Calias et al [9], using an I2S gene knockout mouse model of Hunter syndrome observed that compared with untreated mice, intrathecally administered idursulfase treatment decreased cellular vacuolation in parts of the central nervous system such as, the surface cerebral cortex, cerebellum, and thalamus, indicating that I2S was active within the neural tissue. Here, IDS is linked to mucopolysaccharidosis type 2.