title: Microstructural Integrity of Hippocampal Subregions Is Impaired after Mild Traumatic Brain Injury.
abstract: Mild traumatic brain injury (mTBI) affects a large number of individuals and diffusion tensor imaging can be used to investigate microstructural integrity of brain tissue after mTBI. However, results have varied considerably between studies and gray matter (GM) integrity has been largely neglected in these investigations. Given impaired working memory processing after mTBI and its possible association with Alzheimer's disease, we investigated hippocampal integrity and parcellated this structure into five subregions: subiculum, cornu ammonis (CA) 1, CA 2/3, CA 4/dentate gyrus, and stratum radiatum/lacunosum-moleculare. We also employed shape analysis of bilateral hippocampi to explore whether morphological changes had occurred due to the traumatic injury and conducted neuropsychological memory tests. The sample comprised 15 subjects with mTBI (18-55 years, nine female) and 13 age- and sex-matched healthy control subjects (19-57 years, nine female). Voxelwise analyses showed significantly increased mean diffusivity in patients, compared with controls, in the right hippocampus and three of its five subregions (family-wise error corrected p < 0.05). Additionally, results from probabilistic tractography indicated impaired CA 1 connectivity after mTBI (Benjamini-Hochberg false discovery rate [FDR] corrected p < 0.05). Shape of bilateral hippocampi did not significantly differ between groups (Benjamini-Hochberg FDR corrected p > 0.05). Subjects with mTBI reported more symptoms and performed worse in a non-standard verbal working memory task. Based on these preliminary findings, we were able to demonstrate altered diffusivity of hippocampal subregions following mTBI, indicating impaired GM microstructural integrity. These differences highlight the potential of diffusion imaging for investigation of subtle yet relevant changes in GM microstructure not detected otherwise following mTBI.
authors: 1 Institute for Regenerative Medicine, University of Zurich , Switzerland .
authors: Sandra E
authors: SE
authors: Leh
authors: 1 Institute for Regenerative Medicine, University of Zurich , Switzerland .
authors: Clemens
authors: C
authors: Schroeder
authors: 2 Cognitive Neuroscience Unit, Montreal Neurological Institute , Montreal, Quebec, Canada .|3 Department of Psychology, McGill University Health Centre , Montreal, Quebec, Canada .
authors: Jen-Kai
authors: JK
authors: Chen
authors: 4 Cerebral Imaging Centre, Douglas Mental Health University Institute, McGill University , Montreal, Quebec, Canada .|5 Departments of Psychiatry and Biomedical Engineering, McGill University , Montreal, Quebec, Canada .
authors: M
authors: M
authors: Mallar Chakravarty
authors: 4 Cerebral Imaging Centre, Douglas Mental Health University Institute, McGill University , Montreal, Quebec, Canada .|6 Schulich School of Medicine and Dentistry, Western University , London, Ontario, Canada .
authors: Min Tae M
authors: MT
authors: Park
authors: 7 Defense Research and Development Canada (DRDC) Toronto , Ontario, Canada .
authors: Bob
authors: B
authors: Cheung
authors: 2 Cognitive Neuroscience Unit, Montreal Neurological Institute , Montreal, Quebec, Canada .|8 Department of Psychology, McGill University , Montreal, Quebec, Canada .
authors: Sonja C
authors: SC
authors: Huntgeburth
authors: 9 Research Center , Hôpital du Sacré-Coeur de Montréal, Montreal, Quebec, Canada .
authors: Nadia
authors: N
authors: Gosselin
authors: 1 Institute for Regenerative Medicine, University of Zurich , Switzerland .
authors: Christoph
authors: C
authors: Hock
authors: 2 Cognitive Neuroscience Unit, Montreal Neurological Institute , Montreal, Quebec, Canada .|3 Department of Psychology, McGill University Health Centre , Montreal, Quebec, Canada .
authors: Alain
authors: A
authors: Ptito
authors: 2 Cognitive Neuroscience Unit, Montreal Neurological Institute , Montreal, Quebec, Canada .|8 Department of Psychology, McGill University , Montreal, Quebec, Canada .
authors: Michael
authors: M
authors: Petrides
mesh_terms: D000293:Adolescent; D000328:Adult; D001924:Brain Concussion / Q000150:complications / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D056547:CA1 Region, Hippocampal / Q000000981:diagnostic imaging; D056651:CA2 Region, Hippocampal / Q000000981:diagnostic imaging; D056654:CA3 Region, Hippocampal / Q000000981:diagnostic imaging; D060825:Cognitive Dysfunction / Q000209:etiology / Q000503:physiopathology*; D018891:Dentate Gyrus / Q000000981:diagnostic imaging; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D006624:Hippocampus / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D008875:Middle Aged; D055815:Young Adult
keywords: diffusion tensor imaging; hippocampal subfields; mild traumatic brain injury; shape analysis