The invention disclosed herein describes a novel therapeutic target for motoneuron diseases (altered dynamics of microtubules in neurons); a method for measuring the state of activity of this therapeutic target in subjects with established, incipient, or potential motoneuron disease; the discovery of drug agents that modulate neuronal microtubule dynamics in living subjects with motoneuron diseases; the discovery that administration of such agents, alone or in combinations, can provide marked neuroprotective therapy for living subjects with motoneuron diseases including delay in symptoms and prolongation of survival; and the discovery that monitoring of neuronal microtubule dynamics in subjects with motoneuron diseases, in response to therapeutic interventions, allows diagnostic monitoring for optimization of therapeutic regimen and strategy for individual subjects or for drug trials.