Cerebellar atrophy after severe traumatic head injury in children

Natural Products for the Treatment of Neurodegenerative Diseases

Neurodegenerative diseases are a heterogeneous group of disorders characterized by the progressive degeneration of the structure and function of the central nervous system or peripheral nervous system. Alzheimer's Disease (AD), Parkinson's Disease (PD) and Spinal Cord Injury (SCI) are the common neurodegenerative diseases, which typically occur in people over the age of 60. With the rapid development of an aged society, over 60 million people worldwide are suffering from these uncurable diseases. Therefore, the search for new drugs and therapeutic methods has become an increasingly important research topic. Natural products especially those from the Traditional Chinese Medicines (TCMs), are the most important sources of drugs, and have received extensive interest among pharmacist. In this review, in order to facilitate further chemical modification of those useful natural products by pharmacists, we will bring together recent studies in single natural compound from TCMs with neuroprotective effect.

Resistance, vulnerability and resilience: A review of the cognitive cerebellum in aging and neurodegenerative diseases

In the context of neurodegeneration and aging, the cerebellum is an enigma. Genetic markers of cellular aging in cerebellum accumulate more slowly than in the rest of the brain, and it generates unknown factors that may slow or even reverse neurodegenerative pathology in animal models of Alzheimer's Disease (AD). Cerebellum shows increased activity in early AD and Parkinson's disease (PD), suggesting a compensatory function that may mitigate early symptoms of neurodegenerative pathophysiology. Perhaps most notably, different parts of the brain accumulate neuropathological markers of AD in a recognized progression and generally, cerebellum is the last brain region to do so. Taken together, these data suggest that cerebellum may be resistant to certain neurodegenerative mechanisms. On the other hand, in some contexts of accelerated neurodegeneration, such as that seen in chronic traumatic encephalopathy (CTE) following repeated traumatic brain injury (TBI), the cerebellum appears to be one of the most susceptible brain regions to injury and one of the first to exhibit signs of pathology. Cerebellar pathology in neurodegenerative disorders is strongly associated with cognitive dysfunction. In neurodegenerative or neurological disorders associated with cerebellar pathology, such as spinocerebellar ataxia, cerebellar cortical atrophy, and essential tremor, rates of cognitive dysfunction, dementia and neuropsychiatric symptoms increase. When the cerebellum shows AD pathology, such as in familial AD, it is associated with earlier onset and greater severity of disease. These data suggest that when neurodegenerative processes are active in the cerebellum, it may contribute to pathological behavioral outcomes. The cerebellum is well known for comparing internal representations of information with observed outcomes and providing real-time feedback to cortical regions, a critical function that is disturbed in neuropsychiatric disorders such as intellectual disability, schizophrenia, dementia, and autism, and required for cognitive domains such as working memory. While cerebellum has reciprocal connections with non-motor brain regions and likely plays a role in complex, goal-directed behaviors, it has proven difficult to establish what it does mechanistically to modulate these behaviors. Due to this lack of understanding, it's not surprising to see the cerebellum reflexively dismissed or even ignored in basic and translational neuropsychiatric literature. The overarching goals of this review are to answer the following questions from primary literature: When the cerebellum is affected by pathology, is it associated with decreased cognitive function? When it is intact, does it play a compensatory or protective role in maintaining cognitive function? Are there theoretical frameworks for understanding the role of cerebellum in cognition, and perhaps, illnesses characterized by cognitive dysfunction? Understanding the role of the cognitive cerebellum in neurodegenerative diseases has the potential to offer insight into origins of cognitive deficits in other neuropsychiatric disorders, which are often underappreciated, poorly understood, and not often treated.

Decomposition of leg movements during overground walking in individuals with traumatic brain injury

OBJECTIVE

Walking requires precise coordination of bilateral lower extremity motions at all joints. This ability can be affected by traumatic brain injury (TBI). The study investigated inter-joint coordination of lower extremities during overground walking after TBI.

METHODS

Ten individuals with post-injury ataxia, postural stability and gait abnormalities, as well as 10 sex- and age-matched control subjects were involved in the study. Participants walked at self-selected speed in three experimental conditions: normal walking without any additional task; walking with a narrow base of support, and walking while holding a cup full of water. Inter-joint coordination was analysed as the percentage of gait cycle during which the leg movement was decomposed with 0% indicating simultaneous motion of the two joints (i.e. hip-knee, knee-ankle, and hip-ankle) through the entire gait cycle or 100% indicating motion of only one joint. Decomposition was calculated for each pair of joints and for the left and right leg separately.

