title: Brain structure alterations and cognitive impairment following repetitive mild head impact: An in vivo MRI and behavioral study in rat.
abstract: Mild traumatic brain injury (mTBI) or concussion is a common health issue. Several people repeatedly experience head impact milder than that causing concussion. The present study aimed to confirm the effects of such repeated impact on the brain structure and cognitive abilities. Rat models were established by closed skull weight-drop injury. The animals were anesthetized, subjected to single (s)-sham, s-mTBI, repetitive (r)-sham, and r-mTBI, and recovery times were recorded. MRI, including T2-weighted and diffusion tensor imaging (DTI), as well as, neurological severity scores (mNSS) were assessed for the dynamics of the brain structure and neurological function. Morris water maze (MWM) was used to evaluate the cognitive function. The histological examination of r-mTBI rats revealed the basis of structural changes in the brain. There was no significant difference in the recovery time, MRI, mNSS, and MWM between the s-sham and the s-mTBI groups. Compared with r-sham, r-mTBI induced significant differences in the following aspects. The recovery time was prolonged and beam balance test (BBT) in mNSS increased from day 5. MWM performances were worse even after the BBT was recovered. The volumes of the cortex (CT), hippocampus (HP), and lateral ventricle had changed from day 5, which reached a maximum at day 14. Abnormal DTI parameters were observed in CT, corpus callosum, and HP. Histological analyses showed that both in CT and HP, neuron counts reduced at the end of the experiment. Altogether, these findings indicate that non-symptomatic head injury may result in brain atrophy and cognitive impairment when occurred repeatedly.
authors: Department of Postgraduate, Third Military Medical University, Chongqing, China; Department of Neurosurgery, Chengdu Military General Hospital, Chengdu, China.
authors: Yang
authors: Y
authors: Qin
authors: Department of Geriatrics, Chengdu Military General Hospital, Chengdu, China.
authors: Gai-Li
authors: GL
authors: Li
authors: Department of Geriatrics, Chengdu Military General Hospital, Chengdu, China.
authors: Xian-Hua
authors: XH
authors: Xu
authors: Department of Neurosurgery, Chengdu Military General Hospital, Chengdu, China.
authors: Zhi-Yong
authors: ZY
authors: Sun
authors: Department of Neurosurgery, Chengdu Military General Hospital, Chengdu, China; Department of Neurosurgery, The 306th Hospital of PLA, Beijing, China. Electronic address: 18712482@qq.com.
authors: Jian-Wen
authors: JW
authors: Gu
authors: Department of Radiology, West China Hospital, Sichuan University, Sichuan, China. Electronic address: gaofabao@yahoo.com.
authors: Fa-Bao
authors: FB
authors: Gao
mesh_terms: D000818:Animals; D001284:Atrophy; D001921:Brain / Q000000981:diagnostic imaging* / Q000473:pathology; D001924:Brain Concussion / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000523:psychology*; D060825:Cognitive Dysfunction / Q000000981:diagnostic imaging* / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D056324:Diffusion Tensor Imaging; D004195:Disease Models, Animal; D018450:Disease Progression; D066128:Gray Matter / Q000000981:diagnostic imaging / Q000293:injuries / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D018782:Maze Learning; D009048:Motor Skills; D009929:Organ Size; D017207:Rats, Sprague-Dawley; D066127:White Matter / Q000000981:diagnostic imaging / Q000293:injuries / Q000473:pathology
keywords: Behavior; Diffusion tensor imaging; In vivo studies; MRI; Traumatic brain injury