Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder of adult life, causing weakness and wasting of voluntary muscles, associated in about 50% of cases with a cognitive impairment. ...Pathologically, the disease is characterized by a degeneration of upper and lower motor neurons. A hallmark of the pathological process is the aggregation of the protein TDP43 in the cytoplasm of affected neurons detected in almost 97% of cases. About 15% of cases has a family history.
Currently, only two drugs have been demonstrated to be effective in ALS, riluzole and edaravone, which show only modest effects on disease progression. The quest for disease-modifying therapies in ALS has several obstacles, the most important being the sub-optimal quality of the design of clinical trials, and the clinical and pathological heterogeneity of the disease.
In this paper the pathological mechanisms relevant to ALS and current and future pharmacological and non-pharmacological trials, including gene and stem cells therapies, will be presented.
This article is part of the special issue entitled ‘The Quest for Disease-Modifying Therapies for Neurodegenerative Disorders’.
•ALS is a neurodegenerative disease characterized by the loss of upper and lower motor neurons and frontal cortices.•No effective disease-modifying therapy for ALS is available, with exception of riluzole, and edaravone.•More than 40 drugs are currently under study as possible therapies for ALS, with several potential mechanisms of action.•Several phase 1 or 2 trials are ongoing on mesenchymal and neural stem cells as possible treatment for ALS.
Considerable progress has been made in unraveling the genetic etiology of amyotrophic lateral sclerosis (ALS), the most common form of adult-onset motor neuron disease and the third most common ...neurodegenerative disease overall. Here we review genes implicated in the pathogenesis of motor neuron degeneration and how this new information is changing the way we think about this fatal disorder. Specifically, we summarize current literature of the major genes underlying ALS, SOD1, TARDBP, FUS, OPTN, VCP, UBQLN2, C9ORF72 and PFN1, and evaluate the information being gleaned from genome-wide association studies. We also outline emerging themes in ALS research, such as next-generation sequencing approaches to identify de novo mutations, the genetic convergence of familial and sporadic ALS, the proposed oligogenic basis for the disease, and how each new genetic discovery is broadening the phenotype associated with the clinical entity we know as ALS.
Summary Amyotrophic lateral sclerosis is a progressive adult-onset neurodegenerative disease that primarily affects upper and lower motor neurons, but also frontotemporal and other regions of the ...brain. The extent to which each neuronal population is affected varies between individuals. The subsequent patterns of disease progression form the basis of diagnostic criteria and phenotypic classification systems, with considerable overlap in the clinical terms used. This overlap can lead to confusion between diagnosis and phenotype. Formal classification systems such as the El Escorial criteria and the International Classification of Diseases are systematic approaches but they omit features that are important in clinical management, such as rate of progression, genetic basis, or functional effect. Therefore, many neurologists use informal classification approaches that might not be systematic, and could include, for example, anatomical descriptions such as flail-arm syndrome. A new strategy is needed to combine the benefits of a systematic approach to classification with the rich and varied phenotypic descriptions used in clinical practice.
The disease course of amyotrophic lateral sclerosis (ALS) is rapid and, because its pathophysiology is unclear, few effective treatments are available. Genetic research aims to understand the ...underlying mechanisms of ALS and identify potential therapeutic targets. The first gene associated with ALS was SOD1, identified in 1993 and, by early 2014, more than 20 genes had been identified as causative of, or highly associated with, ALS. These genetic discoveries have identified key disease pathways that are therapeutically testable and could potentially lead to the development of better treatments for people with ALS.
