• Craniocervical junction anomaly. The tip of the odontoid process protrudes above the foramen magnum.
• It can be congenital or acquired. It is often associated with platybase.
• Stenosis of the foramen magnum and compression of the medulla oblongata can result in neurological deficits and even death.
•Basilar intussusception and basilar impression are terms used interchangeably, but in reality, the normal foramen magnum and bony vertebral components are displaced upwards in impression. In intussusception, the skull base is soft.
•Classification is made according to Chiari malformation. There is no chiari in group 1, there are chiari in group 2.
• While brain stem compression is due to the odontoid process in group 1, it is due to decreased posterior fossa volume in group 2.
Platabasis
• Abnormal flattening of the skull base. The angle between the center of the nasion-pituitary fossa and the foramen magnum is more than 143 degrees.
•
