The frontotemporal syndromes of ALS. Clinicopathological correlates

Emotion recognition in amyotrophic lateral sclerosis in a dynamic environment

OBJECTIVE

The aim of our study was to measure the ability of ALS patients to process dynamic facial expressions as compared to a control group of healthy subjects and to correlate this ability in ALS patients with neuropsychological, clinical and neurological measures of the disease.

METHODS

Sixty-three ALS patients and 47 healthy controls were recruited. All the ALS patients also underwent i) the Geneva Emotion Recognition Test (GERT) in which ten actors express 14 types of dynamic emotions in brief video clips with audio, ii) the Edimburgh Cognitive and Behavioral ALS Screen (ECAS) test; iii) the ALS Functional Rating Scale Revised (ALSFRS-R) and iv) the Medical Research Council (MRC) for the evaluation of muscle strength. All the healthy subjects enrolled in the study underwent the GERT.

RESULTS

The recognition of irritation and pleasure was significantly different between ALS patients and the control group. The amusement, despair, irritation, joy, sadness and surprise had been falsely recognized differently between the two groups. Specific ALS cognitive impairment was associated with bulbar-onset phenotype (OR = 14,3889; 95%CI = 3,96-52,16). No association was observed between false emotion recognition and cognitive impairment (F(1,60)=,56,971, p=,45,333). The number of categorical errors was significantly higher in the ALS patients than in the control group (27,66 ± 7,28 vs 17,72 ± 5,29; t = 8723; p = 0.001).

CONCLUSIONS

ALS patients show deficits in the dynamic processing of a wide range of emotions. These deficits are not necessarily associated with a decline in higher cognitive functions: this could therefore lead to an underestimation of the phenomenon.

Pathophysiological Underpinnings of Extra-Motor Neurodegeneration in Amyotrophic Lateral Sclerosis: New Insights From Biomarker Studies

Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) lie at opposing ends of a clinical, genetic, and neuropathological continuum. In the last decade, it has become clear that cognitive and behavioral changes in patients with ALS are more frequent than previously recognized. Significantly, these non-motor features can impact the diagnosis, prognosis, and management of ALS. Partially overlapping neuropathological staging systems have been proposed to describe the distribution of TAR DNA-binding protein 43 (TDP-43) aggregates outside the corticospinal tract. However, the relationship between TDP-43 inclusions and neurodegeneration is not absolute and other pathophysiological processes, such as neuroinflammation (with a prominent role of microglia), cortical hyperexcitability, and synaptic dysfunction also play a central role in ALS pathophysiology. In the last decade, imaging and biofluid biomarker studies have revealed important insights into the pathophysiological underpinnings of extra-motor neurodegeneration in the ALS-FTLD continuum. In this review, we first summarize the clinical and pathophysiological correlates of extra-motor neurodegeneration in ALS. Next, we discuss the diagnostic and prognostic value of biomarkers in ALS and their potential to characterize extra-motor neurodegeneration. Finally, we debate about how biomarkers could improve the diagnosis and classification of ALS. Emerging imaging biomarkers of extra-motor neurodegeneration that enable the monitoring of disease progression are particularly promising. In addition, a growing arsenal of biofluid biomarkers linked to neurodegeneration and neuroinflammation are improving the diagnostic accuracy and identification of patients with a faster progression rate. The development and validation of biomarkers that detect the pathological aggregates of TDP-43 in vivo are notably expected to further elucidate the pathophysiological underpinnings of extra-motor neurodegeneration in ALS. Novel biomarkers tracking the different aspects of ALS pathophysiology are paving the way to precision medicine approaches in the ALS-FTLD continuum. These are essential steps to improve the diagnosis and staging of ALS and the design of clinical trials testing novel disease-modifying treatments.

Neuropathology of Speech Network Distinguishes Bulbar From Nonbulbar Amyotrophic Lateral Sclerosis

Bulbar amyotrophic lateral sclerosis (ALS) is a debilitating neurodegenerative subtype affecting speech and swallowing motor functions as well as associated with the burden of cognitive deficits. The neuroanatomical underpinnings of bulbar ALS are not well understood. The aim of this study was to compare neuropathology of the speech network (SpN) between 3 cases of bulbar-onset ALS (bALS), 3 cases of spinal-onset ALS (sALS) with antemortem bulbar ALS (sALSwB) against 3 sALS without antemortem bulbar ALS (sALSnoB) and 3 controls. Regional distribution and severity of neuronal loss, TDP-43 (transactive response DNA-binding protein of 43 kDa), and tau proteinopathy were examined. All 3 bALS cases showed marked neuronal loss and severe proteinopathy across most SpN regions; sALSwB cases showed no neuronal loss but mild and variable TDP-43 pathology in focal regions; sALSnoB cases demonstrated an absence of pathology. Two bALS cases had coexisting tauopathy in SpN regions, which was not noted in any sALS cases. The findings suggested that bALS may have a distinct neuropathological signature characterized by marked neuronal loss and polypathology in the SpN. Milder TDP-43 pathology in the SpN for sALSwB cases suggested a link between severity of bulbar ALS and SpN damage. Findings support a clinicopathologic link between bulbar symptoms and pathology in the SpN.

