Surgical Treatment of Pituitary Tumors

The pituitary gland is a very important but small piece of tissue located at the base of the brain. This tissue is referred to as a gland because it secretes hormones into the bloodstream to control essential functions of the body, including reproduction, growth during child development, metabolism, response to stress, and the function of the thyroid. The pituitary gland is arguably the most important gland in the human body because it does so many things at one time.

The pituitary gland is divided into two lobes, the anterior and posterior lobes. The anterior lobe makes and secretes six different hormones:

• Thyroid Stimulating Hormone (TSH): Controls the function of the thyroid gland
• Adrenocorticotropic Hormone (ACTH): Stimulates the adrenal glands to release adrenalin
• Follicle Stimulating Hormone (FSH):  Plays a role in puberty and reproduction
• Luteinizing Hormone (LH): Helps control reproduction and sexual development
• Growth Hormone (GH): Controls growth of the body during childhood and adolescence
• Prolactin (PRL): Controls the production of breast milk after pregnancy

The pars intermedia, the boundary between the anterior and posterior lobes, makes and secretes one hormone:

• Melanocyte-stimulating hormone (MSH), which stimulate the production of the protective pigment melanin found in skin cells

The posterior lobe stores and secretes two hormones that originate in the hypothalamus:

• Anti-Diuretic Hormone (ADH): Helps control the balance of water and sodium in the body
• Oxytocin: Helps labor to progress in childbirth, stimultes the flow of breast milk, and promotes infant-parent bonding.

Most glands secrete one hormone, so the pituitary is unusual due to both the complexity of its function and its unique location in the brain, just behind the nose.

Not only does the pituitary gland secrete nine different hormones, some of these hormones control other glands—including the thyroid—so alterations in the function of the pituitary gland can seriously impact an individual’s health and wellbeing.

Hormone imbalances, whether originating from the pituitary gland or another area of the body, are typically treated by endocrinology. Endocrinology is the medical specialty that treats hormone issues, including pituitary problems and other hormone issues such as diabetes.

Pituitary Tumor

The most common type of pituitary tumor is the pituitary adenoma, a noncancerous tumor that forms on the pituitary gland. There are other types of tumors than can form, but the adenoma is by far the most common.

The incidence of diagnosed pituitary tumors is 4.36 people in every 100,000. However, according to autopsy reports and imaging studies, pituitary adenomas are even more common than we thought, with as many as 25% of patients having a small adenoma present in the pituitary gland at some point in their life. 

Pituitary adenomas are categorized in multiple ways. They are benign (noncancerous), invasive adenoma, or cancerous. The tumor may be a secretory tumor, meaning the tumor secretes hormones, or it may not. They are referred to as macroadenoma if they are a centimeter or more in size and are considered microadenoma if they are smaller than a centimeter.

There are other types of tumors that can occur at the pituitary, but most are rare and surgery is performed in a similar way to the procedures that treat adenomas.

Diagnosing a Pituitary Tumor

Pituitary tumors are often diagnosed after a seemingly unrelated problem leads to the diagnosis of this type of brain tumor. For example, a young woman who has never had a child may begin to produce breast milk and lab results may point to a pituitary tumor as the cause of the problem.

That said, many pituitary tumors are referred to as “incidentalomas” when they are found not because of symptoms or problems, but during a workup for something else. In this case, a pituitary tumor might be found during a CT scan of the brain being done because the patient went to the emergency room for a possible stroke. In this case, there were no issues or symptoms due to the adenoma, and it may have never been found if the CT scan had not been done.

Symptoms of Pituitary Tumor

The following are symptoms or conditions you may experience if you have a pituitary tumor:

Hypopituitarism, a condition where one or more hormones secreted by the pituitary gland are impaired, increasing mortality rates through cardiovascular and respiratory diseases. A large adenoma can crush normal pituitary cells and keep them from working properly, leading to various symptoms or conditions of hypopituitarism as well including:

• Diabetes Insipidus, low levels of ADH casues excess water loss in the urine leading to dehydration, confusion, and, in worst cases, coma and death.
• Stunted growth, or dwarfism, caused by a deficiency in GH.
• Addison’s disease, a condition caused by too little ACTH causing less cortisol being secreted from the adrenal glands, leading to low blood pressure, low blood sugar, and high blood levels of potassium.
• Hypothyroidism, caused by low levels of TSH, can cause slow heart rate, weight gain, constipation, and depression/irritability.
• Hypogonadism, caused by low levels of LH and FSH, and leads to issues with sexual development, function, and infertility. Menstrual cycle may be irregular or absent in women, and rarely, gynecomastia, or breast development may occur in men.

