Reversal of emissary vein blood flow in achondroplastic dwarfs.

We used a noninvasive technique--the directional Doppler examination--to determine the direction of flow in an emissary vein of achondroplastic dwarfs. Normally, the direction of flow in this emissary vein is into the orbit. The direction of flow in all 10 achondroplastic dwarfs whom we studied was away from the orbit. This indicates that ophthalmic vein blood flow is reversed in achondroplastic dwarfs, perhaps because there is a pressure gradient between the intracranial and extracranial venous systems.