Delayed hemispheric neuronal loss in severely head-injured patients

Structural neuroimaging markers of normal pressure hydrocephalus versus Alzheimer's dementia and Parkinson's disease, and hydrocephalus versus atrophy in chronic TBI-a narrative review

Introduction

Normal Pressure Hydrocephalus (NPH) is a prominent type of reversible dementia that may be treated with shunt surgery, and it is crucial to differentiate it from irreversible degeneration caused by its symptomatic mimics like Alzheimer's Dementia (AD) and Parkinson's Disease (PD). Similarly, it is important to distinguish between (normal pressure) hydrocephalus and irreversible atrophy/degeneration which are among the chronic effects of Traumatic Brain Injury (cTBI), as the former may be reversed through shunt placement. The purpose of this review is to elucidate the structural imaging markers which may be foundational to the development of accurate, noninvasive, and accessible solutions to this problem.

Methods

By searching the PubMed database for keywords related to NPH, AD, PD, and cTBI, we reviewed studies that examined the (1) distinct neuroanatomical markers of degeneration in NPH versus AD and PD, and atrophy versus hydrocephalus in cTBI and (2) computational methods for their (semi-) automatic assessment on Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) scans.

Results

Structural markers of NPH and those that can distinguish it from AD have been well studied, but only a few studies have explored its structural distinction between PD. The structural implications of cTBI over time have been studied. But neuroanatomical markers that can predict shunt response in patients with either symptomatic idiopathic NPH or post-traumatic hydrocephalus have not been reliably established. MRI-based markers dominate this field of investigation as compared to CT, which is also reflected in the disproportionate number of MRI-based computational methods for their automatic assessment.

Conclusion

Along with an up-to-date literature review on the structural neurodegeneration due to NPH versus AD/PD, and hydrocephalus versus atrophy in cTBI, this article sheds light on the potential of structural imaging markers as (differential) diagnostic aids for the timely recognition of patients with reversible (normal pressure) hydrocephalus, and opportunities to develop computational tools for their objective assessment.

Platelet-like particles reduce coagulopathy-related and neuroinflammatory pathologies post-experimental traumatic brain injury

Coagulopathy may occur following traumatic brain injury (TBI), thereby negatively affecting patient outcomes. Here, we investigate the use of platelet-like particles (PLPs), poly(N-isopropylacrylamide-co-acrylic-acid) microgels conjugated with a fibrin-specific antibody, to improve hemostasis post-TBI. The objective of this study was to diminish coagulopathy in a mouse TBI model (controlled cortical impact) via PLP treatment, and subsequently decrease blood-brain barrier (BBB) permeability and neuroinflammation. Following an acute intravenous injection of PLPs post-TBI, we analyzed BBB permeability, ex vivo coagulation parameters, and neuroinflammation at 24 hr and 7 days post-TBI. Both PLP-treatment and control particle-treatment had significantly decreased BBB permeability and improved clot structure 24 hr post-injury. Additionally, no significant change in tissue sparing was observed between 24 hr and 7 days for PLP-treated cohorts compared to that observed in untreated cohorts. Only PLP-treatment resulted in significant reduction of astrocyte expression at 7 days and percent difference from 24 hr to 7 days. Finally, PLP-treatment significantly reduced the percent difference from 24 hr to 7 days in microglia/macrophage density compared to the untreated control. These results suggest that PLP-treatment addressed acute hypocoagulation and decreased BBB permeability followed by decreased neuroinflammation and fold-change tissue loss by 7 days post-injury. These promising results indicate that PLPs could be a potential therapeutic modality for TBI.

Degeneration of core neural tracts for emotional regulation in a patient with traumatic brain injury: A case report

RATIONALE

Several brain structures, including the orbital prefrontal cortex, ventrolateral prefrontal cortex, dorsolateral prefrontal cortex, amygdala, and anterior cingulate cortex, are considered key structures in the neural circuitry underlying emotion regulation. We report on a patient showing behavior changes and degeneration of core neural tracts for emotional regulation following traumatic brain injury (TBI).

