Inclusion Criteria:  Confirmed diagnosis of MPS IIIA Has the ability to comply with protocol requirements, in the opinion of the investigator  Exclusion Criteria:  Patient's assent is unattainable, or the patient's parent(s), or patient's legally authorized representative(s) is/are unable to understand the nature, scope, and possible consequences of the study, or do/does not agree to comply with the protocol defined schedule of assessments.