Natural history of craniovertebral abnormalities in a single-center study in 54 patients with Hurler syndrome

OBJECTIVE Craniovertebral junction (CVJ) abnormalities are common and well documented in mucopolysaccharidosis type I-Hurler syndrome (MPS IH), often causing severe spinal canal narrowing. However, the requirement for surgical decompression and/or fusion is uncommon. Although hematopoietic cell transplant (HCT) has been shown to prolong the lives of patients with MPS IH, its effect in halting or reversing musculoskeletal abnormalities is less clear. Unfortunately, there are currently no universal guidelines for imaging or indication for surgical interventions in these patients. The goal of this study was to track the progression of the CVJ anatomy in patients with MPS IH following HCT, and to examine radiographic features in patients who needed surgical intervention. METHODS Patients with MPS IH treated at the University of Minnesota with allogeneic HCT between 2008 and 2020 were retrospectively reviewed. Patients who underwent CVJ surgery were identified with chart review. All MPS IH cervical scans were examined, and the odontoid retroflexion angle, clivoaxial angle (CXA), canal width, and Grabb-Oakes distance (pB-C2) were measured yearly for up to 7 years after HCT. Longitudinal models based on the measurements were made. An intraclass correlation coefficient was used to measure interrater reliability. Nine children without MPS IH were examined for control CVJ measurements. RESULTS A total of 253 cervical spine MRI scans were reviewed in 54 patients with MPS IH. Only 4 (7.4%) patients in the study cohort required surgery. Three of them had posterior fossa and C1 decompression, and 1 had a C1-2 fusion. There was no statistically significant difference in the spinal parameters that were examined between surgery and nonsurgery groups. Among the measurements, canal width and CXA varied drastically in patients with different neck positions. Odontoid retroflexion angle and CXA tended to decrease with age. Canal width and pB-C2 tended to increase with age. CONCLUSIONS Based on the data, the authors observed an increase in canal width and pB-C2, whereas the CXA and odontoid retroflexion angle became more acute as the patients aged after HCT. The longitudinal models derived from these data mirrored the development in children without MPS IH. Spinal measurements obtained on MR images alone are not sufficient in identifying patients who require surgical intervention. Symptom monitoring and clinical examination, as well as pathological spinal cord changes on MRI, are more crucial in assessing the need for surgery than is obtaining serial imaging.