PATIENT CONCERNS

A 51-year-old male patient suffered an in-car accident. The patient lost consciousness for approximately 30 days, and his Glasgow Coma Scale score was 3. He underwent stereotactic drainage for traumatic intraventricular and intracerebral hemorrhages. At approximately 6.5-year after onset, he began to show disinhibition behaviors such as shouting with anger, which worsened over time. At approximately 8-year after onset, he showed severe depression signs and disinhibition, including violence.

DIAGNOSES

The patient who showed delayed-onset behavioral changes (disinhibition and depression).

INTERVENTIONS

Diffusion tensor imaging data were acquired at 3 months and 8 years after TBI onset.

OUTCOMES

The patient showed degeneration of core neural tracts for emotional regulation that was associated with delayed behavioral changes following TBI. On both 3-month and 8-year diffusion tensor tractographies (DTTs), the right dorsolateral prefronto-thalamic tract, ventrolateral prefronto-thalamic tract, orbital prefronto-thalamic tract, uncinate fasciculus, and both cinguli were reconstructed whereas other neural tracts were not reconstructed. Compared with the 3-month DTT, all reconstructed neural tracts on the 8-year DTT were narrow, except for the left cingulum, which showed new transcallosal fibers between both anterior cingula. The fractional anisotropy and tract volume of all reconstructed neural tracts were lower on the 8-year DTT than the 3-month DTT, except for the tract volume of left cingulum.

LESSONS

The evaluation of dorsolateral, ventrolateral, and orbital prefronto-thalamic tract, uncinate fasciculus, and cingulum using follow-up DTTs is useful when a patient with TBI shows delayed-onset behavioral problems.

Delayed degeneration of the left fornical crus with verbal memory impairment in a patient with mild traumatic brain injury: A case report

RATIONALE

We report on a patient who showed delayed degeneration of the left fornical crus with verbal memory impairment following mild traumatic brain injury (TBI), which was demonstrated by diffusion tensor tractography (DTT). PATIENT CONCERNS:: fter flexion and hyperextension of her head to the opposite side, the patient experienced a dazed feeling for a while at the time of head trauma. The patient's Glasgow Coma Scale score was 15, and mini-mental state examination score was 30.

DIAGNOSES

A 50-year-old right-handed female with 12 years of education suffered from head trauma resulting from a car accident.

INTERVENTIONS

A The patient showed normal memory function at one year after onset: the Memory Assessment Scale (global memory: 124 (95 percentile (%ile)), verbal memory: 111 (77%ile), and visual memory: 132 (98%ile) (A percentile is a measure used in statistics indicating the value below which a given percentage of observations in a group of observations fall). However, the patient began to experience decline of memory function such as forgetfulness at approximately 1.5 years after onset. On the 2-year evaluation, she showed decrement of memory function (global memory: 108 (70%ile), verbal memory: 86 (18%ile), and visual memory: 129 (97%ile).

OUTCOMES

On 1-year DTT, the integrity of the fornix was well preserved between the fornical column and fornical crus. However, on 2-year DTT, a discontinuation was observed in the left fornical crus.

LESSONS

Delayed degeneration of the left fornical crus was demonstrated in a patient who showed delayed onset of verbal memory impairment following mild TBI.

