A 10-year-old girl had MPS VI (Morateux-Lamy syndrome) with symptomatic cord compression had a falsely reassuring normal supine MRI. An erect spinal X-ray revealed thoracolumbar subluxation

Abstract

Purpose: To alert clinicians to a potential limitation of MRI to detect cord compression. Methodology: A 10-year-old girl from a non-consanguineous family was diagnosed with Morateux-Lamy syndrome (MPS VI) at the age of 13 months. No arylsulphatase B activity detected on leucocytes. She initially presented with symptoms of spinal cord compression at C1 and C2 due to atlanto-axial instability and required a cervical posterior occiput to C5 fusion. Infusions of Naglazyme (1mg/kg every week via an infusaport) was commenced as soon as federal government funding permitted from the age of 2 years and 8 months. Routine 6 monthly clinical assessments of physical examination with annual spinal imaging from diagnosis had remained stable since the cervical spine fusion. At the age of 10 years and 2 months, neurological examination showed deterioration in her gait and sustained clonus bilaterally. She was referred to her orthopedic surgeon who arranged an early MRI. Results: MRI demonstrated a stable spine, compared with the film 6 months previously and no significant cord compression. Her orthopedic surgeon then ordered an erect lateral spinal x-ray that showed marked subluxation at T12/LI junction. This subluxation was not visible on the MRI as in the supine position it corrected. The patient developed urinary incontinence a few days before surgery. Conclusion: This patient demonstrates the importance of further investigation, including erect plain radiography of the whole spine, when an MRI fails to reveal the cause of a patient's symptoms. In this case an erect spinal Xray revealed the pathogenic subluxation.L6124788752016-10-07 <br />