Inferior petrosal sinus
The inferior petrosal sinus is one of the brain's venous blood conductors . It runs below the superior petrosal sinus . The inferior petrosal sinus establishes the connection between the cavernous sinus and the internal jugular vein . It lies in a groove on the inside of the temporal bone and leaves the cranial cavity together with the ninth cranial nerve through the jugular foramen .
Direct catheterization of the inferior petrosal sinus enables blood to be drawn from this blood conductor. Since this directly drains the blood of the pituitary gland , a higher level of ACTH compared to that in another vein is an indication that Cushing's syndrome is caused by an overactive pituitary gland.