Facilitated assessment of tissue loss following traumatic brain injury

All experimental models of traumatic brain injury (TBI) result in a progressive loss of brain tissue. The extent of tissue loss reflects the injury severity and can be measured to evaluate the potential neuroprotective effect of experimental treatments. Quantitation of tissue volumes is commonly performed using evenly spaced brain sections stained using routine histochemical methods and digitally captured. The brain tissue areas are then measured and the corresponding volumes are calculated using the distance between the sections. Measurements of areas are usually performed using a general purpose image analysis software and the results are then transferred to another program for volume calculations. To facilitate the measurement of brain tissue loss we developed novel algorithms which automatically separate the areas of brain tissue from the surrounding image background and identify the ventricles. We implemented these new algorithms by creating a new computer program (SectionToVolume) which also has functions for image organization, image adjustments and volume calculations. We analyzed brain sections from mice subjected to severe focal TBI using both SectionToVolume and ImageJ, a commonly used image analysis program. The volume measurements made by the two programs were highly correlated and analysis using SectionToVolume required considerably less time. The inter-rater reliability was high. Given the extensive use of brain tissue loss measurements in TBI research, SectionToVolume will likely be a useful tool for TBI research. We therefore provide both the source code and the program as attachments to this article.

Evaluation of delayed neuronal and axonal damage secondary to moderate and severe traumatic brain injury using quantitative MR imaging techniques

BACKGROUND AND PURPOSE

Traumatic brain injury (TBI) is a classic model of monophasic neuronal and axonal injury, in which tissue damage mainly occurs at the moment of trauma. There is some evidence of delayed progression of the neuronal and axonal loss. Our purpose was to test the hypothesis that quantitative MR imaging techniques can estimate the biologic changes secondary to delayed neuronal and axonal loss after TBI.

MATERIALS AND METHODS

Nine patients (age, 11-28 years; 5 male) who sustained a moderate or severe TBI were evaluated at a mean of 3.1 years after trauma. We applied the following techniques: bicaudate (BCR) and bifrontal (BFR) ventricle-to-brain ratios; T2 relaxometry; magnetization transfer ratio (MTR); apparent diffusion coefficient (ADC); and proton spectroscopy, by using an N-acetylaspartate/creatine (NAA/Cr) ratio measured in normal-appearing white matter (NAWM) and the corpus callosum (CC). The results were compared with those of a control group.

RESULTS

BCR and BFR mean values were significantly increased (P < or = .05) in patients due to secondary subcortical atrophy; increased T2 relaxation time was observed in the NAWM and CC, reflecting an increase in water concentration secondary to axonal loss. Increased ADC mean values and reduced MTR mean values were found in the NAWM and CC, showing damage in the myelinated axonal fibers; and decreased NAA/Cr ratio mean values were found in the CC, indicating axonal loss.

CONCLUSIONS

These quantitative MR imaging techniques could noninvasively demonstrate the neuronal and axonal damage in the NAWM and CC of human brains, secondary to moderate or severe TBI.

Persistent metabolic crisis as measured by elevated cerebral microdialysis lactate-pyruvate ratio predicts chronic frontal lobe brain atrophy after traumatic brain injury

OBJECTIVE

To determine whether persistent metabolic dysfunction in normal-appearing frontal lobe tissue is correlated with long-term tissue atrophy.

DESIGN

Prospective monitoring with retrospective data analysis.

SETTING

Single-center academic neurointensive care unit.

PATIENTS

Fifteen patients with moderate to severe traumatic brain injury (Glasgow Coma Scale score 3-12).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Hourly cerebral microdialysis was performed for the initial 96 hrs after trauma to determine extracellular levels of glucose, glutamate, glycerol, lactate, and pyruvate in normal appearing frontal lobes. Six months after injury, the anatomical outcome was assessed by measures of global and regional cerebral atrophy using volumetric brain magnetic resonance imaging. The lactate/pyruvate ratio was elevated >40 after traumatic brain injury in most patients, with a mean percent time of 32 +/- 29% of hours monitored. At 6 months after traumatic brain injury, there was a mean frontal lobe atrophy of 12 +/- 11% and global brain atrophy of 8.5 +/- 4.5%. The percentage of time of elevated lactate/pyruvate ratio correlated with the extent of frontal lobe brain atrophy (r = -.56, p < 0.01), but not global brain atrophy (r = -.31, p = 0.20). The predictive effect of lactate/pyruvate ratio was independent of patient age, Glasgow Coma Scale score, and volume of frontal lobe contusion.