Hippocampal synaptic dysfunction in the SOD1G93A mouse model of Amyotrophic Lateral Sclerosis: Reversal by adenosine A2AR blockade

Amyotrophic Lateral Sclerosis (ALS) mostly affects motor neurons, but non-motor neural and cognitive alterations have been reported in ALS mouse models and patients. Here, we evaluated if time-dependent biphasic changes in synaptic transmission and plasticity occur in hippocampal synapses of ALS SOD1^G93A mice. Recordings were performed in hippocampal slices of SOD1^G93A and age-matched WT mice, in the pre-symptomatic and symptomatic stages. We found an enhancement of pre-synaptic function and increased adenosine A_2A receptor levels in the hippocampus of pre-symptomatic mice. In contrast, in symptomatic mice, there was an impairment of long-term potentiation (LTP) and a decrease in NMDA receptor-mediated synaptic currents, with A_2AR levels also being increased. Chronic treatment with the A_2AR antagonist KW-6002, rescued LTP and A_2AR values. Altogether, these findings suggest an increase in synaptic function during the pre-symptomatic stage, followed by a decrease in synaptic plasticity in the symptomatic stage, which involves over-activation of A_2AR from early disease stages.

Chronic Traumatic Encephalopathy

PURPOSE OF REVIEW

This article provides a discussion on the current state of knowledge of chronic traumatic encephalopathy (CTE), with an emphasis on clinical features and emerging biomarkers of the condition.

RECENT FINDINGS

The results of several large brain bank case series among subjects with a history of contact sports or repetitive head trauma have indicated that a high frequency of CTE may exist in this population. However, the true prevalence of CTE among individuals with a history of head trauma remains unknown, given that individuals who experienced cognitive, behavioral, and mood symptoms during life are more likely to have their brains donated for autopsy at death and epidemiologic studies of the condition are lacking. Neuropathologic consensus criteria have been published. Research-based clinical criteria have been proposed and are beginning to be applied, but the definitive diagnosis of CTE in a living patient remains impossible without effective biomarkers for the condition, which is an active area of study.

SUMMARY

The field of CTE research is rapidly growing and parallels many of the advances seen for other neurodegenerative conditions, such as Alzheimer disease decades ago.

Motor Neuron Susceptibility in ALS/FTD

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the death of both upper and lower motor neurons (MNs) in the brain, brainstem and spinal cord. The neurodegenerative mechanisms leading to MN loss in ALS are not fully understood. Importantly, the reasons why MNs are specifically targeted in this disorder are unclear, when the proteins associated genetically or pathologically with ALS are expressed ubiquitously. Furthermore, MNs themselves are not affected equally; specific MNs subpopulations are more susceptible than others in both animal models and human patients. Corticospinal MNs and lower somatic MNs, which innervate voluntary muscles, degenerate more readily than specific subgroups of lower MNs, which remain resistant to degeneration, reflecting the clinical manifestations of ALS. In this review, we discuss the possible factors intrinsic to MNs that render them uniquely susceptible to neurodegeneration in ALS. We also speculate why some MN subpopulations are more vulnerable than others, focusing on both their molecular and physiological properties. Finally, we review the anatomical network and neuronal microenvironment as determinants of MN subtype vulnerability and hence the progression of ALS.

Prion and Prion-Like Protein Strains: Deciphering the Molecular Basis of Heterogeneity in Neurodegeneration

Increasing evidence suggests that neurodegenerative disorders share a common pathogenic feature: the presence of deposits of misfolded proteins with altered physicochemical properties in the Central Nervous System. Despite a lack of infectivity, experimental data show that the replication and propagation of neurodegenerative disease-related proteins including amyloid-β (Aβ), tau, α-synuclein and the transactive response DNA-binding protein of 43 kDa (TDP-43) share a similar pathological mechanism with prions. These observations have led to the terminology of "prion-like" to distinguish between conditions with noninfectious characteristics but similarities with the prion replication and propagation process. Prions are considered to adapt their conformation to changes in the context of the environment of replication. This process is known as either prion selection or adaptation, where a distinct conformer present in the initial prion population with higher propensity to propagate in the new environment is able to prevail over the others during the replication process. In the last years, many studies have shown that prion-like proteins share not only the prion replication paradigm but also the specific ability to aggregate in different conformations, i.e., strains, with relevant clinical, diagnostic and therapeutic implications. This review focuses on the molecular basis of the strain phenomenon in prion and prion-like proteins.

