Brain Surgery-Tumor

There are many types of brain tumors. The most common brain tumors include astrocytomas (there are several different types of astrocytomas), Acoustic Neuromas, Meningiomas, Pituitary tumors and Metastases. The symptoms caused by a tumor vary, depending on the size, location, growth rate and associated edema. Edema is the swelling of the brain around a tumor.

Brain tumors used to be treated by opening the skull and cutting them out. Today, surgery may be performed but it can be done in a much more sophisticated way. Options include minimally invasive surgery using a microscope or an endoscope, surgery guided through a very small hole with the assistance of a computer navigation system, or diagnostic surgery (stereotactic biopsy) through a hole just large enough for a needle. Some tumors can be treated with the Gamma Knife, eliminating the need for open skull surgery. A brief description of the most common tumors is given here.

ASTROCYTOMAS (Astrocytomas, Glioblastoma Multiforme, GBM)

Astrocytomas are the most common brain tumor originating within the brain. Astrocytomas begin within the brain, from cells that support the brain’s neurons. During the cells’ life a wrong signal is given and that cell begins to multiply without control. Tumors in this category can occur anywhere in the brain or spinal cord. They may grow very quickly, causing problems in just a few months, or they can grow slowly over years. The preliminary diagnosis of an astrocytoma is initially made with a CT or MRI of the brain. While many tumors have a characteristic appearance on CT and MRI scans, a biopsy is required to confirm that the tumor is an astrocytoma and to determine its level of “aggressiveness”. Dr. Thompson specializes in stereotactic image-guided brain biopsies using MRI or CT scans and computer planning. Patients are awake during the procedure and usually able to return home the following morning.

Because tumors that originate within the brain generally do not metastasize to elsewhere in the body, the terms “benign” and “malignant” are not used. Astrocytomas are graded on a three-tiered scale. The least aggressive tumors are the low-grade astrocytomas. Low-grade astrocytomas include pilocytic astrocytoma and cerebellar astrocytoma. More aggressive tumors are called anaplastic astrocytomas. The most aggressive tumors are called glioblastoma multiforme or GBM. Although any type of tumor can occur at any age, the more aggressive astrocytomas tend to occur in older patients.

After examining a sample of the tumor under the microscope, the appropriate therapy can be recommended. The aggressiveness of the tumor influences the type of treatments that are recommended. Less aggressive tumors may require little treatment. The more aggressive tumors are best treated with a combination of treatments. Options include stereotactic surgery, open-skull surgery for tumor resection, regular radiation, Gamma Knife, and a variety of medicines (chemotherapy) including chemotherapy wafers that are implanted in the brain. Experimental protocols are available to those patients who wish to examine all options.

The symptoms that effect each patient are the result of the location of the tumor, the amount of edema (swelling) surrounding the tumor, the size of the tumor, and the pressure exerted on the surrounding brain. Tumors may cause stroke like symptoms, but the onset of symptoms is usually much slower.

The average survival for low-grade tumors is approximately 8-10 years. The survival for patients with pilocytic and cerebellar astrocytomas is much better. Low grade astrocytomas may progress to more malignant grades over time. The average survival for GBM without any treatment is only 3 months. Survival is improved with surgery, radiation and chemotherapy. The factors that indicate the best prognosis are the age at the time of diagnosis and the location of the tumor.

Many patients ask whether some environmental agent or behavior caused their tumor. No environmental agent has ever been shown to cause astrocytomas. Both cellular telephones and artificial sweeteners have been suspected to cause brain tumors, but convincing evidence is lacking. Patients can not prevent the development of an astrocytoma. Fortunately, there are many medical and surgical treatments available to patients once they have developed a tumor. Standard treatment options include chemotherapy, radiation therapy, and surgical resection.

ACOUSTIC NEUROMAS

Acoustic neuromas (ANs), correctly defined as vestibular schwannomas, are benign tumors that originate from the abnormal growth of Schwann cells on the vestibular portion of the eighth cranial nerve. Schwann cells insulate and support neurons. Typically, and if unchecked, the tumors extend out of the internal auditory canal to fill the small space between the brainstem and the skull. The misnomer “acoustic neuroma” is well established in the medical community and unlikely to change. The radiographic appearance of ANs is distinct. Other tumors that occur in the same region include meningiomas, epidermoid tumors, and other small lesions that can inhabit the internal auditory canal.

