CT
Axial non-contrast
Axial bone window
Coronal bone window
Sagittal bone window
No intra- or extra-axial collection or haemorrhage. No focal abnormality. Grey-white differentiation is preserved. Ventricular size, sulcal pattern and basal cisterns all appear normal.
Basilar invagination is present with narrowing of the craniocervical junction and mildly impresses on the medulla oblongata/cervical spinal cord. The dens is mildly expanded and sclerotic/irregular with well-circumscribed lobulated lucency/erosion at the posterior aspect of the base of the dens.