RNA-binding proteins with prion-like domains in health and disease

Approximately 70 human RNA-binding proteins (RBPs) contain a prion-like domain (PrLD). PrLDs are low-complexity domains that possess a similar amino acid composition to prion domains in yeast, which enable several proteins, including Sup35 and Rnq1, to form infectious conformers, termed prions. In humans, PrLDs contribute to RBP function and enable RBPs to undergo liquid-liquid phase transitions that underlie the biogenesis of various membraneless organelles. However, this activity appears to render RBPs prone to misfolding and aggregation connected to neurodegenerative disease. Indeed, numerous RBPs with PrLDs, including TDP-43 (transactivation response element DNA-binding protein 43), FUS (fused in sarcoma), TAF15 (TATA-binding protein-associated factor 15), EWSR1 (Ewing sarcoma breakpoint region 1), and heterogeneous nuclear ribonucleoproteins A1 and A2 (hnRNPA1 and hnRNPA2), have now been connected via pathology and genetics to the etiology of several neurodegenerative diseases, including amyotrophic lateral sclerosis, frontotemporal dementia, and multisystem proteinopathy. Here, we review the physiological and pathological roles of the most prominent RBPs with PrLDs. We also highlight the potential of protein disaggregases, including Hsp104, as a therapeutic strategy to combat the aberrant phase transitions of RBPs with PrLDs that likely underpin neurodegeneration.

Chronic Traumatic Encephalopathy: The cellular sequela to repetitive brain injury

This review aims to integrate current literature on the pathogenic mechanisms of Chronic Traumatic Encephalopathy (CTE) to create a multifactorial understanding of the disease. CTE is a progressive neurodegenerative disease, classed as a tauopathy, although it appears the pathogenic mechanisms are more complex than this. It affects those with a history of repetitive mild traumatic brain injury. Currently, there are no treatments for CTE and the disease can only be affirmatively diagnosed in post mortem. Understanding the pathogenesis of the disease will provide an avenue to explore possible treatment and diagnostic modalities. The pathological hallmarks of CTE have been well characterised and have been linked to the pathophysiologic mechanisms in this review. Human studies are limited due to ethical implications of exposing subjects to head trauma. Phosphorylation of tau, microglial activation, TAR DNA-binding protein 43 and diffuse axonal injury have all been implicated in the pathogenesis of CTE. The neuronal loss and axonal dysfunction mediated by these pathognomonic mechanisms lead to the broad psycho-cognitive symptoms seen in CTE.

The chaperone HSPB8 reduces the accumulation of truncated TDP-43 species in cells and protects against TDP-43-mediated toxicity

Aggregation of TAR-DNA-binding protein 43 (TDP-43) and of its fragments TDP-25 and TDP-35 occurs in amyotrophic lateral sclerosis (ALS). TDP-25 and TDP-35 act as seeds for TDP-43 aggregation, altering its function and exerting toxicity. Thus, inhibition of TDP-25 and TDP-35 aggregation and promotion of their degradation may protect against cellular damage. Upregulation of HSPB8 is one possible approach for this purpose, since this chaperone promotes the clearance of an ALS associated fragments of TDP-43 and is upregulated in the surviving motor neurones of transgenic ALS mice and human patients. We report that overexpression of HSPB8 in immortalized motor neurones decreased the accumulation of TDP-25 and TDP-35 and that protection against mislocalized/truncated TDP-43 was observed for HSPB8 in Drosophila melanogaster. Overexpression of HSP67Bc, the functional ortholog of human HSPB8, suppressed the eye degeneration caused by the cytoplasmic accumulation of a TDP-43 variant with a mutation in the nuclear localization signal (TDP-43-NLS). TDP-43-NLS accumulation in retinal cells was counteracted by HSP67Bc overexpression. According with this finding, downregulation of HSP67Bc increased eye degeneration, an effect that is consistent with the accumulation of high molecular weight TDP-43 species and ubiquitinated proteins. Moreover, we report a novel Drosophila model expressing TDP-35, and show that while TDP-43 and TDP-25 expression in the fly eyes causes a mild degeneration, TDP-35 expression leads to severe neurodegeneration as revealed by pupae lethality; the latter effect could be rescued by HSP67Bc overexpression. Collectively, our data demonstrate that HSPB8 upregulation mitigates TDP-43 fragment mediated toxicity, in mammalian neuronal cells and flies.

