Case Study 151 - Basilar invagination Basilar invagination occurs when the top of the second vertebrae moves upward. It can cause the opening in the skull where the spinal cord passes through to the brain (the foramen magnum) to close. It also may press on the lower brainstem. If there is pressure on the lower brainstem, its first symptom may be death. Otherwise symptoms vary depending on whether the spinal cord, brain stem, nerves or their blood supply is affected by the pressure. Symptoms beco