Basilar venous plexus of the posterior fossa: a potential source of error in petrosal sinus sampling.

Sampling of serum from the inferior petrosal sinus can provide important information about the source of elevated adrenocorticotropic hormone (ACTH) levels. This often leads to improved results of pituitary surgery for Cushing disease. The authors describe a successful catheterization technique and illustrate the venous anatomy of the inferior petrosal sinuses and basilar plexus.