QCT in ALS Diagnosis, Mechanistic Understanding and Follow-up

Multidisciplinary management of amyotrophic lateral sclerosis (ALS) can significantly increase survival but also improve the quality of life of patients. The evaluation of cortical-spinal motor neuron damage is currently based only on the assessment of clinical data. However, the alteration of the central motor pathway and conduction can be identified and quantified by different techniques using motor-evoked potentials (MEP). The combined quadriceps test (QCT) has been developed to assess central and peripheral motor pathway conduction. This test allows to quantify central and peripheral part of a mixed disorder, and to detect physiological hyporeflexia or hyperreflexia which, in the case of suspected ALS, can lead to interpretation problems. The evolution of the QCT parameters during the course of pathology will lead to determine the preponderance of an initial central involvement, but also its extension throughout the pathology. The study of these parameters as well as the clinical course of the disease could reveal a correlation between peripheral and central involvement. This link would provide arguments in favor of pathophysiological hypotheses of disease onset and progression. From a prognostic point of view and depending on the quantification of central and peripheral involvement, the QCT would make it possible to characterize the different ALS phenotypes. This phenotypic characterization would help identify prognostic factors at diagnosis. The investigators propose a cohort study with the exploration of central motor neuron damage by QCT during the course of ALS in order to provide arguments for a better mechanistic understanding and follow-up of this disease with a poor prognosis.