Introduction: Down's syndrome is the most common inherited disorder. Some patients develop craniocervical instability. Existing screening guidelines were developed prior to direct imaging of the neuraxis. Here we present predictors for potential deficit using dynamic MRI of the craniocervical junction.
Methods: A retrospective review of Down's patients referred to CHLA Neurosurgery from 2001 – 2015 was carried out. Patients with incomplete records were excluded. Patients were considered symptomatic if they had deficit from neuraxis compression or signal change at the craniocervical junction. The Atlanto-Dental Interval (ADI), Clival Axial Angle (CXA), Cervical Angle (CA) and craniocervical canal diameter (CCD) was measured. Bony abnormalities at the craniocervical junction were also recorded. Data analysis was performed with SPSS. A p-value of 0.05 was significant.
Results: 36 patients met inclusion criteria. Patients averaged 93 months of age on presentation with a follow up of 57 months. No asymptomatic patients developed myelopathy during follow up. 2 patients presented with myelopathy, while 4 had cord signal change. Symptomatic patients had smaller CCD (9.4 mm vs 13.8 mm; p = 0.003) and greater ADI (4.4mm vs 3.0 mm; p = 0.01) on resting MRI . During dynamic imaging, symptomatic patients had significant changes in CCD (5.2 vs 2.7 mm; p <0.001) and ADI (2.8 vs 1.3 mm; p = 0.04). These patients were also more likely to have a bony anomaly (0.5 vs 0.13; p = 0.03).
Conclusions: This study identifies parameters that can be used to identify patients at risk for neurologic injury. A CCD of less than 5 mm or ADI greater than 4.4 mm on static imaging; change greater than 3mm in ADI or 5mm on CCD during dynamic imaging; or any bony abnormality warrants further investigation. Asymptomatic patients without these features should be followed although most do not progress.
Patient Care: By developing measures for potential deficit through direct visualization of the effect on neurologic structures, more precise and evidence based recommendations made be made for timing and indication for intervention. Furthermore, recognizing the natural history of these patients may prevent unnecessary intervention.
Learning Objectives: By the conclusion of this session, participants should be able to:
1) Describe the normal movement parameters of the craniocervical junction and sub axial spine in Down's Syndrome patients; 2) Discuss some potential parameters in Down's syndrome patients corresponding to neurologic compromise; 3) Discuss management options of patients with potential craniocervical instability