Hyperpituitarism happens when your pituitary gland makes too much of one or more hormones.

• Acromegaly, a condition caused by too much GH after individuals stop growing (late adolescence/adulthood), leading to very large hands and feet, and if not treated, coarse facial features. When there is too much GH in childhood, gigantism—extreme height—may result.
• Cushing’s syndrome, a condition that can be caused by too much ACTH, often causes a round face and a hump between the shoulders, and weight gain in the chest and belly.
• Galactorrhea, excess PRL causes production of breast milk in a woman who has not given birth
• Hyperthyroidism, caused by excess TSH, can cause rapid heart beat, tremors, weight loss, anxiety, sweating, and a lump in the front of the throat.

Mass Effect: Symptoms caused by the pressure of the tumor on the structures around it:

• Vision changes, pressure on the optic nerve and optic chiasm can cause loss of visual field, blurred or double vision, color blindness, and loss of peripheral vision.
• Headaches caused by the stretching of pain fibers as the tumor grows
• Dizziness, loss of consciousness
• Nausea, vomiting
• Weakness, fatigue
• Decreased sexual funtion and libido
• Mood changes

When Pituitary Surgery Is Necessary

Many patients with a pituitary adenoma or other type of benign tumor are able to avoid surgery. For patients who have a pituitary adenoma that is not causing problems and requires no medication, surgery is an unnecessary treatment. Other patients are able to avoid surgery by taking medication that controls the hormonal changes caused by a pituitary tumor.

The individuals who are most likely to need surgical intervention are typically the ones who do not respond well to medication, or are having significant problems due to the tumor. These problems can include a change or loss of vision or severe headaches when the tumor is crushing other structures, or other health issues are being caused by hormone imbalances.

Risks of Pituitary Surgery

In addition to the common risks associated with surgery and the risks of anesthesia, surgery to remove a pituitary tumor carries unique risks. The most severe of these risks is severe hormone imbalance caused by damage to the pituitary gland during the procedure. Damage to the gland can impair any or all of the nine hormones secreted by the pituitary gland, and can lead to complex issues that can cause health issues in many areas of the body.

Additional issues that can occur after pituitary surgery include:

• Damage to the pituitary gland. Damage to areas of the pituitary that secrete hormones may require hormone replacement after surgery.
• Spinal fluid leak: It is possible for spinal fluid to leak from the nose after because a hole is drilled into the bone behind the nasal cavity to allow surgery to be performed. If the sterile glue used to “patch” the hole doesn’t completely fill the area, the patient will experience a dripping nose, much like the clear mucus that is present with a cold.
• Meningitis: A brain infection is more likely to occur after brain surgery, as surgery increases the risk of bacteria reaching the brain.
• Visual problems. The nerves that supply vision are close to the area of the pituitary gland can be damaged.
• Intracranial hemorrhage. Damage to blood vessels can cause bleeding inside of the skull.
• Diabetes insipidus: Caused by a hormone imbalance, this condition causes the body to produce very large amounts of urine, leading to dehydration, thirst, and confusion.
• Nasal congestion: congestion is expected for the first week or two following surgery, adn will improve steadily during the recovery period and is usually the result of the surgical instruments irritating the delicate tissues inside the nose.
• Sinus headache: A headache after this type of surgery is very common, and is often described as being like a sinus headache.
  

Before Pituitary Surgery

Prior to surgery on the pituitary gland you can expect to have a CT scan, MRI, or possibly both done to evaluate the size and shape of the gland and the tumor. Lab testing will also be part of the diagnosis of the issue, and many of those lab tests may be repeated prior to surgery if the tumor is causing hormonal imbalances. These pre-surgery labs will establish a baseline for comparison after the surgery is completed, and can help determine if the surgery has resulted in an improvement.

Pituitary Tumor Surgeries

Surgery to remove a pituitary tumor is typically performed by a neurosurgeon, a surgeon specializing in the treatment of disorders of the central nervous system, which includes the brain and spine. In some cases, an ENT (ear, nose, and throat) surgeon may be the surgeon or part of the team performing the surgery. The surgery is performed under general anesthesia, which is given by an anesthesiologist or a nurse anesthetist.

