Head injury at early ages is associated with risk of Parkinson's disease

Update: Protective and risk factors for Parkinson disease

We review the epidemiologic literature on potential protective and risk factors in Parkinson's Disease (PD). Prior research identified numerous possible protective and risk factors. Potential protective factors include tobacco abuse, physical activity, urate levels, NSAID use, calcium channel blocker use, statin use, and use of some α1-adrenergic antagonists. Some potential protective factors could be products of reverse causation, including increased serum urate, tobacco abuse, and coffee-tea-caffeine consumption. Potential risk factors include traumatic brain injury, pesticide exposure, organic solvent exposure, lead exposure, air pollution, Type 2 Diabetes, some dairy products, cardiovascular disease, and some infections including Hepatitis C, H. pylori, and COVID-19. Potential non-environmental risk factors include bipolar disorder, essential tremor, bullous pemphigoid, and inflammatory bowel disease. There is an inverse relationship with PD and risk of most cancers. Though many potential protective and risk factors for PD were identified, research has not yet led to unique, rigorous prevention trials or successful disease-modifying interventions. While efforts to reduce exposure to some industrial toxicants are well justified, PD incidence might be most effectively reduced by mitigation of risks, such as Type 2 Diabetes, air pollution, traumatic brain injury, or physical inactivity, that are general public health intervention targets.

The potential role of chronic pain and the polytrauma clinical triad in predicting prodromal PD: A cross-sectional study of U.S. Veterans

Introduction

The research criteria for prodromal Parkinson disease (pPD) depends on prospectively validated clinical inputs with large effect sizes and/or high prevalence. Neither traumatic brain injury (TBI), post-traumatic stress disorder (PTSD), nor chronic pain are currently included in the calculator, despite recent evidence of association with pPD. These conditions are widely prevalent, co-occurring, and already known to confer risk of REM behavior disorder (RBD) and PD. Few studies have examined PD risk in the context of TBI and PTSD; none have examined chronic pain. This study aimed to measure the risk of pPD caused by TBI, PTSD, and chronic pain.

Methods

216 US Veterans were enrolled who had self-reported recurrent or persistent pain for at least three months. Of these, 44 met criteria for PTSD, 39 for TBI, and 41 for all three conditions. Several pain, sleep, affective, and trauma questionnaires were administered. Participants' history of RBD was determined via self-report, with a subset undergoing confirmatory video polysomnography.

Results

A greater proportion of Veterans with chronic pain met criteria for RBD (36 % vs. 10 %) and pPD (18.0 % vs. 8.3 %) compared to controls. Proportions were increased in RBD (70 %) and pPD (27 %) when chronic pain co-occurred with TBI and PTSD. Partial effects were seen with just TBI or PTSD alone. When analyzed as continuous variables, polytrauma symptom severity correlated with pPD probability (r = 0.28, P = 0.03).

Conclusion

These data demonstrate the potential utility of chronic pain, TBI, and PTSD in the prediction of pPD, and the importance of trauma-related factors in the pathogenesis of PD.

Impact of genetic predisposition to late-onset neurodegenerative diseases on early life outcomes and brain structure

Most patients with late-onset neurodegenerative diseases such as Alzheimer's and Parkinson's have a complex aetiology resulting from numerous genetic risk variants of small effects located across the genome, environmental factors, and the interaction between genes and environment. Over the last decade, genome-wide association studies (GWAS) and post-GWAS analyses have shed light on the polygenic architecture of these diseases, enabling polygenic risk scores (PRS) to estimate an individual's relative genetic liability for presenting with the disease. PRS can screen and stratify individuals based on their genetic risk, potentially years or even decades before the onset of clinical symptoms. An emerging body of evidence from various research studies suggests that genetic susceptibility to late-onset neurodegenerative diseases might impact early life outcomes, including cognitive function, brain structure and function, and behaviour. This article summarises recent findings exploring the potential impact of genetic susceptibility to neurodegenerative diseases on early life outcomes. A better understanding of the impact of genetic susceptibility to neurodegenerative diseases early in life could be valuable in disease screening, detection, and prevention and in informing treatment strategies before significant neural damage has occurred. However, ongoing studies have limitations. Overall, our review found several studies focused on APOE haplotypes and Alzheimer's risk, but a limited number of studies leveraging polygenic risk scores or focused on genetic susceptibility to other late-onset conditions.

Health phenome of Parkinson's patients reveals prominent mood-sleep cluster

Background

Associations between phenotypic traits, environmental exposures, and Parkinson's disease have largely been evaluated one-by-one, piecemeal, and pre-selections. A comprehensive picture of comorbidities, phenotypes, exposures, and polypharmacy characterizing the complexity and heterogeneity of real-world patients presenting to academic movement disorders clinics in the US is missing.

Objectives

To portrait the complexity of features associated with patients with Parkinson's disease in a study of 933 cases and 291 controls enrolled in the Harvard Biomarkers Study.

Methods

The primary analysis evaluated 64 health features for associations with Parkinson's using logistic regression adjusting for age and sex. We adjusted for multiple testing using the false discovery rate (FDR) with £ 0.05 indicating statistical significance. Exploratory analyses examined feature correlation clusters and feature combinations.

Results

Depression (OR = 3.11, 95% CI 2.1 to 4.71), anxiety (OR = 3.31, 95% CI 2.01-5.75), sleep apnea (OR 2.58, 95% CI 1.47-4.92), and restless leg syndrome (RLS; OR 4.12, 95% CI 1.81-12.1) were significantly more common in patients with Parkinson's than in controls adjusting for age and sex with FDR £ 0.05. The prevalence of depression, anxiety, sleep apnea, and RLS were correlated, and these diseases formed part of a larger cluster of mood traits and sleep traits linked to PD. Exposures to pesticides (OR 1.87, 95% CI 1.37-2.6), head trauma (OR 2.33, 95% CI 1.51-3.73), and smoking (OR 0.57, 95% CI 0.43-0.75) were significantly associated with the disease consistent with previous studies. Vitamin supplementation with cholecalciferol (OR 2.18, 95% CI 1.4-3.45) and coenzyme Q10 (OR 2.98, 95% CI 1.89-4.92) was more commonly used by patients than controls. Cumulatively, 43% (398 of 933) of Parkinson's patients had at least one psychiatric or sleep disorder, compared to 21% (60 of 291) of healthy controls.

Conclusions

43% of Parkinson's patients seen at Harvard-affiliated teaching hospitals have depression, anxiety, and disordered sleep. This syndromic cluster of mood and sleep traits may be pathophysiologically linked and clinically important.

