Skull Base Tumors
- The skull base consists of several bones that form the bottom of the head and the bony ridge behind the eyes and nose.
- Many different kinds of tumors can grow in this area. They are more likely to cause symptoms and be diagnosed when they grow large enough to put pressure on the brain.
- Treating skull base tumors is challenging because they can grow deep within the skull and close to critical nerves and blood vessels in the brain, head, neck and spinal cord.
What are the different types of skull base tumor?
Skull base tumors most often grow inside the skull but occasionally form on the outside. They can originate in the skull base as a primary tumor or spread there from a cancer elsewhere in the body as a metastatic brain tumor.
Skull base tumors are classified by tumor type and location within the skull base.
In the front section of the skull base (anterior cranial fossa), which contains the eye sockets and sinuses, the following tumors are more likely:
The central compartment of the skull base (middle cranial fossa) contains the sella turcica, a saddle-shaped bony structure in the skull base where the pituitary gland is located. Tumors arising in this area are called sellar tumors, and may include:
At the back compartment of the skull base (posterior cranial fossa), the following tumors are more common:
Other Skull Base Tumors
Chondromas are very rare benign tumors made of bone cartilage found in the skull. Both the skull base and the paranasal sinuses contain cartilage. Chondromas can develop in this cartilage, typically in people between the ages of 10 and 30.
These tumors grow slowly, but eventually may cause the bone to fracture or grow too much, creating pressure on the brain. In rare instances, chondromas may develop into a cancerous condition called chondrosarcomas.
Though each individual may experience symptoms differently, when a chondroma develops, it may cause visual changes or headache.
Diagnosing a chondroma may include imaging studies such as X-ray, CT scan or MRI to determine the size and location of the tumor.
Encephaloceles are sac-like protrusions of part of the brain and meninges through openings in the skull. These rare birth defects occur when the neural tube, in which the brain and spinal cord form, fails to close completely during fetal development. Skin or, less often, a thin membrane, covers the sac outside the skull.
Encephaloceles can occur in the base of the skull, the top or back of the skull, or between the forehead and nose. Conditions associated with encephaloceles include hydrocephalus (excess accumulation of cerebrospinal fluid in the brain), developmental delays, microcephaly (an abnormally small head), paralysis and seizures.
When an encephalocele occurs, it may cause any or all of the following symptoms:
Diagnosing encephaloceles includes an analysis of the nasal fluid for a protein called beta-2 transferrin which is most only found in cerebrospinal fluid. CT and MRI scans may also be require to determine the location and severity of the leakage.
Hemangiopericytomas are rare tumors that involve the blood vessels. They are most common in the legs, pelvic area, head, neck and brain. Hemangiopericytomas often are painless masses with few or no symptoms.
Most hemangiopericytomas are found in soft tissues but may occur in the skull base, nasal cavity and paranasal sinuses. These tumors may be benign or malignant; cancerous hemangiopericytomas can spread to the bone, lungs or liver.
In addition to a complete medical history and physical examination, diagnostic procedures for hemangiopericytomas may include X-ray, CT scan or MRI to determine the size and location of the tumor.
Hemangiopericytoma treatment involves surgery, involving either a craniotomy or an endonasal endoscopic procedure. The surgeon may recommend treatment with radiation or chemotherapy after surgery to increase the chances of a good outcome.
Skull Base Nasopharyngeal Angiofibroma
Nasopharyngeal angiofibroma, also known as juvenile nasopharyngeal angiofibroma, is a benign tumor in the nose usually found in adolescent boys.
Nasopharyngeal angiofibromas spread into areas around the nose, causing symptoms such as a stuffy nose and bleeding from the nose.
Skull Base Osteoma
Osteomas are benign bony outgrowths (new bone growth) mostly found on the skull and facial bones. If the bone tumor grows on another bone, it is called homoplastic osteoma. If it grows on tissue, it is called eteroplastic osteoma.
