Dilated Optic Nerve Sheath in Mucopolysaccharidosis I: Common and Not Necessarily High Intracranial Pressure

A, Axial T2-weighted MR image of the brain shows white sold lines indicating the retrobulbar ONSD and white dashed lines indicating the midpoint of the ONSD. This patient’s OP was elevated at 31 cm H₂O, while the average ONSD was 5.8 mm at the retrobulbar area and 5.4 mm at the midpoint. B, Axial T2-weighted MR image of the brain shows white solid lines indicating the retrobulbar ONSD and white dashed lines indicating the midpoint ONSD. The courses of the optic nerves in this patient are more tortuous than those in the patient shown in A. This patient’s OP was normal at 17 cm H₂O, while the average ONSD was 8.3 mm at the retrobulbar area and 6.5 mm at the midpoint.