Membrane phospholipid peroxidation promotes loss of dopaminergic neurons in psychological stress-induced Parkinson's disease susceptibility

Parkinson's disease (PD) is a neurodegenerative disorder associated with α-synuclein aggregation and dopaminergic neuron loss in the midbrain. There is evidence that psychological stress promotes PD progression by enhancing glucocorticoids-related oxidative damage, however, the mechanisms involved are unknown. The present study demonstrated that plasma membrane phospholipid peroxides, as determined by phospholipidomics, triggered ferroptosis in dopaminergic neurons, which in turn contributed to stress exacerbated PD-like motor disorder in mice overexpressing mutant human α-synuclein. Using hormonomics, we identified that stress stimulated corticosteroid release and promoted 15-lipoxygenase-1 (ALOX15)-mediated phospholipid peroxidation. ALOX15 was upregulated by α-synuclein overexpression and acted as a fundamental risk factor in the development of chronic stress-induced parkinsonism and neurodegeneration. Further, we demonstrated the mechanism by which corticosteroids activated the PKC pathway and induced phosphatidylethanolamine-binding protein-1 (PEBP1) to form a complex with ALOX15, thereby facilitating ALOX15 to locate on the plasma membrane phospholipids. A natural product isolated from herbs, leonurine, was screened with activities of inhibiting the ALOX15/PEBP1 interaction and thereby attenuating membrane phospholipid peroxidation. Collectively, our findings demonstrate that stress increases the susceptibility of PD by driving membrane lipid peroxidation of dopaminergic neurons and suggest the ALOX15/PEBP1 complex as a potential intervention target.

Lifelong Association of Disorders Related to Military Trauma with Subsequent Parkinson's Disease

BACKGROUND

Trauma-related disorders such as traumatic brain injury (TBI) and posttraumatic stress disorder (PTSD) are emerging as risk factors for Parkinson's disease (PD), but their association with development of PD and independence from comorbid disorders remains unknown.

OBJECTIVE

To examine TBI and PTSD related to early trauma in military veterans using a case-control study.

METHODS

PD was identified by International Classification of Diseases (ICD) code, recurrent PD-specific prescriptions, and availability of 5+ years of earlier records. Validation was performed by chart review by a movement disorder-trained neurologist. Control subjects were matched 4:1 by age, duration of preceding health care, race, ethnicity, birth year, and sex. TBI and PTSD were identified by ICD code and onset based on active duty. Association and interaction were measured for TBI and PTSD with PD going back 60 years. Interaction was measured for comorbid disorders.

RESULTS

A total of 71,933 cases and 287,732 controls were identified. TBI and PTSD increased odds of subsequent PD at all preceding 5-year intervals back to year -60 (odds ratio range: 1.5 [1.4, 1.7] to 2.1 [2.0, 2.1]). TBI and PTSD showed synergism (synergy index range: 1.14 [1.09, 1.29] to 1.28 [1.09, 1.51]) and additive association (odds ratio range: 2.2 [1.6, 2.8] to 2.7 [2.5, 2.8]). Chronic pain and migraine showed greatest synergy with PTSD and TBI. Effect sizes for trauma-related disorders were comparable with established prodromal disorders.

CONCLUSIONS

TBI and PTSD are associated with later PD and are synergistic with chronic pain and migraine. These findings provide evidence for TBI and PTSD as risk factors preceding PD by decades and could aid in prognostic calculation and earlier intervention. © 2023 International Parkinson and Movement Disorder Society. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Peripherally-induced Movement Disorders: An Update

Background

Peripherally-induced movement disorders (PIMD) should be considered when involuntary or abnormal movements emerge shortly after an injury to a body part. A close topographic and temporal association between peripheral injury and onset of the movement disorders is crucial to diagnosing PIMD. PIMD is under-recognized and often misdiagnosed as functional movement disorder, although both may co-exist. Given the considerable diagnostic, therapeutic, and psychosocial-legal challenges associated with PIMD, it is crucial to update the clinical and scientific information about this important movement disorder.

Methods

A comprehensive PubMed search through a broad range of keywords and combinations was performed in February 2023 to identify relevant articles for this narrative review.

Results

The spectrum of the phenomenology of PIMD is broad and it encompasses both hyperkinetic and hypokinetic movements. Hemifacial spasm is probably the most common PIMD. Others include dystonia, tremor, parkinsonism, myoclonus, painful leg moving toe syndrome, tics, polyminimyoclonus, and amputation stump dyskinesia. We also highlight conditions such as neuropathic tremor, pseudoathetosis, and MYBPC1-associated myogenic tremor as examples of PIMD.

Discussion

There is considerable heterogeneity among PIMD in terms of severity and nature of injury, natural course, association with pain, and response to treatment. As some patients may have co-existing functional movement disorder, neurologists should be able to differentiate the two disorders. While the exact pathophysiology remains elusive, aberrant central sensitization after peripheral stimuli and maladaptive plasticity in the sensorimotor cortex, on a background of genetic (two-hit hypothesis) or other predisposition, seem to play a role in the pathogenesis of PIMD.

Traumatic brain injury and risk of Parkinson's disease: a meta-analysis

BACKGROUND

Association between traumatic brain injury (TBI) and Parkinson's disease (PD) has been a hot topic of discussion for a long time. Previous studies reported that the incidence of PD is significantly higher among elderly adults with a history of TBI. Due to contradictory results of previous investigations, we aimed to perform a systematic review and meta-analysis to investigate the role of TBI as a risk factor for PD.

METHODS

We conducted a systematic literature search in the electronic databases PubMed, Web of Science, and Scopus. In this study, we included published papers on the risk of PD in patients with previous TBI compared to the healthy control group.

RESULTS

After the screening, 15 studies entered our systematic review and meta-analysis. The risk ratio of TBI among PD and controls by a combination of 15 studies using a random-effect model was 1.48 (95% CI 1.22-1.74). The prevalence of TBI by a combination of 14 studies was 18% (95% CI 12-24%).

CONCLUSION

Our result suggests that TBI is a major risk factor for developing PD later in life. At this time, there is a lack of populous prospective cohort studies with sufficient follow-up period to provide a well-documented association between the onset of PD and severity, frequency, and location of prior TBI, which warrants special efforts and consideration for years to come.

Inhibition of Caspase 3 and Caspase 9 Mediated Apoptosis: A Multimodal Therapeutic Target in Traumatic Brain Injury

Traumatic brain injury (TBI) is one of the significant causes of death and morbidity, and it is hence a focus of translational research. Apoptosis plays an essential part in the pathophysiology of TBI, and its inhibition may help overcome TBI's negative consequences and improve functional recovery. Although physiological neuronal death is necessary for appropriate embryologic development and adult cell turnover, it can also drive neurodegeneration. Caspases are principal mediators of cell death due to apoptosis and are critical for the required cleavage of intracellular proteins of cells committed to die. Caspase-3 is the major executioner Caspase of apoptosis and is regulated by a range of cellular components during physiological and pathological conditions. Activation of Caspase-3 causes proteolyzation of DNA repair proteins, cytoskeletal proteins, and the inhibitor of Caspase-activated DNase (ICAD) during programmed cell death, resulting in morphological alterations and DNA damage that define apoptosis. Caspase-9 is an additional crucial part of the intrinsic pathway, activated in response to several stimuli. Caspases can be altered post-translationally or by modulatory elements interacting with the zymogenic or active form of a Caspase, preventing their activation. The necessity of Caspase-9 and -3 in diverse apoptotic situations suggests that mammalian cells have at least four distinct apoptotic pathways. Continued investigation of these processes is anticipated to disclose new Caspase regulatory mechanisms with consequences far beyond apoptotic cell death control. The present review discusses various Caspase-dependent apoptotic pathways and the treatment strategies to inhibit the Caspases potentially.

