Achondroplasia

Case Discussion:

Three month old child with achondroplasia.

The clivus is short such that the tip of the odontoid is elevated to
the level of the posterior lip of foramen magnum. At this point, the
AP diameter of the bony craniocervical junction measures only 7 mm.
The cord fills the available subarachnoid space at this level, and
there is impingement on the cord by the posterior lip of foramen
magnum. Subtle T2 hyperintensity is shown in the medulla and in the
upper cord down to the level of junction of odontoid with body of C2.
Some T2 hyperintensity within or below the cruciform ligament raises a
possibility of a little fluid but no evidence of ligamentous disruption
is shown. 

The sagittal images show slight elevation of the anterior cerebellar
tentorium. This is likely due to the relatively small posterior fossa.
The pons and mid brain are unremarkable with plentiful room anteriorly.
The third and lateral ventricles are mildly prominent as are the
cortical subarachnoid spaces but there is no evidence of frank
hydrocephalus. The grey and white matter signal intensities are
normal.

The major venous sinuses are quite prominent within the cranium. There
is a large midline occipital vein beneath the cerebellum which divides
around the foramen magnum and I think the branches enter the jugular
veins at the jugular canals . I believe the jugular foramina are
patent and the upper most jugular veins are visible in the sagittal and
axial images.