Serotonin 2B receptor slows disease progression and prevents degeneration of spinal cord mononuclear phagocytes in amyotrophic lateral sclerosis

Microglia are the resident mononuclear phagocytes of the central nervous system and have been implicated in the pathogenesis of neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS). During neurodegeneration, microglial activation is accompanied by infiltration of circulating monocytes, leading to production of multiple inflammatory mediators in the spinal cord. Degenerative alterations in mononuclear phagocytes are commonly observed during neurodegenerative diseases, yet little is known concerning the mechanisms leading to their degeneration, or the consequences on disease progression. Here we observed that the serotonin 2B receptor (5-HT2B), a serotonin receptor expressed in microglia, is upregulated in the spinal cord of three different transgenic mouse models of ALS. In mutant SOD1 mice, this upregulation was restricted to cells positive for CD11b, a marker of mononuclear phagocytes. Ablation of 5-HT2B receptor in transgenic ALS mice expressing mutant SOD1 resulted in increased degeneration of mononuclear phagocytes, as evidenced by fragmentation of Iba1-positive cellular processes. This was accompanied by decreased expression of key neuroinflammatory genes but also loss of expression of homeostatic microglial genes. Importantly, the dramatic effect of 5-HT2B receptor ablation on mononuclear phagocytes was associated with acceleration of disease progression. To determine the translational relevance of these results, we studied polymorphisms in the human HTR2B gene, which encodes the 5-HT2B receptor, in a large cohort of ALS patients. In this cohort, the C allele of SNP rs10199752 in HTR2B was associated with longer survival. Moreover, patients carrying one copy of the C allele of SNP rs10199752 showed increased 5-HT2B mRNA in spinal cord and displayed less pronounced degeneration of Iba1 positive cells than patients carrying two copies of the more common A allele. Thus, the 5-HT2B receptor limits degeneration of spinal cord mononuclear phagocytes, most likely microglia, and slows disease progression in ALS. Targeting this receptor might be therapeutically useful.

Impaired affective and cognitive theory of mind and behavioural change in amyotrophic lateral sclerosis

OBJECTIVES

Executive and behavioural changes are well-recognised in classical amyotrophic lateral sclerosis (ALS), indicating a subclinical behavioural-variant frontotemporal dementia (bvFTD) in some patients. Social cognitive deficits in ALS have been recently described and an impairment was identified on a simple Theory of Mind (ToM) test, which assesses the judgement of the preference of another through direction of eye gaze. The present study further delineated this deficit, by distinguishing between Affective and Cognitive subcomponents, and determining the relationship to behavioural change, levels of empathy and self-awareness.

METHODS

The Cognitive-Affective Judgement of Preference Test was administered to 33 patients with ALS and 26 controls. Furthermore, a comprehensive neuropsychological battery and detailed behavioural assessment, with measures of empathy and awareness, were included.

RESULTS

Patients with ALS showed a significant impairment in Affective ToM only when compared with healthy controls, with a deficit in 36% of patients; 12% showed an isolated Affective ToM deficit while 24% showed more generic ToM dysfunction. A Cognitive ToM deficit was found in 27% of patients, with 3% showing an isolated Cognitive ToM deficit. The patients with ALS showed reduced empathy (Fantasy scale) and increased behavioural dysfunction with high levels of apathy. In addition, patients with either an Affective and/or Cognitive ToM deficit exhibited poor self-awareness of their performance and abnormalities on verbal fluency, while those with an Affective ToM deficit also displayed higher levels of apathy and a naming deficit.

CONCLUSIONS

Dysfunctional ToM is a prominent feature of the cognitive profile of ALS. This specific difficulty in identifying and distinguishing the feelings and thoughts of another from a self-perspective may underpin the social behavioural abnormalities present in some patients with ALS, manifest as apathy and loss of awareness.

