Occipitalization
§Can have partial or
complete congenital fusion of the atlas to the occiput
§Occipitalization can lead to symptomatic chronic
atlanto-axial instability and cord
impingement
§Symptoms include weakness, atrophy, spasticity,
headache, which are usually slow
onset, but sudden death has been associated with the condition (traumatic in ½, major or minor)
§If the dens is in the foramen magnum, crowding of
anterior elements can result.
Usually asymptomatic if dens lies below the foramen magnum.
§60% have odontoid
> 3mm displaced behind anterior arch of atlas.
§Constricting dural
bands are commonly associated.
§Physical exam findings include short neck, low hairline,
torticollis, restricted neck
motion.
§20% have other
associated congenital anomalies.