RESULTS

Participants with TBI showed greater decomposition indices and poorer inter-joint coordination respectively than control individuals for all joint pairs (p < 0.01). Walking with the narrower base of support or with a cup, increased movement decomposition in the TBI group, but not in the control group.

CONCLUSION

The results revealed post-injury gait impairment that manifests as decomposition of multi-joint motions of the lower extremities during overground walking.

Decomposition of postural movements in individuals with mild TBI while reaching to intercept a moving virtual target

The study analyzed postural and arm movement coordinations in patients with traumatic brain injury (TBI) while standing and reaching for a target moving in a 3D virtual environment. Thirteen individuals with mild TBI and 13 height, sex, and age-matched healthy control individuals were involved. While standing in front of the screen, the participants interacted with the projected environment by reaching for virtual targets. Coordination was analyzed as the percentage of reach-to-intercept cycle time during which their movement toward the target was decomposed with 0% indicating simultaneous motion in three planes or 100% indicating motion in one or two planes only. Decomposition was calculated for the postural movements (DI_p), arm movements (DI_a), and arm-postural coordination (DI_a-p). The latter index represented the percentage of reach-to-intercept cycle time during which either the posture or arm moved alone. DI_p and DI_a-p were larger in the TBI group compared to the control group (p < 0.01). In the TBI group, DI_p and DI_a-p correlated negatively with postural stability (r = - 0.71 and r = - 0.60; p < 0.01). Results suggest that individuals with TBI decompose postural and arm-postural coordinations during a reach-to-intercept task. This may be either a result of impaired postural control or an effort to compensate for instability. These abnormalities should be taken into consideration while planning physical therapy programs for individuals after brain injury.

Regional volumes in brain stem and cerebellum are associated with postural impairments in young brain-injured patients

Many patients with traumatic brain injury (TBI) suffer from postural control impairments that can profoundly affect daily life. The cerebellum and brain stem are crucial for the neural control of posture and have been shown to be vulnerable to primary and secondary structural consequences of TBI. The aim of this study was to investigate whether morphometric differences in the brain stem and cerebellum can account for impairments in static and dynamic postural control in TBI. TBI patients (n = 18) and healthy controls (n = 30) completed three challenging postural control tasks on the EquiTest® system (Neurocom). Infratentorial grey matter (GM) and white matter (WM) volumes were analyzed with cerebellum-optimized voxel-based morphometry using the spatially unbiased infratentorial toolbox. Volume loss in TBI patients was revealed in global cerebellar GM, global infratentorial WM, middle cerebellar peduncles, pons and midbrain. In the TBI group and across both groups, lower postural control performance was associated with reduced GM volume in the vermal/paravermal regions of lobules I-IV, V and VI. Moreover, across all participants, worse postural control performance was associated with lower WM volume in the pons, medulla, midbrain, superior and middle cerebellar peduncles and cerebellum. This is the first study in TBI patients to demonstrate an association between postural impairments and reduced volume in specific infratentorial brain areas. Volumetric measures of the brain stem and cerebellum may be valuable prognostic markers of the chronic neural pathology, which complicates rehabilitation of postural control in TBI.

Effects of traumatic brain injury on locomotor adaptation

BACKGROUND AND PURPOSE

Locomotor adaptation is a form of short-term learning that enables gait modifications and reduces movement errors when the environment changes. This adaptation is critical for community ambulation for example, when walking on different surfaces. While many individuals with traumatic brain injury (TBI) recover basic ambulation, less is known about recovery of more complex locomotor skills, like adaptation. The purpose of this study was to investigate how TBI affects locomotor adaptation.

METHODS

Fourteen adults with TBI and 11 nondisabled comparison participants walked for 15 minutes on a split-belt treadmill with 1 belt moving at 0.7 m/s, and the other at 1.4 m/s. Subsequently, aftereffects were assessed and de-adapted during 15 minutes of tied-belt walking (both belts at 0.7 m/s).

RESULTS

Participants with TBI showed greater asymmetry in interlimb coordination on split-belts than the comparison group. Those with TBI did not adapt back to baseline symmetry, and some individuals did not store significant aftereffects. Greater asymmetry on split-belts and smaller aftereffects were associated with greater ataxia.

DISCUSSION

Participants with TBI were more perturbed by walking on split-belts and showed some impairment in adaptation. This suggests a reduced ability to learn a new form of coordination to compensate for environmental changes. Multiple interacting factors, including cerebellar damage and impairments in higher-level cognitive processes, may influence adaptation post-TBI.

