Brain and spinal cord cancers can grow in the central nervous system, which is known as a primary cancer. They can also travel from other parts of the body, like the lung or breast, and form deposits in the brain or spinal cord; this is called a secondary cancer or brain metastases. Many brain cancers are the result of metastasis (spread) of cancer from other places in the body to the brain.
The Seattle Cancer Care Alliance (SCCA) Brain and Spine Metastases Clinic specializes in treating patients whose cancer has metastasized to the brain or spinal cord.
Anatomy of the brain and spinal cord
The brain is a remarkable three-pound organ housed in, and protected by, the skull. Not only does it control all five senses (taste, smell, sight, hearing and touch), it is responsible for your emotions, thoughts and movement. The right side of the brain controls the left side of your body, and the left side of the brain controls the right side of your body.
Your brain has three main parts: the cerebrum, cerebellum and brain stem.
The cerebrum controls higher brain functions. It has four lobes, each with different tasks:
- Frontal lobe: executive function (management of the brain), decision-making, personality, language, planning and movement
- Parietal lobe: intelligence, reasoning, sensation and reading
- Occipital lobe: vision
- Temporal lobe: language, behavior, hearing, vision, emotions and memory
The cerebellum controls balance, coordination and fine muscle control.
The brain stem controls things we do without thinking, like our heartbeat, breathing and swallowing.
The spinal cord starts at the brain stem and goes to the tailbone. It is about as wide as your little finger and extends the length of your back. Messages are carried from the spinal cord to and from the brain and the rest of the body.
Nerves extend from the spinal cord on each side and go to other parts of the body.
The brain and spinal cord are protected by bony structures — the skull and spinal column.
Meninges are membranes that cover and protect the brain and spinal cord. There are three layers of meninges:
- Dura mater, which is closest to the bone
- Arachnoid, which is loosely around the brain
- Pia mater, which is closely attached to the brain and spinal cord surface
Cerebrospinal fluid (CSF) is a clear, watery liquid between the arachnoid and pia mater that cushions the brain and spinal cord. It is made in the four ventricles, which are large open structures in the brain. The area in the lateral ventricles that makes spinal fluid is called the choroid plexus. About 20cc of spinal fluid is made, but not absorbed, each hour. There is about 140 cc (about half a can of soda) of spinal fluid that surrounds the brain and spine. This fluid flows and circulates around your brain and spine to protect them.
Brain and spinal cord metastases
Treatments for cancers have advanced over the last several years, leading to patients surviving and living longer with cancer. As a result of more effective cancer treatments, the disease has more time to spread to the brain and spinal cord.
Some of the most common primary cancers that spread to the brain are lung, breast, skin, colon, gastrointestinal, kidney and gynecologic cancers, but almost all cancers can spread to the brain.
Cancer that has spread to the brain and spinal cord can be found in the brain, the cerebrospinal fluid or the lining of the brain and spinal cord, which is called the leptomeninges.
Metastatic brain and spinal cord diseases include:
- Leptomeningeal disease, or metastatic cancer that is in the cerebral spinal fluid surrounding the brain and spinal cord
- Brain metastases
Symptoms vary by patient and depend on the location of the brain or spinal cord metastases. Some people may experience only one symptom, while others may have several. Your care team will evaluate your symptoms and help to identify ways to manage them as part of your treatment plan. Common symptoms include:
- Speech difficulty
- Changes in mood or personality
- Changes in sense of touch or other senses
- Loss of balance or coordination
- Other stroke-like symptoms
Primary brain cancer types
Gliomas are cancers that grow from glial cells (also called glia cells), which are supportive cells that hold brain cells called neurons in place. Glial cells provide nutrition and form myelin, which is a covering for nerve cells. Glial cells include astrocytes, oligodendrocytes and ependymal cells.
About half of all primary brain cancers are from glial cells. About one-fifth of all primary spinal cord cancers are from glial cells. Gliomas occur more often in men than women.
Meningiomas are cancers that grow from the brain covering (meninges). About 15 to 25 percent of all primary brain cancers are meningiomas. Meningiomas occur more often in women than men.
Primary cancers from glial cells (gliomas)
Astrocytomas start from brain cells called astrocytes (star-shaped cells). They are the most common type of glioma, slow-growing, and can be anywhere in the brain, but are most often in the cerebrum. If found early, they can often be surgically removed.
Astrocytoma image reprinted by permission from Macmillan Publishers Ltd: Nature Publishing Group, Nature Reviews Cancer, (The Molecular and Genetic Basis of Neurological Tumours), copyright 2002.
There are different grades of astrocytomas:
- Pilocytic astrocytoma (Grade I) grows slowly and usually does not grow into surrounding tissues.
- Low-grade (glioma) astrocytoma (Grade II) grows faster than pilocytic astrocytomas and spreads into surrounding tissues.
- Anaplastic astrocytoma (Grade III) grows faster than low-grade astrocytoma and often recurs.
- Glioblastoma multiforme (Grade IV) is the most common brain cancer. It grows faster than low-grade astrocytomas and mainly occurs in the cerebrum.
- Brain stem gliomas(any grade) are located where the brain and spinal cord meet.
Ependymomas (any grade) grow slowly from the lining of the ventricles of the brain and the hollow central canal of the spinal cord. Well-differentiated ependymomas look much like normal cells and grow slowly. Anaplastic ependymomas do not look like normal cells and grow more quickly than well-differentiated ependymal cancers.
Ependymoma image courtesy of Dr. Trent Tredway.
Oligodendrogliomas begin in brain cells called oligodendrocytes, which provide support around nerves by building a sheath of myelin to cover the nerve cells and pass along electrical nerve impulses.
Genetic testing is important for these cancers because it helps us predict prognosis and treatment response. There are different grades of oligodendroglial cancers:
- Well-differentiated oligodendrogliomas (Grade II) are slow-growing cancers that look very much like normal cells.
- Anaplastic oligodendrogliomas (Grade III) grow more quickly, and the cells do not look like normal cells.
Mixed gliomas start from two types of glial cells, usually astrocytes and oligodendrocytes. Treatment is based on whichever cell type is the most aggressive.
Primary cancers from non-glial cells
Meningiomas grow from the meninges, which are coverings for the brain and spinal cord. They are usually slow-growing and can be one of three grades. Surgery is often used as a treatment, but radiation therapy may also be used.
Pineal tumors occur near the pineal gland, which is located deep inside the brain and produces melatonin. There are several types of pineal tumors; some are cancerous. Some pineal tumors are fast-growing. Surgery may be recommended for these tumors.
Pituitary tumors affect the pituitary gland, which is located at the base of the brain and is responsible for hormones, growth and metabolism. Surgery and radiotherapy are often used for these tumors.
Schwannomas are tumors from schwannoma cells, which form the myelin sheath that covers and protects the nerves. They are usually benign (non-cancerous). There are several types, including the acoustic schwannoma, which is a benign tumor of the nerve that is responsible for hearing. Surgery is the primary treatment, but if a patient has more than one schwannoma, a doctor may recommend surgery followed by radiation therapy.
Primary central nervous system lymphoma is a cancer that develops out of lymphocytes, which are a type of white blood cell. Lymphomas of the brain are a form of non-Hodgkin lymphoma, a cancer that is often associated with the lymph nodes. These cancers are usually near the ventricles of the brain, and there may be multiple tumors. It is quite common for this type of cancer to spread.