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Ylä-Herttuala S, Hakulinen M, Poutiainen P, Lötjönen J, Könönen M, Gröhn H, Vanninen R, Mussalo H, Laitinen T, Mervaala E. Decreased Gray-White Matter Contrast of [11C]-PiB Uptake in Cognitively Unimpaired Subjects with Severe Obstructive Sleep Apnea. J Prev Alzheimers Dis 2022; 9:499-506. [PMID: 35841251 DOI: 10.14283/jpad.2022.24] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
BACKGROUND Very recently, cognitively normal, middle-aged adults with severe obstructive sleep apnea (OSA) were shown to have regional cortical amyloid-β deposits. In the normal brain, amyloid tracer (e.g., [11C]-PiB) uptake is observed in white matter (WM) but not in cortical gray matter (GM), resulting in clear GM-WM contrast. There are no reports on possible changes in this contrast in severe OSA. OBJECTIVES Evaluate changes in the global [11C]-PiB GM-WM contrast and study if factors reflecting clinical and imaging characteristics are associated with them. DESIGN AND SETTING Cross-sectional imaging study. PARTICIPANTS 19 cognitively intact middle-aged (mean 44 years) patients with severe OSA (Apnea-Hypopnea Index >30/h), carefully selected to exclude any other possible factors that could alter brain health. MEASUREMENTS Detailed neuroimaging (amyloid PET, MRI). Signs of possible alterations in amyloid tracer GM-WM contrast and kinetics were studied with static and dynamic [11C]-PiB PET and WM structures with detailed 3.0T MRI. RESULTS Static [11C]-PiB PET uptake showed significantly decreased GM-WM contrast in 5 out of 19 patients. This was already clearly seen in visual evaluation and also detected quantitatively using retention indexes. Dynamic imaging revealed decreased contrast due to alterations in trace accumulation in the late phase of [11C]-PiB kinetics. Decreased GM-WM contrast in the late phase was global in nature. MRI revealed no corresponding alterations in WM structures. Importantly, decreased GM-WM contrast was associated with smoking (p = 0.007) and higher Apnea-Hypopnea Index (p = 0.001). CONCLUSIONS Severe OSA was associated with decreased GM-WM contrast in amyloid tracer uptake, with significant correlation with clinical parameters of smoking and AHI. The results support and further extend the current understanding of the deleterious effect of severe OSA on proper amyloid clearance, possibly reflecting dysfunction of the brain glymphatic system.
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Affiliation(s)
- S Ylä-Herttuala
- Professor Esa Mervaala, M.D., Ph.D. Department of Clinical Neurophysiology, Kuopio University Hospital, POB 100, 70029 KYS, Finland, ORCID ID: 0000-0001-5682-5747, Mobile: +358-44-7113245, , Fax: +358-17-173244
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Shen Q, Heikkinen N, Kärkkäinen O, Gröhn H, Könönen M, Liu Y, Kaarre O, Zhang Z, Tan C, Tolmunen T, Vanninen R. Effects of long-term adolescent alcohol consumption on white matter integrity and their correlations with metabolic alterations. Psychiatry Res Neuroimaging 2019; 294:111003. [PMID: 31726326 DOI: 10.1016/j.pscychresns.2019.111003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Revised: 10/24/2019] [Accepted: 10/25/2019] [Indexed: 12/28/2022]
Abstract
Alcohol-related white matter (WM) microstructural changes have not been fully elucidated in adolescents. We aimed to investigate influences of subclinical alcohol use during adolescence on WM microstructure and to characterize those with serum metabolic alterations. 35 moderate-to-heavy drinkers (15 males, 20 females) and 27 controls (12 males, 15 females) were selected based on their ten-year Alcohol Use Disorders Identification Test scores measured at three time points. Magnetic resonance imaging was conducted at endpoint time. Whole brain analysis of fractional anisotropy (FA) was performed. Diffusivity indices in the significant regions were computed for between-group comparisons and correlation analyses with serum metabolite concentrations. Decreased FA was found in moderate-to-heavy drinking men in anterior corpus callosum, superior/anterior corona radiata and right inferior fronto-occipital fasciculus, accompanied by increased radial diffusivity and a smaller area of reduced axial diffusivity, which correlated with serum metabolites playing roles in energy metabolism, myelination and axonal degeneration. No significant difference in FA was detected between female or mixed-gender moderate-to-heavy drinking subjects and controls, supporting gender differences in the relationship between adolescent alcohol use and neurodevelopmental trajectories. Future researches with longitudinal imaging data are warranted for comprehensive evaluation on potentially reversible effects of alcohol use over adolescent brain.