CONCLUSIONS

Gait adaptation to novel environment demands is impaired in persons with chronic TBI and may be an important skill to target in rehabilitation.

VIDEO ABSTRACT AVAILABLE

(See Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A74) for more insights from the authors.

Training-induced improvements in postural control are accompanied by alterations in cerebellar white matter in brain injured patients

We investigated whether balance control in young TBI patients can be promoted by an 8-week balance training program and whether this is associated with neuroplastic alterations in brain structure. The cerebellum and cerebellar peduncles were selected as regions of interest because of their importance in postural control as well as their vulnerability to brain injury. Young patients with moderate to severe TBI and typically developing (TD) subjects participated in balance training using PC-based portable balancers with storage of training data and real-time visual feedback. An additional control group of TD subjects did not attend balance training. Mean diffusivity and fractional anisotropy were determined with diffusion MRI scans and were acquired before, during (4 weeks) and at completion of training (8 weeks) together with balance assessments on the EquiTest® System (NeuroCom) which included the Sensory Organization Test, Rhythmic Weight Shift and Limits of Stability protocols. Following training, TBI patients showed significant improvements on all EquiTest protocols, as well as a significant increase in mean diffusivity in the inferior cerebellar peduncle. Moreover, in both training groups, diffusion metrics in the cerebellum and/or cerebellar peduncles at baseline were predictive of the amount of performance increase after training. Finally, amount of training-induced improvement on the Rhythmic Weight Shift test in TBI patients was positively correlated with amount of change in fractional anisotropy in the inferior cerebellar peduncle. This suggests that training-induced plastic changes in balance control are associated with alterations in the cerebellar white matter microstructure in TBI patients.

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Brain injury patients and healthy subjects attended 8-weeks of balance training.

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Diffusion MRI and postural tests were acquired before, during and after training.

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Cerebellum and cerebellar peduncles were selected as regions of interest.

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Training-induced changes shown in postural control and inferior cerebellar peduncle

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Correlations between change in balance and change in white matter microstructure

Correlations between white matter integrity and motor function in traumatic brain injury patients

BACKGROUND

Deterioration of motor function is one of several clinical manifestations following traumatic brain injury (TBI) in children and adolescents.

OBJECTIVE

To investigate the relationship between white matter (WM) integrity using diffusion tensor imaging (DTI) and motor functioning in young TBI patients.

METHODS

A group with moderate to severe TBI (n = 24) and a control group (n = 17) were scanned using DTI along with standard anatomical scans. Using ExploreDTI software, WM regions/tracts that carry efferent output (motor) from the brain were evaluated, as well as the corpus callosum, brainstem, internal capsule, and subcortical WM structures. Motor function was assessed using the Movement Assessment Battery for Children (M-ABC), consisting of manual dexterity, ball skills, and static and dynamic balance items.

RESULTS

TBI patients were less successful on the M-ABC than the controls and showed lower WM fractional anisotropy (FA) in the corpus callosum, anterior corona radiata, corticospinal tract, and cerebellum. Decreased FA was associated with lower motor performance in the TBI group but not in the control group.

CONCLUSION

This study provides evidence for a structural alteration of motor pathways and regions in children and adolescents with TBI that are correlated with motor functioning. Further studies may be able to identify therapeutic targets and monitor the effects of new interventions.

Brain-behavior relationships in young traumatic brain injury patients: DTI metrics are highly correlated with postural control

Traumatic brain injury (TBI) is a major cause of impairment and functional disability in children and adolescents, including deterioration in fine as well as gross motor skills. The aim of this study was to assess deficits in sensory organization and postural ability in a young group of TBI patients versus controls by using quantitative force-platform recordings, and to test whether balance deficits are related to variation in structural properties of the motor and sensory white matter pathways. Twelve patients with TBI and 14 controls (aged 8-20 years) performed the Sensory Organisation Test (SOT) protocol of the EquiTest (Neurocom). All participants were scanned using Diffusion Tensor Imaging (DTI) along with standard anatomical scans. Quantitative comparisons of DTI parameters (fractional anisotropy, axial and radial diffusivity) between TBI patients and controls were performed. Correlations between DTI parameters and SOT balance scores were determined. Findings revealed that the TBI group scored generally lower than the control group on the SOT, indicative of deficits in postural control. In the TBI group, reductions in fractional anisotropy were noted in the cerebellum, posterior thalamic radiation, and corticospinal tract. Degree of white matter deterioration was highly correlated with balance deficits. This study supports the view that DTI is a valuable tool for assessing the integrity of white matter structures and for selectively predicting functional motor deficits in TBI patients.