Since 2014, seven additional genes have been associated with ALS (MATR3, CHCHD10, TBK1, TUBA4A, NEK1, C21orf2, and CCNF), all of which were identified by genome-wide association studies, whole genome studies, or exome sequencing technologies. Each of the seven novel genes code for proteins associated with one or more molecular pathways known to be involved in ALS. These pathways include dysfunction in global protein homoeostasis resulting from abnormal protein aggregation or a defect in the protein clearance pathway, mitochondrial dysfunction, altered RNA metabolism, impaired cytoskeletal integrity, altered axonal transport dynamics, and DNA damage accumulation due to defective DNA repair. Because these novel genes share common disease pathways with other genes implicated in ALS, therapeutics targeting these pathways could be useful for a broad group of patients stratified by genotype. However, the effects of these novel genes have not yet been investigated in animal models, which will be a key step to translating these findings into clinical practice.
The identification of these seven novel genes has been important in unravelling the molecular mechanisms underlying ALS. However, our understanding of what causes ALS is not complete, and further genetic research will provide additional detail about its causes. Increased genetic knowledge will also identify potential therapeutic targets and could lead to the development of individualised medicine for patients with ALS. These developments will have a direct effect on clinical practice when genome sequencing becomes a routine and integral part of disease diagnosis and management.
Summary Pain is a largely neglected symptom in patients with amyotrophic lateral sclerosis (ALS) although it is reported by most of these patients. It occurs at all stages of the disease and can be ...an onset symptom preceding motor dysfunction. Pain is correlated with a deterioration in patients' quality of life and increased prevalence of depression. In the later stages of ALS, pain can be severe enough to require increased use of sedative and analgesic drugs, and is among the events that predict clinical deterioration and death. The site of pain depends on the pain type or underlying mechanism (eg, painful cramps, nociceptive pain, or neuropathic pain). Given the multifactorial nature of pain in patients with ALS, different treatments have been suggested, ranging from non-steroidal anti-inflammatory drugs, drugs for neuropathic pain, opioids, and cannabinoids, to physical therapy strategies and preventive assistive devices. Further understanding of the pathophysiology is crucial to drive assessment in clinical trials of therapeutic strategies targeted at specific mechanisms and studies of individualised therapies.
Although amyotrophic lateral sclerosis (ALS) is relatively rare, the socioeconomic significance of the disease is extensive. It is therefore vital to project the epidemiologic trend of ALS. To date, ...there have been few published studies attempting to estimate the number and distribution of ALS cases in the upcoming years. Here we show that the number of ALS cases across the globe will increase from 222,801 in 2015 to 376,674 in 2040, representing an increase of 69%. This increase is predominantly due to ageing of the population, particularly among developing nations. This projection is likely an underestimate due to improving healthcare and economic conditions. The results should be used to inform healthcare policy to more efficiently allocate healthcare resources.
Staging of disease severity is useful for prognosis, decision-making and resource planning. However, no commonly used, validated staging system exists for amyotrophic lateral sclerosis (ALS). Our ...purpose was to develop an ALS staging system (ALS Milano-Torino Staging) that captures the observed progressive loss of independence and function.
Clinical milestones in ALS progression were defined by loss of independence in four key domains on the ALS Functional Rating Scale (ALSFRS): swallowing, walking/self-care, communicating and breathing. Stages were defined as follows: stage 0, functional involvement but no loss of independence on any domain; stages 1-4, number of domains in which independence was lost; and stage 5, death. Staging criteria were applied to patients enrolled in a Quality of Care in ALS (QOC) study; endpoints included function (ALSFRS), quality of life (QOL; Short Form-36) and health service costs. Between-stage transition probabilities were assessed in the QOC study and in a second clinical study of lithium carbonate in ALS.
70/118 (59.3%) participants in the QOC study progressed to higher stages of disease at 12 months compared with their baseline stage. Functional (ALSFRS) and QOL measures were inversely related to disease stage. Health service costs were directly related to increasing disease stages from 0 to 4 (p<0.001). Probabilities for transitioning from a given stage at baseline in both studies were usually greatest for the next highest stage.
The proposed ALS Milano-Torino Staging system correlates well with assessments of function, QOL and health service costs. Further studies are warranted to validate this system.
