Presentation
Pain during full range of neck movements.
Patient Data
Noncontrast high-resolution CT reveals hypoplasia of basiocciput with prebasioccipital arch, basilar invagination, and the possibility of neural dysgenesis (Chiari malformation).
Case Discussion
The study reveals a hypoplastic clivus, suggesting basioccipital hypoplasia. There is basilar invagination, as evidenced by the tip of the dens and the anterior arch of the atlas lying approximately 19 mm above the Chamberlains line. Weckenheims clivus baseline is normal, and Welcher's basal angle is 135 degrees.
A bony arch is noted at the tip of the clivus, which is continuous laterally with the occipital condyles, consistent with the rare occurrence of the prebasioccipital arch. The bilateral atlantooccipital and atlantoaxial joints are normal.
There is also a hypodense fluid attenuation central area in the cervical canal on soft tissue windows caudal to C3 level, which may represent syringomyelia (MRI was recommended).