Animal models of human cerebellar ataxias: a cornerstone for the therapies of the twenty-first century

Cerebellar ataxias represent a group of disabling neurological disorders. Our understanding of the pathogenesis of cerebellar ataxias is continuously expanding. A considerable number of laboratory animals with neurological mutations have been reported and numerous relevant animal models mimicking the phenotype of cerebellar ataxias are becoming available. These models greatly help dissecting the numerous mechanisms of cerebellar dysfunction, a major step for the assessment of therapeutics targeting a given deleterious pathway and for the screening of old or newly synthesized chemical compounds. Nevertheless, differences between animal models and human disorders should not be overlooked and difficulties in terms of characterization should not be occulted. The identification of the mutations of many hereditary ataxias, the development of valuable animal models, and the recent identifications of the molecular mechanisms underlying cerebellar disorders represent a combination of key factors for the development of anti-ataxic innovative therapies. It is anticipated that the twenty-first century will be the century of effective therapies in the field of cerebellar ataxias. The animal models are a cornerstone to reach this goal.

Cerebellum of the premature infant: rapidly developing, vulnerable, clinically important

Brain abnormality in surviving premature infants is associated with an enormous amount of neurodevelopmental disability, manifested principally by cognitive, behavioral, attentional, and socialization deficits, most commonly with only relatively modest motor deficits. The most recognized contributing neuropathology is cerebral white matter injury. The thesis of this review is that acquired cerebellar abnormality is a relatively less recognized but likely important cause of neurodevelopmental disability in small premature infants. The cerebellar disease may be primarily destructive (eg, hemorrhage, infarction) or primarily underdevelopment. The latter appears to be especially common and relates to a particular vulnerability of the cerebellum of the small premature infant. Central to this vulnerability are the extraordinarily rapid and complex developmental events occurring in the cerebellum. The disturbance of development can be caused either by direct adverse effects on the cerebellum, especially the distinctive transient external granular layer, or by indirect remote trans-synaptic effects. This review describes the fascinating details of cerebellar development, with an emphasis on events in the premature period, the major types of cerebellar abnormality acquired during the premature period, their likely mechanisms of occurrence, and new insights into the relation of cerebellar disease in early life to subsequent cognitive/behavioral/attentional/socialization deficits.

Models of traumatic cerebellar injury

Traumatic brain injury (TBI) is a major cause of morbidity and mortality worldwide. Studies of human TBI demonstrate that the cerebellum is sometimes affected even when the initial mechanical insult is directed to the cerebral cortex. Some of the components of TBI, including ataxia, postural instability, tremor, impairments in balance and fine motor skills, and even cognitive deficits, may be attributed in part to cerebellar damage. Animal models of TBI have begun to explore the vulnerability of the cerebellum. In this paper, we review the clinical presentation, pathogenesis, and putative mechanisms underlying cerebellar damage with an emphasis on experimental models that have been used to further elucidate this poorly understood but important aspect of TBI. Animal models of indirect (supratentorial) trauma to the cerebellum, including fluid percussion, controlled cortical impact, weight drop impact acceleration, and rotational acceleration injuries, are considered. In addition, we describe models that produce direct trauma to the cerebellum as well as those that reproduce specific components of TBI including axotomy, stab injury, in vitro stretch injury, and excitotoxicity. Overall, these models reveal robust characteristics of cerebellar damage including regionally specific Purkinje cell injury or loss, activation of glia in a distinct spatial pattern, and traumatic axonal injury. Further research is needed to better understand the mechanisms underlying the pathogenesis of cerebellar trauma, and the experimental models discussed here offer an important first step toward achieving that objective.