The neuropathology of chronic traumatic encephalopathy

Repetitive brain trauma is associated with a progressive neurological deterioration, now termed as chronic traumatic encephalopathy (CTE). Most instances of CTE occur in association with the play of sports, but CTE has also been reported in association with blast injuries and other neurotrauma. Symptoms of CTE include behavioral and mood changes, memory loss, cognitive impairment and dementia. Like many other neurodegenerative diseases, CTE is diagnosed with certainty only by neuropathological examination of brain tissue. CTE is a tauopathy characterized by the deposition of hyperphosphorylated tau (p-tau) protein as neurofibrillary tangles, astrocytic tangles and neurites in striking clusters around small blood vessels of the cortex, typically at the sulcal depths. Severely affected cases show p-tau pathology throughout the brain. Abnormalities in phosphorylated 43 kDa TAR DNA-binding protein are found in most cases of CTE; beta-amyloid is identified in 43%, associated with age. Given the importance of sports participation and physical exercise to physical and psychological health as well as disease resilience, it is critical to identify the genetic risk factors for CTE as well as to understand how other variables, such as stress, age at exposure, gender, substance abuse and other exposures, contribute to the development of CTE.

Review: Prion-like mechanisms of transactive response DNA binding protein of 43 kDa (TDP-43) in amyotrophic lateral sclerosis (ALS)

Amyotrophic lateral sclerosis (ALS) is a fatal devastating neurodegenerative disorder which predominantly affects the motor neurons in the brain and spinal cord. The death of the motor neurons in ALS causes subsequent muscle atrophy, paralysis and eventual death. Clinical and biological evidence now demonstrates that ALS has many similarities to prion disease in terms of disease onset, phenotype variability and progressive spread. The pathognomonic ubiquitinated inclusions deposited in the neurons and glial cells in brains and spinal cords of patients with ALS and fronto-temporal lobar degeneration with ubiquitinated inclusions contain aggregated transactive response DNA binding protein of 43 kDa (TDP-43), and evidence now suggests that TDP-43 has cellular prion-like properties. The cellular mechanisms of prion protein misfolding and aggregation are thought to be responsible for the characteristics of prion disease. Therefore, there is a strong mechanistic basis for a prion-like behaviour of the TDP-43 protein being responsible for some characteristics of ALS. In this review, we compare the prion-like mechanisms of TDP-43 to the clinical and biological nature of ALS in order to investigate how this protein could be responsible for some of the characteristic properties of the disease.

Post-traumatic neurodegeneration and chronic traumatic encephalopathy

Traumatic brain injury (TBI) is a leading cause of mortality and morbidity around the world. Concussive and subconcussive forms of closed-head injury due to impact or blast neurotrauma represent the most common types of TBI in civilian and military settings. It is becoming increasingly evident that TBI can lead to persistent, long-term debilitating effects, and in some cases, progressive neurodegeneration and chronic traumatic encephalopathy (CTE). The epidemiological literature suggests that a single moderate-to-severe TBI may be associated with accelerated neurodegeneration and increased risk of Alzheimer's disease, Parkinson's disease, or motor neuron disease. However, the pathologic phenotype of these post-traumatic neurodegenerations is largely unknown and there may be pathobiological differences between post-traumatic disease and the corresponding sporadic disorder. By contrast, the pathology of CTE is increasingly well known and is characterized by a distinctive pattern of progressive brain atrophy and accumulation of hyperphosphorylated tau neurofibrillary and glial tangles, dystrophic neurites, 43 kDa TAR DNA-binding protein (TDP-43) neuronal and glial aggregates, microvasculopathy, myelinated axonopathy, neuroinflammation, and white matter degeneration. Clinically, CTE is associated with behavioral changes, executive dysfunction, memory deficits, and cognitive impairments that begin insidiously and most often progress slowly over decades. Although research on the long-term effects of TBI is advancing quickly, the incidence and prevalence of post-traumatic neurodegeneration and CTE are unknown. Critical knowledge gaps include elucidation of pathogenic mechanisms, identification of genetic risk factors, and clarification of relevant variables-including age at exposure to trauma, history of prior and subsequent head trauma, substance use, gender, stress, and comorbidities-all of which may contribute to risk profiles and the development of post-traumatic neurodegeneration and CTE. This article is part of a Special Issue entitled 'Traumatic Brain Injury'.

The phenotypic variability of amyotrophic lateral sclerosis

Classic textbook neurology teaches that amyotrophic lateral sclerosis (ALS) is a degenerative disease that selectively affects upper and lower motor neurons and is fatal 3-5 years after onset--a description which suggests that the clinical presentation of ALS is very homogenous. However, clinical and postmortem observations, as well as genetic studies, demonstrate that there is considerable variability in the phenotypic expression of ALS. Here, we review the phenotypic variability of ALS and how it is reflected in familial and sporadic ALS, in the degree of upper and lower motor neuron involvement, in motor and extramotor involvement, and in the spectrum of ALS and frontotemporal dementia. Furthermore, we discuss some unusual clinical characteristics regarding presentation, age at onset and disease progression. Finally, we address the importance of this variability for understanding the pathogenesis of ALS and for the development of therapeutic strategies.