Summary In the past two decades, structural and functional neuroimaging findings have greatly modified longstanding notions regarding the pathophysiology of amyotrophic lateral sclerosis (ALS). ...Neuroimaging studies have shown that anatomical and functional lesions spread beyond precentral cortices and corticospinal tracts, to include the corpus callosum; frontal, sensory, and premotor cortices; thalamus; and midbrain. Both MRI and PET studies have shown early and diffuse loss of inhibitory cortical interneurons in the motor cortex (increased levels of functional connectivity and loss of GABAergic neurons, respectively) and diffuse gliosis in white-matter tracts. In ALS endophenotypes, neuroimaging has also shown a diverse spreading of lesions and a dissimilar impairment of functional and structural connections. A possible role of PET in the diagnosis of ALS has recently been proposed. However, most neuroimaging studies have pitfalls, such as a small number and poor clinical characterisation of patients, absence of adequate controls, and scarcity of longitudinal assessments. Studies involving international collaborations, standardised assessments, and large patient cohorts will overcome these shortcomings and provide further insight into the pathogenesis of ALS.
To assess the association of the degree of severity of motor impairment to that of cognitive impairment in a large cohort of patients with amyotrophic lateral sclerosis (ALS).
This is a ...population-based cross-sectional study on patients with ALS incident in Piemonte, Italy, between 2007 and 2015. Cognitive status was classified according to the revised ALS-FTD Consensus Criteria. The King system and the Milano Torino Staging system (MiToS) were used for defining the severity of motor impairment.
Of the 797 patients included in the study, 163 (20.5%) had ALS-frontotemporal dementia (FTD), 38 (4.8%) cognitive and behavioral impairment (ALScbi), 132 (16.6%) cognitive impairment (ALSci), 63 (7.9%) behavioral impairment (ALSbi), 16 (2.0%) nonexecutive impairment, and 385 (48.2%) were cognitively normal. According to King staging, the frequency of cases with ALS-FTD progressively increased from 16.5% in stage 1-44.4% in stage 4; conversely, the frequency of ALSci, ALSbi, and ALScbi increased from King stage 1 to King stage 3 and decreased thereafter. A similar pattern was observed with the MiToS staging. ALS-FTD was more frequent in patients with bulbar involvement at time of cognitive testing. Patients with
expansion (n = 61) showed more severe cognitive impairment with increasing King and MiToS stages.
Our findings suggest that ALS motor and cognitive components may worsen in parallel, and that cognitive impairment becomes more pronounced when bulbar function is involved. Our data support the hypothesis that ALS pathology disseminates in a regional ordered sequence, through a cortico-efferent spreading model.
To examine dimensionality, reliability and validity of the Amyotrophic Lateral Sclerosis Functional Rating Scale-revised (ALSFRS-R) using traditional classical test theory methods and Rasch analysis ...in order to provide a rationale for possible improvement of its metric quality.
Methodological research on ALSFRS-R collected in a consecutive sample of 485 patients with amyotrophic lateral sclerosis (ALS) attending three tertiary ALS centres.
The ALSFRS-R items showed good internal consistency but dimensionality analysis argues against the use of ALSFRS-R as a single score because the scale lacks unidimensionality. Parallel analysis and exploratory factor analysis revealed three factors representing the following domains: (1) bulbar function; (2) fine and gross motor function; and (3) respiratory function. Rasch analysis showed that all items in each domain fitted the respective constructs to measure, except for item No 9 'climbing stairs' and item No 12 'respiratory insufficiency'. Rating categories did not comply with the criteria for category functioning. Collapsing the scale's 5 level ratings into 3 levels improved its metric quality.
The ALSFRS-R fails to satisfy rigorous measurement standards and should be, at least in part, revised. At present, ALSFRS-R should be considered as a profile of mean scores from three different domains (bulbar, motor and respiratory functions) more than a global total score. Further studies on ALSFRS-R using modern psychometric methods are warranted to confirm our findings and refine the metric quality of this scale, through a step by step process.
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