Cerebellar disorders in childhood: cognitive problems

Over the last decade, increasing evidence of cognitive functions of the cerebellum during development and learning processes could be ascertained. Posterior fossa malformations such as cerebellar hypoplasia or Joubert syndrome are known to be related to developmental problems in a marked to moderate extent. More detailed analyses reveal special deficits in attention, processing speed, visuospatial functions, and language. A study about Dandy Walker syndrome states a relationship of abnormalities in vermis lobulation with developmental problems. Further lobulation or volume abnormalities of the cerebellum and/or vermis can be detected in disorders as fragile X syndrome, Downs's syndrome, William's syndrome, and autism. Neuropsychological studies reveal a relation of dyslexia and attention deficit disorder with cerebellar functions. These functional studies are supported by structural abnormalities in neuroimaging in these disorders. Acquired cerebellar or vermis atrophy was found in groups of children with developmental problems such as prenatal alcohol exposure or extreme prematurity. Also, focal lesions during childhood or adolescence such as cerebellar tumor or stroke are related with neuropsychological abnormalities, which are most pronounced in visuospatial, language, and memory functions. In addition, cerebellar atrophy was shown to be a bad prognostic factor considering cognitive outcome in children after brain trauma and leukemia. In ataxia teleangiectasia, a neurodegenerative disorder affecting primarily the cerebellar cortex, a reduced verbal intelligence quotient and problems of judgment of duration are a hint of the importance of the cerebellum in cognition. In conclusion, the cerebellum seems to play an important role in many higher cognitive functions, especially in learning. There is a suggestion that the earlier the incorrect influence, the more pronounced the problems.

Preterm birth and disruptive cerebellar development: assessment of perinatal risk factors

OBJECTIVE

Abnormal cerebellar development was recently recognized to be related to prematurity. Aim of the present study was to evaluate preterm birth and possible peri- and postnatal risk factors associated with this type of brain injury.

PATIENTS AND METHODS

We report on a series of 35 very low birth weight infants (birth weight 986+/-257g S.D.) born between 24 and 32 weeks of gestation (27.0+/-1.8 weeks of gestation S.D.) sustaining disruption of cerebellar development after preterm birth. Perinatal medical records of study patients were compared to 41 preterm control infants (birth weight 900+/-358g S.D., gestational age 26.3+/-2.1 weeks S.D.) with normal cerebellar development on MRI scan.

RESULTS

A severely compromised postnatal condition with consecutive intubation and catecholamine support was found to be significant risk factor. Additional supratentorial hemorrhagic brain injury followed by posthemorrhagic hydrocephalus, neurosurgical interventions and hemosiderin deposits on the cerebellar surface were significantly related to disruptive cerebellar development. No other differences in perinatal factors were found between the groups.

CONCLUSION

Premature birth between 24 and 32 gestational weeks associated with poor postnatal conditions and complicated supratentorial hemorrhagic brain lesions represents a high-risk situation for disruption of cerebellar development.

The cerebellum in cognitive processes: supporting studies in children

Over the last decade, increasing evidence of cognitive functions of the cerebellum during development and learning processes could be ascertained. Posterior fossa malformations such as cerebellar hypoplasia or Joubert syndrome are known to be related to developmental problems in a marked to moderate extent. More detailed analyses reveal special deficits in attention, processing speed, visuospatial functions and language. A study about Dandy Walker syndrome states a relationship of abnormalities in vermis lobulation with developmental problems. Further lobulation or volume abnormalities of the cerebellum and/or vermis can be detected in disorders as fragile X syndrome, Downs's syndrome or William's syndrome. Neuropsychological studies reveal a relation of dyslexia and attention deficit disorder with cerebellar functions. These functional studies are supported by structural abnormalities in neuroimaging in these disorders. Acquired cerebellar or vermis atrophy was found in groups of children with developmental problems such as prenatal alcohol exposure or extreme prematurity. Also focal lesions during childhood or adolescence such as cerebellar tumour or stroke are related with neuropsychological abnormalities, which are most pronounced in visuo-spatial, language and memory functions. In addition, cerebellar atrophy was shown to be a bad prognostic factor considering cognitive outcome in children after brain trauma and leukaemia. In ataxia teleangiectasia, a neurodegenerative disorder affecting primarily the cerebellar cortex, a reduced verbal IQ and problems of judgment of duration are a hint of the importance of the cerebellum in cognition. In conclusion, the cerebellum seems to play an important role in many higher cognitive functions especially in learning. There is a suggestion that the earlier the incorrect influence the more pronounced the problems.

Cerebellar atrophy in Schimke-immuno-osseous dysplasia

Schimke-immuno-osseous dysplasia is an autosomal-recessive multisystem disorder with the prominent clinical features disproportionate growth failure, progressive renal failure, and T-cell immunodeficiency. Neurological symptoms caused by transient ischemic attacks (TIAs) and strokes are a typical clinical finding in severe SIOD. Cerebral ischemia and white matter changes, moyamoya phenomena and absence of a cerebellar hemisphere and partial absence of the cerebellar vermis have been described in patients with severe SIOD. We present three SIOD patients with atrophy of the caudal parts of the cerebellar vermis (posterior lobule) and of the cerebellar hemispheres. We hypothesize that these cerebellar abnormalities are a continuum of the ongoing vascular disease in severe SIOD.