Due to the unique location of the pituitary gland within the skull but outside the brain, there are two ways the procedure is typically performed.

Transsphenoidal Approach

The most common way a pituitary tumor is removed is the transsphenoidal approach, where the surgeon inserts instruments through the nose or gums, and a hole is made in the sinus that rests between the back of the nose and the brain. Placing a small hole in this bone, called the sphenoid bone, allows direct access to the pituitary gland.

To be clear, the pituitary gland is attached to the brain but rests on the underside of the brain. This allows the gland to be accessed via the nose. The procedure uses an endoscope, a flexible thin tube with a light, camera and small instruments inside. The endoscope is inserted and the surgeon is able to watch the images on a monitor. Tiny instruments inside the scope are used to cut the unwanted tissue away.

In many cases, high quality scans taken prior to the surgery combined with specialized equipment used during the procedure help guide the surgeon to the most direct route to the pituitary gland. Once the path is open, small instruments are used to remove the unwanted tumor tissue.

Once the tumor tissue is removed, a small piece of abdominal fat is placed in the area where the tumor was removed, and the surgeon will seal the hole made in the bone with a bone graft, sterile surgical glue, or both. In most cases, the nostrils will be splinted open to prevent swelling from completely closing off the nasal passages.

Craniotomy Approach

The alternative approach to pituitary surgery is through a craniotomy, where a section of the skull is removed to access the brain directly. This route is far less common and is typically used if the tumor is not accessible through the nasal passage because of its size, or because it has grown into the brain itself. It may also be used if there is an issue with leaking cerebral spinal fluid after an initial procedure on the pituitary gland.

With the advances in technology, there are a variety of surgical techniques that can be used during a craniotomy, including minimally invasive techniques (e.g. creating small windows in the skull through the eyebrow or behind the ear), versus removing larger pieces of skull to minimize the need to manipulate the brain. Image-guided surgery is now commonplace, using 3-D imaging to guide the neurosurgeon directly to the tumor, while making minimal damage to the surrounding nerves, blood vessels, and tissues.

Once a small piece of skull is removed, the covering of the brain, called the dura, is opened and the brain is able to be seen. Once the brain is exposed, a special suction device may be used to gently lift the brain allowing access to the underside of the brain where the pituitary gland rests. The surgeon can directly visualize the gland and can operate using a variety of surgical instruments depending on the size and location of the tumor (e.g. currette, gamma knife, aspiration device).

Once the procedure is complete, the piece of skull is replaced and held there with either glue, wires, or titanium plates and screws. Finally, the skin of the scalp is closed with staples or glue. A biopsy of the tumor is sent to the lab to confirm the diagnosis.

After Pituitary Surgery

Most patients will spend a day or two in the neurological or surgical intensive care for close monitoring after surgery. During that time the staff will pay particular attention to blood tests to determine if the surgery was successful at reducing hormone imbalances, and will also closely monitor urine output to determine if the surgery has caused diabetes insipidus. You will also be monitored closely for postnasal drip or a runny nose, which can be a sign that the patch to close the hole in the sphenoid bone didn’t completely contain the cerebral spinal fluid.

After one to two days in ICU, the patient can be transferred to a step-down or floor unit at the hospital. Most patients are able to return home 3-5 days after surgery with strict instructions not to blow their nose and instructions on how to care for their incision.

Most patients are able to return to the vast majority of their normal activities two weeks after surgery. Some activities that can increase intracranial pressure (pressure within the brain) such as weight lifting, strenuous exercise, bending, and lifting must be avoided for at least a month after surgery, but activities such as working at a desk, walking, and driving are usually possible at the two week mark.

For the initial weeks of recovery is it typical for prescription medication to be given for surgical pain. Additional medications are often given to prevent constipation, as bearing down to have a bowel movement can also increase intracranial pressure and should be avoided. You may receive medicine to reduce nasal congestion and swelling.

During this time, it is normal to experience fatigue, nasal congestion, and sinus type headaches. It is important to report the following to your surgeon: postnasal drip or runny nose that does not stop, fever, chills, excessive urination, excessive thirst, severe headache, and a stiff neck that prevents the chin from touching the chest.

Your follow up visits may be with your neurosurgeon, endocrinologist, ENT, and ophthalmologist if needed. You can expect to have blood tests done to continue to follow your progress and to determine what medication you will need if any, once you have healed.