Inferior petrosal sinus sampling/cavernous sinus sampling test for Cushing’s disease

Cushing’s disease can be difficult to diagnose. High levels of adrenocorticotropic hormone (ACTH) can be a sign of Cushing’s disease, but can also be caused by other tumors or conditions outside the pituitary gland.

A test called cavernous sinus sampling (CSS) helps your doctor diagnose a pituitary tumor causing Cushing’s disease. This test is almost 100% accurate. It can show where in the pituitary gland the tumor is located, even when MRI does not show the tumor clearly.

If you have cavernous sinus sampling, a surgeon puts catheters (thin, hollow tubes) in the veins of both your thighs. The tubes are guided into your cavernous sinus, an area at the base of your head, behind your eyes. This area has many veins (blood vessels). Your surgeon can measure how much blood is flowing away from the pituitary gland on the right and left sides. This provides information about the location of the pituitary tumor.

Cavernous sinus sampling is an outpatient procedure, requiring no overnight hospital stay. During the procedure, you have sedation medication to help you relax and reduce discomfort. The test takes one to two hours. Results are available in one or two days.

Neuroendocrine tests

Measuring your pituitary hormones accurately can require specialized hormone tests coordinated by an experienced doctor or nurse. Sometimes hormone levels are measured more than once, at various times of day or for several hours or days in blood, urine or saliva, or after taking a medication, which is called dynamic testing.

Tests include:

• Baseline hormonal evaluation, which can include measuring your body’s hormone levels by taking blood samples, saliva samples and urine at various times of day, or over the course of a full day.
  • Plasma tests: prolactin, cortisol, ACTH, GH, IGF-1, LH, FSH, testosterone and estradiol, free T4 and TSH.
  • Urine tests for cortisol measurement (over 24 hours).
  • Late-night saliva test for cortisol measurement.
• Dynamic tests, which can include measuring your body’s hormone levels before and after taking certain medications either orally or intravenously.
  • Cosyntropin/ACTH stimulation testing for adrenal insufficiency.
  • GH suppression test or oral glucose tolerance test for acromegaly.
  • Overnight, low-dose and high-dose dexamethasone testing for Cushing’s syndrome.
  • Dexamethasone suppression-CRH stimulation test for Cushing’s syndrome.
  • Insulin tolerance test for GH deficiency.
  • Glucagon stimulation test for GH deficiency.

The OHSU Pituitary Center offers specialized hormone testing for pituitary function and for diagnosis of hormonal oversecretion. Tests are done before and/or after pituitary surgery as needed. Testing services are available to OHSU and community doctors.

Our services include:

• A dedicated neuroendocrine testing facility for performing dynamic studies.
• Patient education about testing methods, pituitary disorders, pituitary surgery and giving injections.
• Dynamic testing, including cosyntropin (ACTH) stimulation tests, growth hormone stimulation and suppression tests, and CRH (corticotrophin-releasing hormone) tests.
• Endocrine therapy injections to replace pituitary hormones or to suppress GH or ACTH production from tumors.

Neuroradiology dynamic imaging

Imaging helps doctors see details of the important structures potentially affected. This is helpful in diagnosing and treating pituitary tumors, including planning for surgery. The OHSU Pituitary Center has access to several types of advanced imaging. This helps us use the best imaging technique for you, so you receive the best care.

At OHSU, imaging results are interpreted by radiologists who exclusively practice neuroradiology, have obtained certification of advance qualification (CAQ) and remain up to date on the latest advances in pituitary imaging techniques and interpretation.

Our advanced imaging and radiation technology includes:

• Rapid dynamic gadolinium-enhanced pituitary imaging that increases detection of pituitary abnormalities by about 10 percent over standard imaging in people with Cushing’s disease.
• 3-Tesla MRI scanners that provide high-resolution images, precisely showing how far a pituitary tumor has spread to nearby organs. This helps doctors plan surgery and evaluate and treat people who may have had an earlier surgery for a pituitary tumor.
• High-field Philips 1-Tesla open MRI scanner that provides high-resolution images. The image resolution is superior to most other open MR scanners.
• 3-Tesla intraoperative magnetic resonance imaging (iMRI) scanner that offers twice the resolution of other available systems. OHSU is one of only a handful of hospitals in the United States to have this technology.
• Trilogy™ stereotactic linear accelerator used to deliver precise radiation treatment. The Trilogy™ stereotactic linear accelerator shortens patient treatment times and minimizes damage to healthy tissue.

