Amyotrophic lateral sclerosis: contemporary concepts in etiopathogenesis and pharmacotherapy

Among the neurodegenerative diseases associated with ageing, amyotrophic lateral sclerosis (ALS) remains the most devastating. The disease inexorably progresses, the vast majority of pharmacotherapies have failed to modify the disease course, death ensues on average within 5 years of symptom onset and increasing numbers of individuals are afflicted with the disease. However, significant advances in our understanding of the natural history of ALS and of the fundamental nature of the biological defect underlying motor neuron degeneration have been gained, providing hope for the development of novel pharmacotherapies for ALS. Among these is the recognition that ALS is a biologically heterogeneous disorder in which genetics, environment and ageing all interrelate. The observation of clinical heterogeneity, with initial clinical manifestations serving as predictors of survivorship, is of considerable importance in designing therapeutic trials. The presence of frontotemporal dysfunction in a subset of patients has led to increased interest in the relationship between ALS and the degenerative tauopathies. Ultimately, the degenerating motor neurons do not die alone. The contribution of both microglia and astrocytes to the degenerative process are increasingly recognised. Understanding how these processes interrelate has become critical to understanding the pharmacotherapy of ALS and in the design of clinical trials. This review will highlight recent epidemiological and neurochemical advances in our understanding of ALS, and place them into the context of understanding the development of novel treatment avenues for this devastating disease.