Parkinson's Disease: Risk Factor Modification and Prevention

The global burden of Parkinson's disease (PD) has increased from 2.5 to 6.1 million since the 1990s. This is expected to rise as the world population ages and lives longer. With the current consensus on the existence of a prediagnostic phase of PD, which can be divided into a preclinical stage and a prodromal stage, we can better define the risk markers and prodromal markers of PD in the broader context of PD pathogenesis. Here, we review this pathogenetic process, and discuss the evidence behind various heritability factors, exposure to pesticides and farming, high dairy consumption, and traumatic brain injuries that have been known to raise PD risk. Physical activity, early active lifestyle, high serum uric acid, caffeine consumption, exposure to tobacco, nonsteroidal anti-inflammatory drugs, and calcium channel blockers, as well as the Mediterranean and the MIND diets are observed to lower PD risk. This knowledge, when combined with ways to identify at-risk populations and early prodromal PD patients, can help the clinician make practical recommendations. Most importantly, it helps us set the parameters for epidemiological studies and create the paradigms for clinical trials.

Olfactory Bulb Excitotoxicity as a Gap-Filling Mechanism Underlying the Link Between Traumatic Brain Injury-Induced Secondary Neuronal Degeneration and Parkinson's Disease-Like Pathology

There is increasing preclinical and clinical data supporting a potential association between Traumatic Brain Injury (TBI) and Parkinson's disease (PD). It has been suggested that the glutamate-induced excitotoxicity underlying TBI secondary neuronal degeneration (SND) might be associated with further development of PD. Interestingly, an accumulation of extracellular glutamate and olfactory dysfunction are both sharing pathological conditions in TBI and PD. The possible involvement of glutamate excitotoxicity in olfactory dysfunction has been recently described, however, the role of olfactory bulbs (OB) glutamate excitotoxicity as a possible mechanism involved in the association between TBI and PD-related neurodegeneration has not been investigated yet. We examined the number of nigral dopaminergic neurons (TH +), nigral α-synuclein expression, the striatal dopamine transporter (DAT) expression, and motor performance after bilateral OB N-Methyl-D-Aspartate (NMDA)-induced excitotoxic lesions in rodents. Bulbar NMDA administration induced a decrease in the number of correct choices in the discrimination tests one week after lesions (p < 0.01) and a significant decrease in the number of nigral DAergic neurons (p < 0.01) associated with an increase in α-synuclein expression (p < 0.01). No significant striatal changes in DAT expression or motor alterations were observed. Our results show an association between TBI-induced SND and PD-related neurodegeneration suggesting that the OB excitotoxicity occurring in TBI SND may be a filling gap mechanism underlying the link between TBI and PD-like pathology.

Case Report: Bilateral Deep Brain Stimulation Implantation on Different Targets for a Parkinson's Disease Patient With a Bullet in the Brain

Patients requiring deep brain stimulation due to intracerebral metallic foreign substances have not been reported elsewhere in the world. Additionally, the long-term effects of metallic foreign bodies on deep brain stimulation (DBS) are unknown. A 79-year-old man with a 5-year history of Parkinson's disease (PD) reported that, 40 years ago, while playing with a pistol, a metallic bullet was accidentally discharged into the left brain through the edge of the left eye, causing no discomfort other than blurry vision in the left eye. DBS was performed due to the short duration of efficacy for oral medication. Because the bullet was on the left subthalamic nucleus (STN) electrode trajectory and the patient's right limb was primarily stiff, the patient received globus pallidus interna (GPi)-DBS implantation in the left hemisphere and STN-DBS implantation in the right hemisphere. During a 6-month postoperative follow-up, the patient's PD symptoms were effectively managed with no noticeable discomfort.

Disorders of Movement due to Acquired and Traumatic Brain Injury

Purpose of Review

Both traumatic and acquired brain injury can result in diffuse multifocal injury affecting both the pyramidal and extrapyramidal tracts. Thus, these patients may exhibit signs of both upper motor neuron syndrome and movement disorder simultaneously which can further complicate diagnosis and management. We will be discussing movement disorders following acquired and traumatic brain injury.

Recent Findings

Multiple functions including speech, swallowing, posture, mobility, and activities of daily living can all be affected. Medical treatment and rehabilitation-based therapy can be especially challenging due to accompanying cognitive deficits and severity of the disorder which can involve multiple limbs in addition to muscles of the face and axial skeleton. Tremor and dystonia are the most reported movement disorders following traumatic brain injury. Dystonia and myoclonus are well documented following hypoxic ischemic brain injuries. Electrophysiological studies such as dynamic surface poly-electromyography can assist with identifying phenomenology, especially differentiating between jerk-like phenomenon and help guide further work up and management. Management with medications remains challenging due to potential adverse effects. Surgical interventions including stereotactic surgery, deep brain stimulation, and intrathecal baclofen pumps have been reported, but most of the evidence supporting them has been limited to primarily case reports except for post-traumatic tremor.

Summary

Brain injury can lead to motor disorders, movement disorders, visual (processing) deficits, and vestibular deficits which often coexist with cognitive deficits making it challenging to treat and rehabilitate these patients. Unfortunately, the evidence regarding the medical management and rehabilitation of brain injury patients with movement disorders is sparse and leaves much to be desired.

Mild repetitive head impacts alter perivascular flow in the midbrain dopaminergic system in awake rats

Head injury is a known risk factor for Parkinson's disease. Disruption in the perivascular clearance of metabolic waste and unwanted proteins is thought to be a contributing factor to disease progression. We hypothesized that repetitive mild head impacts, without evidence of structural brain damage, would increase microgliosis and AQP4 expression and depolarization and alter perivascular flow in the midbrain dopaminergic system. Adult male rats were subjected to sham, or two mild head impacts separated by 48 h. Three weeks later, fully awake rats were imaged using dynamic, contrast-enhanced MRI to follow the distribution of intraventricular gadobenate dimeglumine contrast agent. Images were registered to and analysed using a 3D MRI rat atlas providing site-specific data on 171 different brain areas. Following imaging, rats were tested for cognitive function using the Barnes maze assay. Histological analyses of tyrosine hydroxylase, microglia activation and AQP4 expression and polarization were performed on a parallel cohort of head impacted rats at 20 days post insult to coordinate with the time of imaging. There was no change in the global flux of contrast agent between sham and head impacted rats. The midbrain dopaminergic system showed a significant decrease in the influx of contrast agent as compared to sham controls together with a significant increase in microgliosis, AQP4 expression and depolarization. There were no deficits in cognitive function. The histology showed a significant level of neuroinflammation in the midbrain dopaminergic system 3 weeks post mild repetitive head impact but no loss in tyrosine hydroxylase. MRI revealed no structural brain damage emphasizing the potential serious consequences of mild head impacts on sustained brain neuroinflammation in this area critical to the pathophysiology of Parkinson's.

