The clinical diagnosis of Canavan disease is suggested when the triad of hypotonia, macrocephaly and head lag is present. It is a progressive form of spongy degeneration of the central nervous system but its onset, course, and severity are variable.
The disease is often evident before 6 months of age and survival is limited to a few months or years in infants with such early onset. Such patients have the most severe and rapidly progressive disease. It is noteworthy that, even though such infants do not achieve normal milestones such as sitting and standing, they do often interact socially by laughing, smiling, and reaching for objects. Most young children are quiet and apathetic but some become irritable and develop spasticity as they grow. CNS damage is evident as leukodystrophy on neuroimaging studies but this may not be present in later onset, milder forms of the disease.
Other individuals may have a later and milder juvenile onset of symptoms and may present with delayed speech or motor development late in the first decade. They often attend regular school but may benefit from tutoring and speech therapy. They may live to adolescence or early adulthood. Maldevelopment of the organ of Corti is responsible for hearing deficits in some children.