Before the establishment of N-acetylaspartic aciduria due to aspartoacylase deficiency as the cause of Canavan disease, diagnosis was based on the characteristic clinical features and spongiform encephalopathy, a pathological response shared by a number of other unrelated conditions. Thus confusion exists in the literature about the phenotype of spongiform encephalopathy (Canavan disease), with reports of 'juvenile' and 'congenital' forms, as well as the classical infantile type. In this report, six of 22 patients with infantile-onset Canavan disease survived beyond six years of age. This phenotypical pattern might be the result of better medical management and care, rather than evidence of genetic heterogeneity.