If you have a pituitary disorder, your hormones could be out of balance. You may need medication to decrease hormone secretion and reduce symptoms or to replace the hormones you do not make in enough quantities.

Doctors at the OHSU Pituitary Center are familiar with all medications to treat pituitary disorders, from the proven, older treatments to the most recently approved new medications. Some new medications are very effective at treating pituitary conditions that were previously treated with surgery. If you cannot have surgery or you need additional treatment after surgery, medication is a good option.

Examples of medications used for pituitary tumors include:

• Acromegaly: Somatostatin receptor ligands, such as octreotide (Sandostatin), lanreotide (Somatuline), pasireotide LAR (Signifor LAR).
• Acromegaly: growth hormone antagonists (pegvisomant).
• Prolactinomas and acromegaly: dopamine agonists to control excess secretion of prolactin, bromocriptine and cabergoline.
• Cushing’s disease: pasireotide.
• Mifepristone for hyperglycemia associated with Cushing’s syndrome.

There are many medications used off-label for pituitary tumors, including combination treatment for acromegaly and Cushing’s disease.

Other hormones that you might need to take if the tumor-induced pituitary deficiencies include:

• Glucocorticoids for central adrenal insufficiency
• Thyroid hormone for central hypothyroidism
• Testosterone for central hypogonadism in men
• Estrogen/progesterone replacement for central hypogonadism in women
• GH for GH deficiency

The OHSU Pituitary Center has doctors who are experts in treating pituitary disorders with medication. They will work with you to determine the best medication and dose to reduce symptoms and improve function. Our experts can often tell you how well the drug will work and how long you will likely need to take it. Some medications, as for example dopamine agonists, can control hyperprolactinemia and shrink tumors so well that you can usually stop taking them after some time.

Neuro-ophthalmology for pituitary disorders

Having a pituitary disorder can affect your vision, especially if your pituitary gland is enlarged, which may cause pressure on the optic nerves behind your eyes. The OHSU Pituitary Center works with specialists at OHSU Casey Eye Institute to diagnose and treat pituitary conditions that affect the eyes.

A neuro-ophthalmologist is a doctor who specializes in visual problems that are related to the nervous system, rather than visual problems that come from the eyes themselves. When you are diagnosed with a pituitary disorder, a neuro-ophthalmologist will perform a comprehensive eye examination (including visual field testing) to find out if your vision is affected. Some pituitary tumors develop slowly, so you might not notice vision loss for some time. Pituitary tumors can cause permanent visual loss or permanent peripheral visual field loss.

The neuro-ophthalmologists at the OHSU Casey Eye Institute see patients before and after surgery, as well as in emergencies. They work closely with endocrinologists (hormone system specialists) and neurosurgeons (nervous system surgeons) to treat pituitary disorders.

Your neuro-ophthalmic examination includes:

• Testing of your visual acuity, color vision, field of vision, pupil reaction to the light, as well as eye movements.
• Examination of the back of the eyes (retina and optic nerves) through a dilated eye exam.

Pathology tests for pituitary disorders

The OHSU Pituitary Center has two board-certified neuropathologists who examine tissue from more than 1,000 cases per year. Each year, these samples typically include about 350 muscle and nerve biopsies, 450 brain and spinal cord tumors, more than 100 pituitary surgery cases and 150 outside consultations.

Our specialists examine a patient’s pathology material along with clinical, radiologic and laboratory data. Laboratory tests available for diagnostic analysis include enzyme histochemistry, immunohistochemistry, cytogenetics, molecular pathology and ultrastructural analysis. Processing includes routine staining, special tissue stains, immunohistochemistry for pituitary hormones, proliferative indexing, molecular markers and electron microscopy on selected cases. All tests are carried out in specialized laboratories by dedicated technicians who are experienced in processing neural tissue with rigidly implemented quality assurance strategies.