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Affiliation(s)
- Qin Shen
- Department of Radiology, the Second Xiangya Hospital of Central South University, Changsha, China; Department of Clinical Radiology, Kuopio University Hospital, Kuopio, Finland
| | - Noora Heikkinen
- Department of Clinical Radiology, Kuopio University Hospital, Kuopio, Finland; Doctoral Programme of Clinical Research, School of Medicine, University of Eastern Finland, Kuopio, Finland
| | - Olli Kärkkäinen
- Institute of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, Finland; Department of Forensic Psychiatry, University of Eastern Finland, Niuvanniemi Hospital, Finland; School of Pharmacy, University of Eastern Finland, Kuopio, Finland
| | - Heidi Gröhn
- Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital, Kuopio, Finland
| | - Mervi Könönen
- Department of Clinical Radiology, Kuopio University Hospital, Kuopio, Finland; Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland
| | - Yawu Liu
- Department of Clinical Radiology, Kuopio University Hospital, Kuopio, Finland; Department of Neurology, University of Kuopio, Kuopio, Finland
| | - Outi Kaarre
- Doctoral Programme of Clinical Research, School of Medicine, University of Eastern Finland, Kuopio, Finland; Department of Adolescent Psychiatry, Kuopio University Hospital, Kuopio, Finland
| | - Zishu Zhang
- Department of Radiology, the Second Xiangya Hospital of Central South University, Changsha, China
| | - Changlian Tan
- Department of Radiology, the Second Xiangya Hospital of Central South University, Changsha, China
| | - Tommi Tolmunen
- Department of Psychiatry, Kuopio University Hospital, Kuopio, Finland; Department of Psychiatry, School of Medicine, University of Eastern Finland, Kuopio, Finland
| | - Ritva Vanninen
- Department of Clinical Radiology, Kuopio University Hospital, Kuopio, Finland; Department of Clinical Radiology, School of Medicine, University of Eastern Finland, Kuopio, Finland.
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Gröhn H, Gillick BT, Tkáč I, Bednařík P, Mascali D, Deelchand DK, Michaeli S, Meekins GD, Leffler-McCabe MJ, MacKinnon CD, Eberly LE, Mangia S. Influence of Repetitive Transcranial Magnetic Stimulation on Human Neurochemistry and Functional Connectivity: A Pilot MRI/MRS Study at 7 T. Front Neurosci 2019; 13:1260. [PMID: 31827419 PMCID: PMC6890551 DOI: 10.3389/fnins.2019.01260] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 11/06/2019] [Indexed: 12/13/2022] Open
Abstract
Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation method commonly used in the disciplines of neuroscience, neurology, and neuropsychiatry to examine or modulate brain function. Low frequency rTMS (e.g., 1 Hz) is associated with a net suppression of cortical excitability, whereas higher frequencies (e.g., 5 Hz) purportedly increase excitability. Magnetic resonance spectroscopy (MRS) and resting-state functional MRI (rsfMRI) allow investigation of neurochemistry and functional connectivity, respectively, and can assess the influence of rTMS in these domains. This pilot study investigated the effects of rTMS on the primary motor cortex using pre and post MRS and rsfMRI assessments at 7 T. Seven right-handed males (age 27 ± 7 y.o.) underwent single-voxel MRS and rsfMRI before and about 30-min after rTMS was administered outside the scanner for 20-min over the primary motor cortex of the left (dominant) hemisphere. All participants received 1-Hz rTMS; one participant additionally received 5-Hz rTMS in a separate session. Concentrations of 17 neurochemicals were quantified in left and right motor cortices. Connectivity metrics included fractional amplitude of low-frequency fluctuations (fALFF) and regional homogeneity (ReHo) of both motor cortices, strength of related brain networks, and inter-hemispheric connectivity. The group-analysis revealed few trends (i.e., uncorrected for multiple comparisons), including a mean increase in the concentration of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) after the inhibitory rTMS protocol as compared to baseline in the stimulated (left) motor cortex (+8%, p = 0.043), along with a slight increase of total creatine (+2%, p = 0.018), and decrease of aspartate (-18%, p = 0.016). Additionally, GABA tended to decrease in the contralateral hemisphere (-6%, p = 0.033). No other changes of metabolite concentrations were found. Whereas functional connectivity outcomes did not exhibit trends of significant changes induced by rTMS, the percent changes of few connectivity metrics in both hemispheres were negatively correlated with GABA changes in the contralateral hemisphere. While studies in larger cohorts are needed to confirm these preliminary findings, our results indicate the safety and feasibility of detecting changes in key metabolites associated with neurotransmission after a single 1-Hz rTMS session, establishing the construct for future exploration of the neurochemical, and connectivity mechanisms of cortical responses to neuromodulation.
