What Is Petrosal Sinus Sampling?

Petrosal sinus sampling is an invasive procedure where blood samples are taken from each side of the veins that drain into the pituitary gland. The concentration of a substance called adrenocorticotropic hormone (ACTH) from these veins is compared to that of the ACTH found in the rest of your body. This test is mainly done to identify the exact cause of Cushing syndrome, whether it is rooted in the pituitary or somewhere else. For the procedure, the staff takes blood samples from the petrosal sinuses and the vein in the forearm.

If the hormone level is higher in the sinus sample, the problem stems from the pituitary. However, if the hormone levels are similar between the sinuses and forearm, the root problem lies outside the pituitary.

Cushing syndrome is typically characterized by a high level of the cortisol hormone. Some of the distinctive features of Cushing syndrome include:

• A fatty hump between your shoulders
• A rounded face (moon face)
• Pink or purple stretch marks on your skin

Other effects of Cushing syndrome include:

• High blood pressure
• Bone loss
• Type 2 diabetes

Petrosal sinus sampling helps the physician to rule out other medical conditions that exhibit similar signs and symptoms. Some of the disorders that may have similar symptoms to Cushing syndrome include:

• Polycystic ovarian syndrome
• Depression
• Eating disorders
• Alcoholism

Before the procedure

You will get some instructions on how to prepare for your procedure. They are:

• Stop eating or drinking a few hours before the procedure to ensure that the stomach remains empty.
• Inform the physician if you suspect pregnancy or are breastfeeding.
• Stop taking drugs like Aspirin, Warfarin, Clopidogrel, or other blood thinners a week before the procedure.
• Inform the physician regarding all the prescribed, over the counter, or herbal medications that you take.
• Stop taking alcohol or any recreational drugs 24 hours before the procedure.

During the procedure

You can expect the following things during the procedure:

• The physician inserts an intravenous (IV) cannula into a vein in your arm.
• Next, you will be getting a local anesthetic into the skin of the upper thigh and groin.
• Once the anesthesia sets in, the physician inserts a needle and catheter into a vein located at both sides of your groin.
• After the catheter is in place, the physician removes the needle gently.
• The physician guides the catheter through the main blood vessels in the body to reach the petrosal sinus.
• Once the catheter reaches the petrosal sinus, the physician withdraws blood samples from each gland and the IV cannula in your arm simultaneously.
• Through the IV cannula, the physician might give a medication that promotes hormone production of the pituitary gland.
• After collecting more blood, the physician removes the catheter and applies pressure at the site to prevent bleeding.

After the procedure

• The recovery period may vary anywhere between 2-4 hours. You may get instructions on:
• Limiting the activities for a few days to prevent bleeding.
• Resting in bed by laying flat for a while.

The staff will remove the IV cannula after you recover.