If you have a pituitary tumor, radiation is one of the treatment options. It is used after surgery, or in rare instances instead of surgery. Radiation can shrink a pituitary tumor or keep it from getting larger. You can usually have radiation therapy without staying overnight in the hospital.

The OHSU Pituitary Center uses the most advanced equipment available for radiation therapy. The Novalis Tx radiosurgery platform is used to treat brain tumors and other conditions that require precise treatment. Because the Novalis Tx system is very precise, it destroys tumor cells while protecting healthy tissues nearby. A combination of X-rays, cone beam CT and visualization through an infrared camera are used to ensure accurate targeting of the tumor and close-motion monitoring during treatment delivery.

After you finish radiation treatments, you will have imaging studies (CT scans or MR images) every three to six months for two years. After that, you will have imaging studies once a year. You will also see your doctor to check your pituitary gland, including vision exams and blood tests. Continuing to see your doctor after radiation is complete helps you get the best possible results from your pituitary treatment.

Treating pituitary disorders with surgery

The OHSU Pituitary Center is a leader in new treatments for pituitary disorders. This includes the latest surgery techniques to remove pituitary tumors with less discomfort, allowing you to recover faster.

Most pituitary tumors are removed through the nose, in a procedure called transnasal surgery. Many studies have repeatedly shown that surgeons highly experienced in this procedure get the highest cure rates with the lowest rates of recurrence, postoperative complications and pituitary dysfunction.

Transnasal surgery

In this procedure, the tumor is accessed through the natural air passages of the nose. An ear, nose and throat (ENT) surgeon widens these passages to allow room for the surgical instruments. Once access is provided, the skull base neurosurgeon drills away a thin piece of bone overlaying the tumor. The tumor is then gently removed, taking care to separate it from the normal pituitary gland and surrounding structures. In most cases, the neurosurgeon will use an endoscope (a small, lighted tube with a high-resolution camera) to provide a panoramic view of the tumor and surrounding tissues. In addition, a sophisticated computer navigation system is used to increase the safety and accuracy of the procedure. During surgery, you are asleep with the aid of general anesthesia.

Advantages of minimally invasive pituitary surgery (transsphenoidal surgery):

• No facial or labial incisions.
• Patients can go home the day after surgery, depending on the type of tumor and hormonal abnormalities.
• Low complication rates.
• Preservation of the pituitary gland.
• Complete tumor removal up to 5 cm.

Transcranial surgery

In some cases, an alternative method may be the better choice due to the size and location of the tumor. In these cases, a small incision is made behind the hairline or in the eyebrow to hide the incision. A small piece of bone is removed to reach the tumor. The surgeon uses a high-powered surgical microscope to carefully remove the tumor from the surrounding nerves and arteries of the brain. Our team at the OHSU Pituitary Center has performed hundreds of these specialized surgeries, giving us a depth of experience that is rare to find. All the doctors and surgeons involved have also had special fellowship training in pituitary tumors.

Ask your surgeon which type of surgery is right for your tumor’s size and location.

With any medical condition that involves surgery or extensive treatment, seeking a second medical opinion is a reasonable decision. Many conditions related to the pituitary gland are uncommon and complicated.

Doctors and patients often come to the OHSU Pituitary Center for a second opinion because of our expertise and technology. We are always happy to discuss a case or provide consultation or a second opinion. In fact, we provide more second opinions than any other center in the region. Our well-known experts can review and discuss the options.

You may want a second opinion if:

• You want to confirm your diagnosis of a pituitary tumor or disorder.
• There is more than one treatment option for your condition, and you want more information about which option to follow.
• Your local resources do not have the same high level of comprehensive care for pituitary conditions.
• You have been told your case is unusual, rare or complex.

For those traveling to OHSU, our clinic is conveniently located at the OHSU Center for Health & Healing in Portland’s South Waterfront District. Most patients can be evaluated in a single day.