CONCLUSION

Persistent metabolic crisis, as reflected by an elevated lactate/pyruvate ratio, in normal appearing posttraumatic frontal lobe, is predictive of the degree of tissue atrophy at 6 months.

Hippocampal volume and mood disorders after traumatic brain injury

BACKGROUND

Recent evidence from clinical studies and animal models of traumatic brain injury (TBI) suggest that neuronal and glial loss might progress after the initial insult in selectively vulnerable regions of the brain such as the hippocampus. There is also evidence that hippocampal dysfunction plays a role in the pathogenesis of mood disorders. We examined the relationship between hippocampal damage and mood disorders after TBI and the effect of hippocampal atrophy on the outcome of TBI patients.

METHODS

The study group consisted of 37 patients with closed head injury who were evaluated at baseline and at 3, 6, and 12 months after trauma. Psychiatric diagnosis was made with a structured clinical interview and DSM-IV criteria. Quantitative magnetic resonance imaging scans were obtained at 3-months follow-up.

RESULTS

Patients with moderate to severe head injury had significantly lower hippocampal volumes than patients with mild TBI. Patients who developed mood disorders had significantly lower hippocampal volumes than patients without mood disturbance. Furthermore, there was a significant interaction between mood disorders diagnosis and severity of TBI, by which patients with moderate to severe TBI who developed mood disorders had significantly smaller hippocampal volumes than patients with equivalent severe TBI who did not develop mood disturbance. Finally, reduced hippocampal volumes were associated with poor vocational outcome at 1-year follow-up.

CONCLUSIONS

Our findings are consistent with a "double-hit" mechanism by which neural and glial elements already affected by trauma are further compromised by the functional changes associated with mood disorders (e.g., the neurotoxic effects of increased levels of cortisol or excitotoxic damage resulting from overactivation of glutaminergic pathways). Finally, patients with greater hippocampal damage were less likely to return to a productive life 1 year after trauma.

Day-of-injury computerized tomography, rehabilitation status, and development of cerebral atrophy in persons with traumatic brain injury

OBJECTIVE

To compare day-of-injury (DOI) computerized tomography (CT) findings with acute injury severity markers, disability at acute hospital admission and discharge from inpatient rehabilitation, injury severity markers, and degree of postacute cerebral atrophy on magnetic resonance imaging (MRI).

DESIGN

Retrospective chart review of 240 consecutive traumatic brain injury (TBI) admissions (mean age 31.7 +/- 15.8 yrs) with moderate-to-severe initial brain injury. All DOI CT abnormalities were qualitatively rated. Disability was assessed using the Disability Rating Scale (DRS) and the FIM measure. In a representative subset, cerebral atrophy was determined by the ventricle-to-brain ratio (VBR) method and quantified from MRI scans 25 or more days postinjury.

RESULTS

CT classification resulted in nonsignificant differences in DRS and FIM ratings at the time of discharge from the rehabilitation unit, except in brainstem injury subjects who had significantly higher DRS and lower FIM scores at rehabilitation discharge. At 25 or more days postinjury, presence of any DOI CT abnormality was associated with larger VBR. Increased VBR, as an index of cerebral atrophy, was associated with worse rehabilitation discharge DRS and FIM ratings.

CONCLUSIONS

Other than brainstem injury, DOI CT findings relate poorly to rehabilitation outcome. Presence of DOI CT abnormalities were associated with the development of cerebral atrophy, which was associated with poorer rehabilitation discharge DRS and FIM scores.

Loss of neuronal integrity: a cause of hypometabolism in patients with traumatic brain injury without MRI abnormality in the chronic stage

PURPOSE

Traumatic brain injury (TBI) causes brain dysfunction in many patients. However, some patients have severe brain dysfunction but display no abnormalities on magnetic resonance imaging (MRI). There have been some reports of hypometabolism even in such patients. The purpose of this study was to investigate the relationship between metabolic abnormality and loss of neuronal integrity in TBI patients with some symptoms but without MRI abnormalities.

