Platybasia is an abnormality of the base of the skull in which the angle between the basisphenoid and the basilar portion of the occipital bone is increased.

In normal subjects it varies from 119° to 145° and angle more than this is abnormal.

As such it is not known to produce any neurological disorder but may be associated with basilar invagination.

Basilar impression or platybasia is generally congenital and may be associated with fusion of bodies of some cervical vertebrae.

It may lead to hydrocephalus. The head may be mushroom shaped and neck short.

Diagnosis is made by X-ray examination. Platybasia as such does not produce serious neurological problems and is generally left untouched.