Except for Canavan disease, a genetic disorder characterized by toxic accumulation of N-acetyl aspartate caused by aspartoacylase inactivation (86), down regulation of this metabolite seems to be constant in clinical conditions that associate neuronal dysfunction, including epilepsy (87–89), multiple sclerosis (90), Alzheimer's disease (91, 92), schizophrenia (93, 94), stroke (95), brain injury (96, 97) and brain tumors (98, 99). The gene discussed is ASPA; the disease is Alzheimer disease.