METHODS

The study population comprised ten patients with TBI and ten normal volunteers. All of the patients were examined at least 1 year after the injury. ( 15)O-labelled gas PET and [(11)C]flumazenil (FMZ) positron emission tomography (PET) were carried out. The cerebral metabolic rate of oxygen (CMRO(2)) and binding potential (BP) images of FMZ were calculated. Axial T2WI, T2*WI and FLAIR images were obtained. Coronal images were added in some cases.

RESULTS

All of the patients had normal MRI findings, and all showed areas with abnormally low CMRO(2). Low uptake on BP images was observed in six patients (60%). No lesions that showed low uptake on BP images were without low CMRO(2). On the other hand, there were 14 lesions with low CMRO(2) but without BP abnormalities.

CONCLUSION

These results indicate that there are metabolic abnormalities in TBI patients with some symptoms after brain injury but without abnormalities on MRI. Some of the hypometabolic lesions showed low BP, indicating a loss of neuronal integrity. Thus, FMZ PET may have potential to distinguish hypometabolism caused by neuronal loss from that caused by other factors.

Selective temporal and regional alterations of Nogo-A and small proline-rich repeat protein 1A (SPRR1A) but not Nogo-66 receptor (NgR) occur following traumatic brain injury in the rat

Axons show a poor regenerative capacity following traumatic central nervous system (CNS) injury, partly due to the expression of inhibitors of axonal outgrowth, of which Nogo-A is considered the most important. We evaluated the acute expression of Nogo-A, the Nogo-66 receptor (NgR) and the novel small proline-rich repeat protein 1A (SPRR1A, previously undetected in brain), following experimental lateral fluid percussion (FP) brain injury in rats. Immunofluorescence with antibodies against Nogo-A, NgR and SPRR1A was combined with antibodies against the neuronal markers NeuN and microtubule-associated protein (MAP)-2 and the oligodendrocyte marker RIP, while Western blot analysis was performed for Nogo-A and NgR. Brain injury produced a significant increase in Nogo-A expression in injured cortex, ipsilateral external capsule and reticular thalamus from days 1-7 post-injury (P < 0.05) compared to controls. Increased expression of Nogo-A was observed in both RIP- and NeuN positive (+) cells in the ipsilateral cortex, in NeuN (+) cells in the CA3 region of the hippocampus and reticular thalamus and in RIP (+) cells in white matter tracts. Alterations in NgR expression were not observed following traumatic brain injury (TBI). Brain injury increased the extent of SPRR1A expression in the ipsilateral cortex and the CA3 at all post-injury time-points in NeuN (+) cells. The marked increases in Nogo-A and SPRR1A in several important brain regions suggest that although inhibitors of axonal growth may be upregulated, the injured brain is also capable of expressing proteins promoting axonal outgrowth following TBI.

Pathophysiologic aspects of major depression following traumatic brain injury

Mood disorders, particularly major depression, are the most frequent complication of traumatic brain injury. Major depression is present in about 40% of patients hospitalization for a traumatic brain injury. Anxiety disorders, substance abuse, dysregulation of emotional expression, and aggressive outbursts are frequently associated with major depression, and their coexistence constitutes a marker of a more disabling clinical course. The complex interactions of genetic, developmental, and psychosocial factors determine patients' vulnerability to developing affective disturbances following a traumatic brain injury. Symptoms of depression cluster into the domains of low mood and distorted self-attitude, lack of motivation and anhedonia, subjective cognitive complaints, and hyperactive and disinhibited behavior. It is reasonable to assume that these symptomatic clusters have specific underlying mechanisms that need to be integrated in a comprehensive pathophysiologic model.

