Monitoring amyotrophic lateral sclerosis by biomechanical modeling of speech production

Neuromotor Degenerative Diseases (NDD) affecting mainly sub-thalamic and extra-pyramidal neuromotor structures leave significant marks in speech and phonation correlates. These may be used in the characterization, detection, grading and monitoring diseases and their progress in a non-invasive way. Considering that speech and phonation recording can be carried out using handy and low-cost instrumentation, speech and phonation correlates may be quite adequate candidates to define specific NDD biomarkers for disease progress monitoring protocols. The purpose of the paper is to present the fundamentals of speech articulation biomechanical modeling from the level of signal processing to neuromotor activity inference. This backward pathway involves several inverse problems, which are addressed separately. Results from study cases relevant in Amyotrophic Lateral Sclerosis are presented and discussed. The conclusions of the research show that several correlates may be reliably established, and that monitoring disease state and progress may rely on some biomechanical correlates informing on jaw and tongue neuromotor residual activity. Possible applications of the methodology to other neurodegenerative diseases are also discussed.