ASPA and hereditary disease: This would subsequently result in a hypoosmotic extracellular space, from which it can be removed from the brain.[5] Canavan Disease (CD) is a genetic disorder which causes NAA accumulation in the brain due to a deficiency in the NAA-degrading enzyme aspartoacylase.[2] The disease is characterized by the buildup of excessive fluid within the myelin lamellae, in swollen astrocytes and in extracellular fluid vacuoles.[5] Baslow suggests that this accumulation of NAA is responsible for the macrocephaly in CD.