Diffusion tensor imaging of hippocampal network plasticity
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Diffusion tensor imaging (DTI) has become a valuable tool to investigate white matter integrity in the brain. DTI also gives contrast in gray matter, which has been relatively little explored in studies assessing post-injury structural abnormalities. The present study was designed to compare white and gray matter reorganization in the rat hippocampus after two epileptogenic brain injuries, status epilepticus (SE) and traumatic brain injury (TBI), using ex vivo high-resolution DTI. Imaging was performed at 6–12 months post-injury and findings were compared to histological analyses of Nissl, myelin, and Timm-stained preparations from the same animals. In agreement with the severity of histological damage, fractional anisotropy (FA), axial (D ||) and radial (D ⊥) diffusivities, and mean diffusivity (MD) measurements were altered in the order SE > TBI ipsilaterally > TBI contralaterally. After SE, the most severe abnormalities were found in the dentate gyrus and CA3b–c subfields, in which the mean FA was increased to 125 % (p < 0.001) and 143 % (p < 0.001) of that in controls, respectively. In both subfields, the change in FA was associated with an increase in D || (p < 0.01). In the stratum radiatum of the CA1, FA was decreased to 81 % of that in controls (p < 0.05) which was associated with an increase in D ⊥ (p < 0.01). After TBI, DTI did not reveal any major abnormalities in the dentate gyrus. In the ipsilateral CA3b–c, however, FA was increased to 126 % of that in controls (p < 0.01) and associated with a mild decrease in D ⊥ (p < 0.05). In the stratum radiatum of the ipsilateral CA1, FA was decreased to 88 % of that in controls (p < 0.05). Our data demonstrate that DTI reveals subfield-specific abnormalities in the hippocampus with remarkable qualitative and quantitative differences between the two epileptogenic etiologies, suggesting that DTI could be a valuable tool for follow-up of focal circuitry reorganization during the post-injury aftermath.
KeywordsDiffusion tensor imaging Epilepsy Epileptogenesis Hippocampus Magnetic resonance imaging Mossy fiber sprouting Myelin Status epilepticus Traumatic brain injury
Diffusion tensor imaging
Fluid percussion injury
Magnetic resonance imaging
Region of interest
Traumatic brain injury
This study was supported by the Academy of Finland (A.S., O.G., A.P.), Sigrid Juselius Foundation (A.P.), and UEF-Brain strategic funding from the University of Eastern Finland. We thank Ms. Maarit Pulkkinen for assistance in histology, Dr. Jari Nissinen and Dr. Tamuna Bolkvadze for technical assistance, MSc Juha-Pekka Niskanen for drawing the diffusion ellipsoids, and Dr. Nick Hayward for revising the language of the manuscript.
- Baulac M, Pitkänen A (2008) Research priorities in epilepsy for the next decade—a representative view of the European scientific community. EpilepsiaGoogle Scholar
- Buckmaster PS (2012) Mossy fiber sprouting in the dentate gyrus. In: Noebels JL, Avoli M, Rogawski MA, Olsen RW, Delgado-Escueta AV (eds) Jasper’s basic mechanisms of the epilepsies. Michael A Rogawski, Antonio V Delgado-Escueta, Jeffrey L Noebels, Massimo Avoli and Richard W Olsen, BethesdaGoogle Scholar
- de Lanerolle NC, Lee TS, Spencer DD (2012) Histopathology of human epilepsy. In: Noebels JL, Avoli M, Rogawski MA, Olsen RW, Delgado-Escueta AV (eds) Jasper’s basic mechanisms of the epilepsies. Michael A Rogawski, Antonio V Delgado-Escueta, Jeffrey L Noebels, Massimo Avoli and Richard W Olsen, BethesdaGoogle Scholar
- Hauser WA (1997) Incidence and prevalence. In: Engel J Jr, Pedley TA (eds) Epilepsy: a comprehensive textbook. Lippincott-Raven Publishers, Philadelphia, pp 47–57Google Scholar