Neuroprotective effects of low-intensity transcranial ultrasound stimulation combined with Baicalin intervention on traumatic brain injury in animals

Low-intensity transcranial ultrasound stimulation (LITUS) can improve the inflammatory reaction after traumatic brain injury (TBI), and Baicalin also has a good protective effect on TBI. The purpose of this study was to observe the neuroprotective effect of LITUS combined with Baicalin intervention in the TBI rats. Sprague Dawley (SD) rats were randomly divided into 5 groups (n = 15) which were Sham control group, TBI group, LITUS group, Baicalin group, LITUS combined with Baicalin group (LB group). The rats were scanned with 3.0 T magnetic resonance imager, and the apparent diffusion coefficient (ADC) and the fractional anisotropy (FA) of the brain injury cortical area were determined at 3 h, 1, 3, 7 and 10 d after TBI. The ADC value, FA value, neurological function score and Nissl staining were used to assess the level of brain damage of rats. The results showed that on the 10th day after TBI, the ADC values of the TBI group, the LITUS group and the Baicalin group were remarkable greater than that of the L-B group (all adjusted P <  0.05), FA values were remarkable smaller than that of the L-B group (all adjusted P <  0.05), neurological function scores were remarkable greater than that of the L-B group (all adjusted P <  0.05), and Nissl body loss rates were remarkable greater than that of the L-B group (all adjusted P <  0.001). This study indicated that compared with the LITUS group and the Baicalin group, the L-B group can more effectively reduce level of brain damage after TBI, and the method of LITUS combined with Baicalin intervention was a more effective neuroprotection for brain injury.

Traumatic injury compromises nucleocytoplasmic transport and leads to TDP-43 pathology

Traumatic brain injury (TBI) is a predisposing factor for many neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), and chronic traumatic encephalopathy (CTE). Although defects in nucleocytoplasmic transport (NCT) is reported ALS and other neurodegenerative diseases, whether defects in NCT occur in TBI remains unknown. We performed proteomic analysis on Drosophila exposed to repeated TBI and identified resultant alterations in several novel molecular pathways. TBI upregulated nuclear pore complex (NPC) and nucleocytoplasmic transport (NCT) proteins as well as alter nucleoporin stability. Traumatic injury disrupted RanGAP1 and NPC protein distribution in flies and a rat model and led to coaggregation of NPC components and TDP-43. In addition, trauma-mediated NCT defects and lethality are rescued by nuclear export inhibitors. Importantly, genetic upregulation of nucleoporins in vivo and in vitro triggered TDP-43 cytoplasmic mislocalization, aggregation, and altered solubility and reduced motor function and lifespan of animals. We also found NUP62 pathology and elevated NUP62 concentrations in postmortem brain tissues of patients with mild or severe CTE as well as co-localization of NUP62 and TDP-43 in CTE. These findings indicate that TBI leads to NCT defects, which potentially mediate the TDP-43 pathology in CTE.

Pesticide use and incident Parkinson's disease in a cohort of farmers and their spouses

BACKGROUND

Extensive literature suggests an association between general pesticide use and Parkinson's disease (PD). However, with few exceptions, little is known about associations between specific pesticides and PD.

OBJECTIVE

We evaluated use of pesticides and incident PD in 38,274 pesticide applicators and 27,836 of their spouses in the Agricultural Health Study cohort followed over 20 years.

METHODS

We used self-reported information on ever-use of 50 specific pesticides as of enrollment for both applicators and spouses, and considered intensity-weighted lifetime days (IWLD) reported at enrollment and through the first 5-year follow-up among applicators. We estimated covariate-adjusted hazard ratios (HR) and 95% confidence intervals (CI) using Cox regression. We also examined heterogeneity in associations by history of head injury and chemical resistant glove use.

RESULTS

A total of 373 applicators and 118 spouses self-reported incident doctor-diagnosed PD. Ever-use of the insecticide terbufos (HR:1.31, 95%CI:1.02-1.68) and the herbicides trifluralin (HR:1.29, 95%CI: 0.99-1.70) and 2,4,5-T (HR:1.57, 95%CI:1.21-2.04) was associated with elevated PD risk. On the other hand, diazinon (HR:0.73, 95%CI: 0.58-0.94) and 2,4,5-TP (HR:0.39, 95%CI:0.25-0.62) were associated with reduced risk. We observed heterogeneity in ever-use associations by head injury and chemical-resistant glove use for some pesticides, with higher risk among those who reported a history of head injury, or who did not use gloves. PD risk was also elevated for applicators in the highest category of IWLD for dichlorvos, permethrin (animal use), and benomyl.

CONCLUSIONS

We found evidence of increased PD risk for some pesticides. Our results also suggest higher susceptibility for pesticide-associated PD among individuals with head injury as well as protection with use of chemical resistant gloves, although further research is needed to understand the impact of head injury. Research on current and newer pesticides, including mechanisms relevant to PD, is important given widespread pesticide use.

Mild traumatic brain injury exacerbates Parkinson's disease induced hemeoxygenase-2 expression and brain pathology: Neuroprotective effects of co-administration of TiO2 nanowired mesenchymal stem cells and cerebrolysin

Mild traumatic brain injury (mTBI) is one of the leading predisposing factors in the development of Parkinson's disease (PD). Mild or moderate TBI induces rapid production of tau protein and alpha synuclein (ASNC) in the cerebrospinal fluid (CSF) and in several brain areas. Enhanced tau-phosphorylation and ASNC alters the molecular machinery of the brain leading to PD pathology. Recent evidences show upregulation of constitutive isoform of hemeoxygenase (HO-2) in PD patients that correlates well with the brain pathology. mTBI alone induces profound upregulation of HO-2 immunoreactivity. Thus, it would be interesting to explore whether mTBI exacerbates PD pathology in relation to tau, ASNC and HO-2 expression. In addition, whether neurotrophic factors and stem cells known to reduce brain pathology in TBI could induce neuroprotection in PD following mTBI. In this review role of mesenchymal stem cells (MSCs) and cerebrolysin (CBL), a well-balanced composition of several neurotrophic factors and active peptide fragments using nanowired delivery in PD following mTBI is discussed based on our own investigation. Our results show that mTBI induces concussion exacerbates PD pathology and nanowired delivery of MSCs and CBL induces superior neuroprotection. This could be due to reduction in tau, ASNC and HO-2 expression in PD following mTBI, not reported earlier. The functional significance of our findings in relation to clinical strategies is discussed.

Effect of long-term particulate matter exposure on Parkinson's risk

Environmental pollution is a critical predisposing factor underlying neurodegenerative diseases, but the association between particulate matter (PM) exposure and Parkinson's disease (PD) remains unclear. This study aimed to evaluate the association between long-term PM2.5/PM10 exposure and PD risk. We searched the PubMed, Ovid Medline, EMBASE, Cochrane Library, and Web of Science citation databases to select studies about the relationship between long-term PM exposure and PD risk. The association was assessed using meta-analysis, and subgroup analysis was carried out on the basis of the types of PM (PM2.5 and PM10). Among the 611 articles identified from the databases, we selected six articles, including three cohort studies and three case-control studies, which collectively involved 10,077,029 participants. With every 10 μg/m³ increment, the relative risks (RRs) and 95% confidence intervals (CIs) were 1.03 (0.98, 1.07), 1.21 (0.95, 1.54), and 1.01 (0.97, 1.05) for the total PM, PM2.5, and PM10, respectively. In the current study, no statistically substantial association was observed between long-term PM2.5/PM10 exposure and PD incidence. However, further large-scale prospective studies are needed to determine the association.

