Basilar invagination

Diagnosis

Craniocervical junction abnormality where the tip of the odontoid process projects above the foramen magnum.
👉 see Radiographic lines - Basilar invagination for measurement and threshold

Often coexists with platybasia.

Association

Congenital

Conditions with maldevelopment of the craniocervical junction → cervical myelopathy in the second and third decades of life.

• Atlanto-occipital assimilation
• Klippel-Feil syndrom
• Chiari I malformation

Acquired

Due to bone softening/destruction or chronic instability at the craniocervical junction

• Rheumatoid arthritis with pannus
• Paget disease of the bone
• Osteomalacia / Rickets
• Hyperparathyroidism