Chronic traumatic encephalopathy: a spectrum of neuropathological changes following repetitive brain trauma in athletes and military personnel

Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disease that occurs in association with repetitive traumatic brain injury experienced in sport and military service. In most instances, the clinical symptoms of the disease begin after a long period of latency ranging from several years to several decades. The initial symptoms are typically insidious, consisting of irritability, impulsivity, aggression, depression, short-term memory loss and heightened suicidality. The symptoms progress slowly over decades to include cognitive deficits and dementia. The pathology of CTE is characterized by the accumulation of phosphorylated tau protein in neurons and astrocytes in a pattern that is unique from other tauopathies, including Alzheimer’s disease. The hyperphosphorylated tau abnormalities begin focally, as perivascular neurofibrillary tangles and neurites at the depths of the cerebral sulci, and then spread to involve superficial layers of adjacent cortex before becoming a widespread degeneration affecting medial temporal lobe structures, diencephalon and brainstem. Most instances of CTE (>85% of cases) show abnormal accumulations of phosphorylated 43 kDa TAR DNA binding protein that are partially colocalized with phosphorylated tau protein. As CTE is characterized pathologically by frontal and temporal lobe atrophy, by abnormal deposits of phosphorylated tau and by 43 kDa TAR DNA binding protein and is associated clinically with behavioral and personality changes, as well as cognitive impairments, CTE is increasingly categorized as an acquired frontotemporal lobar degeneration. Currently, some of the greatest challenges are that CTE cannot be diagnosed during life and the incidence and prevalence of the disorder remain uncertain. Furthermore, the contribution of age, gender, genetics, stress, alcohol and substance abuse to the development of CTE remains to be determined.

The neuropathology of sport

The benefits of regular exercise, physical fitness and sports participation on cardiovascular and brain health are undeniable. Physical activity reduces the risk for cardiovascular disease, type 2 diabetes, hypertension, obesity, and stroke, and produces beneficial effects on cholesterol levels, antioxidant systems, inflammation, and vascular function. Exercise also enhances psychological health, reduces age-related loss of brain volume, improves cognition, reduces the risk of developing dementia, and impedes neurodegeneration. Nonetheless, the play of sports is associated with risks, including a risk for mild TBI (mTBI) and, rarely, catastrophic traumatic injury and death. There is also growing awareness that repetitive mTBIs, such as concussion and subconcussion, can occasionally produce persistent cognitive, behavioral, and psychiatric problems as well as lead to the development of a neurodegeneration, chronic traumatic encephalopathy (CTE). In this review, we summarize the beneficial aspects of sports participation on psychological, emotional, physical and cognitive health, and specifically analyze some of the less common adverse neuropathological outcomes, including concussion, second-impact syndrome, juvenile head trauma syndrome, catastrophic sudden death, and CTE. CTE is a latent neurodegeneration clinically associated with behavioral changes, executive dysfunction and cognitive impairments, and pathologically characterized by frontal and temporal lobe atrophy, neuronal and axonal loss, and abnormal deposits of paired helical filament (PHF)-tau and 43 kDa TAR deoxyribonucleic acid (DNA)-binding protein (TDP-43). CTE often occurs as a sole diagnosis, but may be associated with other neurodegenerative disorders, including motor neuron disease (CTE-MND). Although the incidence and prevalence of CTE are not known, CTE has been reported most frequently in American football players and boxers. Other sports associated with CTE include ice hockey, professional wrestling, soccer, rugby, and baseball.