Skull base osteomas are slow growing and generally cause no symptoms. However, large osteomas in some locations may cause problems with breathing, vision or hearing.
Petrous Apex Lesions
Petrous apex lesions are abnormalities that occur in the tip of the bone in the skull next to the middle ear. The most common type of petrous apex lesion is benign cholesterol granulomas, which are cysts. Other petrous apex lesions include cholesteatomas, petrous apicitis, petrous apex effusion, and bone cancer.
Most petrous apex lesions are benign. However, patients with other types of cancer may develop metastatic petrous apex lesions, which are malignant tumors that originate as cancer elsewhere in the body and then spread to the brain.
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What are the signs and symptoms of skull base tumor?
Symptoms appear slowly as the tumor grows and puts pressure on vital structures in the brain such as the pituitary gland, the optic nerve and the carotid arteries.
Specific symptoms depend on the type, location and size of the tumor. For example, tumors involving the skull base and nose can affect breathing and sense of smell. Some tumors in the pituitary gland can affect vision and swallowing.
In general, common symptoms of skull base tumors include:
Altered sense of smell
Blurred or double vision
Other symptoms may include:
Loss of balance
Nausea and vomiting
What are the risk factors of skull base tumor?
There are no obvious causes for the development of skull base tumors. Risk factors may include:
Previous radiation therapy to the head to treat an infection of the scalp, or tumors of the head, neck or brain
Exposure to chemicals, including vinyl chloride, arsenic and herbicides
Certain genetic conditions
How are skull base tumors diagnosed?
Diagnosing skull base tumors starts with a physical exam including questions about your symptoms, and personal and family health history.
A neurological exam will check your vision, hearing, balance, coordination, reflexes and ability to think and remember.
Imaging of the brain may include:
Computed tomography (CT or CAT scan)
Bone scan, in which radioactive material is injected into your bloodstream. The tumor absorbs the material and a special camera is used to produce an image using a computer. This way your doctor can locate the bone tumor and detect any spread of cancer into other organs.
Positron emission tomography (PET) scans that can detect changes in cells as they grow. Often used in conjunction with a CT, a PET/CT identifies tumor cells injected with a radioactive glucose so they can be compared with normal parts of the brain.
Endoscopy, which uses a thin, lighted instrument to examine the nasal passages.
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Skull Base Tumor Treatment
When a skull base tumor is diagnosed, the next course of action is recommended by a team of specialists who work together to determine and perform the most appropriate procedure for each patient.
Treatment for skull base tumors and conditions may include any combination of observation, surgery and radiation therapy depending on:
The location of the tumor
The extent of the tumor and whether it is benign or malignant
Your general health and preferences regarding potential treatment options
For a small skull base tumor that does not cause any significant symptoms, your doctor may recommend observation. If time passes and the tumor does not grow or affect your function, you may not need further treatment.
There are a variety of surgical approaches to treat skull base brain tumors, including craniotomy.
Most patients with skull base tumor (about 90 percent) can be treated with less invasive endoscopic endonasal surgery. These procedures help the surgeon gain access to tumors through the nose and remove them without having to make large incisions across the face or skull.
Other minimally invasive approaches can reach tumors in the brain or skull base through a small incision in the eyebrow or from behind the ear:
If the patient's tumor is benign and in a part of the skull base where neurosurgeons can safely remove it completely, surgery may be the only treatment needed.
Endoscopic Skull Base Brain Tumor Surgery
In this podcast Johns Hopkins neurosurgeon Gary Gallia talks about minimally invasive endoscopic endonasal surgery for skull base brain tumors.
Your doctors may recommend use of radiation therapy after surgery for especially malignant tumors or for those located in areas of the brain where surgical removal is unsafe. Radiation methods include external beam radiation therapy and stereotactic radiosurgery.
Diagnosed with a malignant skull base tumor declared inoperable by other surgeons, Sofia, a Connecticut teenager, came to Johns Hopkins and had her tumor removed with a transnasal endoscopic approach.