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Affiliation(s)
- Heidi Gröhn
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States.,Diagnostic Imaging Center, Kuopio University Hospital, Kuopio, Finland
| | - Bernadette T Gillick
- Department of Rehabilitation Medicine, University of Minnesota, Minneapolis, MN, United States
| | - Ivan Tkáč
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States
| | - Petr Bednařík
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States.,Department of Biomedical Imaging and Image-guided Therapy, High Field MR Centre, Medical University of Vienna, Vienna, Austria
| | - Daniele Mascali
- Museo Storico della Fisica e Centro Studi e Ricerche "Enrico Fermi", Rome, Italy
| | - Dinesh K Deelchand
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States
| | - Shalom Michaeli
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States
| | - Gregg D Meekins
- Department of Neurology, University of Minnesota, Minneapolis, MN, United States
| | | | - Colum D MacKinnon
- Department of Neurology, University of Minnesota, Minneapolis, MN, United States
| | - Lynn E Eberly
- Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, MN, United States
| | - Silvia Mangia
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States
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Siiki A, Jesenofsky R, Löhr M, Nordback I, Kellomäki M, Gröhn H, Mikkonen J, Sand J, Laukkarinen J. Biodegradable biliary stents have a different effect than covered metal stents on the expression of proteins associated with tissue healing in benign biliary strictures. Scand J Gastroenterol 2016; 51:880-5. [PMID: 27003149 DOI: 10.3109/00365521.2016.1156153] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Benign biliary strictures (BBS) are primarily treated endoscopically with covered self-expandable metal stents (CSEMS). Biodegradable biliary stents (BDBS) may be the future of endoscopic therapy of BBS. The aim was to assess the expression of proteins related to tissue healing in BBS compared with the intact bile duct (BD), and to study the protein expression after therapy with CSEMS or BDBS. METHODS Pigs with ischemic BBS were endoscopically treated either with BDBS or CSEMS. Samples were harvested from pigs with intact BD (n = 5), untreated BBS (n = 5), and after six months of therapy with BDBS (n = 4) or CSEMS (n = 5) with subsequent histologic analysis. Two-dimensional electrophoresis with protein identification was performed to evaluate protein expression patterns. RESULTS In BBS, the expression of galectin-2 and annexin-A4 decreased, compared to intact BD. Treatment with biodegradable stents normalized galectin-2 level; with CSEMS therapy it remained low. Transgelin expression of intact BD and BBS remained low after BDBS treatment but increased after CSEMS therapy. Histologic analysis did not show unwanted foreign body reaction or hyperplasia in the BD in either group. CONCLUSIONS The expression of proteins related to tissue healing in BBS is different after treatment with biodegradable stents and CSEMS. Treatment with biodegradable stents may bring protein expression towards what is seen in intact BD. BDBS seem to have a good biocompatibility.