Network diffusion modeling predicts neurodegeneration in traumatic brain injury

Objective

Traumatic brain injury (TBI) is a heterogeneous disease with multiple neurological deficits that evolve over time. It is also associated with an increased incidence of neurodegenerative diseases. Accordingly, clinicians need better tools to predict a patient’s long‐term prognosis.

Methods

Diffusion‐weighted and anatomical MRI data were collected from 17 adolescents (mean age = 15y8mo) with moderate‐to‐severe TBI and 19 healthy controls. Using a network diffusion model (NDM), we examined the effect of progressive deafferentation and gray matter thinning in young TBI patients. Moreover, using a novel automated inference method, we identified several injury epicenters in order to determine the neural degenerative patterns in each TBI patient.

Results

We were able to identify the subject‐specific patterns of degeneration in each patient. In particular, the hippocampus, temporal cortices, and striatum were frequently found to be the epicenters of degeneration across the TBI patients. Orthogonal transformation of the predicted degeneration, using principal component analysis, identified distinct spatial components in the temporal–hippocampal network and the cortico‐striatal network, confirming the vulnerability of these networks to injury. The NDM model, best predictive of the degeneration, was significantly correlated with time since injury, indicating that NDM can potentially capture the pathological progression in the chronic phase of TBI.

Interpretation

These findings suggest that network spread may help explain patterns of distant gray matter thinning, which would be consistent with Wallerian degeneration of the white matter connections (i.e., “diaschisis”) from diffuse axonal injuries and multifocal contusive injuries, and the neurodegenerative patterns of abnormal protein aggregation and transmission, which are hallmarks of brain changes in TBI. NDM approaches could provide highly subject‐specific biomarkers relevant for disease monitoring and personalized therapies in TBI.

Traumatic brain injury preceding clinically diagnosed α-synucleinopathies: A case-control study

OBJECTIVE

To determine the association between traumatic brain injury (TBI) and any clinically diagnosed α-synucleinopathy including Parkinson disease (PD), dementia with Lewy bodies (DLB), PD dementia (PDD), and multiple system atrophy (MSA).

METHODS

Using the medical records-linkage system of the Rochester Epidemiology Project, we identified incident cases of α-synucleinopathies in Olmsted County, Minnesota, from 1991 to 2010, matching by age (±1 year) at symptom onset and sex to controls. We reviewed records of cases and controls to detect TBI prior to clinical-motor onset of any α-synucleinopathies. We based severity (possible, probable, and definite) upon the Mayo Classification System for TBI Severity. Using conditional-logistic regression, we calculated the odds ratio (OR) of all α-synucleinopathies and type, adjusting for coffee intake and smoking.

RESULTS

TBI frequency was lower among cases (7.0%) than controls (8.2%). No association was found between TBI and all α-synucleinopathies in multivariable analyses (OR 0.90, 95% confidence interval [CI] 0.54-1.52). No association presented when examining the number of TBIs, TBI severity, time between TBI exposure and index date, age at index date, or sex. When stratifying by each individual α-synucleinopathy, we did not identify any associations between TBI and PD, DLB, or PDD. Among the MSA group, 1 (6.4%) and 0 controls experienced a TBI (OR could not be estimated).

CONCLUSIONS

In this nested case-control population-based analysis, TBI was not associated with subsequent α-synucleinopathies in general or any individual α-synucleinopathy. This did not change based on the temporality or the severity of the TBI. Our findings may be limited by the study power.

Traumatic Brain Injuries: Unreported and Untreated in an Army Population

Introduction

In 2008, it was reported that 19.5% of service members previously deployed experienced a mild traumatic brain injury (mTBI). Fifty-seven percent of those did not seek medical care. It was suggested that concerns with seeking care involved confidentiality and career issues. Objective: This study addressed mTBI history, medical treatment history, and stigmas associated with mTBI/concussion.

Materials and Methods

An anonymous questionnaire was developed. Data collection occurred throughout March 2018 in conjunction with Brain Injury Awareness Month activities.

Results

All 5,174 volunteers were Army; 86% male; 87% were between 18 and 34 years old; 89% had &lt;14 years in the military; 35% had a combat deployment; and 10% reported having one or more mTBIs in their military careers. Of the Soldiers who reported a concussion, 52% sought medical care. Of those not seeking care, 64% reported they did not think the injury required care, followed by 18% fearing negative impact on their career. Twenty-eight percent who experienced an mTBI versus 11% who have not reported that there is a stigma associated with an mTBI.

Conclusions

Soldiers sometimes failed to report their suspected concussions and did not seek medical care. Educational efforts may increase reporting of and medical screening for potentially concussive events. Future research to determine the ramifications of unreported and untreated mTBIs/concussions is recommended.

The impact of traumatic brain injury on cognitive and neuropsychiatric symptoms of Parkinson's disease

The objective was to determine whether a history of traumatic brain injury (TBI) was associated with Parkinson's Disease (PD) and specific cognitive, motor, and neuropsychiatric symptoms. A cross-sectional cohort study of 120 participants aged 60-85 years old (48 females) were recruited (69 PD and 51 healthy controls). Assessments included demographic information, neuropsychological tests, a motor evaluation, neuropsychiatric questionnaires, and the Brain Injury Screening Questionnaire. A history of TBI or number of TBIs was not significantly related to an increased risk of developing PD or poorer motor scores on the United Parkinson Disease Rating Scale part 3. There was a significant negative correlation between number of TBI's and mean z-scores of global cognition (r_s(69) = -0.338, p = 0.004), executive function (r_s(69) = -0.251, p = 0.038), memory (r_s(69) = -0.262, p = 0.029), and language (r_s(69) = -0.245, p = 0.042), and a significant positive correlation on the Beck Depression Inventory II (r_s(69) = 0.285, p = 0.018) and the Patient Health Questionnaire-9 (PHQ-9) (r_s(69) = 0.326, p = 0.006) in the PD group only. In conclusion, a history of TBI was negatively associated with cognition and positively associated with depressive symptoms in patients with PD, but not with motor symptoms.

The Changing Landscape of Parkinson Epidemiologic Research

Despite recent successes in understanding the genetics of Parkinson’s disease (PD), the causes of late-onset sporadic PD remain elusive. Many of the epidemiologic findings on PD etiology have been challenged by alternative explanations such as reverse causation. This is mainly because PD often takes decades to develop before it can be diagnosed late in life. Convincing evidence shows that this prodromal stage of PD is characterized by various prodromal symptoms such as olfactory impairment and rapid-eye-movement sleep behavior disorder (RBD). As they likely reflect PD pathogenesis years, if not decades, before nigrostriatal involvement, research on these symptoms may represent an unprecedented opportunity to dissect the etiology of PD. Using PD prodromal symptoms as intermediate phenotypes, we may be able to identify factors that contribute to the development of these symptoms and factors that modify their progression to clinical PD. Further, this line of research will also enable examinations of novel etiological hypotheses of PD development such as the microbiome and prion hypotheses. In this article, the author used olfactory impairment and RBD as examples to illustrate the promises and challenges of epidemiologic research on prodromal symptoms to understand PD etiology.

