Overview
Skull base tumors are growths that form at the area of the skull just behind the eyes and nose, beneath the brain. The base of the skull is where important blood vessels and nerves come together with the spinal cord. The base of the skull also separates the brain from the neck.
Tumors also may be called masses, growths or lesions. These tumors can grow inside or outside the skull. They may be benign (noncancerous) or malignant (cancerous). Some skull base tumors may not cause any symptoms, but others can cause symptoms that affect your senses, such as vision or hearing, and the way that your nervous system works.
Even noncancerous skull base tumors can be dangerous. These tumors may press on the blood vessels, nerves and brain tissue in the skull base. This may lead to hearing loss, vision problems, dizziness and other issues that affect safety and well-being.
Types of skull base tumors
Types of skull base tumors are characterized by whether they are cancerous or noncancerous, and where the tumors grow in the base of the skull. Some tumors start growing somewhere else in the body and expand into the skull base.
There are many types of skull base tumors. Some of the more common types of noncancerous, also known as benign, skull base tumors include:
- Acoustic neuroma. Also called a vestibular schwannoma, this type of tumor grows on two of the nerves that help with hearing and balance. Acoustic neuromas usually grow slowly.
- Meningioma. This type of skull base tumor begins growing in the cells of the membrane lining the brain and spinal cord. This membrane is called the meninges. Rarely, meningiomas may be cancerous and grow aggressively.
- Pituitary tumor. This type of tumor forms in a pea-sized gland, called the pituitary gland, found in the skull base.
- Paraganglioma. This type of tumor usually grows in the head and neck area. While it's possible for a paraganglioma to be cancerous, it usually is not.
- Osteoma. This type of tumor is made of dense bone tissue. Osteomas grow slowly and form on the bones of the skull base. They also may be found in the sinuses.
Other rare types of benign skull base tumors include craniopharyngiomas, granular cell tumors and angiofibromas.
Malignant tumors
Some of the more common types of cancerous, also known as malignant, skull tumors include:
- Chordomas. These types of tumors tend to grow slowly, beginning in the bones of the skull base or spine. Chordomas often cause problems with vision and hearing, balance, and headaches.
- Chondrosarcomas. These tumors often develop in bones but also may grow in the nearby soft tissue called cartilage. Chondrosarcomas can occur in the bones of the skull base. These tumors usually grow slowly.
- Carcinomas. There are several kinds of skull base carcinomas, including adenoid cystic carcinomas, nasopharyngeal carcinomas, squamous cell carcinomas and adenocarcinomas. These tumors may grow in the salivary glands, the nasal cavity, the sinuses, and the head and neck area. Adenoid cystic carcinomas often grow slowly, but they tend to spread to nearby nerves and tissues.
- Olfactory neuroblastomas. These are very rare tumors that grow in the nasal cavity. They also are called esthesioneuroblastomas. These tumors can cause nosebleeds and loss of smell and may spread into the areas around the eyes and brain.
Symptoms
Symptoms of skull base tumors are different based on the size of the tumor, the kind of tumor, and where the tumor is growing in the skull base.
Some of the most common symptoms of skull base tumors are:
- Headaches.
- Neck pain.
- Changes in vision — blurry or double vision, or loss of vision.
- Changes in hearing — hearing loss or ringing in the ears.
- Problems with walking and balance.
- Clumsiness or other problems with coordination.
- Hoarse voice.
- Problems with breathing or swallowing.
- Changes in the sense of smell.
- Nosebleeds.
Skull base tumors may not cause any symptoms. Or the symptoms may be mild and general. Some symptoms may be headaches or problems with balance. Skull base tumors may be found by accident during imaging scans or other tests to find the cause of other symptoms.
When to see a doctor
Make an appointment with a doctor or other healthcare professional if you have any symptoms that worry you.
Causes
Experts aren't sure what causes most skull base tumors. Most skull base tumors seem to develop without any clear cause. It's thought that some skull base tumors, particularly acoustic neuromas, likely are caused by genetic conditions passed down in families. But several other factors also may contribute. These factors include exposure to radiation and harmful chemicals.
