Pituitary Tumors
Tumors of the pituitary gland are usually benign; however, they can cause severe hormonal disruption and can adversely affect vision if they grow to a large enough size. Very large tumors can affect memory and can cause blindness and other serious neurological problems. In addition, many pituitary tumors produce excessive amounts of pituitary hormones that can affect the body in many ways. Treatment must address the issue of the tumor and its effect on surrounding structures, as well as the hormonal problems that the tumor produces.
Types Of Pituitary Tumors
Pituitary adenomas are benign tumors that arise from the pituitary gland. Pituitary tumors are rarely malignant. They are common tumors that arise from the pituitary gland located at the base of the brain. If they grow large enough, they can compress the optic nerves causing serious vision problems. Small pituitary tumors are known as microadenomas. Larger pituitary tumors are called macroadenomas.
Some pituitary tumors produce excessive amounts of hormones that can disrupt the body's metabolism. The most common type of hormonally active pituitary tumor is the prolactinoma. Excess prolactin in the blood may lead to irregular or absent menstrual periods in women (amenorrhea), decreased libido (sex drive) and erectile dysfunction (ED) in men. In addition, prolactinomas can cause infertility or inappropriate milk production by the breast in both men and women. A number of medicines are available to treat this disorder so that surgery is needed only infrequently. Most patients with prolactinomas are treated by endocrinologists, who are medical specialists, rather than neurosurgeons. However, surgery is still used to treat large tumors that threaten vision and in patients who do not tolerate medical therapy.
Other hormone-producing pituitary tumors include those that cause Cushing's Disease and acromegaly. Too much adrenocorticotropic hormone (ACTH) leads to overproduction of cortisol by the adrenal glands, giving rise to a disorder called Cushing's Disease. This leads to a particular kind of obesity, high blood pressure and many other problems. Surgical removal of these tumors can restore normal hormone production in many cases and relieve the adverse effects of the excess cortisol. Acromegaly results from excessive production of growth hormone by a pituitary tumor and is associated with coarsening of facial features, thickening of the soft tissues of the face, hands and feet, high blood pressure, diabetes mellitus and excessive sweating.
Also, pituitary tumors compress the normal pituitary gland and can adversely affect its function. Some pituitary tumors can be treated medically with drugs like bromocryptine and octreotide. Others must be treated surgically. For some patients, conventional radiation therapy and gamma knife (radiosurgery) can be used effectively as well.
Regardless of hormone production, all pituitary tumors can cause problems due to their size and location. This is because they can compress both the normal pituitary gland and the surrounding structures. Just as the tumor can produce an excess of a single pituitary hormone, a deficiency of the other pituitary hormones can arise as a result of compression of the normal pituitary gland by the tumor. Pituitary tumors can also cause vision problems by growing upwards against the optic nerves, which are essential for vision. Surgery to remove such tumors can relieve the pressure on the optic nerves and protect the patient's vision.
Pituitary Adenoma
These are common tumors that arise from the pituitary gland located at the base of the brain. If they grow large enough, they can compress the optic nerves causing serious vision problems. Such tumors are called macroadenomas.
Smaller tumors are known as microadenomas. Some pituitary tumors produce excessive amounts of hormones that can disrupt the body's metabolism. Pituitary tumors compress the normal pituitary gland and can adversely affect its function. Some pituitary tumors can be treated medically with drugs like bromocryptine and octreotide. Others must be treated surgically. For some patients, conventional radiation therapy and gamma knife (radiosurgery) can be used effectively as well.
Craniopharyngioma
This tumor grows at the base of the brain and arises from the band of tissue that connects the part of the brain known as the hypothalamus to the pituitary gland. They can grow to a large size and disrupt hormonal function and cause severe impairment of vision and other neurological functions. Craniopharyngiomas occur in both adults and in children and generally consist of solid tumor tissue and a fluid-filled tumor cyst. Treatment usually involves microneurosurgery; however, radiation therapy and gamma knife (radiosurgery) may be used in some cases as well.
Transsphenoidal Surgery
1. What is transsphenoidal surgery?
Most pituitary tumors can be removed by way of a transsphenoidal approach. This operation is carried out through the sphenoid sinus, which is located directly behind the nose. Rarely, a craniotomy, in which the skull is opened to reach the tumor, is required. The sella turcica (or just "sella") is a bony cup at the base of the skull located behind the sphenoid sinus. The sella holds the pituitary gland and any associated tumor. Many neurosurgeons use a direct transnasal approach to the sella, in which an incision is made in the back of the nose to enter the front of the sphenoid sinus directly. It is also possible to make an incision along the front of the nasal septum, and create a narrow tunnel back to the sphenoid sinus. Finally, it is possible to make an incision under the lip and enter the nasal cavity and then the sphenoid sinus. This is called a "sublabial" approach.
The opening through which transsphenoidal surgery is performed is long and narrow. Therefore, visual aids are necessary for the neurosurgeon to see the tumor with clarity. A number of tools are available to help see the pituitary gland and the tumor through this narrow channel. These tools include high powered operating microscopes and rigid fiberoptic endoscopes. The operating microscope allows "binocular" vision with high quality optics. This is very important for tiny tumors, like those responsible for causing Cushing's Disease. The endoscope provides a wider field of view, but usually with "Cmonocular" images projected on a video monitor. Both means of visualization are highly effective.