Traumatic Brain Injury and Age of Onset of Dementia with Lewy Bodies

BACKGROUND

Traumatic brain injury (TBI) with loss of consciousness (LOC) has been associated with earlier onset of mild cognitive impairment, frontotemporal dementia, Parkinson's disease, and Alzheimer's disease (AD), but has not been examined as a risk factor for earlier onset of dementia with Lewy bodies (DLB).

OBJECTIVE

The purpose of this study was to assess the association between a history of TBI and the age of onset of DLB.

METHOD

Data from 576 subjects with a clinical diagnosis of DLB were obtained from the National Alzheimer's Coordinating Center (NACC). Analyses of Covariance examined whether self-reported history of remote TBI with LOC (i.e., >1 year prior to the first Alzheimer's Disease Center visit) was associated with earlier DLB symptom onset.

RESULTS

Controlling for sex, those with a history of remote TBI had an approximately 1.5-year earlier clinician-estimated age of onset (F = 0.87, p = 0.35) and 0.75-years earlier age of diagnosis (F = 0.14, p = 0.71) of DLB compared to those without a history of TBI, though the differences did not reach statistical significance. Analysis of subjects with autopsy-confirmed diagnoses was underpowered due to the low number of TBI+ subjects.

CONCLUSIONS

Remote TBI with LOC was not significantly associated with DLB onset, despite being a significant risk factor for cognitive decline and earlier age of onset in other neurodegenerative conditions. Replication of these results using a larger cohort of DLB subjects with and without a TBI history who have undergone autopsy is indicated, as our TBI+ subjects did show a slightly earlier onset of about 1.5 years. Further investigations into other potential DLB risk factors are also warranted.

The interplay of aging, genetics and environmental factors in the pathogenesis of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is characterized by dopaminergic neuronal loss in the substantia nigra pars compacta and intracellular inclusions called Lewy bodies (LB). During the course of disease, misfolded α-synuclein, the major constituent of LB, spreads to different regions of the brain in a prion-like fashion, giving rise to successive non-motor and motor symptoms. Etiology is likely multifactorial, and involves interplay among aging, genetic susceptibility and environmental factors.

MAIN BODY

The prevalence of PD rises exponentially with age, and aging is associated with impairment of cellular pathways which increases susceptibility of dopaminergic neurons to cell death. However, the majority of those over the age of 80 do not have PD, thus other factors in addition to aging are needed to cause disease. Discovery of neurotoxins which can result in parkinsonism led to efforts in identifying environmental factors which may influence PD risk. Nevertheless, the causality of most environmental factors is not conclusively established, and alternative explanations such as reverse causality and recall bias cannot be excluded. The lack of geographic clusters and conjugal cases also go against environmental toxins as a major cause of PD. Rare mutations as well as common variants in genes such as SNCA, LRRK2 and GBA are associated with risk of PD, but Mendelian causes collectively only account for 5% of PD and common polymorphisms are associated with small increase in PD risk. Heritability of PD has been estimated to be around 30%. Thus, aging, genetics and environmental factors each alone is rarely sufficient to cause PD for most patients.

CONCLUSION

PD is a multifactorial disorder involving interplay of aging, genetics and environmental factors. This has implications on the development of appropriate animal models of PD which take all these factors into account. Common converging pathways likely include mitochondrial dysfunction, impaired autophagy, oxidative stress and neuroinflammation, which are associated with the accumulation and spread of misfolded α-synuclein and neurodegeneration. Understanding the mechanisms involved in the initiation and progression of PD may lead to potential therapeutic targets to prevent PD or modify its course.

Neuroradiological Changes Following Single or Repetitive Mild TBI

Objectives

To test the hypothesis that there are differences in neuroradiological measures between single and repeated mild traumatic brain injury using multimodal MRI.

Methods

A closed-head momentum exchange model was used to produce one or three mild head injuries in young adult male rats compared to non-injured, age and weight-matched controls. Six-seven weeks post-injury, rats were studied for deficits in cognitive and motor function. Seven-eight weeks post-injury changes in brain anatomy and function were evaluated through analysis of high resolution T2 weighted images, resting-state BOLD functional connectivity, and diffusion weighted imaging with quantitative anisotropy.

Results

Head injuries occurred without skull fracture or signs of intracranial bleeding or contusion. There were no significant differences in cognitive or motors behaviors between experimental groups. With a single mild hit, the affected areas were limited to the caudate/putamen and central amygdala. Rats hit three times showed altered diffusivity in white matter tracts, basal ganglia, central amygdala, brainstem, and cerebellum. Comparing three hits to one hit showed a similar pattern of change underscoring a dose effect of repeated head injury on the brainstem and cerebellum. Disruption of functional connectivity was pronounced with three mild hits. The midbrain dopamine system, hippocampus, and brainstem/cerebellum showed hypoconnectivity. Interestingly, rats exposed to one hit showed enhanced functional connectivity (or hyperconnectivity) across brain sites, particularly between the olfactory system and the cerebellum.

Interpretation

Neuroradiological evidence of altered brain structure and function, particularly in striatal and midbrain dopaminergic areas, persists long after mild repetitive head injury. These changes may serve as biomarkers of neurodegeneration and risk for dementia later in life.

Lower Posttraumatic α-Synuclein Level Associated With Altered Default Mode Network Connectivity Following Acute Mild Traumatic Brain Injury

This study aimed to investigate the changes of α-synuclein in serum and its relationship with default mode network (DMN) connectivity after acute mild traumatic brain injury (mild TBI). Fifty-two patients with mild TBI at the acute phase and 47 matched healthy controls were enrolled in the study. All participants received resting-state functional magnetic resonance imaging (fMRI) and neuropsychological assessments. Relations between the levels of α-synuclein in serum and clinical assessments were obtained using multivariate linear regression. Results showed that the patients with lower α-synuclein presented more complaints on post-concussion symptoms and depression. Moreover, patients with high levels of α-synuclein exhibited significantly decreased functional connectivity in the left precuneus and increased functional connectivity in both the left anterior cingulate cortex and ventro-medial prefrontal cortex (MPFC) compared with patients with low levels of α-synuclein. These findings supported that α-synuclein may modulate the functional connectivity within the DMN and suggest the feasibility of using α-synuclein as an objective biomarker for diagnosis and prognosis of mild TBI.

Is traumatic brain injury a risk factor for neurodegeneration? A meta-analysis of population-based studies

Background

To determine the association of prior traumatic brain injury (TBI) with subsequent diagnosis of neurodegeneration disease.

Methods

All studies from 1980 to 2016 reporting TBI as a risk factor for diagnoses of interest were identified by searching PubMed, Embase, study references, and review articles. The data and study design were assessed by 2 investigators independently. A meta-analysis was performed by RevMan 5.3.

Results

There were 18 studies comprising 3,263,207 patients. Meta-analysis revealed a significant association of prior TBI with subsequent dementia. The pooled odds ratio (OR) for TBI on development of dementia, FTD and TDP-43 associated disease were 1.93 (95% CI 1.47–2.55, p < 0.001), 4.44 (95% CI 3.86–5.10, p < 0.001), and 2.97 (95% CI 1.35–6.53, p < 0.001). However, analyses of individual diagnoses found no evidence that the risk of Alzheimer’s disease, and Parkinson’s disease in individuals with previous TBI compared to those without TBI.