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Affiliation(s)
- Antti Siiki
- a Department of Gastroenterology and Alimentary Tract Surgery , Tampere University Hospital , Tampere , Finland
| | - Ralf Jesenofsky
- b Department of Medicine II , University of Heidelberg , Mannheim , Germany
| | - Matthias Löhr
- c Karolinska University Hospital, Gastrocentrum , Huddinge , Sweden
| | - Isto Nordback
- a Department of Gastroenterology and Alimentary Tract Surgery , Tampere University Hospital , Tampere , Finland
| | - Minna Kellomäki
- d Biomaterials and Tissue Engineering Group, BioMediTech and Department of Electronics and Communications Engineering , Tampere University of Technology , Tampere , Finland
| | - Heidi Gröhn
- e Department of Clinical Physiology and Nuclear Medicine , Kuopio University Hospital , Kuopio , Finland
| | - Joonas Mikkonen
- d Biomaterials and Tissue Engineering Group, BioMediTech and Department of Electronics and Communications Engineering , Tampere University of Technology , Tampere , Finland
| | - Juhani Sand
- a Department of Gastroenterology and Alimentary Tract Surgery , Tampere University Hospital , Tampere , Finland
| | - Johanna Laukkarinen
- a Department of Gastroenterology and Alimentary Tract Surgery , Tampere University Hospital , Tampere , Finland
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Miettinen PS, Jauhiainen AM, Tarkka IM, Pihlajamäki M, Gröhn H, Niskanen E, Hänninen T, Vanninen R, Soininen H. Long-Term Response to Cholinesterase Inhibitor Treatment Is Related to Functional MRI Response in Alzheimer's Disease. Dement Geriatr Cogn Disord 2016; 40:243-55. [PMID: 26305064 DOI: 10.1159/000435948] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/12/2015] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Treatment of Alzheimer's disease (AD) with cholinesterase inhibitors (ChEI) enhances cholinergic activity and alleviates clinical symptoms. However, there is variation in the clinical response as well as system level changes revealed by functional MRI (fMRI) studies. METHODS We investigated 18 newly diagnosed mild AD patients with fMRI using a face recognition task after a single oral dose of rivastigmine, a single dose of placebo and 1-month treatment with rivastigmine. The clinical follow-up took place at 6 and 12 months. RESULTS MMSE score difference between baseline and the follow-ups showed a positive correlation with fMRI activation difference between treatment and placebo in the right prefrontal cortex. A negative correlation was found for the left prefrontal cortex and the left fusiform gyrus. In addition, greater signal intensity in the right versus the left fusiform gyrus predicted a response to ChEI with increasing MMSE scores during the follow-up with 77.8% sensitivity and 77.8% specificity. CONCLUSIONS The increased fMRI activation by cholinergic stimulation in brain areas associated with the processing of the visual task reveals still functioning brain networks and a subsequent positive effect of ChEI on cognition. Thus, fMRI may be useful for identifying AD patients most likely to respond to treatment with ChEI.
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Affiliation(s)
- Pekka S Miettinen
- Department of Neurology, University of Eastern Finland, Kuopio, Finland
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Kallioniemi E, Könönen M, Säisänen L, Gröhn H, Julkunen P. Functional neuronal anisotropy assessed with neuronavigated transcranial magnetic stimulation. J Neurosci Methods 2015; 256:82-90. [PMID: 26335800 DOI: 10.1016/j.jneumeth.2015.08.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Revised: 08/02/2015] [Accepted: 08/25/2015] [Indexed: 01/28/2023]
Abstract
BACKGROUND Transcranial magnetic stimulation (TMS) can evaluate cortical excitability and integrity of motor pathways via TMS-induced responses. The responses are affected by the orientation of the stimulated neurons with respect to the direction of the TMS-induced electric field. Therefore, besides being a functional imaging tool, TMS may potentially assess the local structural properties. Yet, TMS has not been used for this purpose. NEW METHOD A novel principle to evaluate the relation between function and structure of the motor cortex is presented. This functional anisotropy is evaluated by an anisotropy index (AI), based on motor evoked potential amplitudes induced with different TMS coil orientations, i.e. different electric field directions at a cortical target. To compare the AI with anatomical anisotropy in an explorative manner, diffusion tensor imaging-derived fractional anisotropy (FA) was estimated at different depths near the stimulation site. RESULTS AI correlated inversely with cortical excitability through the TMS-induced electric field at motor threshold level. Further, there was a trend of negative correlation between AI and FA. COMPARISON WITH EXISTING METHODS None of the existing methods alone can detect the relationship between direct motor cortex activation and local neuronal structure. CONCLUSIONS The AI appears to provide information on the functional neuronal anisotropy of the motor cortex by coupling neurophysiology and neuroanatomy within the stimulated cortical region. The AI could prove useful in the evaluation of neurological disorders and traumas involving concurrent structural and functional changes in the motor cortex. Further studies on patients are needed to confirm the usability of AI.
