Glossary term:

Basilar invagination

We can envisage the skull, in simple terms, as ball sitting on top of a pipe, the latter representing the spinal column. We refer to the point where the two join together as the craniovertebral junction. Normally the shape of this junction is like a funnel, with the lower part of the cerebellum sitting in the mouth of the funnel and the cervical part of the spinal cord being in the stem. The term basilar invagination describes an anatomical state where the “pipe” (i.e. the uppermost part of the spinal column) is pushed up into the lower half of the “ball” (i.e. the posterior fossa of the cranial cavity). This results in a distortion of the normal bony anatomy at the craniovertebral junction. This sometimes (but not always) causes some physical distortion of the brain stem, which may lead to the development of neurological symptoms. Basilar invagination may develop secondary to certain rare disorders that lead to softening of bone but, more often, they are seemingly just the way that the individual is made. Read more