An estimated 2,200 AN are diagnosed annually in the United States, with an incidence of 0.78-1.15 cases/100,000. ANs are caused by a spontaneous or inherited loss of a tumor suppressor gene on chromosome 22. ANs are the one of the hallmarks of the inherited and spontaneous Neurofibromatosis type II syndrome.

ANs most often present with a loss of hearing on the side of tumor growth, tinnitus (ringing in the ear) or difficulty with balance. As the tumors grow, within the auditory canal, they compress the vestibular and cochlear nerves, causing loss of hearing and balance. As the tumors grow within the cerebellopontine angle, the facial nerve is stretched over the surface of the tumor capsule. Other initial presentations include headaches, loss of sensation on the same side of the face, facial weakness, double vision, nausea, vomiting, difficulty swallowing and loss of taste. As the tumor extends along the brainstem, it can compress the trigeminal nerve above or cranial nerves below. Interestingly, facial sensation is often impaired before facial weakness occurs, even though the nerve for facial movement is displaced earlier and more extensively by the tumor. As tumors grow, they can compress the brainstem, causing progressive weakness, difficulty with balance and coordination, hyperactive reflexes, and hydrocephalus. Occasionally smaller ANs can cause hydrocephalus by secreting proteins that obstruct the absorption of cerebrospinal fluid.

The growth of ANs may be quite variable. Tumors may grow with a consistent rate, or they may have periods of rapid growth alternating with periods of minimal growth. Overall, the growth rate of ANs is estimated to be 2-mm annually. Unfortunately, the growth rate of any one tumor can not be predicted with any certainty.

The current treatment options for ANs include: observation, a variety of microsurgical excision techniques, or stereotactic radiosurgery (Gamma Knife). With the new diagnosis of a small or asymptomatic AN, many clinicians used to recommend observation with serial imaging studies. Surgery was only recommended when growth was documented or symptoms developed. With the advent of stereotactic radiosurgery, this may no longer be the best option. Gamma Knife radiosurgery techniques allow minimally invasive treatment of tumors, providing a better than 97% chance of tumor control, with few risks. The Gamma Knife focuses 201 small beams of radiation on the tumor to arrest tumor growth, while exposing the surrounding brainstem and cranial nerves to a very small dose of radiation. Observation may still be a reasonable option for older patients with tumors causing no or few symptoms.

When an AN is diagnosed, the approach is often chosen according to the tumors size, the status of hearing, the patient’s related signs and symptoms and the surgeons experience. Among the microsurgical options, the translabyrinthian approach (through the bone containing the hearing apparatus) was designed to allow the removal of small or large tumors within the auditory canal and early identification and preservation of the facial nerve. This approach unfortunately sacrifices any functional hearing. Selected small tumors, particularly when hearing preservation is the goal, can be approached via a middle fossa approach. Larger tumors tend to be removed through the posterior fossa (behind the ear) approach. The greatest risk of surgical resection is facial weakness or paralysis. Other risks of microsurgery include deafness, dysequilibrium, double vision, cerebrospinal fluid leaks, and infection. In choosing the best therapy, patients and their physicians must consider the age and health of the patient, the size of the tumor, the symptoms, the risks of each procedure and the treatment goals.

MENINGIOMAS

Meningiomas comprise 20 percent of all brain tumors. Meningiomas originate from arachnoid cap cells of the brain and spinal cord, not from the dura mater. The arachnoid is a thin layer that covers both the brain and the spinal cord. Meningiomas may occur anywhere that there is arachnoid, including inside the ventricles of the brain. The most frequent locations are the along the midline, over the convexity of the skull, or along the skull base.

Most meningiomas occur spontaneously, without a precipitating genetic or environmental defect. Patients with neurofibromatosis have a high incidence of meningiomas. Radiation exposure has also been shown to induce the growth of meningiomas. There is a slightly greater prevalence of meningiomas in women compared with men.