Differential autophagy power in the spinal cord and muscle of transgenic ALS mice

Amyotrophic lateral sclerosis (ALS) is a motoneuron disease characterized by misfolded proteins aggregation in affected motoneurons. In mutant SOD1 (mutSOD1) ALS models, aggregation correlates to impaired functions of proteasome and/or autophagy, both essential for the intracellular chaperone-mediated protein quality control (PQC), and to a reduced mutSOD1 clearance from motoneurons. Skeletal muscle cells are also sensitive to mutSOD1 toxicity, but no mutSOD1 aggregates are formed in these cells, that might better manage mutSOD1 than motoneurons. Thus, we analyzed in spinal cord and in muscle of transgenic (tg) G93A-SOD1 mice at presymptomatic (PS, 8 weeks) and symptomatic (S, 16 weeks) stages, and in age-matched control mice, whether mutSOD1 differentially modulates relevant PQC players, such as HSPB8, BAG3, and BAG1. Possible sex differences were also considered. No changes of HSPB8, BAG3, and BAG1 at PS stage (8 weeks) were seen in all tissues examined in tg G93A-SOD1 and control mice. At S stage (16 weeks), HSPB8 dramatically increased in skeletal muscle of tg G93A-SOD1 mice, while a minor increase occurred in spinal cord of male, but not female tg G93A-SOD1 mice. BAG3 expression increased both in muscle and spinal cord of tg G93A-SOD1 mice at S stage, BAG1 expression increased only in muscle of the same mice. Since, HSPB8-BAG3 complex assists mutSOD1 autophagic removal, we analyzed two well-known autophagic markers, LC3 and p62. Both LC3 and p62 mRNAs were significantly up-regulated in skeletal muscle of tg G93A-SOD1 mice at S stage (16 weeks). This suggests that mutSOD1 expression induces a robust autophagic response specifically in muscle. Together these results demonstrate that, in muscle mutSOD1-induced autophagic response is much higher than in spinal cord. In addition, if mutSOD1 exerts toxicity in muscle, this may not be mediated by misfolded proteins accumulation. It remains unclear whether in muscle mutSOD1 toxicity is related to aberrant autophagy activation.

Neuropathology of frontotemporal lobar degeneration: a review

Frontotemporal lobar degeneration (FTLD) is the second most common cause of presenile dementia. Three main clinical variants are widely recognized within the FTLD spectrum: the behavioural variant of frontotemporal dementia (bvFTD), semantic dementia (SD) and progressive non-fluent aphasia (PNFA). FTLD represents a highly heterogeneous group of neurodegenerative disorders which are best classified according to the main protein component of pathological neuronal and glial inclusions. The most common pathological class of FTLD is associated with the TDP-43 protein (FTLD-TDP), while FTLD-Tau is considered slightly less common while the FTLD-FUS (Fused in sarcoma protein) pathology is rare. In this review, these three major pathological types of FTLD are discussed.

Structural imaging differences and longitudinal changes in primary lateral sclerosis and amyotrophic lateral sclerosis

Magnetic resonance imaging measures have been proposed as objective markers to study upper motor neuron loss in motor neuron disorders. Cross-sectional studies have identified imaging differences between groups of healthy controls and patients with amyotrophic lateral sclerosis (ALS) or primary lateral sclerosis (PLS) that correlate with disease severity, but it is not known whether imaging measures change as disease progresses. Additionally, whether imaging measures change in a similar fashion with disease progression in PLS and ALS is unclear. To address these questions, clinical and imaging evaluations were first carried out in a prospective cross-sectional study of 23 ALS and 22 PLS patients with similar motor impairment and 19 age-matched healthy controls. Clinical evaluations consisted of a neurological examination, the ALS Functional rating scale-revised, and measures of finger tapping, gait, and timed speech. Age and ALSFRS score were not different, but PLS patients had longer duration of symptoms. Imaging measures examined were cortical thickness, regional brain volumes, and diffusion tensor imaging of the corticospinal tract and callosum. Imaging measures that differed from controls in a cross-sectional vertex-wise analysis were used as regions of interest for longitudinal analysis, which was carried out in 9 of the ALS patients (interval 1.26 ± 0.72 years) and 12 PLS patients (interval 2.08 ± 0.93 years). In the cross-sectional study both groups had areas of cortical thinning, which was more extensive in motor regions in PLS patients. At follow-up, clinical measures declined more in ALS than PLS patients. Cortical thinning and grey matter volume loss of the precentral gyri progressed over the follow-up interval. Fractional anisotropy of the corticospinal tracts remained stable, but the cross-sectional area declined in ALS patients. Changes in clinical measures correlated with changes in precentral cortical thickness and grey matter volume. The rate of cortical thinning was greater in ALS patients with shorter disease durations, suggesting that thickness decreases in a non-linear fashion. Thus, cortical thickness changes are a potential imaging marker for disease progression in individual patients, but the magnitude of change likely depends on disease duration and progression rate. Differences between PLS and ALS patients in the magnitude of thinning in cross-sectional studies are likely to reflect longer disease duration. We conclude that there is an evolution of structural imaging changes with disease progression in motor neuron disorders. Some changes, such as diffusion properties of the corticospinal tract, occur early while cortical thinning and volume loss occur later.

