Pathophysiological and pathochemical mechanisms of central motor disorders in amyotrophic lateral sclerosis

A complex study of pathophysiological characteristics of corticospinal systems was performed in patients with amyotrophic sclerosis (ALS) by transcranial magnetic resonance stimulation (TMRS) and estimation of the levels of mediatory amino acids in the cerebrospinal fluid (CSF). There was a time course of changes in the excitability of cortical motor neurons (MNs) and in the functional status of the pyramidal tract as ALS progressed. The large cortical MNs were found to be afflicted just at early stages by further involving their axonal systems into the pathological process. As a result, mainly fine slowly conducting axons of MNs functioned at the later stages of the disease. Neurochemical changes correlated with the duration of the disease and were supposed to play an important role in the pathogenesis of ALS. Besides, a significant correlation revealed by TMRS between the pathology of the corticospinal tract and the cerebrospinal fluid levels of glutamate confirmed the role of glutamate as a the main neurotransmitter of this motor system. The results of the study also confirm the significance of excitotoxic mechanisms in central motor disorders in ALS.