Typically, meningiomas are very slowly growing tumors that compress the surrounding brain or spinal cord. When the tumor becomes large enough, it may cause symptoms. The type of symptoms the tumor causes is directly related to its location. These tumors can also cause a significant amount of swelling in the surrounding brain, known as edema. The edema can also cause neurological problems. Fortunately, when the tumor is treated, the edema and the symptoms may go away.

There are some unique concerns with meningiomas in pre-menopausal women and women taking estrogen supplements. Some meningioma cells have been shown to have estrogen receptors. There are a numbers of documented cases of meningiomas that have grown rapidly during pregnancy.

The traditional treatment of meningiomas has been surgical resection. A complete resection is curative, but difficult to obtain. Microscopic cells may spread along the bone or coverings of the bone. Recurrence rates are as high as 10-20% for completely resected tumors. The rare malignant meningioma has a higher recurrence rate. Meningiomas may now be treated with the Gamma Knife. Long-term studies have shown upto a 97% control rate. Residual tumors, after surgical resection, may also be treated with the Gamma Knife. Many meningiomas are “incidental findings,” on brain scans obtained for other reasons. It may be reasonable to observe some meningiomas with sequential brain imaging, reserving treatment for tumors that have documented growth or the development of symptoms.

METASTATIC BRAIN TUMORS

Metastatic brain tumors are tumors that have spread to the brain from a tumor somewhere else in the body. Most commonly, cells from the original tumor travel to another location in the bloodstream. As the tumor cells enter the capillaries in a distant part of the body, they become fixed and begin to multiply.

Metastatic brain tumors are the most common type of brain tumor. Between 100,000 and 200,000 patients are diagnosed annually with brain metastasis in the United States. The most common brain metastases are from lung, breast, colon and kidney cancer and malignant melanoma. Metastasis may occur anywhere in the brain or spinal cord, their coverings, or the vertebral bodies.

Metastatic tumors to the brain can be asymptomatic or can cause seizures, headaches, nausea, vomiting, or focal neurological symptoms based upon their location, size, and surrounding edema. The symptoms usually develop slowly, unlike a stroke. Patients may develop one or more brain metastasis. The number and location of metastases are best seen on a contrasted MRI scan. Treatment options include steroid medications, anti-seizure medications, surgical resection, fractionated radiation, Gamma Knife radiosurgery, and combined therapies. The ideal therapy depends on the number and location of the metastases, the extent of disease elsewhere in the body, and the patients overall condition.

Historically, the presence of brain metastasis caused both patients and doctors to lose hope in fighting the patient’s disease. This does not have to be true today. Image-guided (computer guided) surgery allows some deep tumors to be resected with minimal disruption of surrounding tissues. The Gamma Knife can successfully treat multiple brain metastases, including tumors deep within the brain and brainstem. Today, patients can live a long life, with an excellent quality of life, after the diagnosis of brain metastasis.

Traditional therapy of single metastasis has been whole brain radiation, occasionally with a boost to the affected region, or surgery combined with whole brain radiation. The surgical resection of solitary metastasis coupled with radiation therapy has been shown to improve survival compared to radiation therapy alone. The delayed complications of whole brain fractionated radiation in long term survivors include cognitive disorders and other signs of adverse radiation effects.

Gamma Knife radiosurgery is changing the long-standing management of brain metastasis. The Gamma Knife can achieve many of the same goals as resection, (tumor control, reduced mass effect), one of the goals of fractionated radiation therapy (the treatment of multiple lesions) and can effectively treat deeply located tumors that are not considered for resection. For patients with solitary metastasis, the Gamma Knife may allow the avoidance of standard radiation therapy and its potential complications. In conjunction with standard radiation, the Gamma Knife can provide rapid improvement in peri-tumoral edema, local tumor control, and prolonged survival compared with standard radiation alone. Gamma Knife radiosurgery provides nearly equivalent tumor control rates for breast, lung, and renal cell carcinoma, as well as melanoma. With control of brain metastasis, the management of systemic disease becomes the survival-limiting factor. Gamma Knife radiosurgery has the additional benefits of 1-2 day hospital stays.

