The current study evaluates the passage of the atlantal segment of the vertebral
artery through the atlas to the cranial cavity in the case of occipitalisation,
and searches for potential bony obstacles that constrict the lumen of the vertebral
artery.
Morphometric analysis was performed of the ossified atlanto-occipital articulation
of the dry adult male skull, particularly in the region of the posterior arch
of the atlas.
The distance between the floor of the right groove for the vertebral artery and
the occipital bone was measured using a digital sliding caliper. On the left side,
measurements of the diameters of the inlet and outlet of the canal for the
vertebral artery were performed using the same technique.
Fusion of the left portion of the posterior arch of the atlas with the occipital
bone caused significant narrowing of the space around the normally existing
groove for the vertebral artery, and converted it into the canal. The size of the
intracranial opening of the canal for the vertebral artery was measured as
3.8 mm x 4.7 mm, whereas the inlet to the canal was 5.4 mm x 7.0 mm. The
diameter of the canal decreases, particularly at the entrance into the cranial
cavity; therefore, compression of the vertebral artery within the canal seems to
be possible. (Folia Morphol 2011; 70, 4: 287–290