2. How is the tumor removed?
The tumor is usually soft and can be removed with small surgical instruments called ring curettes. In order to remove a large tumor through a small hole, the tumor itself usually has to be divided into smaller pieces. Some tumors which have grown beyond the confines of the bony sella cannot be completely removed. Tumors that grow sideways into the cavernous sinus (a collection of large veins next to the pituitary gland) usually cannot be completely removed. This is because that area contains important nerves controlling muscles of the eye and the carotid artery, which supplies blood to the brain. Tumors hat extend high up between the optic nerves can be removed in one operation if they can be made to fall downward into the sella during the procedure. Sometimes the removal of large tumors has to be staged into two operations, to allow time for the uppermost portion of the tumor to fall into the sella where it can be reached on a subsequent operation. Frequently, patients undergoing transsphenoidal surgery will have a tube placed in their lower back. During surgery, fluid can be infused into the spinal canal to assist in collapsing the tumor into the surgical opening, where the neurosurgeon can extract it more easily. At the end of the operation, the drain may be left in for several days if any spinal fluid leakage through the surgical opening was noted at the time of tumor removal. If no leakage is noted art the time of surgery, the drain is usually removed before the patient awakens.
3. Is surgery necessary for all pituitary tumors?
No. Tumors that produce large amounts of the hormone prolactin usually respond to medical therapy so that surgery is not required. Small hormonally inactive (non-secreting) tumors, less than one centimeter in size (termed a "microadenomas"), can sometimes be followed with serial MRIs to monitor for progressive enlargement before considering surgery. Some small pituitary tumors grow very slowly or apparently not at all over long periods of time. Tumors that cause acromegaly or Cushing's Disease so that the hormonal problems can be brought under control rapidly. This is because the hormonal effects of Cushing's Disease and acromegaly can cause serious injury to major organs like the heart if left untreated. Tumors that do not secrete hormones are usually treated surgically as well. Also, surgery is generally recommended for larger tumors that represent a serious and imminent threat to vision due to optic nerve compression.
4. What are the risks of transsphenoidal surgery?
The most common risk is damage to the normal pituitary gland. For pituitary macroadenomas, this happens between 5-10% of the time. This means that new hormone replacement might be required after the surgery, possibly including thyroid hormone, cortisone and estrogen or testosterone. Damage to the posterior pituitary gland may produce diabetes insipidus, leading to excessive urination and thirst. This can be controlled with a nasal spray or pill containing a medication called DDAVP. Diabetes insipidus can be permanent. There are a number of other risks of transsphenoidal surgery. A spinal fluid leak sometimes occurs because pituitary tumors are separated from the spinal fluid by a very thin membrane, which often is impossible to preserve during surgery. In order to prevent a spinal fluid leak, the tumor bed is packed with a small piece of abdominal fat taken from the abdomen. Despite these efforts, spinal fluid leaks can still occur. If a leak persists, there is a risk of a serious infection, called meningitis. If a spinal fluid leak occurs it may require a second operation to patch the leak. Transsphenoidal surgery also carries a very small risk of damaging the carotid artery, which is located in the cavernous sinus close to the pituitary gland. This is a potentially life threatening complication which could lead to severe blood loss, a stroke, or death. It occurs very infrequently, when the operation is performed by an expert pituitary surgeon, but the risk cannot be reduced to zero by any known means. There could also be post-operative bleeding into residual tumor tissue or into the area around the pituitary gland. This could cause pressure on the optic nerves and lead to blindness or partial visual loss. This rare complication could require re-operation to remove the blood clot.
5. How will I feel after the surgery?
You will have nasal stuffiness that will improve over a few weeks. You can take decongestants which will help these symptoms. It is common to feel fatigued after the surgery and this gradually improves. The timing of your return to work will depend on your job requirements. The average time off is 3-4 weeks.
6. How is the success of surgery measured?
For hormone-producing tumors (Cushing's Disease, acromegaly, prolactinomas), blood and urine tests in the days or weeks following surgery usually provide the answer. For non-secreting tumors, pituitary MRI scans are used to determine success. Because the surgeon works only from the inside of the tumor, it is sometimes difficult to tell how much tumor remains during the procedure. Tumors that extend into the cavernous sinus and around either of the carotid arteries are rarely removed completely. A postoperative MRI scan is usually obtained 6-12 weeks after the surgery. This helps the physicians to determine whether further treatment is required. If the tumor is a hormone-producing adenoma, your endocrinologist will measure your hormone levels postoperatively to determine how well your tumor is controlled.
7. What are my chances of being cured?
Patients with Cushing's disease usually have small tumors (microadenomas) and are surgically cured 80-90% of the time. Patients with acromegaly often have larger, more invasive tumors which are harder to cure surgically. The success rate with growth-hormone secreting macroadenomas is about 60%. Non-secreting tumors are often macroadenomas as well. Whether a macroadenoma can be removed completely, depends upon its relationship to the cavernous sinus and the surrounding bone. If it has not grown into these areas, a surgical cure may be achievable. If the tumor has grown into an area where it is not possible for the surgeon to operate safely, it may not be surgically curable. However, such tumors can often be "de-bulked" away from the optic nerves in order to protect vision. Radiation therapy may be required to control further tumor growth and prevent its recurrence.
8. What if some tumor is left behind after an attempt at transsphenoidal surgical removal?
Most pituitary tumors grow slowly. Therefore, following incomplete surgical excision, re-growth tends to be slow and recurrence may take some time to become evident. As a result, regular and long-term follow-up is strongly advised in most cases. If there is a substantial amount of tumor remaining after a transsphenoidal operation, radiation therapy can be used to halt further growth of the residual tumor. If only a small amount of tumor remains, it can often be followed with MRI scans, with deferral of further treatment until there s evidence of re-growth. If there is residual tumor after surgery for acromegaly, Cushing's Disease, or prolactinomas, re-operation is sometimes advised. In addition, medical treatments may be available to help control excess hormone secretion or counteract its effects. These medications, which are prescribed by an endocrinologist, can sometimes be used instead of radiation therapy.
