Pneumoencephalography is a no-longer performed investigation that allowed imaging of the contours of the brain and ventricles by the deliberate introduction of air into the subarachnoid space.

This was achieved initially by a needle passed directly into the ventricles (via the fontanelles or a borehole). Small amounts of CSF were withdrawn and replaced with room air. The process repeated over and over until no more CSF could be obtained .

Later, it was realized that air inserted into the lumbar theca (via puncture) could be maneuvered into desired subarachnoid spaces by careful position and tilting of the head.

History and etymology

The procedure was developed by Walter E. Dandy (1886–1946) an American pediatric neurosurgeon who practised at Johns Hopkins Hospital .