Skull Base Tumors

Skull base brain tumors are the growth of abnormal or uncontrolled cells in the part of the brain that meets the base of the skull. Most skull base tumors are primary, meaning that they develop in the brain and do not spread to other parts of the body. Most of the tumors that occur at the skull base are benign (not cancerous).

Skull base tumors that are benign grow slowly. They can be life threatening, however, because they are invasive. As a skull base tumor grows, it pushes and stretches nerve tissue. Once the tumor expands to a certain point, it begins to destroy brain tissue, cause pressure in the skull to increase, or compress the brain. The tumor may shift the brain or push it against the skull. This can cause the brain to become damaged or swell (edema) or fluid to build up (hydrocephalus). The result may be permanent brain damage or death. The most common skull base brain tumors are:

Chondrosarcoma;
Chordoma;
Craniopharyngioma;
Glomus jugulare;
Meningioma;
Pituitary tumor; and
Schwannoma.

WHAT ARE THE SYMPTOMS?

Symptoms of a skull base brain tumor depend on how big the tumor is, how quickly it grows, and what part of the brain it affects. Symptoms of skull base tumors may include:

Headache, usually worse in the morning;
Vomiting;
Drowsiness;
First-time seizures;
Loss of sensation in an arm or leg;
Difficulty with balance and coordination;
Dizziness;
Vision loss or double vision;
Hearing loss;
Tinnitus (ringing in the ears);
Speech difficulties;
Hoarseness;
Difficulty swallowing;
Facial pain, twitching, or paralysis; and
Change in personality.

The only skull base tumor that has very different symptoms is a pituitary tumor. Pituitary tumors may cause symptoms both by mass effect on surrounding tissue and by secreting pituitary hormones in excess amounts. Symptoms of a pituitary tumor may include:

Very tall stature;
Disproportionate face, hands, and feet;
Rounding face;
Excess sweating;
Joint pains;
High blood pressure;
Easy bruising; and
Stretch marks.

CAUSES AND RISK FACTORS

Physicians do not know what causes skull base brain tumors. The following may increase a person's risk for these types of tumors:

Exposure to radiation;
Exposure to certain chemicals; and
Family history of brain tumor.

DIAGNOSIS

To diagnose a brain tumor, a physician will take a complete medical history and conduct a physical exam. In addition, patients may undergo any of the following tests to help a physician diagnose a brain tumor:

Computed tomography (CT) scan;
Dynamic CT scan;
Magnetic resonance imaging (MRI);
Dynamic MRI;
Functional MRI (fMRI);
Flow Sensitive MRI (FS MRI);
Magnetic resonance angiography (MRA);
Magnetic resonance spectroscopy (MRS);
Positron emission tomography (PET) scan;
Cerebrospinal fluid examination;
Endocrine evaluation;
Perimetry; and
Stereotactic biopsy.

TREATMENT APPROACH

Skull base tumors sit under the brain, making them very difficult to access with surgery. Often, a combination of treatments is used. Treatment options may include: Observation. This may be particularly prudent for elderly people.

Medication. Medications used to treat skull base tumors include steroids to reduce swelling and inflammation and anti-convulsants to control seizures.

Shunt. If a brain tumor causes fluid to build up on the brain, a patient may need a shunt inserted into the brain. A shunt is a long, thin tube threaded under the skin to another part of the body--often the abdomen. The shunt drains excess cerebrospinal fluid from the brain to the abdomen, where it is absorbed.

Surgery. Surgery has long been the primary treatment for skull base tumors but because of their difficult location and the risk of causing serious neurological injury, surgeons now use other techniques, such as radiation, quite frequently. Surgery is often combined with embolization and radiation.

A common type of surgery is craniotomy, in which a surgeon makes a small incision in the scalp and removes as much of the tumor as possible through the hole.

A surgeon may access a skull base tumor using endoscopic surgery. This minimally invasive, microsurgery technique means approaching a skull base tumor in one of a variety of ways.

Radiation therapy. This treatment uses high-energy rays to prevent cancer cells from growing and dividing.

Chemotherapy. Chemotherapy can be used as a primary or secondary treatment for some skull base tumors. The chemotherapy medications are administered as pills or intravenously, and are usually given in 4- to 6-week cycles.

Embolization. With this interventional treatment, angiography is used to highlight the patient's blood vessels. Then a catheter is threaded to the tumor, and embolization material is injected into the blood vessels feeding the tumor. This cuts off the supply of blood to the tumor, starving it or selectively delivering a chemotherapeutic agent to the tumor.

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