Conclusions

History of TBI is not associated with the development of subsequent neurodegeneration disease. Care must be taken in extrapolating from these results because no suitable criteria define post TBI neurodegenerative processes. Therefore, further research in this area is needed to confirm these questions and uncover the link between TBI and neurodegeneration disease.

Chronic Upregulation of Cleaved-Caspase-3 Associated with Chronic Myelin Pathology and Microvascular Reorganization in the Thalamus after Traumatic Brain Injury in Rats

Traumatic brain injury (TBI) is associated with long-term disabilities and devastating chronic neurological complications including problems with cognition, motor function, sensory processing, as well as behavioral deficits and mental health problems such as anxiety, depression, personality change and social unsuitability. Clinical data suggest that disruption of the thalamo-cortical system including anatomical and metabolic changes in the thalamus following TBI might be responsible for some chronic neurological deficits following brain trauma. Detailed mechanisms of these pathological processes are not completely understood. The goal of this study was to evaluate changes in the thalamus following TBI focusing on cleaved-caspase-3, a specific effector of caspase pathway activation and myelin and microvascular pathologies using immuno- and histochemistry at different time points from 24 h to 3 months after controlled cortical impact (CCI) in adult Sprague-Dawley rats. Significant increases in cleaved-caspase-3 immunoreactivity in the thalamus were observed starting one month and persisting for at least three months following experimental TBI. Further, the study demonstrated an association of cleaved-caspase-3 with the demyelination of neuronal processes and tissue degeneration in the gray matter in the thalamus, as reflected in alterations of myelinated fiber integrity (luxol fast blue) and decreases in myelin basic protein (MBP) immunoreactivity. The immunofluorescent counterstaining of cleaved-caspase-3 with endothelial barrier antigen (EBA), a marker of blood-brain barrier, revealed limited direct and indirect associations of cleaved caspase-3 with blood-brain barrier damage. These results demonstrate for the first time a significant chronic upregulation of cleaved-caspase-3 in selected thalamic regions associated with cortical regions directly affected by CCI injury. Further, our study is also the first to report that significant upregulation of cleaved-caspase-3 in selected ipsilateral thalamic regions is associated with microvascular reorganization reflected in the significant increases in the number of microvessels with blood-brain barrier alterations detected by EBA staining. These findings provide new insights into potential mechanisms of TBI cell death involving chronic activation of caspase-3 associated with disrupted cortico-thalamic and thalamo-cortical connectivity. Moreover, this study offers the initial evidence that this upregulation of activated caspase-3, delayed degeneration of myelinated nerve fibers and microvascular reorganization with impaired blood-brain barrier integrity in the thalamus might represent reciprocal pathological processes affecting neuronal networks and brain function at the chronic stages of TBI.

Traumatic Brain Injury, Chronic Traumatic Encephalopathy, and Alzheimer Disease

Traumatic brain injury (TBI) is a major health and economic burden. With increasing aging population, this issue is expected to continue to rise. Neurodegenerative disorders are more common with aging population in general regardless of history of TBI. Recent evidence continues to support a relation between a TBI and neurocognitive decline later in life (such as in athletes and military). This article summarizes the pathologic and clinical effects of TBI (regardless of severity) on the later development of dementia in individuals 65 years or older.

Factors associated with dream enacting behaviors among US farmers

INTRODUCTION

Dream enacting behavior (DEB) during REM sleep is a characteristic feature of REM sleep behavior disorder (RBD), the most specific prodromal symptom for Parkinson's disease (PD) and related synucleinopathies.

METHODS

We screened for DEB among 20,591 male farmers in 2013-2015 using a validated question, and examined its association with pesticide uses and other potential risk factors reported about twenty years ago in 1993-1997. We reported odds ratios (OR) and 95% confidence intervals (CI) from multivariable logistic regression models.

RESULTS

A total of 1623 (7.9%) farmers reported having had DEB. Farmers with DEB were more likely to report other nonmotor and motor symptoms of PD with age-adjusted ORs ranging from 1.9 to 3.0. DEB prevalence varied little by age, but was significantly associated with current smoking (adjusted OR: 1.4, 95%CI: 1.2, 1.6), daily alcohol drinking (OR: 1.4, 95%CI: 1.1, 1.6), a history of head injury (OR: 1.3, 95%CI: 1.2, 1.5), and being married (OR: 1.4, 95%CI: 1.1, 1.7). We identified significant associations for several pesticides, especially cyclodiene organochlorines and pyrethroids, with adjusted ORs ranging from 1.2 to 1.5. The results were similar after excluding PD cases or when farmers with at least three DEB episodes in life were considered as DEB cases.

CONCLUSIONS

This study suggests that DEB are not rare among male farmers. Findings on potential risk factors for DEB are intriguing, and given the close link between RBD and PD, these associations should be further investigated.

Mild TBI and risk of Parkinson disease: A Chronic Effects of Neurotrauma Consortium Study

OBJECTIVE

Our aim was to assess risk of Parkinson disease (PD) following traumatic brain injury (TBI), including specifically mild TBI (mTBI), among care recipients in the Veterans Health Administration.

METHODS

In this retrospective cohort study, we identified all patients with a TBI diagnosis in Veterans Health Administration databases from October 2002 to September 2014 and age-matched 1:1 to a random sample of patients without TBI. All patients were aged 18 years and older without PD or dementia at baseline. TBI exposure and severity were determined via detailed clinical assessments or ICD-9 codes using Department of Defense and Defense and Veterans Brain Injury Center criteria. Baseline comorbidities and incident PD more than 1 year post-TBI were identified using ICD-9 codes. Risk of PD after TBI was assessed using Cox proportional hazard models adjusted for demographics and medical/psychiatric comorbidities.

RESULTS

Among 325,870 patients (half with TBI; average age 47.9 ± 17.4 years; average follow-up 4.6 years), 1,462 were diagnosed with PD during follow-up. Compared to no TBI, those with TBI had higher incidence of PD (no TBI 0.31%, all-severity TBI 0.58%, mTBI 0.47%, moderate-severe TBI 0.75%). In adjusted models, all-severity TBI, mTBI, and moderate-severe TBI were associated with increased risk of PD (hazard ratio [95% confidence interval]: all-severity TBI 1.71 [1.53-1.92]; mTBI 1.56 [1.35-1.80]; moderate-severe TBI 1.83 [1.61-2.07]).

CONCLUSIONS

Among military veterans, mTBI is associated with 56% increased risk of PD, even after adjusting for demographics and medical/psychiatric comorbidities. This study highlights the importance of TBI prevention, long-term follow-up of TBI-exposed veterans, and the need to determine mechanisms and modifiable risk factors for post-TBI PD.