Mild in vitro trauma induces rapid Glur2 endocytosis, robustly augments calcium permeability and enhances susceptibility to secondary excitotoxic insult in cultured Purkinje cells

Mild brain trauma results in a wide range of neurological symptoms that are not easily explained by the primary pathology. Purkinje neurons of the cerebellum are selectively vulnerable to brain trauma, including indirect remote trauma to the forebrain. This vulnerability manifests itself as a selective and delayed cell loss, for which the underlying mechanisms are poorly understood. Alterations to the surface expression of calcium impermeable AMPA receptors (GluR2-containing) may mediate post-traumatic calcium overload, and initiate biochemical cascades that ultimately cause progressive cell death. Our current study examined this hypothesis using an in vitro model of mild Purkinje trauma, delivered by an elastic stretch at 2.5-2.9 pounds per square inch (psi). This mild trauma alone did not increase cell loss as measured by propidium iodide (PI) uptake (at 20 h) compared to uninjured controls. However, there was a marked increase in cell loss, when cells following mild trauma, were exposed to 10 microM AMPA for 1 h compared to either mild trauma or AMPA exposure alone. Mild injury rendered Purkinje neurons significantly more permeable to AMPA-stimulated (4 microM) calcium influx at 15 min post-injury, including a sustained calcium plateau. This effect was eliminated by inhibiting protein kinase C-dependent GluR2 endocytosis with 2 microM Go6976 or blocking the calcium pore of GluR1/3 containing AMPARs with 500 nM 1-naphthylacetyl spermine (Naspm). Nifedipine (2 microM) eliminated the calcium plateau following mild injury but not the initial spike of Ca2+ increase. These results suggest that mild injuries resulted in a rapid AMPA receptor subtype switch (GluR2 was replaced by GluR1/3), which in turn resulted in an enhanced Ca2+ permeability. We further confirmed this by immunocytochemistry. Dendritic GluR2 co-localization with the pre-synaptic marker synaptophysin was markedly down-regulated at 15 min following mild stretch (P < 0.01), indicative of a rapid decrease in the synaptic expression of receptors containing this subunit. Carboxyfluorescence (CBF) assays revealed that mild stretch did not alter membrane integrity. Finally, we demonstrated that the combination of 500 nM Naspm and 5 nM Go6976 conferred a powerful neuroprotective effect on Purkinje cells by effectively eliminating the effects of mild stretch combined with AMPA in 95% of cells. These results represent a newly described mechanism rendering neurons susceptible to secondary injuries following trauma. Prevention of GluR2 endocytosis may be critical in the development of pharmacotherapies aimed at mild, seemingly inconsequential trauma, to avoid ensuing secondary damage.

Distribution of microstructural damage in the brains of professional boxers: a diffusion MRI study

PURPOSE

To investigate and localize cerebral abnormalities in professional boxers with no history of moderate or severe head trauma.

MATERIALS AND METHODS

Diffusion tensor imaging (DTI) was used to determine the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) in the brains of 81 professional male boxers and 12 male control subjects. Voxel-based analysis (VBA) of both the diffusion and anisotropy values was performed using statistical parametric mapping (SPM). From this objective analysis, regions of microstructural abnormalities in the brains of the boxers were located.

RESULTS

Increases in the ADC, and decreases in FA were identified in deep white matter (WM), while decreases in ADC were identified in cortical gray matter (GM). Regions of positive correlation between ADC and age were also found in both the boxer and control groups, although the regions and strength of the correlation were not the same in each group.

CONCLUSION

Using VBA, we localized previously unreported abnormalities in the brains of professional boxers. These abnormalities are assumed to reflect cumulative (chronic) brain injury resulting from nonsevere head trauma.

Cerebellar atrophy following mild head injury in a 4-year-old girl

Cerebellar atrophy following severe head injury in infants has been described in imaging studies. We report the case of a 4-year-old girl who died of accidental hypothermia. Three weeks before, she had sustained head injury after falling on the back of her head with linear fracture of the occipital bone. Neuropathological examination of the girl's brain revealed cerebellar atrophy with specific loss of Purkinje cells. We present findings of detailed neuropathological studies and discuss possible mechanisms of posttraumatic cerebellar atrophy. To the best of our knowledge, cerebellar atrophy following mild head injury in man has not been described morphologically so far.

