The present disclosure provides methods and materials for diagnosis and treatment of neuronal disorder. The methods may include (a) determining a longitudinal trend in an expression level of phosphoglycerate dehydrogenase (PHGDH) in the subject over an observation period of time or an amount of extracellular RNA (exRNA) produced from transcription of the PHGDH gene; and (b) administering to the subject an effective amount of a therapy for managing or treating the neuronal disorder, if the longitudinal trend indicates that the expression level of PHGDH or exRNA is increased during the observation period. The neuronal disorder is managed or treated in the subject.