Abstract
The term amyotrophic lateral sclerosis (ALS) comprises a heterogeneous group of fatal neurodegenerative disorders of largely unknown etiology characterized by the upper motor neurons (UMN) and/or lower motor neurons (LMN) degeneration. The development of brain imaging biomarkers is essential to advance in the diagnosis, stratification and monitoring of ALS, both in the clinical practice and clinical trials. In this review, the characteristics of an optimal imaging biomarker and common pitfalls in biomarkers evaluation will be discussed. Moreover, the development and application of the most promising brain magnetic resonance (MR) imaging biomarkers will be reviewed. Finally, the integration of both qualitative and quantitative multimodal brain MR biomarkers in a structured report will be proposed as a support tool for ALS diagnosis and stratification.
Highlights
Amyotrophic lateral sclerosis (ALS), known as motor neuron disease, comprises a heterogeneous group of fatal neurodegenerative disorders of largely unknown etiology characterized by the degeneration of upper motor neurons (UMN) and/or lower motor neurons (LMN) in the primary motor cortex, brain stem, and spinal cord (Kiernan et al, 2011; Al-Chalabi et al, 2016)
These methods are not exclusive for magnetic resonance (MR) imaging, and they can be used with other imaging techniques (Segovia et al, 2017a,b; Ortiz et al, 2019) and even with clinical, molecular, and genetic biomarkers applied to build a model of the pathology (Latourelle et al, 2017)
In the MR evaluation of an ALS patient, we suggest an assessment of the corticospinal tract (CST) in the subcortical precentral white matter and in the posterior limb of the internal capsules on FLAIR images; and an assessment of the motor cortex subregions corresponding to the bulbar, upper limbs and lower limbs motor neurons on susceptibility-weighted imaging (SWI)
Summary
Amyotrophic lateral sclerosis (ALS), known as motor neuron disease, comprises a heterogeneous group of fatal neurodegenerative disorders of largely unknown etiology characterized by the degeneration of upper motor neurons (UMN) and/or lower motor neurons (LMN) in the primary motor cortex, brain stem, and spinal cord (Kiernan et al, 2011; Al-Chalabi et al, 2016). ALS has been considered a neurodegenerative disease that exclusively affects motor neurons, leading to progressive muscle weakness. Convincing evidence supports the notion that it is a multisystem disease not limited to motor areas alone but involving extramotor areas as well (Al-Chalabi et al, 2016) and causing a variable degree of cognitive, behavioral or dysautonomic symptoms (Al-Chalabi et al, 2016; Arlandis et al, 2017). The median age of onset is 55 years and the incidence and prevalence of ALS are 1–2 and 4–6 per 100,000 each year, respectively, with a lifetime ALS risk of 1/600–1/1,000 (Beghi et al, 2006)
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