Cerebellar injury: clinical relevance and potential in traumatic brain injury research

A treatment for traumatic brain injury (TBI) remains elusive despite compelling evidence from animal models for a variety of therapeutic targets. Numerous animal models have been developed to address the wide spectrum of mechanisms involved in the progression of secondary injury after TBI. Evidence from well-established models such as the fluid percussion injury (FPI) device, cortical impact model, and the impact acceleration model has demonstrated diffuse pathophysiological mechanisms throughout various brain structures. More specifically, we have recently extended characterization of the FPI model to include pathophysiological changes in the cerebellum following unilateral fluid percussion. Data suggest that the cerebellum is susceptible to selective Purkinje cell loss as well as white matter dysfunction. Despite the cerebellum's low profile in TBI research, there is evidence to warrant further study of the cerebellum to examine mechanisms of neuronal death and traumatic axonal injury. Furthermore, evidence from clinical literature and basic science suggests that some components of TBI pathophysiology have a basis in cerebellar dysfunction. This review highlights some of the recent findings in cerebellar trauma and builds an argument for including the cerebellum as a model to assess mechanisms of secondary injury and its potential contribution to the pathology of TBI.

Heavy neurofilament accumulation and alpha-spectrin degradation accompany cerebellar white matter functional deficits following forebrain fluid percussion injury

Evidence for diffuse traumatic axonal injury (TAI) in clinical cases and animal models of traumatic brain injury (TBI) indicate that pathophysiological mechanisms extend to regions remote from the injury epicenter. The potential for indirect cerebellar trauma contributing to TBI pathophysiology is of significance since impairment of motor function and coordination is a common consequence of TBI but is also a domain associated with cerebellar function. The relationship between cerebellar white matter structure and function following traumatic head injury has not been examined. Using the fluid percussion injury (FPI) device applied unilaterally in the forebrain, evoked compound action potential (CAP) recordings from cerebellar white matter of Sprague-Dawley rats indicated a spatial and temporal pattern of electrophysiological deficits throughout the cerebellar vermis. The posterior and middle lobules of the cerebellum exhibited significant declines in evoked CAP amplitude compared to sham controls (p=0.004, p=0.005, respectively). Duration of the CAP decay also increased, suggesting that functional white matter deficits were a combination of axonal loss and compromised axonal integrity. Functional white matter deficits persisted at 14 days post-injury in the posterior and middle regions of the cerebellum. Evidence of heavy chain neurofilament (NF200) degradation was observed at 1 day post-injury by Western blot. Immunohistochemistry labeling for NF200 indicated the presence of highly immunoreactive NF200 axonal swellings consistent with morphological features of TAI. alpha-Spectrin degradation was also observed between 1 and 14 days post-injury. This study demonstrates the electrophysiological consequences of cerebellar white matter injury and a temporal profile of NF200 and spectrin degradation following forebrain FPI.

Injury severity determines Purkinje cell loss and microglial activation in the cerebellum after cortical contusion injury

Clinical evidence suggests that the cerebellum is damaged after traumatic brain injury (TBI) and experimental studies have validated these observations. We have previously shown cerebellar vulnerability, as demonstrated by Purkinje cell loss and microglial activation, after fluid percussion brain injury. In this study, we examine the effect of graded controlled cortical impact (CCI) injury on the cerebellum in the context of physiologic and anatomical parameters that have been shown by others to be sensitive to injury severity. Adult male rats received mild, moderate, or severe CCI and were euthanized 7 days later. We first validated the severity of the initial injury using physiologic criteria, including apnea and blood pressure, during the immediate postinjury period. Increasing injury severity was associated with an increased incidence of apnea and higher mortality. Severe injury also induced transient hypertension followed by hypotension, while lower grade injuries produced an immediate and sustained hypotension. We next evaluated the pattern of subcortical neuronal loss in response to graded injuries. There was significant neuronal loss in the ipsilateral cortex, hippocampal CA2/CA3, and laterodorsal thalamus that was injury severity-dependent and that paralleled microglial activation. Similarly, there was a distinctive pattern of Purkinje cell loss and microglial activation in the cerebellar vermis that varied with injury severity. Together, these findings emphasize the vulnerability of the cerebellum to TBI. That a selective pattern of Purkinje cell loss occurs regardless of the type of injury suggests a generalized response that is a likely determinant of recovery and a target for therapeutic intervention.