Autoreactive antibodies against neurons and basal lamina found in serum following experimental brain contusion in rats

BACKGROUND

Brain trauma is a risk factor for delayed CNS degeneration which may be attenuated by anti-inflammatory treatment. CNS injuries may cause anti-brain reactivity. This study was undertaken to analyze the pattern of delayed post-traumatic anti-brain immunity in experimental brain contusion.

METHOD

Adult Sprague-Dawley and Lewis rats were subjected to experimental brain contusions. For B-cell investigations, serum was obtained from contused, control and naïve rats, and used for immunohistochemistry on slices of rat brains to first detect autoreactive IgG and IgM antibodies in rat serum. Secondly, anti-rat IgG and IgM antibodies were used to search for auto-antibodies already bound to the brain tissue. Double staining with rat-serum and NeuN or anti-GFAP antibody was used to detect anti-neuronal and anti-astrocytic antibodies, respectively. For T-cell reactivity, cells from brains and cervical lymph nodes of rats were used in FACS analysis and elispot with MBP and MOG stimulation.

FINDINGS

Anti-vascular basal lamina IgG antibodies were detected at three months in 6/8 rats, following experimental contusion. Anti-neuronal IgG antibodies were detected 2 weeks after experimental contusion and sham surgery, while naïve controls were negative. Individual rats showed a prolonged response, or an anti-astrocytic staining. Tissue bound anti-self IgG or IgM was not detected in the brain tissue. Anti-MBP or anti-MOG T-cell responses were not detectable.

CONCLUSIONS

Experimental brain trauma and to some degree even sham surgery lead to an individually variable pattern of specific anti-brain reactive B-cells, while a T-cell response did not seem to be a consequence of moderate experimental contusion. The mere presence of anti brain-antibodies may be epiphenomenal, but could also be pathogenic for delayed degeneration. It is reasonable to regard the presence of an actual anti-brain reactivity as a potential threat to brain tissue integrity.

Caspase 7: increased expression and activation after traumatic brain injury in rats

Caspases, a cysteine proteinase family, are required for the initiation and execution phases of apoptosis. It has been suggested that caspase 7, an apoptosis executioner implicated in cell death proteolysis, is redundant to the main executioner caspase 3 and it is generally believed that it is not present in the brain or present in only minute amounts with highly restricted activity. Here we report evidence that caspase 7 is up-regulated and activated after traumatic brain injury (TBI) in rats. TBI disrupts homeostasis resulting in pathological apoptotic activation. After controlled cortical impact TBI of adult male rats we observed, by semiquantitative real-time PCR, increased mRNA levels within the traumatized cortex and hippocampus peaking in the former about 5 days post-injury and in the latter within 6-24 h of trauma. The activation of caspase 7 protein after TBI, demonstrated by immunoblot by the increase of the active form of caspase 7 peaking 5 days post-injury in the cortex and hippocampus, was found to be up-regulated in both neurons and astrocytes by immunohistochemistry. These findings, the first to document the up-regulation of caspase 7 in the brain after acute brain injury in rats, suggest that caspase 7 activation could contribute to neuronal cell death on a scale not previously recognized.

Lateral fluid percussion brain injury: a 15-year review and evaluation

This article comprehensively reviews the lateral fluid percussion (LFP) model of traumatic brain injury (TBI) in small animal species with particular emphasis on its validity, clinical relevance and reliability. The LFP model, initially described in 1989, has become the most extensively utilized animal model of TBI (to date, 232 PubMed citations), producing both focal and diffuse (mixed) brain injury. Despite subtle variations in injury parameters between laboratories, universal findings are evident across studies, including histological, physiological, metabolic, and behavioral changes that serve to increase the reliability of the model. Moreover, demonstrable histological damage and severity-dependent behavioral deficits, which partially recover over time, validate LFP as a clinically-relevant model of human TBI. The LFP model, also has been used extensively to evaluate potential therapeutic interventions, including resuscitation, pharmacologic therapies, transplantation, and other neuroprotective and neuroregenerative strategies. Although a number of positive studies have identified promising therapies for moderate TBI, the predictive validity of the model may be compromised when findings are translated to severely injured patients. Recently, the clinical relevance of LFP has been enhanced by combining the injury with secondary insults, as well as broadening studies to incorporate issues of gender and age to better approximate the range of human TBI within study design. We conclude that the LFP brain injury model is an appropriate tool to study the cellular and mechanistic aspects of human TBI that cannot be addressed in the clinical setting, as well as for the development and characterization of novel therapeutic interventions. Continued translation of pre-clinical findings to human TBI will enhance the predictive validity of the LFP model, and allow novel neuroprotective and neuroregenerative treatment strategies developed in the laboratory to reach the appropriate TBI patients.

