What are Skull Base Tumors and How to Manage Them?

The brain is an incredibly complex organ made up of nerve cells and soft tissues. It is divided into several different parts, all of which are protected by the skull. At the base of the skull is a bone that supports the four brain components — the frontal lobe, temporal lobe, brain stem, and cerebellum. The skull base is the floor of the skull which is located behind the eyes and nose, and it’s where the brain sits. It is made up of five bones — frontal, ethmoid, sphenoid, temporal, and occipital.

Skull base tumors are caused by abnormal cells growing in the tissues surrounding the brain — in the area behind the nose and eyes, near the ear, and along the base of the brain. The good news is that not all skull base tumors are cancerous (malignant) — in fact, many are not cancerous (benign). However, even benign skull base tumors can cause harmful symptoms and for this reason, all skull base tumors need to be investigated by a team of specialists.

Skull base tumors will usually grow inside the skull but occasionally they’ll form on the outside. They can start in the skull base as a primary tumor, or they can spread there from a cancer elsewhere in the body — this is called metastasis.

Different Types of Skull Base Tumors

Skull base tumors are classified by tumor type and where they’re located within the skull base. They can occur in the meninges — the outer covering of the brain — the sinuses, pituitary gland, and the skull bone (osteosarcoma).

The front section of the skull-base, where the eye sockets and the sinuses are contained is called the anterior cranial fossa. This area is most likely to have the following tumors:

• Meningioma
• Olfactory neuroblastoma (esthesionerublastoma)
• Paranasal sinus cancer

The middle cranial fossa is the central compartment of the skull base. The sella turcica is a bony structure in this central part of the skull base where the pituitary gland is found. Tumors that are found in this area are known as sellar tumors and they include:

• Pituitary adenomas
• Craniopharyngioma
• Rathke’s cleft cyst

The back compartment of the skull base is called the posterior cranial fossa. The most common tumors in this area include:

• Acoustic neuroma
• Chondrosarcoma
• Chordoma
• Epidermoid tumor
• Meningioma

Skull base tumors are often close to critical areas of the brain, and this can make surgery difficult and sometimes dangerous.

What Causes Skull Base Tumors?

There’s not one single reason why some people get skull base tumors, and scientists believe there are various genetic and environmental factors that may contribute to the growth of a tumor. These may include:

• Inherited genetic conditions
• Toxic chemical exposure
• Previous radiation treatment

In other cases, skull base tumors appear to occur without any apparent cause. Scientists are still researching whether a head injury can lead to a tumor.

Symptoms of Skull Base Tumors

The symptoms of skull base tumors are dependent on the location and size of the tumor. They may gradually appear over time and increase in severity as the tumor grows and puts pressure on the brain. Tumors involving the pituitary gland can cause hormone and vision problems, and sinus tumors can affect smell and breathing.

Some of the more common skull base tumor symptoms include:

• Headaches
• Blurred or double vision
• Altered sense of smell
• Hearing loss
• Breathing difficulties
• Nausea and vomiting
• Loss of balance
• Nose bleeds
• Difficulty swallowing
• Memory loss
• Nose bleeds
• Facial pressure
• Top teeth numbness
• Changes in mental state

It’s important that you have any new or worsening symptoms checked out.

Skull Base Tumor Diagnosis

Skull base tumor diagnosis starts with a discussion of your symptoms and a physical examination including questions about your personal and family health history. A neurological evaluation which includes checking your balance, hearing, vision, reflexes, coordination, and memory and thinking abilities.

Once the initial evaluation has taken place, you may require brain imaging, which can include:

• Magnetic resonance imaging (MRI)
• Bone scan
• Computed tomography (CT or CAT scan)
• Positron emission tomography (PET)
• Endoscopy

Brain imaging will help the specialist confirm the diagnosis.

How to Treat a Skull Base Tumor

Once the skull base tumor is diagnosed, your team of specialists will put together an action plan that is dependent on the type of tumor, the location, and your general health. Skull base tumors are difficult to treat because they are located deep inside the brain, so surgery is only possible for certain cases.

Treatments May Include

Observation: A small, benign skull base tumor that is not causing significant symptoms may be recommended for radiographic surveillance alone. If the tumor grows or new symptoms develop, it may prompt a new recommendation for an interventional treatment.

Surgery: Skull base tumors are broadly categorized according to a few parameters, such as whether they come from the anterior or lateral skull base, and whether the pathology is thought to be benign (e.g., pituitary adenoma, vestibular schwannoma) or malignant (e.g., sinonasal malignancy, metastatic disease, esthesioneuroblastoma).

Among anterior skull base lesions such as pituitary tumors, most respond well to an endoscopic endonasal approach, which is a minimally invasive technique for removing the tumor through the sinuses without the need for a skin incision or craniotomy. These operations are typically conducted by a skull base neurosurgeon with the assistance of a rhinologist.

Larger or more aggressive anterior tumors, and most lateral tumors need a formal craniotomy, which may be completed by a similar team for anterior operations, or by a skull base neurosurgeon with a neuro-otologist for lateral tumors such as a vestibular schwannoma.

For all tumor types, the operative plan is customized to the individual patient and disease, striving for the most minimal approach that will provide the best outcome.

Radiosurgery: Stereotactic radiosurgery, also known as Gamma Knife, is a highly effective radiation treatment system that is particularly well-suited to skull base tumors, as it is so precise. It also provides long-term benefits for patients with benign tumors.

These treatments are performed by skull base neurosurgeons together with radiation oncologists, and can be performed on an outpatient basis, typically needing 1-3 sessions where the head is kept still during treatment with either a frame or a mask for 30-60 minutes while the radiation is delivered. Some tumors respond well to front-line radiosurgery as an alternative to surgery, while in other circumstances it may be better suited a second-line role if a disease recurs after the initial surgery.

Additional Treatments

In addition to core management strategies of observation, endoscopic or open resection, and stereotactic radiosurgery, a range of other treatment strategies may be included in the long-term management of skull base tumors. Depending on the tumor type, location, and behavior, options may include:

• Chemotherapy
• Radiation therapy
• Proton beam therapy
• Endovascular embolization
• Endocrine therapy
• Immunotherapy

Who Does the Surgery?

Because skull base tumors can be difficult to remove, you will have a team of specialists including:

• Neurosurgeons with skull base expertise
• Otolaryngologists (e.g., ear, nose, and throat surgeons) with subspecialty training in either rhinology or neuro-otology

Your OU Health multidisciplinary skull base team offers a full range of cutting-edge tools and techniques for modern skull base surgery. Your team of specialists work together to provide the best plan and outcome for the treatment and removal of your skull base tumor.

“We have deep experience across neurosurgical and ENT subspecialties, including expanded endoscopic endonasal surgery, stereotactic radiosurgery, minimally invasive or “keyhole” craniotomies, and of course all the traditional open approaches,” said Christopher Graffeo, M.D., M.S., assistant professor of Neurosurgery at OU Health. “Perhaps most importantly, we pride ourselves on individualizing all our treatment recommendations to the needs of each patient, and we have a very strong track record of achieving excellent outcomes for the patients who trust us to take responsibility for their skull base care.”

OU Health Skull Base Tumor Specialists

Learn more about our neurosurgery services and treatment, request an appointment or get a second opinion, or find out more about the skull base tumor multidisciplinary team at OU Health by calling (405) 271-4912.