Structural and functional alterations of cerebellum following fluid percussion injury in rats

Cerebellum was shown to be vulnerable to traumatic brain injury (TBI) in experimental animals. However, the detailed pathological and functional changes within the cerebellum following TBI are not known. Using our established cerebellum fluid percussion injury (FPI) model, we characterized the temporal pattern and the nature of structural damage following FPI, as well as the functional changes of Purkinje cells in response to climbing fiber activation. Our results showed that 60% of Purkinje cells died within the first 24 h following moderate FPI. In contrast, clusters of densely stained shrunken granule cells were stained positive for terminal deoxynucleotidyl transferase-mediated UTP nick end labeling (TUNEL) in 1, 3 or 7 days following FPI animals. We also observed an accompanying structural damage to the cerebellar white matter tract. Disconnected axonal fibers appeared 1 day post-FPI, and loss of white matter fibers were visible 3 and 7 days post-FPI. Massive accumulation of beta-amyloid precursor protein (betaAPP) was found in the white matter tracts and molecular layer in the cerebellum of 1, 3 or 7 days FPI animals. Our functional study showed that the majority of Purkinje cells from 1 day and all cells from 3 to 7 days post-FPI had distorted membrane potential and synaptic responses to climbing fiber activation. These results suggested that there is a co-related structural and functional deterioration with a specific temporal pattern in the cerebellum following FPI. These observations provide a basis for future mechanistic investigations aiming to realize neuroprotection from cerebellar neuronal death and loss of cerebellar functionality.

Purkinje cell vulnerability to mild and severe forebrain head trauma

Pathophysiological changes in the cortex, thalamus, and hippocampus have been implicated as contributors to motor and cognitive deficits in a number of animal models of traumatic brain injury (TBI). Indirect cerebellar injury may contribute to TBI pathophysiology because impairment of motor function and coordination are common consequences of TBI, but are also domains associated with cerebellar function. However, there is a lack of direct evidence to support this claim. Hence, in this study, a dose-response relationship of the cerebellum's susceptibility was determined at four grades of fluid percussion injury (1.5, 2.0, 2.5, and 3.0 atm) applied in the right lateral cerebral cortex of adult male Sprague-Dawley rats. Evidence suggests primary and secondary injury mechanisms resulting in selective cerebellar Purkinje neuron (PN) loss, whereas interneurons of the molecular layer were spared. The posterior region of the cerebellar vermis displayed significant PN loss (p = 0.001) at 1 day postinjury, whereas the gyrus of the horizontal fissure and gyrus of lobules III and IV exhibited delayed PN loss at higher levels of injury severity. Interestingly, neither terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) or cleaved caspase-3 colocalized with PNs at any time point or injury severity. Expression of calbindin-28k increased in regions of greatest PN loss, suggesting that the surviving PNs possess higher calcium-buffering capacities, which may account for their survival.

Susceptibility weighted imaging: neuropsychologic outcome and pediatric head injury

Traumatic brain injury is among the most frequent pediatric neurologic disorders in the United States, affecting multiple aspects of neuropsychologic functioning. This study assessed the efficacy of susceptibility weighted imaging as a predictor of long-term neuropsychologic functioning after pediatric brain injury compared with magnetic resonance spectroscopic imaging. Susceptibility weighted imaging is a relatively new method that is considered superior to traditional magnetic resonance imaging sequences for detecting hemorrhagic diffuse axonal injury. In this study, imaging and spectroscopy were acquired 6 +/- 4 days after injury. Measures of neuropsychologic functioning were administered to 18 children and adolescents 1-4 years post injury. Negative correlations between lesion number and volume with neuropsychologic functioning were demonstrated. Lesion volume explained over 32% of the variance in cognitive performance, explaining at least an additional 20% beyond injury severity and age at injury alone and 19% beyond magnetic resonance spectroscopic metabolite variables. Exploratory analyses resulted in notable trends, with lesions in deeper brain regions more strongly associated with poorer neuropsychologic performance. Improved detection of the extent of diffuse axonal injury following a brain injury will allow for a better understanding of its association with long-term outcome, which in turn can improve prognostic efficacy for effective treatment planning.

Imaging of sequelae of head trauma

The imaging of head trauma has been one of the fundamental cornerstones of neuroradiology. As the practice of neuroimaging has matured, great strides have been made in the diagnostic as well as prognostic armamentarium available to physicians. Given the vast diversity of trauma mechanisms and clinical pathways, new advanced imaging technologies have had a lasting impact on the detection, description, and depiction of head trauma. Furthermore, these new tools are allowing the imaging specialist to function not only as an interpreter of what is seen but as a 21st century radiographic oracle. We present a comprehensive review of the imaging findings of sequlae of traumatic brain injury and the growing correlation of new neuroimaging techniques and neurotraumatic outcomes.