Diagnosing Skull Base Tumors
There are many types of skull base tumors. Doctors at NYU Langone diagnose both cancerous and noncancerous tumors, which have varying symptoms depending on their location.
If a tumor occurs near the optic nerve, which carries information from the eye to the brain, vision problems may result. If it is located near the nasal cavity, nosebleeds or trouble breathing through the nose may occur.
A tumor located near the brainstem, which connects the brain to the spinal cord, may press on nerves. This can cause numbness or weakness in the arms or legs and even difficulty with walking and balance. A tumor located near nerves that run from the ears to the brain may cause hearing and balance problems and ringing in the ears.
Tumors can also press on the nerves that run from the face to the brain, causing facial numbness. Skull base tumors of the nasopharynx can cause hoarseness. Some tumors can press on nerves that cause the vocal cords to stop moving, producing hoarseness and a weak voice, as well as difficulty swallowing.
The cause of skull base tumors is largely unknown, although some genetic conditions may raise the risk of certain types. For example, a condition called neurofibromatosis type 2 may increase the risk of developing acoustic neuroma and other nerve sheath tumors.
To diagnose a skull base tumor, an NYU Langone doctor conducts a physical exam to look for symptoms such as nosebleeds or trouble breathing through the nose. He or she may perform vision and hearing tests and a neurological exam to check your reflexes, balance, and ability to move muscles. Our doctors may also order one or more other procedures to diagnose skull base tumors.
NYU Langone doctors usually use the results of an MRI scan to diagnose a skull base tumor. MRI uses a magnetic field and radio waves to create three-dimensional images of structures in your body. This imaging test is especially useful for viewing the soft tissues of the skull base. Before the scan, specialists may inject a contrast dye into a vein to enhance the MRI images.
Tumors in the skull base form close to the bones and may cause bone destruction; remodeling, which is the replacement of old bone tissue with new bone tissue; or excess bone formation. Chordomas and chondrosarcomas are especially prone to destroying the bones of the skull base.
A CT scan is a sensitive method for viewing bone changes, and is used in conjunction with MRI scans to diagnose and study the tumor and surrounding structures. CT and MRI scans are also used together to help plan surgery.
A PET scan may help a doctor determine whether a skull base tumor is cancerous and what type it is. During this test, a doctor injects radioactive glucose, or sugar, into a vein. This substance collects in cancerous tissue and appears on PET scan images. Your doctor may also use a PET scan to produce images of the entire body if a cancerous tumor may have spread.
If imaging tests indicate that the tumor is growing into important blood vessels or is getting its blood supply from surrounding blood vessels, your doctor may order an angiogram. This X-ray test creates images of the blood vessels.
Before the X-ray, specialists inject a contrast dye into arteries that lead to the skull base to create more detailed images of the tumor and surrounding blood vessels.
During an angiogram, doctors may also decide to perform an embolization of the tumor. This involves injecting substances into the vessels that supply blood to the tumor to block them. This technique also reduces bleeding during surgery. An angiogram is most often performed to examine meningiomas, glomus jugulare tumors, and juvenile angiofibromas.
Nasal Endoscopy and Laryngoscopy
Doctors perform these tests to see if there is a mass visible in the nasal cavity or nasopharynx, the area behind the nose in the upper part of the throat.
Laryngoscopy involves putting an endoscope—a thin, lighted, tube with a video camera on the end—into the throat and windpipe to check the vocal cords and their movement.
Our doctors use nasal endoscopy to examine the nasal cavity and sinuses in people who are having nosebleeds or trouble breathing through the nose. During this procedure, specialists insert an endoscope through the nose to look for tumors. Nasal endoscopy can be performed in the doctor’s office using a topical anesthetic.
Doctors sometimes perform a biopsy—in which they remove a small piece of tissue for examination under a microscope—to help diagnose skull base tumors. If an imaging test doesn’t provide enough information about a tumor, a doctor may take a tissue sample during a nasal endoscopy.
If doctors can’t reach a tumor by doing an endoscopy, they may perform a stereotactic biopsy, a surgical procedure to remove a tiny amount of the tumor using a small, needle-like probe. A three-dimensional computer navigation system, which uses CT or MRI images of the skull base, helps physicians locate the tumor.
A biopsy may not be necessary if imaging tests clearly show what type of tumor is present. Instead, your doctor examines the skull base tumor tissue after performing surgery to remove part or all of it.
If a tumor is neither causing any symptoms nor growing rapidly during a period of observation, a biopsy may not be necessary.
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