Mucopolysaccharidoses: overview of neuroimaging manifestations

The mucopolysaccharidoses are a heterogeneous group of inherited lysosomal storage disorders, characterized by the accumulation of undegraded glycosaminoglycans in various organs, leading to tissue damage. Mucopolysaccharidoses include eight individual disorders (IS [Scheie syndrome], IH [Hurler syndrome], II, III, IV, VI, VII and IX). They have autosomal-recessive transmission with the exception of mucopolysaccharidosis II, which is X-linked. Each individual disorder has a wide spectrum of phenotypic variation, depending on the specific mutation, from very mild to very severe. The skeletal and central nervous systems are particularly affected. The typical clinical presentation includes organomegaly, dysostosis multiplex with short trunk dwarfism, mental retardation and developmental delay. In this article, we review the neuroimaging manifestations of the different types of mucopolysaccharidoses including the dysostosis multiplex of the skull and spine as well as the various central nervous system complications. These include white matter injury, enlargement of the perivascular spaces, hydrocephalus, brain atrophy, characteristic enlargement of the subarachnoid spaces as well as compressive myelopathy. The correlation between several of the neuroimaging features and disease severity remains controversial, without well-established imaging biomarkers at this time. Imaging has, however, a crucial role in monitoring disease progression, in particular craniocervical junction stenosis, cord compression and hydrocephalus, because this allows for timely intervention before permanent damage occurs.