It's likely that a combination of factors in genes and the environment cause skull base tumors.
Risk factors
While experts don't know exactly what causes most skull base tumors, there are several factors that are thought to increase the risk of developing skull base tumors. The risk factors for skull base tumors include:
- Genetic conditions. Inheriting certain conditions through changes in genes can cause some types of skull base tumors. These changes in genes can cause the growth of tumor cells. Neurofibromatosis type 1 (NF1) and neurofibromatosis type 2 (NF2) are genetic conditions that can cause acoustic neuromas and other types of skull base tissues.
- Exposure to certain chemicals. Prolonged exposure to toxic substances such as vinyl chloride, herbicides and arsenic may increase the risk of developing skull base tumors called carcinomas, particularly in the nasal and sinus areas. Cancer-causing substances such as asbestos, formaldehyde and wood dust have been linked to the development of certain skull base cancers, particularly sinonasal cancers. Exposure to high particulate air pollution — where there are solid particles in the air that may be breathed into the lungs — and radon also are associated with some tumors, especially meningiomas. These chemicals can cause mutations in the cells lining the sinuses and nasal cavity, leading to cancer.
- History of radiation exposure. Having prior radiation therapy, especially targeted at the head and neck area, may contribute to the growth of skull base tumors.
- Frequent sinus infections. Having sinus infections can be a risk factor for certain types of tumors at the skull base, particularly in the nasal cavity and paranasal sinuses.
- Hormonal changes. These are thought to play a role in the development of certain skull base tumors. It's thought that the changes in hormones during puberty may contribute to the growth of some of these tumors. Pituitary gland tumors also are affected by changes in hormones.
- Family history. Having a family history of tumors or genetic conditions such as neurofibromatosis, multiple endocrine neoplasia or other hereditary cancer syndromes increases the risk of developing skull base tumors.
- Previous history of tumors. If you've previously been diagnosed with a tumor, particularly in the head or neck, you may be at increased risk of developing a secondary skull base tumor. This may be due to factors such as previous radiation treatment or shared risk factors for tumors.
- Smoking and alcohol consumption. These factors are linked to an increased risk of certain skull base tumors, such as squamous cell carcinoma of the sinuses or the nasopharynx. The nasaopharynx is the top part of the throat that connects it to the nasal cavity.
It's important to note that having any of these risk factors doesn't mean that you will have a skull base tumor. Not everyone with these risk factors has a skull base tumor. Some people develop tumors without having any known risk factors.
Complications
Complications of skull base tumors are usually caused by the tumors growing and pressing into blood vessels, nerves and other tissues, including the brain.
Complications of the nervous system may include:
- Problems with vision.
- Hearing loss.
- Weakness or numbness in the face.
- Difficulty swallowing or speaking.
- Difficulty breathing.
- Seizures.
- Headaches.
- Cerebrospinal fluid leaks.
- Water buildup on the brain, which can increase pressure inside the skull and cause headaches, nausea and vomiting.
Other complications may include:
- Changes in hormone levels.
- Infections, such as meningitis.
- Problems with memory, concentration, mood or behavior.
- Problems with balance, coordination and walking.
- Stroke or bleeding in the brain.
- Problems with the eustachian tube in the ear.
Sometimes skull base tumors can spread. Noncancerous skull base tumors generally do not spread. Cancerous skull base tumors can grow into nearby tissues and spread to the lymph nodes, lungs, liver or other parts of the body. Chordomas, chondrosarcomas, sinonasal carcinomas and olfactory neuroblastomas are more likely than other types of skull base tumors to spread throughout the body.
Whether or not skull base tumors spread, and how quickly they do so, depends on the type and grade of the tumor. High-grade cancerous tumors are more aggressive. They likely will spread more quickly than low-grade tumors. The grade of a tumor shows how different the tumor cells are from healthy cells. High-grade tumors have irregular cells and tend to grow and spread very quickly.