Prevalence and prognostic impact of comorbidities in amyotrophic lateral sclerosis

BACKGROUND AND PURPOSE

Amyotrophic lateral sclerosis (ALS) is characterized by rapidly progressive paralysis of striated muscles due to the loss of upper and lower motor neurons. The disease leads to death within 2-5 years, mainly due to respiratory failure. The pathogenesis of ALS is still unexplained for the most part. In this study, we aimed to determine the prevalence of different cardiovascular, metabolic, and neuropsychiatric comorbidities in a large ALS cohort and to evaluate their influence on the disease course.

METHODS

A cohort of 514 patients with ALS of our ALS outpatient clinic was investigated retrospectively with reference to known prognostic factors and comorbidities. The prevalence of concomitant diseases was compared with the data from the German general population. Uni- and multivariate survival analyses were performed using the Cox proportional hazards model and Kaplan-Meier analysis.

RESULTS

The prevalence of cardiovascular diseases and cardiovascular risk factors was significantly lower in patients with ALS compared to the German general population, whilst the prevalence of dementia, parkinsonism, and depressive symptoms was significantly higher in the ALS cohort. None of the investigated comorbidities had an influence on the disease course or on the survival of patients.

CONCLUSIONS

Persons with cardiovascular diseases or risk factors seem to be at lower risk of ALS. Although these diseases are apparently somehow protective regarding ALS susceptibility, their presence did not modify disease progression and survival in patients with ALS. Our study further confirms the well-known continuum between ALS and dementia. It also suggests a link with other neurodegenerative diseases such as Parkinson's disease.

Drosophila Answers to TDP-43 Proteinopathies

Initially implicated in the pathogenesis of CFTR and HIV-1 transcription, nuclear factor TDP-43 was subsequently found to be involved in the origin and development of several neurodegenerative diseases. In 2006, in fact, it was reported for the first time the cytoplasmic accumulation of TDP-43 in ubiquitin-positive inclusions of ALS and FTLD patients, suggesting the presence of a shared underlying mechanism for these diseases. Today, different animal models of TDP-43 proteinopathies are available in rodents, nematodes, fishes, and flies. Although these models recapitulate several of the pathological features found in patients, the mechanisms underpinning the progressive neuronal loss observed in TDP-43 proteinopathies remain to be characterized. Compared to other models, Drosophila are appealing because they combine the presence of a sophisticated brain with the possibility to investigate quickly and massively phenotypic genetic modifiers as well as possible therapeutic strategies. At present, the development of TDP-43-related Drosophila models has further strengthened the hypothesis that both TDP-43 “loss-of-function” and “gain-of-function” mechanisms can contribute to disease. The aim of this paper is to describe and compare the results obtained in a series of transgenic and knockout flies, along with the information they have generated, towards a better understanding of the mechanisms underlying TDP-43 proteinopathies.

[Frontotemporal dementias]

Frontotemporal dementias (FTD) account for only 5-7% of all dementia aetiologies. However, FTD is one common form of dementia in the presenile period with a symptom onset between an age of 45 and 65 years. FTD are clinically classified into a group of rare genetic variants, the behavioural variant, primary progressive aphasias and a variant including motor neuron symptoms (FTD-MNS). In recent years the pathobiological characteristics of some FTD variants was clarified, demonstrating a pathological accumulation of TAR-DNA binding protein 43 (TDP-43) as a common pathological substrate. The revised diagnostic criteria of the behavioural variant of the FTD require at least three of six clinically discriminating features (disinhibition, apathy, loss of sympathy, perseverative behaviours, hyperorality and dysexecutive neuropsychological profile). The primary progressive aphasias are classified in a nonfluent/agrammatic variant, a logopenic variant and a semantic variant according to clinical and imaging features. Movement disorders and more precisely a Parkinsonian syndrome can be part of the FTD spectrum. Some clinical features overlap the clinical diagnosis of a progressive supranuclear paralysis and the corticobasal ganglionic degeneration. A causal therapy does not exist and medical treatment is directed at the patient's key symptoms. Different agents such as serotonin reuptake inhibitors, tricyclic antidepressants, atypical neuroleptics, carbamazepine, valproate, lamotrigine and when indicated also acetylcholinesterase inhibitors are potentially helpful. All together, theses medical treatments have a low level of evidence. Non-pharmacological therapies such as physiotherapy, occupational therapy, speech therapy and disease-specific education of the patient and their relatives are important to ensure a safe residential environment and daily routine.