Basilar Invagination

BACKGROUND: Basilar invagination is a developmental anomaly of the craniovertebral junction in which the odontoid abnormally prolapses into the foramen magnum. It is often associated with other osseous anomalies of the craniovertebral junction, including atlanto-occipital assimilation, incomplete ring of C1, and hypoplasia of the basiocciput, occipital condyles, and atlas. Basilar invagination is also associated with neural axis abnormalities, including Chiari malformation, syringomyelia, syringobulbia, and hydrocephalus. Patients frequently present with neurologic symptoms and deficits and warrant surgical treatment to prevent progression. OBJECTIVE: To review the management of basilar invagination. METHODS: The literature was reviewed in reference to the evaluation and management of basilar invagination, with particular emphasis on the surgical treatment. RESULTS: Reducible basilar invagination may be treated with posterior decompression and stabilization. Ventral decompression may be necessary for basilar invagination with neural compression that is not reducible with axial cervical traction. Posterior cervical stabilization is necessary after ventral decompression. Modern rod and screw systems combined with autogenous bone graft enable correction of deformity, immediate stabilization, and high fusion rates. CONCLUSION: Basilar invagination is a developmental anomaly and commonly presents with neurologic findings. Treatment is typically surgical and involves anterior decompression followed by posterior stabilization for irreducible invagination and posterior decompression and stabilization for reducible invagination.