Atlas assimilation: spectrum of associated radiographic abnormalities, clinical presentation, and management in children below 10 years.

OBJECTIVE: To analyze the varied presentation and management of atlas assimilation with associated radiographic abnormalities in children in the MRI era
METHODS: Database analysis of 313 children (less than 10 years)
RESULTS: Atlas assimilation (AA) was associated with atlantoaxial dislocation in 12, abnormal skull base and Chiari I abnormality in 42, C2-C3 segmentation failure and instability and Chiari I abnormality in 74, and condylar hypoplasia and basilar invagination in 74. Proatlas segmentation failures were 54, atlantoaxial rotary dislocation in 26 with Goldenhar's syndrome, abnormal C1 atlas posterior arch causing dynamic compression of cord in 31 children. Vascular compromise was documented in 26 children. The study encompassed ages 6 months to 10 years. Cranial nerves commonly affected were glossopharyngeal, vagal, and hypoglossal nerves. Children below 2 years presented with torticollis, failure to thrive, difficulty swallowing, and motor and sensory deficits. Craniovertebral junction instability associated with AA was treated with custom-built craniocervical orthosis below 5 years. Closed reduction of instability or basilar invagination was attempted with neuromuscular blockade under anesthesia and traction above age 5 years. Successful reduction was treated with dorsal foramen magnum and atlas decompression with occiput-C2 dorsal fusion using rib grafts below the age of 5 years and instrumentation after that. Follow-up was 2 to 32 years. Neurological recovery was seen in nearly all patients.
CONCLUSIONS: Children with atlas assimilation and associated abnormalities may be symptomatic in early childhood. The treatment depends on the age and tailored to the abnormalities present. The long-term results have been successful.