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Affiliation(s)
- Elisa Kallioniemi
- Department of Clinical Neurophysiology, Kuopio University Hospital, P.O. Box 100, FI-70029 KYS, Finland; Department of Applied Physics, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland.
| | - Mervi Könönen
- Department of Clinical Neurophysiology, Kuopio University Hospital, P.O. Box 100, FI-70029 KYS, Finland; Department of Clinical Radiology, Kuopio University Hospital, P.O. Box 100, FI-70029 KYS, Finland
| | - Laura Säisänen
- Department of Clinical Neurophysiology, Kuopio University Hospital, P.O. Box 100, FI-70029 KYS, Finland; Institute of Clinical Medicine, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland
| | - Heidi Gröhn
- Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital, P.O. Box 100, FI-70029 KYS, Finland
| | - Petro Julkunen
- Department of Clinical Neurophysiology, Kuopio University Hospital, P.O. Box 100, FI-70029 KYS, Finland; Department of Applied Physics, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland
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Jokivarsi KT, Hiltunen Y, Gröhn H, Tuunanen P, Gröhn OHJ, Kauppinen RA. Estimation of the onset time of cerebral ischemia using T1rho and T2 MRI in rats. Stroke 2010; 41:2335-40. [PMID: 20814006 DOI: 10.1161/strokeaha.110.587394] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Time of ischemia onset is the most critical factor for patient selection for available drug treatment strategies. The purpose of this study was to evaluate the abilities of the absolute longitudinal rotating frame (T(1ρ)) and transverse (T(2)) MR relaxation times to estimate the onset time of ischemia in rats. METHODS Permanent middle cerebral artery occlusion in rats was used to induce focal cerebral ischemia and animals were imaged with multiparametric MRI at several time points up to 7 hours postischemia. Ischemic parenchyma was defined as tissue with apparent diffusion coefficient of water <70% from that in the contralateral nonischemic brain. RESULTS The difference in the absolute T(1ρ) and T(2) between ischemic and contralateral nonischemic striatum increased linearly within the first 6 hours of middle cerebral artery occlusion. The slopes for T(1ρ) and T(2) fits for both tissue types were similar; however, the time offsets were significantly longer for both MR parameters in the cortex than in the striatum. CONCLUSIONS T(1ρ) and T(2) MRI provide estimates for the onset time of cerebral ischemia requiring regional calibration curves from ischemic brain. Assuming that patients with suspected ischemic stroke are scanned by MRI within this timeframe, these MRI techniques may constitute unbiased tools for stroke onset time evaluation potentially aiding the decision-making for drug treatment strategies.
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Immonen RJ, Kharatishvili I, Gröhn H, Pitkänen A, Gröhn OHJ. Quantitative MRI predicts long-term structural and functional outcome after experimental traumatic brain injury. Neuroimage 2008; 45:1-9. [PMID: 19101638 DOI: 10.1016/j.neuroimage.2008.11.022] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Revised: 11/19/2008] [Accepted: 11/21/2008] [Indexed: 11/16/2022] Open
Abstract
In traumatic brain injury (TBI) the initial impact causes both immediate damage and also launches a cascade of slowly progressive secondary damage. The chronic outcome disabilities vary greatly and can occur several years later. The aim of this study was to find predictive factors for the long-term outcome using multiparametric, non-invasive magnetic resonance imaging (MRI) methodology and a clinically relevant rat model of fluid percussion induced TBI. Our results demonstrated that the multiparametric quantitative MRI (T(2), T(1rho), trace of the diffusion tensor D(av), the extent of hyperintense lesion and intracerebral hemorrhage) acquired during acute and sub acute phases 3 h, 3 days, 9 days and 23 days post-injury has potential to predict the functional and histopathological outcome 6 to 12 months later. The acute D(av) changes in the ipsilateral hippocampus correlated with the chronic spatial learning and memory impairment evaluated using the Morris water maze (p<0.05). Similarly, T(1rho), T(2) and D(av) correlated with hippocampal atrophy and with histologically quantified neurodegeneration (p<0.01). The early lesion volume and quantitative MRI changes in the perilesional region prefigured the final lesion extent (p<0.01). Furthermore, the severity of acute intracerebral hemorrhage correlated with the final cortical atrophy (p<0.05), hippocampal atrophy (p<0.01), and also with the water maze performance (p<0.01). We conclude that, assessment of early quantitative MRI changes in the hippocampus and in the perifocal area may help to predict the long-term outcome after experimental TBI.