PITUITARY TUMORS

Pituitary tumors are slowly growing tumors that originate from one of the varied cell types that comprise the anterior pituitary gland. The pituitary gland is located at the base of the brain in the middle of the brain, several centimeters behind the bridge of the nose, and below the optic nerves. The pituitary gland controls endocrine function by the secretion of growth hormones, thyroid hormones, sex hormones, steroid hormones, and water regulatory hormones.

Pituitary tumors comprise approximately 10% of all brain tumors and tend to occur in patients who are 30-50 years of age. The incidence is equivalent for men and women. Patients may present with evidence of excessive pituitary hormones, a deficiency of hormones, or symptoms from pressure on the surrounding structures. Tumors that grow upward may compress the optic nerves and impair vision. Tumors that extend to the side, invading the cavernous sinus, may compress the third, fourth, fifth, or sixth cranial nerves, as well as envelop the carotid artery.

The management of pituitary tumors requires the active involvement of an endocrinologist and sometimes an ophthalmologist and a neurosurgeon. When the pituitary tumor causes a deficiency of hormones, replacement medications are available. Additionally, there are several medicines available to treat pituitary tumors, prior to considering surgery. Surgery is considered when tumors are unresponsive to medications, impair the endocrine system, or cause neurological symptoms.

The surgical resection of pituitary tumors may be approached by several techniques. Dr. Thompson prefersto use an endoscope, passing through the nose and sphenoid sinus, directly to the base of the pituitary gland. This is the most direct and least destructive approach. The endoscope allows excellent visualization for tumor resection, avoids an incision in the mouth, and minimizes patient discomfort. Patients usually are often well enough to return home the day after surgery, but are observed in the hospital for 2-3 days to monitor hormone and water regulation.

Surgery remains the procedure of choice for the rapid treatment of a pituitary tumor that is pressing on the surrounding brain and nerves or is producing abnormal quantities of hormones. The Gamma Knife is an effective alternative for patients who do not require urgent decompressive surgery (i.e. no optic nerve compression), rapid normalization of endocrine abnormalities, or those who suffer from recurrent tumors despite medical and surgical intervention. The treatment goals for pituitary tumors are control of tumor growth, cessation of abnormal hormone secretion when present, and avoidance of new neurological injury. Tumor control can be achieved in 94% of tumors. Cortisol secretion has been normalized or reduced in 62.5% of patients within two years. Growth Hormone levels has been normalized in 67% of patients, and significantly improved in most of the remaining patients. None of our patients developed pituitary insufficiency as a consequence of radiosurgery.

BRAIN TUMOR TREATMENTS

Craniotomy
Stereotactic Surgery
Computer Guided Surgery
Gamma Knife Radiosurgery
Radiation Therapy
Chemotherapy
Observation

PUBLICATIONS:

Thompson TP, Kondziolka D. “Acoustic Neuroma”, Encyclopedia of the Neurological Sciences, Aminoff MJ, Daroff RB (eds), Vol. 1, pp 14-16, Academic Press, San Diego. March 2003

Thompson TP, Lunsford LD, Flickinger JC. Radiosurgery for hemangiomas of the cavernous sinus and orbit. Neurosurg 47(3): 778-783, 2000

Thompson, TP, Lunsford LD, Kondziolka D. Successful management of sellar and suprasellar arachnoid cysts with stereotactic intracavitary irradiation: an expanded report of four cases. Neurosurgery 46(6): 1518-1523, 2000

Thompson TP, Lunsford LD, Kondziolka D. Distinguishing Recurrent Tumor and Radiation Necrosis with Positron Emission Tomography versus Stereotactic Biopsy. Stereotactic and Functional Neurosurgery. 73:9-14, 1999

Wakabayashi T, Kajita Y, Hatano N, Thompson TP, Nagasaka T, Yoshida J. Clinicopathological study of oligodendroglial tumors: the effectiveness of interferon Beta, ACNU/MCNU, and radiation (IAR/IMR) for anaplastic tumors. Brain Tumor Pathol 17:29-33, 2000

Maesawa S, Kondziolka D, Thompson TP, Flickinger JC, Lunsford LD. Brain metastases in patients with no known primary tumor. Cancer 89(5): 1095-1101, 2000