Head trauma and Parkinson's disease: results from an Italian case-control study

We evaluated the possible association between head trauma and Parkinson's disease (PD). The FRAGAMP (Fattori di Rischio Ambientali e Genetici Associati alla Malattia di Parkinson) study is a large Italian multicenter case-control study carried out to evaluate the possible role of environmental and genetic factors in PD. Cases and controls were enrolled from six movement disorders centers located in the Central-Southern Italy. A standardized questionnaire was administered to record demographic, epidemiological, and clinical data. Positive history of head trauma was considered only if the head trauma preceded the onset of PD. All cases and controls underwent a standard neurological examination. Adjusted ORs and 95% CI were estimated using multivariate analysis (logistic regression). Four hundred ninety-two PD patients (292 men and 200 women) and 459 controls (160 men and 299 women) were enrolled in the study. A positive history for head trauma was reported by 106 (21.5%) PD patients and by 62 (13.5%) healthy controls. Multivariate analysis (OR adjusted by age, sex, family history, coffee smoking, and alcohol consumption) showed a significant positive association between PD and head trauma with an adjusted OR of 1.50 (95%CI 1.04-2.17; p value 0.03). In agreement with literature data, our study supports the positive association between head trauma and PD.

Prospective clinical biomarkers of caspase-mediated apoptosis associated with neuronal and neurovascular damage following stroke and other severe brain injuries: Implications for chronic neurodegeneration

Acute brain injuries, including ischemic and hemorrhagic stroke, as well as traumatic brain injury (TBI), are major worldwide health concerns with very limited options for effective diagnosis and treatment. Stroke and TBI pose an increased risk for the development of chronic neurodegenerative diseases, notably chronic traumatic encephalopathy, Alzheimer's disease, and Parkinson's disease. The existence of premorbid neurodegenerative diseases can exacerbate the severity and prognosis of acute brain injuries. Apoptosis involving caspase-3 is one of the most common mechanisms involved in the etiopathology of both acute and chronic neurological and neurodegenerative diseases, suggesting a relationship between these disorders. Over the past two decades, several clinical biomarkers of apoptosis have been identified in cerebrospinal fluid and peripheral blood following ischemic stroke, intracerebral and subarachnoid hemorrhage, and TBI. These biomarkers include selected caspases, notably caspase-3 and its specific cleavage products such as caspase-cleaved cytokeratin-18, caspase-cleaved tau, and a caspase-specific 120 kDa αII-spectrin breakdown product. The levels of these biomarkers might be a valuable tool for the identification of pathological pathways such as apoptosis and inflammation involved in injury progression, assessment of injury severity, and prediction of clinical outcomes. This review focuses on clinical studies involving biomarkers of caspase-3-mediated pathways, following stroke and TBI. The review further examines their prospective diagnostic utility, as well as clinical utility for improved personalized treatment of stroke and TBI patients and the development of prophylactic treatment chronic neurodegenerative disease.

Moderate traumatic brain injury increases the vulnerability to neurotoxicity induced by systemic administration of 6-hydroxydopamine in mice

Moderate traumatic brain injury (TBI) might increase the vulnerability to neuronal neurodegeneration, but the basis of such selective neuronal susceptibility has remained elusive. In keeping with the disruption of the blood-brain barrier (BBB) caused by TBI, changes in BBB permeability following brain injury could facilitate the access of xenobiotics into the brain. To test this hypothesis, here we evaluated whether TBI would increase the susceptibility of nigrostriatal dopaminergic fibers to the systemic administration of 6-hydroxydopamine (6-OHDA), a classic neurotoxin used to trigger a PD-like phenotype in mice, but that in normal conditions is unable to cross the BBB. Adult Swiss mice were submitted to a moderate TBI using a free weight-drop device and, 5h later, they were injected intraperitoneally with a single dose of 6-OHDA (100mg/kg). Afterwards, during a period of 4weeks, the mice were submitted to a battery of behavioral tests, including the neurological severity score (NSS), the open field and the rotarod. Animals from the TBI plus 6-OHDA group displayed significant motor and neurological impairments that were improved by acute l-DOPA administration (25mg/kg, i.p.). Moreover, the observation of the motor deficits correlates with (i) a significant decrease in the tyrosine hydroxylase levels mainly in the rostral striatum and (ii) a significant increase in the levels of striatal glial fibrillary acidic protein (GFAP) levels. On the whole, the present findings demonstrate that a previous moderate TBI event increases the susceptibility to motor, neurological and neurochemical alterations induced by systemic administration of the dopaminergic neurotoxin 6-OHDA in mice.

Modelling idiopathic Parkinson disease as a complex illness can inform incidence rate in healthy adults: the PR EDIGT score

Fifty-five years after the concept of dopamine replacement therapy was introduced, Parkinson disease (PD) remains an incurable neurological disorder. To date, no disease-modifying therapeutic has been approved. The inability to predict PD incidence risk in healthy adults is seen as a limitation in drug development, because by the time of clinical diagnosis ≥ 60% of dopamine neurons have been lost. We have designed an incidence prediction model founded on the concept that the pathogenesis of PD is similar to that of many disorders observed in ageing humans, i.e. a complex, multifactorial disease. Our model considers five factors to determine cumulative incidence rates for PD in healthy adults: (i) DNA variants that alter susceptibility (D), e.g. carrying a LRRK2 or GBA risk allele; (ii) Exposure history to select environmental factors including xenobiotics (E); (iii) Gene-environment interactions that initiate pathological tissue responses (I), e.g. a rise in ROS levels, misprocessing of amyloidogenic proteins (foremost, α-synuclein) and dysregulated inflammation; (iv) sex (or gender; G); and importantly, (v) time (T) encompassing ageing-related changes, latency of illness and propagation of disease. We propose that cumulative incidence rates for PD (PR ) can be calculated in healthy adults, using the formula: PR (%) = (E + D + I) × G × T. Here, we demonstrate six case scenarios leading to young-onset parkinsonism (n = 3) and late-onset PD (n = 3). Further development and validation of this prediction model and its scoring system promise to improve subject recruitment in future intervention trials. Such efforts will be aimed at disease prevention through targeted selection of healthy individuals with a higher prediction score for developing PD in the future and at disease modification in subjects that already manifest prodromal signs.

Combination therapies for neurobehavioral and cognitive recovery after experimental traumatic brain injury: Is more better?

Traumatic brain injury (TBI) is a significant health care crisis that affects two million individuals in the United Sates alone and over ten million worldwide each year. While numerous monotherapies have been evaluated and shown to be beneficial at the bench, similar results have not translated to the clinic. One reason for the lack of successful translation may be due to the fact that TBI is a heterogeneous disease that affects multiple mechanisms, thus requiring a therapeutic approach that can act on complementary, rather than single, targets. Hence, the use of combination therapies (i.e., polytherapy) has emerged as a viable approach. Stringent criteria, such as verification of each individual treatment plus the combination, a focus on behavioral outcome, and post-injury vs. pre-injury treatments, were employed to determine which studies were appropriate for review. The selection process resulted in 37 papers that fit the specifications. The review, which is the first to comprehensively assess the effects of combination therapies on behavioral outcomes after TBI, encompasses five broad categories (inflammation, oxidative stress, neurotransmitter dysregulation, neurotrophins, and stem cells, with and without rehabilitative therapies). Overall, the findings suggest that combination therapies can be more beneficial than monotherapies as indicated by 46% of the studies exhibiting an additive or synergistic positive effect versus on 19% reporting a negative interaction. These encouraging findings serve as an impetus for continued combination studies after TBI and ultimately for the development of successful clinically relevant therapies.