Common patterns of bcl-2 family gene expression in two traumatic brain injury models

Cell death/survival following traumatic brain injury (TBI) may be a result of alterations in the intracellular ratio of death and survival factors. Bcl-2 family genes mediate both cell survival and the initiation of cell death. Using lysate RNase protection assays, mRNA expression of the anti-cell death genes Bcl-2 and Bcl-xL, and the pro-cell death gene Bax, was evaluated following experimental brain injuries in adult male Sprague-Dawley rats. Both the lateral fluid-percussion (LFP) and the lateral controlled cortical impact (LCI) models of TBI showed similar patterns of gene expression. Anti-cell death bcl-2 and bcl-xL mRNAs were attenuated early and tended to remain depressed for at least 3 days after injury in the cortex and hippocampus ipsilateral to injury. Pro-cell death bax mRNA was elevated in these areas, usually following the decrease in anti-cell death genes. These common patterns of gene expression suggest an important role for Bcl-2 genes in cell death and survival in the injured brain. Understanding the regulation of these genes may facilitate the development of new therapeutic strategies for a condition that currently has no proven pharmacologic treatments.

Cerebral blood flow at one year after controlled cortical impact in rats: assessment by magnetic resonance imaging

Progressive tissue loss and delayed cognitive deficits are seen in rats during the initial year after experimental traumatic brain injury (TBI). As much as 10% of parenchymal volume is lost even in the contralateral hemisphere by 1 year after controlled cortical impact (CCI) in rats. Progressive declines in cerebral blood flow (CBF) are also associated with advanced age and neurodegenerative diseases. Surprisingly, the long-term effects of TBI on CBF remain undefined. CBF was quantified by continuous arterial spin-labeled magnetic resonance imaging (MRI) and measurements of spin-lattice relaxation time in a slice through the plane of injury at 1 year after experimental TBI produced by CCI (n = 4) or sham surgery (n = 4) in rats. CBF was quantified in six regions of interest (ROIs) that were anatomically identified on the control images in each hemisphere and included a medial cortical segment (contusion-enriched, beneath the impact site, on the ipsilateral side) cortex, hippocampus, thalamus, amygdala/pyriform cortex, and hemisphere. At 1 year after injury, CBF was dramatically (96%) reduced in structures within the large cystic lesion that was seen in three of four rats and variably included cortex and hippocampus. Overall, there was an 80% reduction in CBF in the ipsilateral medial cortical segment comparing CCI and sham groups. Similarly, 52% and 67% reductions were seen in CBF in the cortical and hippocampal ROIs ipsilateral to impact (CCI vs. sham), respectively. These are regions both with marked CBF disturbances early after injury and that ultimately suffer considerable tissue loss over the 1-year interval. However, at 1 year after CCI, CBF was not different from sham in other ROIs, including ipsilateral thalamus, or either contralateral hippocampus or hemisphere. We conclude that, at 1 year after CCI, CBF is reduced in anatomic structures at or near the impact site, including injured cortex and hippocampus, and this translates into a reduction in hemispheric CBF. However, despite both significant occult tissue loss ipsilateral and contralateral to the injury and delayed cognitive deficits, widespread reductions in CBF are not observed. This suggests the possibility of remodeling or repackaging of the brain that preserves CBF outside of the cystic lesion.