volumes defined by abnormal T2, ADC, and FA showed similar temporal patterns, peaking around Day 2 and returning toward normal on Day 14; 6) the temporal profiles of lesion volumes were consistent with behavioral scores assessed by forelimb placement and forelimb foot fault tests; and 7) at 14 d post-TBI, there was substantial tissue recovery by MRI, which could either reflect true tissue recovery or reabsorption of edema. Histology performed 14 d post-TBI, however, showed a small cavitation and significant neuronal degeneration surrounding the cavitation in S1FL. Thus, the observed improvement of behavioral scores likely involves both functional recovery and functional compensation.
authors.affiliation: 1 Research Imaging Institute, University of Texas Health Science Center at San Antonio , San Antonio, Texas.
authors.forename: Justin Alexander
authors.initials: JA
authors.lastname: Long
authors.forename: Lora Talley
authors.initials: LT
authors.lastname: Watts
authors.forename: Jonathan
authors.initials: J
authors.lastname: Chemello
authors.forename: Shiliang
authors.initials: S
authors.lastname: Huang
authors.forename: Qiang
authors.initials: Q
authors.lastname: Shen
authors.forename: Timothy Q
authors.initials: TQ
authors.lastname: Duong
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D001930:Brain Injuries / Q000473:pathology* / Q000503:physiopathology; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D020127:Recovery of Function
keywords: TBI; behavioral assessments; controlled cortical impact; diffusion tensor imaging; immunohistochemistry; quantitative magnetic resonance imaging