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Affiliation(s)
- Riikka J Immonen
- Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences, University of Kuopio, Finland
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Immonen RJ, Kharatishvili I, Niskanen JP, Gröhn H, Pitkänen A, Gröhn OHJ. Distinct MRI pattern in lesional and perilesional area after traumatic brain injury in rat--11 months follow-up. Exp Neurol 2008; 215:29-40. [PMID: 18929562 DOI: 10.1016/j.expneurol.2008.09.009] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Revised: 08/29/2008] [Accepted: 09/08/2008] [Indexed: 11/30/2022]
Abstract
To understand the dynamics of progressive brain damage after lateral fluid-percussion induced traumatic brain injury (TBI) in rat, which is the most widely used animal model of closed head TBI in humans, MRI follow-up of 11 months was performed. The evolution of tissue damage was quantified using MRI contrast parameters T(2), T(1rho), diffusion (D(av)), and tissue atrophy in the focal cortical lesion and adjacent areas: the perifocal and contralateral cortex, and the ipsilateral and contralateral hippocampus. In the primary cortical lesion area, which undergoes remarkable irreversible pathologic changes, MRI alterations start at 3 h post-injury and continue to progress for up to 6 months. In more mildly affected perifocal and hippocampal regions, the robust alterations in T(2), T(1rho), and D(av) at 3 h to 3 d post-injury normalize within the next 9-23 d, and thereafter, progressively increase for several weeks. The severity of damage in the perifocal and hippocampal areas 23 d post-injury appeared independent of the focal lesion volume. Magnetic resonance spectroscopy (MRS) performed at 5 and 10 months post-injury detected metabolic alterations in the ipsilateral hippocampus, suggesting ongoing neurodegeneration and inflammation. Our data show that TBI induced by lateral fluid-percussion injury triggers long-lasting alterations with region-dependent temporal profiles. Importantly, the temporal pattern in MRI parameters during the first 23 d post-injury can indicate the regions that will develop secondary damage. This information is valuable for targeting and timing interventions in studies aiming at alleviating or reversing the molecular and/or cellular cascades causing the delayed injury.
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Affiliation(s)
- Riikka J Immonen
- Biomedical NMR research group, Biomedical Imaging Unit, Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences, University of Kuopio, P.O.B. 1627, FIN-70211 Kuopio, Finland
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Michaeli S, Gröhn H, Gröhn O, Sorce DJ, Kauppinen R, Springer CS, Uğurbil K, Garwood M. Exchange-influencedT2ρcontrast in human brain images measured with adiabatic radio frequency pulses. Magn Reson Med 2005; 53:823-9. [PMID: 15799068 DOI: 10.1002/mrm.20428] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Transverse relaxation in the rotating frame (T(2rho)) is the dominant relaxation mechanism during an adiabatic Carr-Purcell (CP) spin-echo pulse sequence when no delays are used between pulses in the CP train. The exchange-induced and dipolar interaction contributions (T(2rho,ex) and T(2rho,dd)) depend on the modulation functions of the adiabatic pulses used. In this work adiabatic pulses having different modulation functions were utilized to generate T(2rho) contrast in images of the human occipital lobe at magnetic field of 4 T. T(2rho) time constants were measured using an adiabatic CP pulse sequence followed by an imaging readout. For these measurements, adiabatic full passage pulses of the hyperbolic secant HSn (n = 1 or 4) family having significantly different amplitude-and frequency-modulation functions were used with no time delays between pulses. A dynamic averaging (DA) mechanism (e.g., chemical exchange and diffusion in the locally different magnetic susceptibilities) alone was insufficient to fully describe differences in brain tissue water proton T(2rho) time constants. Measurements of the apparent relaxation time constants (T(2) (dagger)) of brain tissue water as a function of the time between centers of pulses (tau(cp)) at 4 and 7 T permitted separation of the DA contribution from that of dipolar relaxation. The methods presented assess T(2rho) relaxation influenced by DA in tissue and provide a means to generate T(2rho) contrast in MRI.
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Affiliation(s)
- Shalom Michaeli
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota School of Medicine, 2021 6th Street SE, Minneapolis, MN 55455, USA.
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